## No full-text available

To read the full-text of this research,

you can request a copy directly from the authors.

here, we propose a full-optical tunable Add/Drop filter based on single (SR) and double-vertically (DR) aligned Kerr-like nonlinear photonic crystal ring resonators (PCRRs). Silicon (Si) nano-crystal is used as the nonlinear material inside and outside of PCRRs. The minimum optical power required to turn–on/turn–off the SR and DR filters are 2000 mW/μm2, and 150 mW/μm2 respectively. We believe since the DR filter has a higher Q-factor rather than SR and also since the optical power reads more nonlinear rods with a longer time to pass the structure, thus the optical power required is much lower (10 folds). In addition, the minimum power required to 1 nm redshift the center operating wavelength of SR filter is 125 mW/μm2 (i.e. ΔnNL = 0.005) and for DR is as low as 8 mW/μm2. Performance of the Add/Drop filter structure is simulated by means of finite difference time domain (FDTD) method, in which the simulations showed an ultra-compact size structure with a promising ultrafast tune-ability speeds on the order of below 10ps.

To read the full-text of this research,

you can request a copy directly from the authors.

... The photonic band gap refers an area of photonic crystal structure, where not any wavelength is capable of propagation [2]. Different optical devices have been designed and presented based on photonic crystal such as optical sensors, switches, optical gates, filters, multiplexers, demultiplexers, and waveguides, with advantages such as high efficiency, small size, high processing speed, and low power consumption [3][4][5][6][7][8][9][10]. ...

... A filer design can be used in the design of demultiplexer structures and other optical devices. The add-drop filter that was designed by Mansouri-Birjandi et al. [8] in 2016 was capable of fast response, low power consumption, and integration with several communication channels, as well as adjustability in non-linear mode. It needs the minimum light power required for switching on/off. ...

In this paper, 2-channel and 4-channel optical demultiplexers have been designed based on photonic crystal nano-ring resonator. The structure of both demultiplexers is based on the use of a photonic crystal filter. The mean quality factor of 2828, mean transfer factor of 95%, mean cross-talk of − 25.07 dB, and an inter-channel distance of 7.4 nm are among the structural advantages of the 2-channel demultiplexer. The advantages of the 4-channel demultiplexer include the mean quality factor of 4525, mean channel power transfer factor of 95%, and maximum and minimum channel cross-talk of − 19.6 and − 40.4, respectively. Also, the inter-channel difference is 7.8 nm and mean channel width is 0.375 nm. Moreover, the simplicity of the structure and the small size are among the characteristics of these designs. The proposed 2-channel and 4-channel demultiplexers can be used in WDM systems, especially DWDM systems.

... To realise all-optical processing at the speed of terabytes per second, electronic devices must be replaced by the all-optical devices [1][2][3]. These devices include filters [4], optical sensors [5], demultiplexers [6], logic gates [7,8], and so on. ...

... In the two-dimensional photonic crystals, the refractive index of the environment varies periodically in two directions. According to their properties, photonic crystals can be used to design and implement all-optical devices [4][5][6][7][8]. One of the important properties of photonic crystal lattices is the photonic band gap. ...

Using a two-dimensional photonic crystal lattice, a compact and simple structure has been introduced in the present paper to construct an all-optical half adder. The designed structure operates under the interference effect. The phase difference has been created in different states by putting the point defects and the difference in the length of the input waveguides. To do analyses, the finite-difference time-domain method and the plane wave expansion have been used. The advantages of this design include the small dimensions, high possibility of construction, compatibility with the silicon-based technology, and equality of the output power in the logic states 0 and 1. The contrast ratio calculated for the port Sum and the port Carry has been equal to 9.3 and 8.22 dB. The response time has been equal to 0.22 ps, generating the data transfer rate of 4.55 Tbps.

... Further, the role of structural design in photonic crystal ring resonators (PCRR) in realizing compact optical devices was investigated (Alipour-Banaei et al. 2015a;Mehdizadeh et al. 2016;Rakhshani and Mansouri-Birjandi 2014). These devices can be spectrally tailored based on their rod's refractive index, the structures' lattice constant, and the design parameters of the rod such as radius, and height (Farmani et al. 2020;Mansouri-Birjandi et al. 2016;Tavousi et al. 2017). Furthermore, the spectrally selective resonances in PCRR devices can be tuned to create either a blue or red shift based on the desired application (Naghizade and Saghaei 2021). ...

Fast and compact optoelectronic devices are highly sought after for applications in high-speed signal processing in optical communication networks. One approach to realizing such devices is through all-optical digital logic circuits. One of the main building blocks of such circuits is a decoder. In this work, we present a novel design for a tunable optoelectronic 2-to-4 binary decoder. The presented structure is realized by utilizing three photonic crystal (PhC) ring resonators. Each PhC ring resonator is formed by silicon rods encircled by silica (SiO2) rods coated with graphene nanoshells (GNSs). By adjusting the chemical potential of GNS with a proper gate voltage, we can tune the desired PhC resonant mode. The fundamental PhC microstructure’s photonic band structure is analyzed by using the plane wave expansion method. Furthermore, the finite-difference time-domain technique is used to solve Maxwell's equations and analyze the light propagation within the structure. Our numerical results reveal that 0.8 ps and 0.3 ps are the maximum rise and fall times for the final structure, respectively and the total size of this device is 850 µm². Due to the short rise and fall times and its size which are among very important features in high-speed systems, the proposed design could be utilized for high-speed signal processing systems in miniaturized optical communication network devices.

... SiO2 has negligible loss and low thermal sensitivity in the near-infrared wavelength range [18][19][20]. Photonic crystal ring resonators (PCRR) are well-known structures because they have excellent characteristics in realizing various compact optical devices [21][22][23][24][25]. Resonant modes of a PCRR depends on several physical parameters such as rod radius, lattice constant, and rods' refractive index [26][27][28][29][30][31]. In recent reports, researchers have shown that a PCRR can be used as an optical filter, and blueshift or redshift may occur in the resonant mod by changing any of these parameters [13,23]. ...

This paper reports a novel design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods coated with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for ‘SUM’ and ‘CARRY’. The plane wave expansion technique is used to study the photonic band structure of the fundamental photonic crystal (PhC) microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra. Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 μm² area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems.

... SiO2 has negligible loss and low thermal sensitivity in the nearinfrared wavelength range [18][19][20]. Photonic crystal ring resonators (PCRR) are well-known structures because they have excellent characteristics in realizing various compact optical devices [21][22][23][24][25]. Resonant modes of a PCRR depends on several physical parameters such as rod radius, lattice constant, and rods' refractive index [26][27][28][29][30][31]. In recent reports, researchers have shown that a PCRR can be used as an optical filter, and blueshift or redshift may occur in the resonant mod by changing any of these parameters [13,23]. ...

This paper reports a new design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods covered with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for 'SUM' and 'CARRY'. The plane wave expansion technique is used to study the photonic band structure of the fundamental PC microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra. Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 µm ² area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems.

... Photonic crystals (PCs) have broad application in the fields of ultrahigh speed and high capacity networks, optical computing and signal processing systems [1][2][3][4]. They have attracted wide spread attention for the high response, small sizes, low loss, simple structures, low power consumption, and integrated applications [5][6][7][8][9][10]. In recent years, a variety of schemes were used for designing optical logic structures based on photonic crystals. ...

In this study, we are going to design all optical 1-bit comparator by combining wave interference and threshold switching methods. The final structure composed of two nonlinear ring resonators and seven waveguides. The functionality of the suggested logical structure is analyzed and simulated by using plane wave expansion (PWE) and finite difference time domain (FDTD) methods. According to results, the proposed all
optical 1-bit comparator has faster response and smaller footprint than all previous works. The maximum ON-OFF contrast ratio, delay time and area of the suggested optical comparator are about 16.67 dB, 1.8 ps, and 513 µm2, respectively.

... Therefore, they are more popular among researchers. Resonant modes of a PCRR depend on several key parameters such as rod radius, dielectric constant, and position of the PhC unit cells (Biswas et al. 2020;Farmani et al. 2020;Mansouri-Birjandi et al. 2016;Naghizade and Sattari-Esfahlan 2017;Tavousi et al. 2017). By changing every parameter, the blue or redshift occurs at resonant modes. ...

This paper proposes a new all-optical full-adder design based on nonlinear X-shaped pho-tonic crystal (PhC) resonators. The PhC-based full-adder consists of three input ports, two X-shaped PhC resonators (X-PCRs), and two output ports. The dielectric rods made of silicon and nonlinear rods composed of doped glass are used to design the X-PCRs. Two well-known plane wave expansion and finite difference time domain methods are applied to study and analyze the photonic band structure and light propagation inside the PhC, respectively. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear Kerr effect appears and manages the direction of light propagation inside the structure. The maximum time delay and footprint of the proposed full-adder are about 2.5 ps and 663 μm^2 , making it an appropriate adder for high-speed data processing systems.

