Design and fabrication of GaAs OMIST photodetector

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of A1As layer that is grown by MBE form the Ultra-Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage V-s, sufficient incident light can switch OMIST from high impedance low current"off"state to low impedance high current "on"state. The absorbing material of OMIST is GaAs, so if the wavelength of incident light within 600 similar to 850nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.

Growth and fabrication of high performance 980nm strained InGaAs quantum well lasers using novel hybrid material system of InGaAsP and AlGaAs

In this paper, we report on the design, growth and fabrication of 980nm strained InGaAs quantum well lasers employing novel material system of Al-free active region and AlGaAs cladding layers. The use of AlGaAs cladding instead of InGaP provides potential advantages in laser structure design, improvement of surface morphology and laser performance. We demonstrate an optimized broad-waveguide structure for obtaining high power 980nm quantum well lasers with low vertical beam divergence. The laser structure was grown by low-pressure metalorganic chemical vapor deposition, which exhibit a high internal quantum efficiency of similar to 90% and a low internal loss of 1.5-2.5 cm(-1). The broad-area and ridge-waveguide laser devices are both fabricated. For 100 mu m wide stripe lasers with cavity length of 800 mu m, a low threshold current of 170mA, a high slope efficiency of 1.0W/A and high output power of more than 3.5W are achieved. The temperature dependences of the threshold current and the emitting spectra demonstrate a very high characteristic temperature coefficient (T-o) of 200-250K and a wavelength shift coefficient of 0.34nm/degrees C. For 4 mu m-width ridge waveguide structure laser devices, a maximum output power of 340mW with GOD-free thermal roll-over characteristics is obtained.

Simulation and fabrication of thermo-optic variable optical attenuators based on multimode interference coupler

A type of thermo-optic variable optical attenuator based on multimode interference coupler is proposed. The optical field propagation properties of the devices are simulated using finite difference beam propagation method. The propagation loss of the fabricated device is 2-4.2 dB at the wavelength range 1510-1610 nm. The total power consumption is 370 mW and the maximum attenuation is more than 25 dB, which almost can meet the requirements of optical fiber communication systems.

The fabrication of thick SiO2 layer by anodization

Silicon-based silica waveguide (SiO2/Si) devices have huge applications in optical telecommunication. SiO2 up to 25-mu m thick is necessary for some passive SiO2/Si waveguide devices. Oxidizing porous silicon to obtain thick SiO2 as cladding layer is presented. The experimental results of porous layer and oxidized porous layer formation were given. The relationship between cracking of SiO2 and temperature varying rate was given experimentally. Such conclusions are drawn: oxidation rate of porous silicon is several orders faster than that of bulk silicon; appropriate temperature variation rate during oxidation can prevent SiO2 on silicon substrates from cracking, and 25 mu m thick silicon dioxide layer has been obtained. (C) 2000 Elsevier Science B.V. All rights reserved.

Stability improvement of selective oxidation during the fabrication of InGaAs/GaAs vertical cavity surface emitting laser

The effects of the carrier gas flow and water temperature on the oxidation rate for different reaction temperatures were investigated. The optimum conditions for stable oxidation were obtained. Two mechanisms of the oxidation process are revealed. One is the flow-controlling process, which is unstable. The other is the temperature-controlling process, which is stable. The stable region decreases for higher reaction temperatures. The simulation results for the stable oxidation region are also given. With optimum oxidation conditions, the stability and precision of the oxidation can be dramatically improved.

Fabrication and luminescence characterization of two-dimensional GaAs-based photonic crystal nanocavities

This paper describes the design and fabrication process of a two-dimensional GaAs-based photonic crystal nanocavity with InAs quantum dots (QDs) emitters and analyzes the optical characteristics of cavity modes at room temperature. The micro-luminescence spectrum recorded from the nanocavities exhibits a narrow optical transition at the lowest order resonance wavelength of about 1137 nm with about 1 nm emission linewidth. In addition, the spectra of photonic crystal nanocavities processed under different etching conditions show that the verticality of air hole sidewall is an important factor determing the luminescence characteristics of photonic crystal nanocaivties. Finally,,the variance of resonant modes is also discussed as a function of r/a ratio and will be used in techniques aimed at improving the probability of achieving spectral coupling of a single QD to a cavity mode.

Fluorescence Hydrogen Peroxide Probe Based on a Microstructured Polymer Optical Fiber Modified with a Titanium Dioxide Film

A highly sensitive microstructured polymer optical fiber (MPOF) probe for hydrogen peroxide was made by forming a rhodamine 6G-doped titanium dioxide film on the side walls of array holes in an MPOF. It was found that hydrogen peroxide only has a response to the MPOF probe in a certain concentration of potassium iodide in sulfuric acid solution. The calibration graph of fluorescence intensity versus hydrogen peroxide concentration is linear in the range of 1.6 x 10(-7) mol/L to 9.6 x 10(-5) mol/L. The method, with high sensitivity and a wide linear range, has been applied to the determination of trace amounts of hydrogen peroxide in a few real samples, such as rain water and contact lens disinfectant, with satisfactory results.

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO(2)(-)) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 x 10(-4) g/ml-5.0 x 10(-3) g/ml. The method possesses case of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results. (C) 2010 Elsevier B.V. All rights reserved