Mode analysis of photonic crystal polarization beam splitter and its application in integrated circuits design - art. no. 698437

In this work, the guided modes of a photonic crystal polarization beam splitter (PC-PBS) are studied. We demonstrate that the transmission of a low-loss photonic crystal 120 degrees waveguide bend integrated with the PBS will be influenced if the PBS is multi-moded. We propose a single-moded PC-PBS structure by introducing deformed structures, and it shows twice the enhancement of the transmission. This device with remarkable improvement of performance is promising in the use of photonic crystal integrated circuits design.

The whispering gallery mode in photonic crystal ring cavity - art. no. 698438

Whispering gallery modes (WGMs) in microcavities possess ultra-high cavity Q factor. Such microcavity are easy to be fabricated, so WGMs have attracted much attention in the area of photonics and integrated photonic circuits. It is well known that the effect of total internal reflection restricts the size of this mirocavity. Such drawback goes against the integration of photon. However, the photonic crystal microcavities (PCMC) make a breakthrough recently. The WGMs in the PCMC are possible to gain both ultra-high Q and ultra-small mode volume. In this paper, the property of the mode in photonic crystal ring cavity is analyzed by FDTD and PWE. By modifying the airholes in the corners of the ring cavity, we can obtain the WGM. Also the Q factor of WGM in photonic crystal ring cavity is calculated. This favors the design of the photonic crystal microcavity components.

Superluminescent diode monolithically integrated with novel Y-branch by bundle integrated waveguide for fiber optic gyroscope - art. no. 68380D

We have developed a novel InP-based, ridge-waveguide photonic integrated circuit (PIC), which consists of a 1.1-um wavelength Y-branch optical waveguide with low loss and improved far field pattern and a 1.3-um wavelength strained InGaAsP-InP multiple quantum-well superluminescent diode, with bundle integrated guide (BIG) as the scheme for monolithic integration. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10 mW at 120 mA with no threshold and saturation. Spectral characteristics of about 30 nm width and less than I dB modulation are achieved using the built-in anti-lasing ability of Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12 degrees x8 degrees, resulting in good fiber coupling. The compactness, simplicity in fabrication, good superluminescent performance, low transmission loss and estimated low coupling loss prove the BIG and Y-branch method to be a feasible way for integration and make the photonic integrated circuit of Y-branch and superluminescent diode an promising candidate for transmitter and transceiver used in fiber optic gyroscope.

High Q microring resonator in silicon-on-insulator rib waveguides - art. no. 68380J

A high quality (Q) factor microring resonator in silicon-on-insulator rib waveguides was fabricated by electron beam lithography, followed by inductively coupled plasma etching. The waveguide dimensions were scaled down to submicron, for a low bending loss and compactness. Experimentally, the resonator has been realized with a quality factor as high as 21,200, as well as a large extinction ratio 12.5dB at telecommunication wavelength near 1550nm. From the measured results, propagation loss in the rib waveguide is determined as low as 6.900/cm. This high Q microring resonator is expected to lead to high speed optical modulators and bio-sensing devices.

Realization of SOI submicrometer optical waveguide components - art. no. 68380L

Submicrometer channel and rib waveguides based on SOI (Silicon-On-Insulator) have been designed and fabricated with electron-beam lithography and inductively coupled plasma dry etching. Propagation loss of 8.39dB/mm was measured using the cut-back method. Based on these so-called nanowire waveguides, we have also demonstrated some functional components with small dimensions, including sharp 90 degrees bends with radius of a few micrometers, T-branches, directional couplers and multimode interferometer couplers.

Characterization of high-speed optoelectronics devices based optical and electrical spectra analyses - art. no. 68380Q

In this paper, we presents the characterization technique of high-speed optoelectronics devices based electrical and optical spectra, which is as important access to the devices performance as the prevalent vector network analyzer (VNA) sweeping method. The measurement of additional modulation of laser and frequency response of photodetector from electrical spectra, and the estimation of the modulation indexes and the chirp parameters of directly modulated lasers based on optical spectra analysis, are given as examples.

Design of Si-based Electro-optical modulator employed dual capacitors - art. no. 68381B

Electro-optical modulator with dual capacitors is designed and based on this design basic configuration of device is realized in laboratory. Exceeding GHz switching speed and high phase modulation efficiency can be expected with this device.

Single-negative negative index metamaterials with broad bandwidth - art. no. 683109

The theoretical method to design negative refractive index metamaterials by single negative permittivity metamaterials is presented. By designing the electric and magnetic response metamaterials separately, the complexity of the design work can be simplified a lot. For the magnetic response metamaterials, the metallic post structure is adopted. Varying the height of the post, the response wavelength can be adjusted linearly. For electric metamaterials, wire-mesh structure is adopted. The effective material parameters, including refractive index, impedance, permittivity and permeability are given. Such a structure has negative refractive index during a broad frequency band and easy to design.

High efficiency fiber to waveguide optical coupler in silicon-on-insulator-based slot waveguides - art. no. 68310R

We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed coupler can be used in chip-to-chip communication.

