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ABSTRACT: The structural dependence of factors which mainly affect a bending loss property is theoretically investigated in all-solid photonic bandgap fibers. A design principle for realizing a low bending loss is successfully figured out.
Lasers and Electro-Optics (CLEO) and Quantum Electronics and Laser Science Conference (QELS), 2010 Conference on; 06/2010
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ABSTRACT: We propose a novel concept of cladding structure in all-solid photonic bandgap fibers. It promises low bending and confinement losses with single-mode operation. The mechanism is based on the new concept of heterostructured cladding.
Optical Communication, 2009. ECOC '09. 35th European Conference on; 10/2009
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ABSTRACT: In this paper, we investigate the ultimate low loss property for several realistic core shapes in triangular-type air-guiding photonic bandgap fibers (PBGFs) through a full-vector modal solver based on the finite element method. We show that the surface mode free condition is expressed as a normalized silica-ring thickness T = 0.5 for any core size and the cladding structural parameters, regardless the core radius of the silica-ring is one of the main factors of dominating the surface mode's condition, and the wavelength range of the PBG changes on varying the structural parameters of the cladding. Moreover, we propose a novel type of PBGF without surface mode, which exhibits lower scattering losses caused by surface roughness of the silica-ring in comparison to 19 cell-core PBGFs and suppresses the mode coupling between fundamental-like and higher order modes when compared to 37 cell-core PBGFs.
Journal of Lightwave Technology 07/2008; 26(12):1602-1612. · 2.78 Impact Factor
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ABSTRACT: Numerical design strategies are presented to achieve efficient broad or narrow band-pass filters based on index-guiding, solid-core, and single-mode photonic crystal fibers (PCFs). The filtering characteristics have been verified through BPM solver. By scaling the pitch constant, the bandpass window can be shifted accordingly. The fiber design constitutes a fluorine-doped central core, enlarged air-holes surrounding the down-doped core, and small air-holes in the cladding. The proposed bandpass filter is based on controlling the leakage losses, so one can tune filter characteristics simply by changing its length. From numerical simulations we show that for large values of air-hole diameter in the first ring, the bandpass window is narrow, while for low doping concentration and small sized air-holes in the first ring, bandpass window is very broad. We also simulate how the hole-size and number of rings in the PCF cladding affects the device characteristics. We find that a 5-cm long PCF with down-doped core and eleven rings of air-holes can result in approximately 440 nm 3-dB bandwidth with more than 90% of transmission. The longer device has reduced transmission and smaller 3-dB bandwidth. Tolerance analysis has also been performed to check the impact of fiber tolerances on the performance of the PCF bandpass filter. It has been observed that the decrement in cladding hole-diameter by 1% reduces the transmission to 21% from its peak value of 93%, however +/-1% tolerance in the inner hole-diameter degrades the transmission to 75% from its peak.
Optics Express 07/2008; 16(13):9459-67. · 3.59 Impact Factor
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ABSTRACT: We theoretically address the thermo-optical response of multicore photonic crystal fiber (PCF) couplers infiltrated with nematic liquid crystals (LCs). The proposed PCF coupler consists of two identical cores separated by a third one which acts as a liquid crystal resonator. With an appropriate choice of the design parameters associated with the liquid crystal core, phase matching at a single wavelength can be achieved, thus enabling thermo-tunable narrow-band resonant directional coupling between the input and the output cores. The verification of the proposed coupler design is ensured through an accurate PCF analysis based on finite element and beam propagation methods. The enhanced thermo-optical properties of LC-based PCF couplers are highly attractive for photo-thermal sensing applications.
Journal of Lightwave Technology 04/2008; 26(6):663-669. · 2.78 Impact Factor
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ABSTRACT: We propose a novel design method for low-loss one-dimensional planar-photonic crystal coupled-cavity waveguide (CCW). The calculated intrinsic losses in the proposed CCW are 2 orders of magnitude lower than those in previously reported CCW structure.
Optical Fiber communication/National Fiber Optic Engineers Conference, 2008. OFC/NFOEC 2008. Conference on; 03/2008
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ABSTRACT: The birefringence and polarization-mode dispersion characteristics of dispersion-compensating hole-assisted fibers are analyzed numerically. It is revealed that distortion in air-holes leads to high birefringence and also shifts the dispersion by plusmn2% to its optimum value.