... Thus, they are more popular among designers. A large number of parameters, including the radius of the dielectric rod, the lattice constant, the type of rod arrangement, the dielectric constant, and the PhC unit cells' position, affect the resonant's intensity and frequency modes [14][15][16][17][18][19]. By changing every parameter, the blue or redshift occurs at resonant modes. ...

In this paper, we report a new design of all-optical full-adder using two nonlinear resonators. The PhC-based full-adder consists of three input ports (A, B, and C for input bits), two nonlinear resonant cavities, several waveguides, and two output ports (for the Sum and Carry). Eight silicon rods and a nonlinear rod composed of doped glass form each resonant cavity. The well-known plane wave expansion technique is used to calculate the photonic band structure. It shows a wide photonic bandgap in the wavelength range of 1365 nm to 2074 nm covering the C and L optical transmission bands. The finite-difference time-domain method is applied to study the light propagation inside the full-adder. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear optical Kerr effect appears and controls the direction of light emitted inside the structure as desired. The maximum time delay and footprint of the proposed full-adder are about 3ps and 758.5 µm ² , respectively. Therefore, due to the low time delay and small footprint, the presented design can be used as a basic mathematical operator in the all-optical arithmetic logic unit.

... When light with TM polarization is applied to the metal structure, SPPs are excited (Kik and Brongersma 2007;Maier 2007). Add-drop lters, logic gates, multiplexers, and speci cally switches are various types of plasmonic devices that attracted lots of scientist's attentions (Bashiri andFasihi 2019: Fasihi 2014;Ghadrdan and Mansouri-Birjandi 2013;Mansouri-Birjandi et al. 2016;Monfared et al. 2020;Negahdari et al. 2019). Plasmonic switches are in the range of nanometres with fast response, low input power, and high transmission e ciency. ...

In this paper, we proposed an all-optical plasmonic switch based on metal-insulator-metal (MIM) structures. We used the intrinsic nonlinear properties of gold to implement the switch. The proposed switch consists of a bus waveguide side coupled with a pair of asymmetric vertical cavities. We obtained the transmission spectrum of the structure for low input intensities. The results showed that a sharp dip occurs at the wavelength of 860 nm. Due to the nonlinear properties of gold and the nonlinear Kerr effects, the proposed switch has a high transmission ratio of about 0.8 and a low threshold power of 0.07 mW/µm ² . The threshold power of the structure with and without using the gold nanostructure shows a reduction of 50%. The result showed that the proposed switch has the potentiality to be applied in the plasmonic integration circuits.

... Anyone who wants to design all optical computing and processing systems require different optical devices such as optical logic gates [5][6][7], Optical filters [8][9][10], decoders [11][12][13][14], encoders [15][16][17][18], multiplexer [19], demultiplexer [20][21][22][23], adders [24][25][26], comparators [27][28][29][30][31][32] and data converters [33,34]. All of these structures can be designed using different mechanisms inside two dimensional photonic crystals (2D-PhCs). ...

In this paper, a novel all optical half subtractor based on threshold switching mechanism was
proposed which has one bias port, two input ports and two output ports. The proposed design
will be realized by three nonlinear resonant rings and eight waveguides. To analyze and simulate
the proposed structure, we employed plane wave expansion (PWE) and finite difference time do-
main (FDTD) methods. Based on the comparison results, low power consumption, compactness,
ultra-fast operation and high contrast ratio are the main advantages of designed all optical half
subtractor compared with the previous structures. The ON-OFF contrast ratios for output ports (D
and B ports) are about 10.31 dB and 14.96 dB, respectively. Also, the maximum rise, fall and de-
lay times of the proposed structure are about 0.8 ps, 0.45 ps and 1.3 ps, respectively.

... Scalability, small size, and no need for electrical bias are the main advantages of PhC-based devices [10][11][12][13][14]. In recent years, several PhC-based devices such as optical filters [15][16][17][18][19][20][21][22], demultiplexers [23][24][25][26][27][28][29], logic gates [30][31][32][33][34][35][36][37][38], decoders [39][40][41][42][43], encoders [44][45][46][47][48], and analog-to-digital converters [49][50][51][52][53][54] have been proposed. ...

In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm2 demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

... Thus, waveguides in a PhC can be created by removing one or more rows of dielectric rods. PhC-based structures are excellent choices for designing many types of optical devices such as optical filters [3][4][5][6][7][8], PhC fibers [9][10][11][12][13][14][15][16][17][18], multiplexers and demultiplexers [19][20][21][22][23][24][25][26], encoders and decoders [27][28][29][30], switches [31][32][33][34][35][36], logic gates [37][38][39][40][41][42], analog to digital converters (ADCs) [43][44][45][46][47][48][49], and sensors [50][51][52][53][54][55][56][57]. In recent years, photonic sensors have been widely studied and fabricated because of the increasing demand for sensing applications in the health care, food quality, control defense, security, automobiles, aerospace, and so on. ...

In view of the large scientific and technical interest in the MEMS accelerometer sensor and the limitations of capacitive, resistive piezo, and piezoelectric methods, we focus on the measurement of the seismic mass displacement using a novel design of the all-optical sensor (AOS). The proposed AOS consists of two waveguides and a ring resonator in a two-dimensional rod-based photonic crystal (PhC) microstructure, and a holder which connects the central rod of a nanocavity to a proof mass. The photonic band structure of the AOS is calculated with the plane-wave expansion approach for TE and TM polarization modes, and the light wave propagation inside the sensor is analyzed by solving Maxwell’s equations using the finite-difference time-domain method. The results of our simulations demonstrate that the fundamental PhC has a free spectral range of about 730nm covering the optical communication wavelength-bands. Simulations also show that the AOS has the resonant peak of 0.8 at 1.644µm, quality factor of 3288, full width at half maximum of 0.5nm, and figure of merit of 0.97. Furthermore, for the maximum 200nm nanocavity displacements in the x- or y-direction, the resonant wavelengths shift to 1.618µm and 1.547µm, respectively. We also calculate all characteristics of the nanocavity displacement in positive and negative directions of the x-axis and y-axis. The small area of 104.35µm2 and short propagation time of the AOS make it an interesting sensor for various applications, especially in the vehicle navigation systems and aviation safety tools.

... Also, the proposed PhCs are mechanically unstable due to their geometry and must be integrated on dielectric insulators such as silica (SiO 2 ) to overcome this issue [7,8]. Beside the optical logic gates [9][10][11][12][13], encoders [14][15][16], decoders [2,17,18], optical filters [19][20][21][22][23][24][25], demultiplexers [26][27][28][29][30], switches [17,31,32], interferometers [33,34], as well as optical memories and modulators [33,35], are other cases of the key optical components designed based on PhCs. Developing optical devices based on photonic crystal fibers (PCFs) can overcome many of the PhCs weaknesses mentioned by several research groups. ...

An encoder logic gate is a combinational circuit that performs the coding operation on the input binary data, and 2ⁿ input lines are encoded with n bits. In this paper, we present a new design of a high-speed all-optical 4 to 2 encoder using a solid-core photonic crystal fiber (PCF) composed of pure silica. The proposed structure consisting of an optical buffer and two optical OR gates has four input ports and two output ports in a square lattice of PCF. The plane-wave expansion method is used to compute the band structure of the encoder, and the beam propagation method is applied to calculate the transmission and the electric field distribution of optical light inside the device. We demonstrate that the proposed 4 to 2 encoder can operate in the C-band, ranging from 1530 nm to 1565 nm, which is an appropriate device for telecommunication applications. The numerical results demonstrate that the normalized transmission values less than 0.02% and greater than 95% are supposed to be logic 0 and logic 1, respectively. The maximum delay of the encoder is 0.3 ps, and its total footprint is 50 µm × 30 µm×3 mm; thus, due to the relatively simple and low-cost fabrication of PCFs and their applications in photonics-based systems, the proposed device can be used in optical communications and networking.

... Thus, by removing one or more rows of dielectric rods, a waveguide in PCs can be created. Such structures are suitable tools for designing many types of optical filters (Rakhshani and Mansouri-Birjandi 2013;Sattari-Esfahlan 2017a, 2019;Mansouri-Birjandi et al. 2016;Zhang et al. 2018;Guo et al. 2019;Aliee et al. 2020;Naghizade and Saghaei 2020a), switches (Mehdizadeh et al. 2016a;Beggs et al. 2009;Saghaei and Van 2019;Kowsari and Saghaei 2018), logic gates (Salmanpour et al. 2015;Karkhanehchi et al. 2017;Vali-Nasab et al. 2019;Sani et al. 2020a;Naghizade and Saghaei 2020b), multiplexers and demultiplexers (Mehdizadeh et al. 2016b;Sattari-Esfahlan 2017b, 2018;Mehdizadeh and Soroosh 2016;Rakhshani and Mansouri-Birjandi 2014;Asgari and Granpayeh 2017;Manzacca et al. 2007), encoders and decoders (Moniem 2016;Mehdizadeh et al. 2017a;Salimzadeh and Alipour-Banaei 2018;Alipour-Banaei et al. 2015), analog to digital converters (Rostami and Rostami 2003;Tavousi et al. 2016;Fasihi 2014;Mehdizadeh et al. 2017b;Youssefi et al. 2012;Sani et al. 2020b, c;Parandin et al. 2018), PC fibers (Ebnali-Heidari et al. 2014;Saghaei 2017Saghaei , 2018Saghaei et al. 2015Saghaei et al. , 2016Saghaei and Ghanbari 2017;Ghanbari et al. 2018;Kalantari et al. 2018;Raei et al. 2018), sensors (Nair and Vijaya 2010;Jágerská et al. 2010;Tavakoli et al. 2019;Liu and Salemink 2012;Tabrizi and Pahlavan 2020), and many other applications. ...

