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ABSTRACT: This paper demonstrates the optical nonlinearity in opto-mechanical ring resonators that consist of a bus waveguide and two ring resonators, which is induced by the optical gradient force and characterized by the Kerr-like coefficient. Each ring resonator has a free-hanging arc that is perpendicularly deformable by an optical gradient force and subsequently this deformation changes the effective refractive index (ERI) of the ring resonator. The change of the ERI induces optical nonlinearity into the system, which is described by an equivalent Kerr coefficient (Kerr-like coefficient). Based on the experimental results, the Kerr-like coefficient of the ring resonator system falls in the range from 7.64 × 10<sup>-12</sup> to 2.01 × 10<sup>-10</sup> m<sup>2</sup>W<sup>-1</sup>, which is at least 6-order higher than the silicon's Kerr coefficient. The dramatically improved optical nonlinearity in the opto-mechanical ring resonators promises potential applications in low power optical signal processing, modulation and bio-sensing.
Optics Express 07/2012; 20(16):18005-15. · 3.59 Impact Factor
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ABSTRACT: A pressure sensor with a 200 µm diaphragm using silicon nanowires (SiNWs) as a piezoresistive sensing element is developed and optimized. The SiNWs are embedded in a multilayered diaphragm structure comprising silicon nitride (SiNx) and silicon oxide (SiO2). Optimizations were performed on both SiNWs and the diaphragm structure. The diaphragm with a 1.2 µm SiNx layer is considered to be an optimized design in terms of small initial central deflection (0.1 µm), relatively high sensitivity (0.6% psi−1) and good linearity within our measurement range.
Journal of Micromechanics and Microengineering 04/2012; 22(5):055012. · 2.11 Impact Factor
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ABSTRACT: This paper reports a nano-opto-mechanical pressure sensor based on nano-scaled ring resonator. The pressure is measured through the output spectrum shift which is induced via mechanical deformation of the ring resonator. The sensitivity as high as 1.47 pm/kPa has been experimentally achieved which agrees with numerical prediction. Due to the strong variation of sensitivity with different ring radius and thickness of the diaphragm, the pressure sensor can be used to form an array structure to detect the pressure distribution in highly accurate measurement with low-cost advantages. The nano-opto-mechanical pressure sensor has potential applications such as shear stress displacement detection, pressure wave detector and pressure mapping etc.
Optics Express 04/2012; 20(8):8535-42. · 3.59 Impact Factor
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Terahertz Science and Technology. 12/2011; 4(4):208-229.
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ABSTRACT: A slow-wave structure (SWS) consisting of a planar helix with straight-edge connections and incorporating a coplanar waveguide feed has been designed for operation at W-band and has been fabricated using microfabrication technique. On-wafer cold measurements have been carried out on a number of fabricated SWSs, and the results are reported here for the first time. The parameters measured are return loss, attenuation, and phase velocity, and the results cover a frequency range of 70-100 GHz. Cold-test parameters of the SWS have been also obtained using simulations, and the effects of fabrication, such as surface roughness, have been accounted for by estimating effective conductivity of different parts of the microfabricated structures. The measured and simulated results match well. The effects of silicon wafer resistivity have been also discussed. Planar helical SWSs fabricated in this manner have application in traveling-wave tubes operating at millimeter wave and higher frequencies.
IEEE Transactions on Electron Devices 12/2011; · 2.32 Impact Factor
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ABSTRACT: Presented is a resistive, vertically oriented, silicon electromechanical cantilever switch, fabricated with a two-mask top-down CMOS-compatible process. The fabricated switch has a vertical height of approximately 500 nm, a tip width of 35 nm, and an airgap of 30 nm between the cantilever and two lateral gates. Preliminary testing results show an initial pull-in voltage of 17 V with contact held by van der Waals forces even in the absence of actuation voltage. Subsequent switching occurs at 25 V. With low-cost fabrication and high integration density, the vertical nanoelectromechanical (NEM) switch is a promising candidate for memory and computing applications.