Optical Fiber communication/National Fiber Optic Engineers Conference, 2008. OFC/NFOEC 2008. Conference on; 03/2008
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ABSTRACT: We propose a design method for single-polarization photonic crystal fibers with improved beam quality by introducing the resonant coupling between the central core and the elliptical cores arranged on either side of the central core.
Winter Topical Meeting Series, 2008 IEEE/LEOS; 02/2008
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ABSTRACT: We have numerically investigated the Raman lasing characteristics of a highly nonlinear photonic crystal fiber (HNPCF). HNPCF Raman lasers are designed to deliver outputs at 1.3 microm and 1.48 microm wavelengths through three and six cascades of Raman Stokes cavities when the pumps of 1117 nm and 1064 nm are injected into HNPCF module, respectively. A quantum efficiency of approximately 47% was achieved in a short length of HNPCF for 1.3 microm lasing wavelength. The HNPCF design is modified further to operate in single-mode fashion keeping intact its Raman lasing characteristics. The modified HNPCF design consists of two air-hole rings where the higher-order modes in the central core are suppressed by enhancing their leakage losses drastically, thus ceasing their propagation in the short length of HNPCF. On the other hand, the fundamental mode is well confined to the central core region, unaffecting its lasing performances. Further, the lasing characteristics of HNPCF at 1480 nm are compared with conventional highly nonlinear fiber Raman laser operating at 1480 nm. It is found that one can reduce the fiber length by five times in case of HNPCF with nearly similar conversion efficiency.
Optics Express 02/2008; 16(2):549-59. · 3.59 Impact Factor
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ABSTRACT: The bend-insensitive lasing characteristics of a newly designed ytterbium-doped photonic crystal fiber (YPCF) are evaluated numerically. The designed YPCF remains single-mode and possesses large-mode-area of 1400 microm(2) at 1064 nm wavelength with the beam quality factor (M(2)) of 1.15, suggesting a diffraction-limited and continuous-wave lasing operation. The doped-region size is optimized for maximum conversion efficiency and it is found through numerical simulations that the doped radius should be more than 21 microm. The "mode expansion", which is the self-expansion of the fundamental mode within the doped region with wavelength increments on bending the fiber, is the basic physical mechanism to give the bend-insensitive lasing performances of YPCF. It leads to an unusual variation of overlap factor when the wavelength is increased. A 41 cm long piece of YPCF demonstrates more than 83% of slope efficiency with 75% of conversion efficiency when pumped with a 975 nm laser source delivering an input power of 1 W.
Optics Express 02/2008; 16(2):579-91. · 3.59 Impact Factor
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ABSTRACT: This paper theoretically describes effective suppression of higher order modes (HOMs) in realistic large-hollow-core photonic band-gap fibers (PBGFs) and utilizes the use of this class of waveguides for low-loss data-transmission applications and high-power beam delivery systems. The proposed design strategy is based on the resonant-coupling mechanism of central air-core modes with defected outer core modes. By incorporating six 7-unit-cell air cores in the cladding of the PBGF with sixfold symmetry, it is possible by resonantly coupling the light corresponding to the HOMs in a central 19-unit-cell core into the outer 7-unit-cell core, thus significantly increasing the leakage losses of the HOMs in comparison to those of fundamental mode. We consider a realistic PBGF structure with hexagonal airholes having rounded corners and derive a surface-mode-free condition of a silica-ring thickness surrounding the hollow core for both 7-unit-cell and 19-unit-cell cores. Verification regarding the propagation properties of the proposed design is ensured with a PBGF analysis based on a finite element modal solver. Numerical results show that the leakage losses of the HOMs can be enhanced in a level of at least three orders of magnitude over 200-nm wavelength range in comparison to those of the fundamental mode, while in addition, we show that the incorporation of a realistic air core with optimized silica-ring thickness can eliminate surface modes and achieve strong confinement into the central core and very low eta-factor for the fundamental mode.