In view of the large scientific and technical interest in the frequency-selective all-optical devices, and some optical filters limitations, we focus on the design and analysis of a novel ultra-narrowband all-optical filter. The proposed structure consists of input/output wave-guides and a resonator in a microstructured photonic crystal that encompasses silicon rods. We study the effects of the variations of rod radius, the lattice constant, and the refrac-tive index of the filter on the resonance wavelength, quality factor, transmission, and full width at half maximum (FWHM) by solving Maxwell's equations using the finite-difference time-domain method. The numerical results show that the proposed filter with a lattice constant of a = 540 nm, central resonant rod radius of 216 nm, and the rod radius of r = 0.2a has a resonant wavelength of λ r = 1253 nm, the quality factor of Q f = 3288, FWHM of 0.26 nm and broad free spectral range of FSR = 790 nm while this filter for r = 0.26a has λ r = 1552 nm, Q f = 5542, FWHM of 0.28 nm, and FSR = 720 nm. Some promising characteristics, such as its short propagation time and a small area of 102.6 µm 2 make this optical filter an interesting candidate for use in photonic integrated chips.

... These structures are the suitable choice for the realization of active and passive optical devices. PhCs can, therefore, be used for the design and fabrication of all-optical switches (Li et al. 2006;Liu et al. 2010;Shiramin et al. 2018), logic gates (Xu and Lipson 2007;Alipour-Banaei et al. 2014;Fu et al. 2013;Andalib and Granpayeh 2009), filters (Fan et al. 1998;Qiang et al. 2007;Robinson and Nakkeer 2013;Mansouri-Birjandi et al. 2016), multiplexers and demultiplexers (Koshiba 2001;Jiu-Sheng et al. 2015;Rakhshani and Mansouri-Birjandi 2013), decoders (Parandin et al. 2018a), analog to digital converters (Mehdizadeh et al. 2017;Youssefi et al. 2012;Sani et al. 2020;Tavousi et al. 2016;Tavousi and Mansouri-Birjandi 2018) and so on. Logic gates are the building blocks of every logic circuit. ...

In this paper, we propose an all-optical high-speed half adder based on linear defects in a photonic crystal (PhC) structure composed of silicon rods. The proper design of half adder results in no need to increase the intensity of the input optical signal for the appearance of the nonlinear Kerr effect, which leads to diverting the incoming light toward the desired output. The proposed device consists of four optical waveguides and a defect in a square lattice PhC. Two famous plane wave expansion and finite difference time domain methods are used to study and analyze photonic band structure and light propagation inside the PhC, respectively. The presented structure, the ON-OFF contrast ratios for Sum and Carry, are 16dB and 14dB, respectively. Our simulation results reveal the proposed half adder has a maximum delay time of 0.7 ps with a total footprint of 158 um2. Due to very low delay time, high contrast ratio, and small footprint that they are more crucial in modern optoelectronic technologies, this structure can be used in the next generation of all-optical high-speed central processing units.

... So far, various all-optical devices based on the PC platform have been introduced. These designs come in a variety of applications, such as filters [10,11], demultiplexers [12,13], logic gates [14,15], and sensors [16,17]. Due to the PC devices' small size, low power consumption, and basis in complementary metal-oxide semiconductor (CMOS) technology, scientists hope for the design of optical integrated circuits. ...

In this paper, an ultracompact all-optical encoder based on a photonic crystal nanoresonator was designed. The proposed structure consists of several waveguides and two nanoresonators. The nanoresonators were designed by reducing the radius of the dielectric rods. To analyze the all-optical encoder, plane-wave expansion and finite-difference time-domain methods were, respectively, applied to calculate the bandgap diagram and to obtain the transmission and propagation of optical field. The contrast ratio, delay time, data transfer speed, and total footprint of the logic gate equaled 9.51 dB, 0.24 ps, 4.16 Tb/s, and ${148}\;\unicode{x00B5} {{\rm m}^2}$148µm2, respectively. In addition to these parameters, two new parameters were investigated: the range of optical power required, and the frequency range for better logic gate efficiency. Due to the ultracompacted size, low power consumption, low delay time, and simplicity of structure, this all-optical encoder is suitable for use in low-power optical integrated circuits.

... These structures are the suitable choice for the realization of active and passive optical devices. PhCs can, therefore, be used for the design and fabrication of all-optical switches (Li et al. 2006;Liu et al. 2010;Shiramin et al. 2018), logic gates (Xu and Lipson 2007;Alipour-Banaei et al. 2014;Fu et al. 2013;Andalib and Granpayeh 2009), filters (Fan et al. 1998;Qiang et al. 2007;Robinson and Nakkeer 2013;Mansouri-Birjandi et al. 2016), multiplexers and demultiplexers (Koshiba 2001;Jiu-Sheng et al. 2015;Rakhshani and Mansouri-Birjandi 2013), decoders (Parandin et al. 2018a), analog to digital converters (Mehdizadeh et al. 2017;Youssefi et al. 2012;Sani et al. 2020;Tavousi et al. 2016;Tavousi and Mansouri-Birjandi 2018) and so on. Logic gates are the building blocks of every logic circuit. ...

Half adder and half subtractor are the basic building blocks of an arithmetic logic unit used in every optical central processing unit (CPU) to provide computational operators. In this paper, we aim to design an ultrafast all-optical half adder based on nonlinear ring resonators. The proposed structure consists of the concurrent designs of the AND and XOR logic gates inside a rod-based photonic crystal microstructure. The linear dielectric rods made of silicon and nonlinear dielectric rods composed of doped glass are used to design the nonlinear ring resonators as the fundamental blocks of a half adder. We demonstrate as the intensity of the incoming light increases, the nonlinear Kerr efect appears, and the total refractive index increases. It diverts the direction of light propagation to the desired nonlinear ring resonator depending on the signal wavelength, the radius of rods and lattice constant. Finally, after several resonances, the light is coupled to the output. Our numerical simulations using a two-dimensional finite-difference time-domain method reveal depending on the light intensity, the maximum and minimum transmissions of the half adder are 100% and 96%, respectively. The calculations also show the delay of the designed half adder is 3.6 ps. Due to the small area of 249.75 µm 2, the proposed half adder is an appropriate candidate for photonic integrated circuits used in the next generation of all-optical CPUs.

... The possibility of having bending, a high response, low power consumption, and compact sizes are the main characteristics that made PhC-based structures interesting for the researchers [4]. Recently, many efforts have been done for designing optical logic gates [5][6][7][8][9][10][11][12], filters [13][14][15], adders [16][17][18], decoders [19][20][21][22], encoders [23][24][25], flip-flops [26,27], and analog to digital converters [28][29][30]. ...

In this paper, a compact optical high-speed 1-bit comparator was proposed based on photonic crystals. Inthis structure, the nonlinear rods were used at the cross-connecting point of two optical waveguides. The opticaltransmission and reflection from these rods depend on the amount of the optical intensity. In response to thedifferent states of the input ports, different values of the optical power reach these rods and the interferencepatterns make the correct function of the output ports. The refractive index and the Kerr coefficient of nonlinearrods are 1.4 and 10-14 m2/W, respectively. The footprint of the structure is 55 μm2 which is much smaller than theprevious works. Besides, the lower delay time is the other advantage of this work compared with the previousworks. Based on the simulation results, the proposed structure can be used in integrated optical circuits.

... PCs are structures composed of periodic layers with different dielectric constants and demonstrate useful characteristics such as photonic band gap (PBG) [3], slow light regime [5][6][7], and self-collimation [8][9][10][11]. Because of their compact size and the aforementioned properties, they are promising candidates in realizing all-optical devices such as optical waveguides [10][11][12], filters [13][14][15][16][17][18], demultiplexers [19][20][21][22][23][24][25], switches [26][27][28][29][30], logic gates [31][32][33][34][35][36], encoders [37][38][39][40][41][42], decoders [43][44][45][46][47][48], and analog-to-digital converters [49][50][51][52][53][54]. ...