Accurate vibration detection of a rough surface - art. no. 683118

Based on the semiconductor laser whose spectral line with width is compressed to be less than 1.2Mhz, a system was designed to measure and improve the amplitude and frequency of the real-time microvibration with sinusoidal modulation. real-time microvibration measurement was executed without alignment problem in the interferometry; and low-frequency disturbance of environment could be eliminated. Suggestions were also given to consummate the system. The system also has resistance against the low frequency disturbance of the environment.

High-efficiency GaN-based blue LEDs grown on nano-patterned sapphire substrates for solid-state lighting - art. no. 684103

Nano-patterning sapphire substrates technique has been developed for nitrides light-emitting diodes (LEDs) growths. It is expected that the strain induced by the lattice misfits between the GaN epilayers and the sapphire substrates can be effectively accommodated via the nano-trenches. The GaN epilayers grown on the nano-patterned sapphire substrates by a low-pressure metal organic chemical vapor deposition (MOCVD) are characterized by means of scanning electron microscopy (SEM), high-resolution x-ray diffraction (HRXRD) and photoluminescence (PL) techniques. In comparison with the planar sapphire substrate, about 46% increment in device performance is measured for the InGaN/GaN blue LEDs grown on the nano-patterned sapphire substrates.

The influence of substrate nucleation on HVPE-grown GaN thick films - art. no. 684105

Thick GaN films were grown on sapphire in a home-made vertical HVPE reactor. Effect of nucleation treatments on the properties of GaN films was investigated, including the nitridation of sapphire, low temperature GaN buffer and MOCVD-template. Various material characterization techniques, including AFM, SEM, XRD, CL and PL have been used to assess these GaN epitaxial films. It was found that the surface of sapphire after high temperature nitridation was flat and showed high density nucleation centers. In addition, smooth Ga-polarity surface of epitaxial layer can be obtained on the nitridation sapphire placed in air for several days due to polarity inversion. This may be caused by the atoms re-arrangement because of oxidation. The roughness of N-polarity film was caused by the huge inverted taper domains, which can penetrate up to the surface. The low temperature GaN buffer gown at 650 degrees C is favorable for subsequent epitaxial film, which had narrow FWHM of 307 arcsec. The epitaxial growth on MOCVD-template directly came into quasi-2D growth mode due to enough nucleation centers, and high quality GaN films were acquired with the values of the FWHM of 141 arcsec for (002) reflections. After etching in boiled KOH, that the total etch-pit density was only 5 x 106 cm(-2) illustrated high quality of the thick film on template. The photoluminescence spectrum of GaN film on the MOCVD-template showed the narrowest line-width of the band edge emission in comparison with other two growth modes.

Improvement of GaN-based light emitting diodes performance grown on sapphire substrates patterned by wet etching - art. no. 684107

An effective approach to enhance the light output power of InGaN/GaN light emitting diodes (LED) was proposed using pyramidal patterned sapphire substrates (PSS). The sapphire substrates were patterned by a selective chemical wet etching technique. GaN-based LEDs were fabricated on patterned sapphire substrates through metal organic chemical deposition (MOCVD). The LEDs fabricated on patterned sapphire substrates exhibit excellent device performance compared to the conventional LEDs fabricated on planar sapphire substrates in the case of the same growth and device fabricating conditions. The light output power of the LEDs fabricated on patterned sapphire substrates was about 37% higher than that of LEDs on planar sapphire substrates at an injection current of 20 mA. The significant enhancement is attributable to the improvement of the quality of GaN-based epilayers and improvement of the light extraction efficiency by patterned sapphire substrates.

Optimized design on high-power GaN-based Micro-LEDs - art. no. 684108

The structure of micro-LEDs was optimized designed. Optical, electrical and thermal characteristics of micro-LEDs were improved. The optimized design make micro-LEDs suitable for high-power device. The light extraction efficiency of micro-LEDs was analyzed by the means of ray tracing. The results shows that increasing the inclination angle of sidewall and height of mesa, and reducing the absorption of p and n electrode can enhance the light extraction efficiency of micro-LEDs. Furthermore, the total light output power can be boosted by increasing the density of micro-structures on the device. The high-power flip-chip micro-LEDs were fabricated, which has higher quantum efficiency than conventional BALED's. When the number of microstructure in micro-LEDs was increased by 57%, the light output power was enhanced 24%. Light output power is 82.88mW at the current of 350mA and saturation current is up to 800mA, all of these are better than BALED which was fabricated in the same epitaxial wafer. The IN characteristics of micro-LEDs are almost identical to BALED.

Characterization of bulk ZnO single crystal grown by a CVT method - art. no. 68410F

Hall effect, photoluminescence spectroscopy (PL), mass spectroscopy and X-ray diffraction have been used to study bulk ZnO single crystal grown by a closed seeded chemical vapor transport method. Enhancement of n-type electrical conduction and increase of nitrogen concentration are observed of the ZnO samples after high temperature annealing. The results suggest that vacancy is dominant native defect in the ZnO material. These phenomena are explained by a generation of shallow donor defect and suppression of deep level defects in ZnO after the annealing.