Journal of Lightwave Technology 10/2007; · 2.78 Impact Factor
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ABSTRACT: We theoretically investigate the intense tunable nanofocusing of light in certain families of metallo-dielectric nanograin particles and topologically defected nanocylinders, mediated by thermoplasmonic resonances. By using versatile numerical algorithms, based on either exact 3-D electromagnetic scattering from canonical geometries, or discrete dipole approximation modeling for particles with arbitrary shapes, associated with the spectral as well as the thermooptical response of the proposed classes of plasmonic nanostructures, we identify the mechanisms responsible for the enhanced tunable thermoplasmonic resonances, by varying the ambient temperature. In addition it is found that the plasmonic resonances are also sensitive to the electric properties of the host medium, thus enabling this novel class of plasmonic nanoparticles to be used as fluidic (liquid/gas) sensors. Our investigation is expected to remove an essential obstacle in the development of nanosensing platforms with high sensitiveness to temperature fluctuations and ultracompact size, thus making the proposed plasmonic resonators excellent candidates for future nanoplasmonic sensing systems.
IEEE Transactions on Nanotechnology 10/2007; · 2.29 Impact Factor
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ABSTRACT: We theoretically investigate the intense nano-focusing of light through a novel family of metallo-dielectric nano-particles mediated by thermo-plasmonic resonances. The results show a significant sensitivity of the plasmonic resonance to temperature and environmental fluctuations.
Lasers and Electro-Optics, 2007. CLEO 2007. Conference on; 06/2007
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ABSTRACT: The Raman gain efficiency and chromatic-dispersion of a hole-assisted fiber with and without minimum allowable bending radius are measured. Numerical predictions from the theory are shown to be in good agreement with the experimental results.
Lasers and Electro-Optics, 2007. CLEO 2007. Conference on; 06/2007
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ABSTRACT: For original paper see N. J. Florous et al., ibid., vol.18, no.15, p.1663 (2006) and for comment see M. Antkowiak and R. Kotynski, ibid., vol.19, no.10, p.795 (2007). Florous et al. presented calculations of thermal sensitivity of photonic crystal fibers (PCFs) with elliptical holes. In their Comment Antkowiak and Kotynski compared these results with those obtained by them previously. They also included improved calculations of the thermooptics effect contribution to the polarimetric sensitivity of PCF and, on this basis, presented a critical analysis of the calculations given in both papers. Florous et al. reply to the comments regarding the thermooptical sensitivity calculations in birefringent photonic crystal fibers (PCFs). They address the major scientific differences in the propagation characteristics of the proposed PCFs between their original letter and the comments
IEEE Photonics Technology Letters 06/2007; · 2.19 Impact Factor
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ABSTRACT: We describe the operation of an inline temperature sensor based on the inclusion of metallic nanoparticles into a photonic crystal fiber. A robust sensing platform for spectroscopy and optical switching applications can be designed.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: The condition for single-mode operation in photonic band-gap fibers (PBGFs) is investigated. If the silica-ring satisfies an anti-resonant condition, the PBGF with a realistic core exhibits a single-mode operation over a wide wavelength range.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: The introduction of coupled-resonator optical waveguides to ring resonators in the IIR filter configuration enables a miniaturized interleaver with wide flat-top passbands. A wavelength-insensitive photonic crystal directional coupler with two decoupling points is also presented.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: By using an accurate numerical method we show that both the higher-order peaks and main peak of the SBS in hole-assisted-fibers can be enhanced by more than 3-dB, by appropriate selection of the design parameters.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: We have experimentally measured the Raman gain efficiency (RGE) and chromatic dispersion (CD) of a hole-assisted fiber (HAF). The RGE of a HAF was characterized using standard pump on/off technique while the CD of the fiber was measured using optical network analyzer. Theoretical simulations of the modal characteristics and the RGE of HAF were carried out using an accurate full-vectorial finite element method. Further, the bending effects on the CD and the RGE of a HAF with a smallest feasible bending radius are demonstrated. It was found that the CD increases while the RGE is decreased by bending HAF in a smallest bending radius of 5 mm. Numerical predictions from the theory are shown to be in good agreement with the experimental results.
Optics Express 04/2007; 15(6):2974-80. · 3.59 Impact Factor