In this paper, an all-optical photonic crystal-based switch containing a graphene resonant ring has been presented. The structure has been composed of 15 × 15 silicon rods for a fundamental lattice. Then, a resonant ring including 9 thick silicon rods and 24 graphene-SiO2 rods was placed between two waveguides. The thick rods with a radius of 0.41a in the form of a 3 × 3 lattice were placed at the center of the ring. Graphene-SiO2 rods with a radius of 0.2a were assumed around the thick rods. These rods were made of the graphene monolayers which were separated by SiO2 disks. The size of the structure was about 70 µm2 that was more compact than other works. Furthermore, the rise and fall times were obtained by 0.3 ps and 0.4 ps, respectively, which were less than other reports. Besides, the amount of the contrast ratio (the difference between the margin values for logics 1 and 0) for the proposed structure was calculated by about 82%. The correct switching operation, compactness, and ultra-fast response, as well as the high contrast ratio, make the presented switch for optical integrated circuits.

... In 2000, Pendry brought forward a superlens for a negative index response [2] and Smith realized negative refraction by using periodic continuous metallic wires and periodic split ring resonators with effective negative permittivity ε and permeability µI [3]. Thus, the experimental and theoretical studies on NIMs became more vibrant by virtue of their intriguing electromagnetic properties and have been extensively studied for many potential applications such as detection [4,18] and optical filters [5,19,20]. However, the experimental demonstration of conventional negative refraction materials, which involved metals and worked around the plasma frequencies, suffered significant Ohmic loss and narrow frequency bands. ...

... Photonic band gap [2, 3], self-collimation [4-6], optical wave guiding [7,8], wavelength selection [9, 10], threshold switching [11][12][13][14] are the most significant properties of PhCs. These properties give them the capability to be used in designing optical devices such as filters [9,[15][16][17][18][19][20][21][22][23], demultiplexers [24][25][26][27][28][29][30][31], logic gates [12, [32][33][34][35][36][37][38][39][40], data converters [41][42][43][44], adders [6, [45][46][47][48][49], decoders [50][51][52][53][54] and encoders [55][56][57][58][59]. ...

Optical logic gates are very important structures required for creating all-optical digital signal processing systems. Optical XOR and XNOR gates can be used for designing optical adders and optical comparators, respectively. In this paper we proposed a novel structure which can be used for simultaneous implementation of optical XOR and XNOR logic gates. The proposed structure was designed using a nonlinear photonic crystal ring resonator. The delay time for XOR and XNOR gates are 1.7 and 3 ps, respectively.

... It has been proven that PhCs have great potential for designing different kinds of optical devices. For example, these structures can be used for designing optical communication components such as optical filters [4][5][6][7][8][9], demultiplexers [10][11][12][13][14][15], or analogto-digital converters [16][17][18][19][20][21]. Also, they can be used for designing optical components required for all-optical data processing such as optical logic gates [22][23][24][25][26], adders [27][28][29], comparators [30][31][32], decoders [33][34][35][36], encoders [37][38][39][40], multiplexers [41], and demodulators [42]. ...

Optical logic devices are the inevitable need for the future all optical computing and data processing. In this paper we are going to design and propose an all optical half subtractor using photonic crystal structure. The proposed structure will be realized using both threshold switching and beam interference. Finite difference time domain method used for analyzing the proposed structure. The simulation results show that the contrast ratio for D and B ports are 8 dB and 12 dB respectively. Also the maximum the maximum rise and fall times are 1 ps and 0.6 ps respectively.

... It has been proven that PhCs have great potential for designing different kinds of optical devices. For example, these structures can be used for designing optical communication components such as optical filters [4][5][6][7][8][9], demultiplexers [10][11][12][13][14][15], or analogto-digital converters [16][17][18][19][20][21]. Also, they can be used for designing optical components required for all-optical data processing such as optical logic gates [22][23][24][25][26], adders [27][28][29], comparators [30][31][32], decoders [33][34][35][36], encoders [37][38][39][40], multiplexers [41], and demodulators [42]. ...

A two-dimensional photonic-crystal-based structure was used for designing a novel structure for realizing an all-optical half-subtractor. The proposed structure was designed by combining the phase shift keying technique with the optical beam interference mechanism. The proposed structure works completely in the linear region, and therefore it does not require a high amount of optical power. The delay time for the proposed structure is about 2 ps.

... In addition, use of photonic devices instead of electronic components, has grown steadily in recent years (Gramotnev and Bozhevolnyi 2010). For example, as a telecommunication application, sending and receiving data by optical fibers have been taken much attention by many researchers to utilize and optimize the facilities of optical telecommunication infrastructures (Mansouri-Birjandi et al. 2016;Jin et al. 2010). One of the fundamental steps to use optical devices in various systems is to provide PICs in nanometer dimensions, as the alternative of the electronic integrated circuits. ...

In this paper, a new nanoscale plasmonic differential detector of wave intensities is proposed. This structure can be useful for calibration applications and for finding out if a wave intensity is high enough to pass a threshold level or not. Next, a nanoscale plasmonic uni-directional waveguide is presented. The distinction of this waveguide with similar cases is that the one-way wave-guiding is provided by adding a properly located controlling source, without employing any non-reciprocal material. This feature can be used in many applications that only uni-directional wave propagation is desirable. Both structures have been designed in metal–insulator–metal structure including cavity resonators. The operations are based on the coupling of the wave from input waveguides to the cavity resonators and decoupling to output waveguides in the cavity resonance wavelengths. The simulation results of performance of the structures, as elements applicable to photonic integrated circuits, have been obtained using the numerical method of the finite difference time domain.

... The other popular method used for designing PhC-based logic devices is based on nonlinear resonators. The optical behavior of a nonlinear resonator can be controlled with optical power (Mansouri-Birjandi et al. 2016;Tavousi et al. 2017). For example Sharifi et al. (2016) proposed NOR/XNOR/AND gates using nonlinear directional couplers. ...

Arithmetic logic unit (ALU) is the core of any digital processing systems. For creating an all optical ALU one needs basic logic gates such as optical NOT, OR and AND gates along with an optical full adder and optical multiplexer. In this paper we aim to design and propose these three basic logic gates using nonlinear photonic crystal ring resonators. The simulations will be done using plane wave expansion and finite difference time domain methods. The proposed structures work based on controlling the optical behavior of the nonlinear resonators using optical power. The simulation results show that the switching threshold for this resonant ring is about 15 mW/μm². Reduced delay times and switching optical power are the main advantages of the proposed structures. Also by adding two resonant rings in input ports we reduced the cross reflection between the input ports.

... Recently, many different plasmonic devices such as all optical switches (AOS) Mansouri-Birjandi 2016, 2017;Emadi et al. 2017;Sahu 2016;Liu et al. 2015;Min and Veronis 2009), ring resonators (RRs) Granpayeh 2014, 2015), filters Wei et al. 2017;Mansouri-Birjandi et al. 2016;Dideban et al. 2017;Neutens et al. 2012;Shi et al. 2015;Khani et al. 2018aKhani et al. , 2019, sensors (Kwon 2013;Chen et al. 2016;Xie et al. 2015;Rakhshani et al. 2018;Rakhshani and Mansouri-Birjandi 2016, b, 2018a, demultiplexers (Rakhshani and Mansouri-Birjandi 2016;Wu 2014;Wang et al. 2011;Khani et al. 2018b), splitters (Farahani et al. 2013;Yu et al. 2014), directional couplers (Petráček et al. 2013;Nozhat and Granpayeh 2012;Magno et al. 2013), Mach-Zehnder interferometers Janjan et al. 2017) and logic gates (Goudarzi et al. 2016;Salmanpour et al. 2015;Ooi et al. 2014) have been proposed in the literature. ...

In this paper, compact all-optical XOR and XNOR gates based on different configurations of metal-insulator-metal plasmonic ring resonators (PRRs) have been proposed. Square and octagon-shaped rings have been used in this case. The logic gates have been simulated using the two-dimensional finite-difference time-domain numerical method, with a conventional perfectly matched layer as the absorbing boundary condition of the area under simulation. The phenomenon of Fano resonance is employed by the proposed gates to excite ON/OFF states. As a result, a large value of contrast ratio (C.R.) is obtained. The results show that the values of C.R. of XNOR and XOR gates for square-shaped PRR are 22.66 and 22.9 dB, respectively and the values of C.R. of XNOR and XOR gates for octagon-shaped PRR are 23.01 and 23.52 dB, respectively. Also, it is shown that the octagon shaped gates have higher transmission ratios than other proposed configurations. The proposed optical logic gates can be used as key components in optical communications and for designing compact plasmonic devices.

... In recent years, it has been shown that PhCs have great potentials for realizing wide variety of optical devices such as optical filters (Mansouri-Birjandi et al. 2016;Musavizadeh et al. 2015;Alipour-Banaei et al. 2016c;Dideban et al. 2017;Tavousi et al. 2017), demultiplexers Radhouene et al. 2015Radhouene et al. , 2016aRadhouene et al. , 2017aTavousi 2018), switches Mehdizadeh et al. 2016aMehdizadeh et al. , 2017aOuahab and Naoum 2016;Radhouene et al. 2016b), logic gates (D'souza and Mathew 2016;Talebzaveh et al. 2016;Parandin and Karkhanehchi 2017;haq Shaik and Rangaswamy 2017;Goudarzi et al. 2016;Alipour-Banaei et al. 2016a, b), sensors (Zhang et al. 2016;Guo et al. 2016;Radhouene et al. 2017b;Dorfner et al. 2009;Tavousi et al. 2018;Rakhshani et al. 2018;Turduev et al. 2017), power splitters (Huang et al. 2015;Wang and He 2015), analog to digital converters (Mehdizadeh et al. 2017b, c) … etc. In spite of having different functionalities, all of these devices have a common point that all of them can be designed based on optical resonators. ...