Electronics Letters 07/2011; · 0.96 Impact Factor
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ABSTRACT: This paper presents a pressure sensor array based on optical force using Nano-opto-mechanical Systems (NOMS). It consists of a deformable diaphragm and a waveguide array. When pressure is applied on the diaphragm, the gap between the diaphragm and the waveguide is reduced. The induced optical force deforms the waveguide and change the optical loss. In the experiment, it measures up to 32 dB optical output modulation when the pressure is changed from 0 kPa to 250 kPa. The proposed waveguide pressure sensor array has advantages such as high sensitivity (0.128 dB/kPa) and feasibility of mapping the pressure distributions, which result in potential applications such as microphone acoustics sensors and bio-medical sensors.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: In this paper, the microfluidic switchable absorptive metamaterials (MMs) filter in the gigahertz region is designed. It consists of a microfluidic network between the electrical resonator and the metal plate. The absorption frequency of the tunable MMs absorber can be tuned by pumping different liquids into the microchannel using the microfluidic technology. Based on the designed absorptive MMs, the absorptive peak can be shifted by introducing a microfluidic layer with frequency tunability up to 20% and absorption change up to 90%. By introducing the tunability in absorption frequency of MMs, it has great potential in the applications of filter and sensor / detector for biomedical applications.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: In this paper, a Nano-opto-mechanical (NOM) switch is designed, simulated and experimentally demonstrated, using the electromagnetically induced transparency (EIT)-like effects of coupled-ring resonator. The control of the switch is realized by optical force between the silicon waveguide and the dielectric substrate. As the injection pump power increases from 0 to 6 mW, the normalized power of transmission peak at 1553.3 nm decreases from 1 to 0.02, and the position of the initial transmission peak has a 7.8-GHz red shift. The proposed NOM switch can be potentially applied in all-optical network.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: This work presents an opto-mechanical linear actuator utilizing the gradient optical force between two identical parallel waveguides. The actuator size shrinks to nanoscale dimensions. Theoretical study shows that the actuator deflection is controlled over optical signals and linearly proportional to the applied optical power. Such optical actuator takes full advantages of the nanotechnology, and has many advantages over their electrostatic comb-drive counterparts, most importantly immunity to electromagnetic interference and mechanical shock, and avoiding the problem of side instability.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: This paper presents a Nano-opto-mechanical actuator, which is driven by optical radiation force. The actuator consists of two waveguides, two identical ring resonators, and an actuator with Bragg reflector. Light is injected into the waveguides and coupled to the Bragg reflector via the ring resonator. The actuator is displaced by the optical force. The achieved maximum displacement of the actuator is 500.2 nm with the optical power up to 200 mW. The optical actuator has merits of high resolution (2.501 nm/mW), approximately perfect linear displacement and contact-free optical drive, which results in potential applications such as precise distance control, tunable laser, and weak force detection.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: A tunable laser based on double-ring external resonant cavity is designed, fabricated and tested. The double-ring resonator external cavity consists of a silicon waveguide ring resonator, a p-i-n doped silicon ring resonator, and a superluminescent diode (SLED). The laser is fabricated on a SOI wafer and the wavelength is tuned by injecting electrical currents to p-i-n structures. In the experiment, it measures 45.8 nm wavelength tuning with 110 GHz channel spacing and the average output power is approximately -8 dBm. It advances in high tuning speed, large side mode suppression ratio, and low manufacture cost, such has potential applications in high speed WDM networks.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: A Nano-opto-mechanical pressure sensor using optical force is reported in this paper. The pressure sensor consists of a square diaphragm, a ring resonator and four waveguides. By applying a pressure ranging from 900 kPa to 990 kPa, the output intensity ratio sensitivity of -2.272 /kPa is achieved. Compared with traditional MEMS pressure sensor, the proposed ring pressure sensor has advantages such as higher sensitivity and resolution, which could be applied to acoustic pressure sensors and microphones etc.
Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 2011 16th International; 07/2011
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ABSTRACT: A 2-D silicon phononic crystal (PnC) slab of a square array of cylindrical air holes in a 10-μm-thick freestanding silicon plate with line defects is characterized as a cavity-mode PnC resonator. A piezoelectric aluminum nitride (AlN) film is employed as the interdigital transducers to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS compatible. Both the band structure of the PnC and the transmission spectrum of the proposed PnC resonator are analyzed and optimized using finite-element method. The measured quality factor ( Q factor) of the microfabricated PnC resonator is over 1000 at its resonant frequency of 152.46 MHz. The proposed PnC resonator shows promising acoustic resonance characteristics for radio-frequency communications and sensing applications.
IEEE Electron Device Letters 07/2011; · 2.85 Impact Factor
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ABSTRACT: Nitride-based power flip-chip (FC) LEDs with Cu submount were proposed and prepared. With a much higher thermal conductivity, it was found that we can achieve a lower operation voltage under high-current injections and lower junction temperature from the FC LEDs with Cu submount. Compared with the power FC LEDs with Si submount, the reliability of the proposed device was also better.
IEEE Journal of Selected Topics in Quantum Electronics 09/2009; · 3.78 Impact Factor
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ABSTRACT: Nitride-based power flip-chip (FC) LEDs with Cu submount were proposed and prepared. With a much higher ther-mal conductivity, it was found that we can achieve a lower operation voltage under high-current injections and lower junction temper-ature from the FC LEDs with Cu submount. Compared with the power FC LEDs with Si submount, the reliability of the proposed device was also better.
IEEE Journal of Selected Topics in Quantum Electronics 01/2009; 15. · 3.78 Impact Factor
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ABSTRACT: We report the fabrication of InGaN–GaN power flip-chip (FC) light-emitting diodes (LEDs) with a roughened sapphire backside surface prepared by grinding. It was found that we can increase output power of the FC LED by about 35% by roughening the backside surface of the sapphire substrate. The reliability of the proposed device was also better, as compared to power FC LEDs with a conventional flat sapphire backside surface. Index Terms—Flip-chip, grinding, InGaN–GaN light emitting diodes (LEDs), rough sapphire surface.
01/2009; 27(15).
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ABSTRACT: We have prepared bulk p-AlInGaN layers and light-emitting diodes (LEDs) with p-AlInGaN surface layers by metal-organic chemical vapor deposition. By properly control the TMAl and TMIn flow rates, we could match the lattice constant of p-AlInGaN to that of GaN. It was found that surface of the LED with p-AlInGaN layer was rough with a high density of hexagonal pits. Although the forward voltage of the LED with p-AlInGaN layer was slightly larger, it was found that we can enhance the output power by 54% by using p-AlInGaN surface layer.
IEEE Transactions on Electron Devices 11/2005; · 2.32 Impact Factor
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ABSTRACT: Surface morphologies of the metal-organic chemical vapor deposition-grown p-GaN layers with and without Si treatment were investigated by atomic force microscope and scanning electron microscope. It was found that Si treatment resulted in a much rougher sample surface due to the formation of a thin Si<sub>x</sub>N<sub>y</sub> layer. It was also found that forward voltage of the Si-treated InGaN-GaN light-emitting diode (LED) was slightly higher than that of conventional LED without Si treatment. However, it was also found that such Si treatment could also result in a much larger LED output intensity.
IEEE Photonics Technology Letters 09/2005; · 2.19 Impact Factor
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ABSTRACT: The latest generation of CMOS-MEMS accelerometer has measured mechanical Brownian noise-limited resolution of 45 μg/√(Hz) at 1 atm. A modified pre-amplifier design with sub-threshold transistor dc biasing is robust against leakage paths to positive and negative supplies and has an input referred noise of 14.6 nV/√(Hz) at the 2 MHz modulation frequency. The accelerometer proof mass is purposely sized to have equivalent mechanical Brownian noise. An array approach to improve the noise floor further is proposed and fabricated.
Micro Electro Mechanical Systems, 2005. MEMS 2005. 18th IEEE International Conference on; 03/2005