Quality factor and refractive index sensitivity are significant parameters in designing optical devices based on ring resonators such as filters, demultiplexers, switches in which the ring resonator is considered as an elementary componant. In this paper, we propose a photonic crystal ring resonator with super-ellipse shaped core. The proposed ring resonator placed between two parallels waveguides (bus waveguide and drop waveguide). The transmission efficiency of the proposed ring resonator at λ = 1547.3 nm is about 95% with bandwidth and quality factor values equal to 0.7 nm and 2210, respectively. Simulation results show that the resonance sensitivity upon refractive index variation of coupling, outer layer, adjacent and scattering rods are Δλ/Δn = 0.2 nm/0.01, Δλ/Δn = 0.225 nm/0.01, Δλ/Δn = 0.125 nm/0.01 and Δλ/Δn = 0.05 nm/0.01, respectively. The finite different time domain and plane wave expansion methods are used to calculate the outputs spectrum and band gap, respectively.

... Light confinement and control are the two important features in photonic crystals (PCs). 1,2 Subsequently, many scientists have focused their studies on PCs to design and investigate various optical devices, such as optical filters, 3,4 Bragg reflection, 5 demultiplexers (DMUX), [6][7][8][9][10][11][12][13] circulators, 14 power splitters, 15,16 sensors, 17,18 and switches. 19 Photonic integrated circuit has a special charm to optical communication and optical computing. ...

We present the numerical simulation of an all‐optical demultiplexer using 2D photonic crystal ring resonators for optical communications systems. The structure consists of three ring resonators, one bus waveguide, and three drop waveguides. The photonic crystal of the demultiplexer has a square‐shaped structure made up of silicon rods with lattice constant a = 548 nm, filling factor(r/a) of 0.18, where r is the radius of the rods, and linear refractive index of n = 3.4. The structure can filter three standard wavelengths with 4.2 nm channel spacing between the wavelengths. From the simulations, the mean quality factor and transmission efficiency of our structure are computed to be respectively 4936 and 96.5%, at wavelengths very close to 1.55 μm. The minimum and maximum values of crosstalk are −18.6 dB and −34.6 dB, respectively. The footprint of the device is 293.7 μm², which is suitable for photonic integrated circuits. The optical characteristics and the behavior of the proposed demultiplexer have been achieved by means of finite‐difference time‐domain (FDTD) method.

... The main purpose of this choice is because its refractive index matches our need for calibrating the resonance wavelength at λ = 1550 nm. The coupling region's rods radius and mateial are the same as lattice rods radius and material [37,55]. ...

In this effort, a wavelength-division demultiplexer (WDM) is presented. The proposed device is formed by means of horizontal cascading of hetero-structure photonic crystal (PhC) ring resonators (RRs). In order to design this structure, four octagonal-shaped PhCRRs are horizontally connected. Each PhCRR creates a unique channel and has with a variable resonant wavelength. To achieve the required WDM channel spacing, every PhCRR is tuned to a unique resonant wavelength which is premeditated using various design parameters such as ring's dielectric constant, surrounding medium's dielectric constant, lattice dielectric constant, lattice constant in x or/and z direction and etc. Considering the ambient medium as air, rods dielectric constant as n = 3.6, and the PhC lattice with a = 558 nm in square type; the quality factor (Q) and drop efficiency of the base unit are found as 3100 and 100%, respectively, for operating at λ0 = 1550 nm. The simulation results are achieved by means of finite difference time domain (FDTD) method. These results show that the proposed WDM structure has a good performance in terms of average transmitted power higher than 95 ± 4%, reasonable channel spacing, low channel crosstalk (about -24db in worst case), and finally narrow full width half maximum (FWHM) bandwidth. The overall footprint of the proposed structure is calculated to be about ∼140 μm², which makes this device a promising one for on-chip optical applications.

... Integration possibility and scalability make PhCs as interesting structures for designing all-optical devices [4]. In recent years, some PhC-based optical devices such as optical add/drop filters [5][6][7][8], sensors [3,9,10], logic gates and switches [11][12][13][14][15][16][17][18][19][20][21][22][23], demultiplexers [24][25][26], analog to digital converters [27][28][29][30], digital to analog converters [31], encoders [32][33][34][35], adders [36,37] and power splitters [38][39][40] have been proposed. ...

In this paper, an all-optical 2-to-4 decoder based on photonic crystal nonlinear ring resonators is proposed. The designed decoder has one enable port which can control decoding operation. Using nano-crystal ring resonators, the threshold switching intensity is decreased to 13 W/µm2. The maximum frequency and total size of the device are obtained to be 160 GHz and 16×23 µm2 respectively. All output characteristics of the proposed decoder seem to be beneficial for being employed in optical integrated circuits.

... In order to tune the resonance at desired wavelength, the effect of hub rods radius variation was also studied. Since this method was not able to shift the resonance with desired amount, the PhC lattice constant variation scaling policy was used [56,57]. The scaling role implies that a1/λ1 = a2/λ2. ...

Lab-on-a-chip integrated optical biosensors have shown useful in non-invasive detection of biomaterials. Furthermore they are immune to electromagnetic interference rather than their electronic counterparts. In this paper, an all-optical photonic crystal (PhC)-based biosensor is presented. The biosensor is made up of two PhC-based W1 waveguides which are critically coupled to a PhC-based ring-resonator (RR). The hub of the ring is designed in an all-circular quasi-crystal fashion to enhance output efficiency as well as easy injection of analyte. This PhCRR can distinguish 85±15% of amplitude change via resonant wavelength shift of 0.75±0.15 nm, or equally a 0.005 change in the refractive index unit (RIU). By introducing any change in the optical characteristics of desired biomaterials (i.e. refractive index of glycated hemoglobin), the resonance frequency of resonator changes and due to its high quality factor and sensitivity, a large amplitude difference appears in the output. The proposed glycated hemoglobin biosensor works in the wavelength interval of 1.545-1.565 µm, and its quality factor, figure of merit (FOM) and sensitivity are calculated to be 2500±500, 1400±200 RIU-1 and 690±50 nm/RIU, respectively. The simulations are performed in two-dimensional and finite difference time domain (FDTD) algorithm is used to numerically solve time-dependent Maxwell-equations within propagation domain.

A multichannel plasmonic switch consisted of four metal–insulator–metal (MIM) waveguides and an equilateral triangle resonator (ETR) with a silver bar is proposed. Calculated by coupled mode theory (CMT) and standing wave theory, structural transmittance characteristics are numerically studied by finite difference time domain (FDTD) method. And the results show that the transmission spectrum of the ETR with a silver bar, coupled with a MIM waveguide, can be adjusted by increasing the height and width of the bar. As for the switch, varying with structural parameters of the bar, the transmission spectra in three ports can be tuned by rotating the bar into different angles. And this multichannel plasmonic switch owes a high on/off contrast ratio (R=36 dB). The proposed switch has potential application value in the area of telecommunication and all-optical signal procession.

In this paper, analysis of tunable optical filter based on Sagnac effect tuning is presented using a fiber-optic ring resonator (FORR) and the responses of the filters for different FORR and Sagnac loop parameters under steady-state conditions are investigated. Formulation of the optical filter response is presented by considering with/without single and multiple Sagnac loop effects. Effects of the FORR parameters of filter response are studied and analyzed under different parametric conditions for the maximum transmission intensity. The simulation results show that the filter responses are affected strongly by the Sagnac loop and the FORR parameters. With the Sagnac effect, it is shown that full-width at half maximum (FWHM) would increase by increasing the phase difference Δ ϕ from 0 to 0.20 radian, beyond which it will start decreasing. The difference in FWHM value in this range of Δ ϕ variations is found to be about 3.77 nm. Between the first and the second resonances at wavelengths 1395 and 1538 nm, the free spectral range (FSR) is found to be 140 nm. In multiple loops effects, by increasing the number of loop turn N , the values of FSR would reduce. For Δ ϕ = 0.3 and N = 1, 2, 3, the values of FSR are obtained as 144, 74, 47 nm, respectively.

All optical analog to digital converters will play crucial roles in the future generation of all optical data processing. Cascading optical limiters is a suitable method for designing all optical analog to digital converters. In this paper an optical limiter was proposed using two nonlinear photonic crystal ring resonator, then by cascading 4 optical limiters an structure was proposed for realizing a 5-bit all optical converter. With the help of two examples the correct operation of the proposed structure was confirmed. The total foot print of the proposed structure is about 1796 mm2.

Advanced optical materials with rational designs and tunable light transmission have been drawing increasing interest due to their great potential in energy‐efficient buildings and on‐demand optical devices. Mechanoresponsive smart windows (SWs) can modulate light transmittance by mechanical actuation, showing high energy efficiency, low cost, and chemical stability. However, current research mainly focuses on tensile strain‐responsive SWs that typically require a large strain to achieve optical transparency switching‐which causes great inconvenience to practical application and fatigue damage to matrix materials. Herein, a novel shear‐responsive SW with high strain sensitivity is fabricated by vertically fixing a Fe3O4@SiO2 nanochains (NCs) array in an elastic polyacrylamide matrix. The flexible SW exhibits optically transparent with all NCs standing vertically to the SW surface at initial relaxation state, which enables a good shielding effect, with NCs tilting along the shearing direction as the strain applied. Critically, a rather small shear displacement (1.5 mm) applied on the surface of SW gives rise to tunable optical states varying from the transparency state of 65% transmittance to the opaque state of 10%. The as‐prepared SW with novel tuning modulation, high shear strain sensitivity, and optical angle‐dependence holds promising potential in smart windows, optical switches, anti‐voyeurism, and etc. A new mechanoresponsive smart window using shear strain to tune optical transmittance is fabricated by vertically fixing a Fe3O4@SiO2 nanochain array in an elastic polyacrylamide (PAM) matrix. By harnessing the shutter effect of nanochains in the PAM hydrogel, a small shear strain applied on the surface of the hydrogel will give rise to tunable optical states varying from transparency to opaque state.

In this paper, we report a new design of an all-optical full-adder using two nonlinear resonators. The PhC-based full-adder consists of three input ports (A, B, and C for input bits), two nonlinear resonant cavities, several waveguides, and two output ports (for the SUM and CARRY). Eight silicon rods and a nonlinear rod composed of doped glass form each resonant cavity. The well-known plane wave expansion technique is used to calculate the photonic band structure. It shows a wide photonic bandgap in the wavelength range of 1365-2074 nm covering the C and L optical transmission bands. The finite-difference time-domain method is applied to study the light propagation inside the full-adder. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear optical Kerr effect appears and controls the direction of light emitted inside the structure as desired. The maximum time delay and footprint of the proposed full-adder are about 3 ps and 758.5 μm^2 , respectively. Therefore, due to the low time delay and small footprint, the presented design can be used as a basic mathematical operator in the all-optical arithmetic logic unit.

This paper proposes a new all-optical full-adder design based on nonlinear X-shaped photonic crystal (PhC) resonators. The PhC-based full-adder consists of three input ports, two X-shaped PhC resonators (X-PCRs), and two output ports. The dielectric rods made of silicon and nonlinear rods composed of doped glass are used to design the X-PCRs. Two well-known plane wave expansion and finite difference time domain methods are applied to study and analyze the photonic band structure and light propagation inside the PhC, respectively. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear Kerr effect appears and manages the direction of light propagation inside the structure. The maximum time delay and footprint of the proposed full-adder are about 2.5ps and 663 μm 2, making it an appropriate adder for high-speed data processing systems.

All optical logic gates are building blocks for all optical data processors. One way of designing optical logic gates is using threshold switching which can be realized by combining an optical resonator with nonlinear Kerr effect. In this paper we showed that a novel structure consisting of nonlinear photonic crystal ring resonator which can be used for realizing optical NAND/NOR and majority gates. The delay time of the proposed NAND/NOR and majority gates are 2.5 ps and 1.5 ps respectively. Finite difference time domain and plane wave expansion methods were used for simulating the proposed optical logic gates. The total footprint of the proposed structure is about 988 μm ² .

Photonic crystal has equally influenced the light propagation as the atom of crystal has on electrons. The optical filters are one of the remarkable applications of the photonic crystal. In the proposed paper an add/drop filter has been designed using two ring resonators. The shape of the resonators is a curved edge shape. The design layout has been performed using Opti-FDTD and the simulation results show 100% of add efficiency and 90% of drop efficiency. In addition to this MATLAB software has been also used and with further enhancement, a five-channel de-multiplexer has been proposed with a transmitted efficiency of more than 97% and the average quality factor of 781 has been determined.

Smart optical materials are drawing more and more attention due to their wide application in energy conservation, wearable sensors, optical tuning and medical devices. However, current smart optical materials, including electroresponsive, thermoresponsive, and mechanoresponsive materials, are greatly restricted in practical applications due to their long response time, complicated preparation and high cost. This study develops a novel magnetically tunable smart optical material with swift and high-contrast optical switching based on 1D [email protected] nanochains (NCs), which have the large shape anisotropy of one-dimensional structure and the superparamagnetic properties of Fe3O4 particles. The material exhibited clear transparent state when NCs were arranged parallel to the viewing direction under an applied magnetic field, while it showed good shielding effect when the NCs were randomly oriented upon removal of the field. The light transmittance could be dynamically adjusted over the wide range of 20%~80% through a small applied magnetic field of 50~100 Oe, which is superior to most current reported systems. This swift, sensitive and reversible response is attributed to the good responsivity of magnetic nanochains. Also, an effective model was proposed to explain the transmittance modulation scheme and forecast its optical potential. The large tunable range and low triggered field make [email protected] NCs an advantageous candidate for application in smart windows, optical switchers and other fields.

In this paper, a novel hourglass-shaped ring resonator based on square lattice of GaAs in air is proposed for the design of a high sensitive all optical filter. The proposed structure guarantees a transmission efficiency of 100% and a high Q-factor of 2578.5. Moreover, some parameters variation such as refractive index, rods radius and lattice constant are investigated in order to show their effects on the transmission efficiency, the Q-factor, the central wavelength and the bandwidth. The results demonstrate that the proposed structure is very sensitive upon the refractive index variation of the total structure, such that the refractive index sensitivity to the refractive index of total structure is Δλ/Δn = 3.9 nm /0.02.

In this paper an add/drop filter based on a two dimensional (2D) photonic crystal ring resonator (PCRR) is proposed and its performance is studied. This device is comprised of a hexagonal PCRR between two parallel waveguides formed by creating line defects in a 2D lattice structure with an array of 20 × 20 Si (Silicon) rods in air host. The lattice constant a is 636 nm and the radius of silicon (Si) rods r is 0.2a. The size of the add/drop filter is 6 μm × 6 μm. We have achieved nearer to 100% dropping efficiency when the wavelength (λ) of the optical input signal is 1.55 μm. Optical signal can be made to drop at a different port by varying its wavelength or radius of Si rods. Simulation of the device is performed using a licensed RSoft FullWAVE tool based on a finite difference time domain (FDTD) simulator. The proposed structure could be used as an add/drop filter in the wavelength division multiplexing.

A novel photonic crystal channel drop filter (PCCDF) is proposed to drop four coarse wavelength division multiplexing (CWDM) channels at 1490 nm, 1510 nm, 1530 nm and 1550 nm. A special coupled dual-loop design was used for multichannel forward/backward dropping for the first time. Due to the reduced number of the dropping resonators with this design, the proposed multichannel PCCDF has a very compact size (338 μ m²). High transmission efficiencies at the four ITU wavelengths (87.87%, 93.99%, 85.40% and 84.24%) can be obtained simultaneously. Furthermore, the same dimension parameters (lattice constant and rod radius) of the dual-loop resonators are helpful for easy fabrication. The proposed device could be used in future photonic integrated circuit-based CWDM communication systems.

Optical reversible gates are required in realizing all optical digital data processing. In reversible gates, there is a one by one mapping between the input and output ports which helps us to recover the inputs from the outputs. In this paper we aim to design and propose all optical reversible XOR and XNOR gates based on electromagnetic scattering phenomenon in nonlinear photonic crystal structures. For realizing the proposed structures a special resonator was proposed which consists of two cross connected waveguides along with some linear and nonlinear defect rods. The proposed structure will be simulated using finite difference time domain method. The simulation results show that the maximum time delay for the proposed structures is about 10 ps. The truth tables for the both structures prove that there is one by one mapping between the inputs and outputs of the proposed structures.

All-optical comparators play crucial roles in all-optical data processing systems. In this paper, we proposed a novel structure for realizing an all-optical comparator, which can compare two 1-bit binary codes. For this purpose, we used three nonlinear resonant rings. The final structure has two input and three output ports. The maximum rise and fall times for the proposed structure are about 1.5 and 2 ps, respectively.

All optical comparators play crucial roles in all optical data processing systems. In this paper we proposed a novel structure for realizing an all optical comparator, which can compares two 1-bit binary codes. For this purpose we used 4 nonlinear resonant rings. The final structure has two input –namely X and Y_ and three output ports –namely F1, F2 and F3-. The maximum time delay of the proposed structure is about 6 ps. The results show that, when X and Y are the same, only F3 is ON, when X is ON and Y is OFF, only F1 is ON and finally when Y is ON and X is OFF, only F2 is ON.

As a basic type of linear defects, the PhC ring resonators are considered the most fascinating elements to be used in photonics integrated circuits for applications such as dense wavelength division multiplexing and Optical filtering that are among the most important components of the telecommunication systems. This article proposes two different optical channel add-drop filters (CDFs) based on rod-type two-dimensional square-lattice all-circular photonic crystal ring resonator. In the studied ring-type PhC cavity, there are some modes that are analogous to whispering gallery (WG) modes. For the proposed all-circular PhC ring resonator, the WG-like mode with the azimuthal mode number \(m=10\), couples out from cavity to the drop waveguide. Although because of the absence of perfectly circular symmetry, these WG-like modes are not exactly degenerate but they form a close doublet. The normalized frequencies (\(a/\lambda \)) of the doublets of \(m=10\) are \(a/\lambda =0.3684\), and 0.3645 and their \(Q\)-factors are 1050, 866 respectively. By selecting appropriate coupling distance between the PhC ring resonator and side-coupled \(W_{1}\) waveguide, the CDFs are formed. For a TM polarized Gaussian source, the drop efficiency of both filters is more than 99.8 % in the 1.535–1.625 \(\upmu \hbox {m}\) wavelength interval. The photonic bandgap and the WG-like modes of the PhC ring resonator are calculated using the PWE method, and the \(Q\)-factor of modes and the transmission spectra of CDFs are calculated using 2D-FDTD method.

Materials that can bend light in the opposite direction to normal ('left-handed' materials) reverse the way in which refraction usually works - this negative refractive index is due to simultaneously negative permeability and permittivity. Here we demonstrate negative refraction of electromagnetic waves in a two-dimensional dielectric photonic crystal that has a periodically modulated positive permittivity and a permeability of unity. This experimental verification of negative refraction is a step towards the realization of a 'superlens' that will be able to focus features smaller than the wavelength of light.

We have used femtosecond pump-probe spectroscopy to study the ultrafast nonlinear response of AlGaAs two-dimensional photonic crystal waveguides in the near-infrared spectral region. The modulation of the reflectivity spectra due to the refractive index change produced by photogenerated carriers was measured. We observed an instantaneous pump-induced shift in the wavelength of a photonic resonance at 882 nm with a fast decay time of approximate to8 ps. The magnitude of the reflectivity change was very large at wavelengths close to the photonic resonance, with a maximum value of DeltaR/R>30% at 877 nm. These results confirm the excellent potential of photonic crystal waveguides in ultrafast nonlinear switching applications. (C) 2003 American Institute of Physics.

Three-dimensional photonic crystal structures were fabricated with laser microfabrication techniques through two-photon-absorption photopolymerization of resin. Significant band-gap effects in the infrared wavelength region were observed from “layer-by-layer” structures. © 1999 American Institute of Physics.

Values up to gamma=7 x 10(6)/(W km) for the nonlinear parameter are feasible if silicon-on-insulator based strip and slot waveguides are properly designed. This is more than three orders of magnitude larger than for state-of-the-art highly nonlinear fibers, and it enables ultrafast all-optical signal processing with nonresonant compact devices. At lambda=1.55 microm we provide universal design curves for strip and slot waveguides which are covered with different linear and nonlinear materials, and we calculate the resulting maximum gamma.

We explore a new passive optical limiter design using transverse modulation instability in the one-dimensional photonic crystal (PC) using x(3) materials. The performance of PC optical limiters strongly depends on the choice of the materials and the geometry and it improves as the duration of the incident pulse is extended. PC optical limiter performance is compared with that of a device made from homogeneous material. We identify three criteria for benchmarking the PC optical limiter. We also include a discussion of the advantages and disadvantages of PC optical limiters for real world applications.

We present an electro-optical switch implemented in coupled photonic crystal waveguides. The switch is proposed and analyzed using both the FDTD and PWM methods. The device is designed in a square lattice of silicon posts in air as well as in a hexagonal lattice of air holes in a silicon slab. The switching mechanism is a change in the conductance in the coupling region between the waveguides and hence modulating the coupling coefficient and eventually switching is achieved. Conductance is induced electrically by carrier injection or is induced optically by electron-hole pair generation. Low insertion loss and optical crosstalk in both the cross and bar switching states are predicted.

Using an array of m x n nonlinear ring resonators (m = 1, 3, 5, and n = 1, 2, 3) coupled to the upper arm of a Mach-Zehnder interferometer (MZI), we have proposed an all-optical switch structure. Using a 5 x 3 array, we have shown the possibility of designing an all-optical switching device with a threshold intensity as low as 15 mW/m(2) and switching window of approximately 35 ps. While using m x 1 arrays, we have achieved switching windows smaller than 10 ps, at the expense of higher switching thresholds, ranging from 37 to 55 mW/m(2). The whole structure is based on a square lattice photonic crystal of lattice constant a = 600 nm, formed by rods of radius r = 90 nm in an air background. The linear rods' refractive index is taken to be the same as that of Si(0.75)Ge(0.25); i.e., n(r) = 3.6, whereas the nonlinear rod's refractive index and Kerr index parameter are taken to be n(0) = 1.4 and n(2) = 10(-14) m(2)/W. The center wavelength at which the nonlinear rings are designed to make the resonance is taken to be lambda(0) = 1550 nm in free space.

The objective of the paper is the assessment of the accuracy of a
conventional FDTD code in the computation of the near and far-field scattering
characteristics of a circular dielectric cylinder. We excite the cylinder with
an electric or magnetic line current and demonstrate the failure of the
two-dimensional FDTD algorithm to characterize accurately the emission rate and
the field patterns near high-Q whispering-gallery-mode resonances. This is
proven by comparison with the exact series solutions. The computational errors
in the emission rate are then studied at the resonances still detectable with
FDTD, i.e. having Q-factors up to 10^3.

"Photonic Crystals" details recent progress in the study of photonic crystals, ranging from fundamental aspects to up-to-date applications, in one unified treatment. It covers most of the worldwide frontier fields in photonic crystals, including up-to-date fabrication techniques, recent and future technological applications, and our basic understanding of the various optical properties of photonic crystals. Brand-new theoretical and experimental data are also presented. The book is intended for graduate course students and specialists actively working in this field, but it will also be useful for newcomers, especially the extensive chapter dealing with fundamental aspects of photonic crystals, which paves the way to a full appreciation of the other topics addressed.

at lower frequency regime, altering the surface structure modifies the characteristics of propagating effective surface plasmons (ESPs), particularly their interaction with light. Movement of an electron beam in the proximity of the surface of a structured metallic grating excite these ESPs, which due to existence of a velocity phase match, they are able to emit terahertz (THz) waves known as Smith-Purcell (SP) radiation. By introducing a femtosecond perturbation (a single electron bunch), the important characteristics of a desired grating is revealed. Through our 3-D investigations, we find the incoherent THz radiation frequency span, and moreover we confirm that the frequency of the ESP is always less than the minimum SP frequency. Additionally, we find that the maximum of signal amplitude is distributed around 90°, only if the grating width is comparable to the longest SP wavelength. Also we learned that by increasing the grating length, the magnitude and spectral resolution of the radiation increases too. In order to study the coherent (superradiant) radiation, we use a train of electron bunches with variable bunch-to-bunch distances, and we calculate the radiation angle of the coherent SP signal. Simulations on the generation of SP radiation at THz frequencies are performed with the help of the 3D particle-in-cell (PIC) finite integral method, in which the results agree very well with previously reported 2D simulations.

We present a photonic crystal all-optical bistable switch configuration consisting of crossing perpendicular waveguides geometry with instantaneous Kerr nonlinearity. A microcavity is added to the signal waveguide which is coupled with the defect at the waveguide intersection to increase the transmission contrast. We demonstrate with the finite-difference time-domain method that such a configuration can function as a low crosstalk and high contrast all-optical switch.

This paper proposes novel photonic devices and circuits composed of circular and fan-shaped microdisks. Using the finite difference time domain (FDTD) method, we investigated propagation characteristics of light in fundamental elements, the coupler of closely placed disks and the butt-joint of disks. The coupler can be used for extracting the light from a disk laser. It was shown that the efficiency of the light extraction can be over 70% by the coupler. A mode size converter and a tunable filter combined with couplers were numerically demonstrated. The joint can be applied to a compact and sophisticate optical wiring in a large scale circuit, since the joint loss estimated was as low as 0.1 dB. [IEEE ]

A new design for concurrent implementation of all-optical half-adder and AND & XOR logic gates based on nonlinear photonic crystal ring resonator has been proposed. The finite different time domain and plane wave expansion methods are used to analyze the behavior of the structure. The ring resonator has a low switching time of about 0.85 ps and low switching power equal to
$277\,\text{ mW}/\upmu \text{m}^{2}$
277
mW
/
μ
m
2
. The simulation results show that the contrast ratio is 12.78 dB for AND gate and 5.67 dB for XOR gate. Moreover, the operational wavelength of the input ports is
$1.55\,\upmu \text{m}$
1
.
55
μ
m
. Since the structure has a simple geometric shape with clear operating principle, it is potentially applicable for photonic integrated circuits.

We demonstrate the construction of reasonably long and non-polarization changing photonic fiber waveguide using Teflon which is a readily available and highly flexible material. Due to its relatively low loss coefficient, the possibility of preparing longer photonic fiber waveguide, which has the potential of guiding intense THz radiation, can be easily attained.

We report fabrication of ultra-fast optical switches operated at a wavelength of 1064nm using spin-coated one-dimensional polymeric photonic crystals doped with nonlinear-optical dyes. The optical switches are controlled either by an applied electric-field voltage or by a pump light by use of two different optical-configurations. The response time of the electro-optic switch and the all-optical switch are limited by the applied voltage and the laser used, respectively. The polymeric photonic crystals can be easily fabricated with low cost.

The real and imaginary parts of third-order nonlinear susceptibility χ(3) have been measured for silicon nanocrystals embedded in SiO2 matrix, formed by high temperature annealing of SiOx films prepared by plasma-enhanced chemical vapor deposition. Measurements have been performed using a femtosecond Ti–sapphire laser at 813 nm using the Z-scan technique with maximum peak intensities up to 2×1010 W/cm2. The real part of χ(3) shows positive nonlinearity for all samples. Intensity-dependent nonlinear absorption is observed and attributed to two-photon absorption processes. The absolute value of χ(3) is on the order of 10−9 esu and shows a systematic increase as the silicon nanocrystalline size decreases. This is due to quantum confinement effects. © 2002 American Institute of Physics.

Guided-wave single-mode propagation of subpicosecond terahertz (THz) pulses in a plastic photonic crystal fiber has been experimentally demonstrated. The plastic photonic crystal fiber is fabricated from high-density polyethylene tubes and filaments. The fabricated fiber exhibits the low loss and relatively low dispersive propagation of THz pulses within the experimental bandwidth of 0.1–3 THz. © 2002 American Institute of Physics.

We report experimental demonstration of very fast nonlinear response around 1.5 mum in an InP-based two-dimensional photonic crystal. The nonlinearity produced by low pump powers via carrier induced nonlinear refractive index, leads to an efficient wavelength shift of a photonic crystal resonance observed in reflectivity. Thus we show that it is possible to obtain round the clock (rise and recovery) switching times shorter than 10 ps with contrast ratio higher than 80%. (C) 2004 American Institute of Physics.

The ability to rapidly tune the properties of a photonic crystal nanocavity and 'program' it to store light for more than a nanosecond brings optical memory a step closer.

We have proposed an ultracompact all-optical photonic crystal AND gate based on nonlinear ring resonators, consisting of two Kerr nonlinear photonic crystal ring resonators inserted between three parallel line defects. We have employed a Si nanocrystal as the nonlinear material for its appropriate nonlinear properties. The gate has been simulated and analyzed by finite difference time domain and plane wave expansion methods. The proposed logic gate can operate with a bit rate of about
120
Gbits
∕
s
.

We numerically analyze ultra-refraction and slow-light in lithium niobate photonic crystals in order to investigate and then optimize the efficiency of a tunable photonic crystal superprism. In contrast to a passive superprism 1-to-N demultiplexer, we describe a tunable bandpass filter with only three output ports. The electro-optic effect in lithium niobate is used to achieve tunability, with the filter bandwidth shifting in wavelength as the refractive index of the superprism is modified by an externally applied electric field. Such a device could be used to realize a compact and fast wavelength multiplexer/demultiplexer for telecommunications or optical interconnect applications. We calculate constant frequency dispersion contours (plane-wave expansion) to identify initial configurations that show significant ultra-refraction, and verify the expected behavior of light propagation inside the structure using 2D FDTD (finite difference time domain) simulations. We show that the voltage requirements of such an electro-optically tunable superprism could potentially be relaxed by exploiting the enhancement of the electro-optic effect recently discovered by our group [M. Roussey, M.-P. Bernal, N. Courjal, D. Van Labeke, F.I. Baida, Electro-optic effect exaltation on lithium niobate photonic crystals due to slow photons. Appl. Phys. Lett. 89 (24) (2006) 241110], which we believe to be due to the presence of slow-light in the nanostructure. We present a methodology that readily identifies superprism design points showing both strong ultra-refraction as well as low group velocity. However, we find that this improved voltage efficiency comes at the cost of reduced operating bandwidth and increased insertion losses due to proximity to the band-edge.

A new structure for a 4-bit full optical analog to digital converter (A/D) using Kerr-like nonlinear two-port ring resonator will be presented. By controlling the system parameters such as the coupling, the loss coefficients and the ring length, we propose a suitable optical A/D circuit which operates similar to successive approximation method. Our proposed idea can be easily realized by integrated optical circuit techniques (OIC).

We have fabricated and built three-dimensional photonic band-gap crystals with band-gap frequencies larger than 500 GHz. We built the crystals by stacking micromachined (110) silicon wafers. The transmission and dispersion characteristics of the structures were measured by an all-electronic terahertz spectroscopy setup. The experimental results were in good agreement with theoretical calculations. To our knowledge, our new crystal has the highest reported photonic band-gap frequency.

We present here an optical add-drop filter (ADF) design based on ultra-compact photonic crystal ring resonators (PCRRs). The normalized transmission spectra for single-ring and dual-ring configurations have been investigated by using the two-dimensional finite-difference time-domain (FDTD) technique in a square lattice dielectric-rod photonic-crystal structure. With the introduction of four scatterers at the corners of quasisquare- ring PCRR, high wavelength selectivity and close to 100% drop efficiency can be obtained. Both backward- and forward-dropping were achieved by controlling the coupling efficiency between two PCRR rings for resonant modes with different symmetry. The resonant-mode quality factor Q and the wavelength tunability were also analyzed, opening opportunities for PCRRs as ultra-compact filters, optical add-drop multiplexers, electrooptical N x N switches and electrooptical modulators.

A novel all-optical switching structure based on a photonic crystal directional coupler is proposed and analyzed. Efficient optical switching is achieved by modifying the refractive index of the coupling region between the coupled waveguides by means of an optical control signal that is confined in the central region. Small length (around 1.1 mm) and low optical power consumption (over 1.5 W) are the main features estimated for this switching structure.

The quest for all-optical signal processing is generally deemed to be impractical because optical nonlinearities are usually weak. The emerging field of nonlinear photonic crystals seems destined to change this view dramatically. Theoretical considerations show that all-optical devices using photonic crystal designs promise to be smaller than the wavelength of light, and to operate with bandwidths that are very difficult to achieve electronically. When created in commonly used materials, these devices could operate at powers of only a few milliwatts. Moreover, if these designs are combined with materials and systems that support electromagnetically induced transparency, operation at single-photon power levels could be feasible.

We review photonic applications of dielectric whispering-gallery mode (WGM) resonators-tracing the growth of the technology from experiments with levitating droplets of aerosols to ultrahigh-Q solid state crystalline and integrated on-chip microresonators.

An integrated micron-size all-optical Si switch capable of 94.7 GHz operation frequency is presented. The device consists of a microring resonator formed by Si/SiO<sub>2</sub> slot-waveguides with a low-index nonlinear optical material in the slot region. Strong optical confinement in the slot permits an achievement of low switching power of 6.2 mW.

160 Gbit/s full time-division demultiplexing using a semiconductor
optical amplifier hybrid integrated demultiplexer on a planar lightwave
circuit is demonstrated. Error-free, demultiplexing from a 160 Gbit/s
signal to eight-channel, 20 Gbit/s signals is successfully demonstrated

The authors present a novel all-optical time-division
demultiplexer capable of simultaneously outputting multiple channels at
speeds of >100 Gbit/s. Its operation is based on time-wise local
chirp compensation of a down-chirped clock pulse through cross-phase
modulation (XPM) induced by a signal pulse stream. Error-free,
simultaneous six-channel-output, 100 to 6.3 Gbit/s demultiplexing is
successfully demonstrated

This paper proposes novel photonic devices and circuits composed of circular and fan-shaped microdisks. Using the finite difference time domain (FDTD) method, we investigated propagation characteristics of light in fundamental elements, the coupler of closely placed disks and the butt-joint of disks. The coupler can be used for extracting the light from a disk laser. It was shown that the efficiency of the light extraction can be over 70% by the coupler. A mode size converter and a tunable filter combined with couplers were numerically demonstrated. The joint can be applied to a compact and sophisticate optical wiring in a large scale circuit, since the joint loss estimated was as low as 0.1 dB

Photonics Optical Electronics in Modern Communications (The Oxford Series in Electrical and Computer Engineering)

- A Yariv
- P Yeh

A. Yariv, P. Yeh, Photonics Optical Electronics in Modern Communications (The Oxford Series in Electrical and Computer
Engineering), Oxford University Press, Inc., New York, NY, USA,
2006.

- A Taflove
- S C Hagness

A. Taflove, S.C. Hagness, Computational Electrodynamics, vol.
160, Artech House, Boston, 2000.

- K Sakoda

K. Sakoda, Optical Properties of Photonic Crystals, vol. 80,
Springer, 2005.