Long period grating for 3-5 mu m quantum-well infra-red photodetectors

By considering all possible high order diffracted waves, the authors calculate the coupling efficiency of long period gratings for 3-5 mu m quantum-well infra-red photodetectors (QWIPs) on the basis of the modal expansion model (MEM). A large coupling efficiency for 3-5 mu m QWIPs has been demonstrated. This greatly reduces the difficulties in fabricating 3-5 mu m grating coupled QWIPs and opens the way to fabricate high performance 3-5 mu m and two colour QWIPs image arrays.

STUDY OF THE LONG-TERM STABILITY OF THE EFFECTIVE CONCENTRATION OF IONIZED SPACE CHARGES (N-EFF) OF NEUTRON-IRRADIATED SILICON DETECTORS FABRICATED BY VARIOUS THERMAL-OXIDATION PROCESSES

Experimental study of the reverse annealing of the effective concentration of ionized space charges (N-eff, also called effective doping or impurity concentration) of neutron irradiated high resistivity silicon detectors fabricated on wafers with various thermal oxides has been conducted at room temperature (RT) and elevated temperature (ET). Various thermal oxidations with temperatures ranging from 975 degrees C to 1200 degrees C with and without trichlorethane (TCA), which result in different concentrations of oxygen and carbon impurities, have been used. It has been found that, the RT annealing of the N-eff is hindered initially (t < 42 days after the radiation) for detectors made on the oxides with high carbon concentrations, and there was no carbon effect on the long term (t > 42 days after the radiation) N-eff reverse annealing. No apparent effect of oxygen on the stability of N-eff has been observed at RT. At elevated temperature (80 degrees C), no significant difference in annealing behavior has been found for detectors fabricated on silicon wafers with various thermal oxides. It is apparent that for the initial stages (first and/or second) of N-eff reverse annealing, there may tie no dependence on the oxygen and carbon concentrations in the ranges studied.

A Broadband Long-Wavelength Superluminescent Diode Based on Graded Composition Bulk InGaAs

A novel unselective regrowth buried heterostructure long-wavelength superluminescent diode （SLD） with a graded composition bulk InGaAs active region is developed by metalorganic vapor phase epitaxy （MOVPE）. At a 150mA injection current, the full width at half maximum of the emission spectrum of the SLD is about 72nm, ranging from 1602 to 1674nm. The emission spectrum is smooth and flat. The ripple of the spectrum is less than 0.3dB at any wavelength from 1550 to 1700nm. An output power of 4.3mW is obtained at a 200mA injection current under continuous-wave operation at room temperature. This device is suitable for the applications of light sources for gas detectors and L-band optical fiber communications.

Theoretical Analysis of Gain and Threshold Current Density for Long Wavelength GaAs-Based Quantum-Dot Lasers

Quantum dot gain spectra based on harmonic oscillator model are calculated including and excluding excitons. The effects of non-equilibrium distributions are considered at low temperatures. The variations of threshold current density in a wide temperature range are analyzed and the negative characteristic temperature and oscillatory characteristic temperature appearing in that temperature range are discussed. Also,the improvement of quantum dot lasers＇ performance is investigated through vertical stacking and p-type doping and the optimal dot density, which corresponds to minimal threshold current density,is calculated.

Stable Temperature Characteristics of InAs/GaAs Quantum Dots at Long Wavelength Emission

The time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1. 48 μtm emission is obtained at room temperature. Temperature dependent PL measurements show that the PL intensity of the emission is very steady. It decays only to half as the temperature increases from 15 K to room temperature, while at the same time, the intensity of the other emission decreases by a factor of 5 orders of magnitude. These two emissions are attributed to large-size QDs and short period superlattices (SLs), respectively. Large-size QDs are easier to capture and confine carriers,which benefits the lifetime of PL, and therefore makes the emission intensity insensitive to the temperature.

High power AlGaInP laser diodes with zinc-diffused window mirror structure

The technology of zinc-diffusion to improve catastrophic optical damage (COD) threshold of compressively strained GaInP/AlGaInP quantum well laser diodes has been introduced. After zinc-diffusion, about 20-μm-long region at each facet of laser diode has been formed to serve as the window of the lasing light. As a result, the COD threshold has been significantly improved due to the enlargement of bandgap by the zinc-diffusion induced quantum well intermixing, compared with that of the conventional non-window structure. 40-mW continuous wave output power with the fundamental transverse mode has been realized under room temperature for the 3.5-μm-wide ridge waveguide diode. The operation current is 84 mA and the slope efficiency is 0.74 W/A at 40 mW. The lasing wavelength is 656 nm.

Long-wavelength SiGe/Si MQW resonant-cavity-enhanced photodetectors (RCE-PD) for application in optical fiber communication network

　

Long-wavelength Si-based MQW photodetectors for application in optical fiber communication

Si-based SiGe/Si strained MQW long-wavelength photodetectors (PD) with cycle type (Ring Shape) waveguide (CWG) and resonant-cavity-enhanced (RCE) structure have been investigated for the first time for improving the quantum efficiency and response time. The results show that the responsivities are higher than that of conventional PD with a same Ge content reported previously. In addition, RCE-PD has an obvious narrow band response with FWHM less than 6nm.

The development of long - Term ambulatory pH monitoring system and its clinical application

This paper introduced a long-term ambulatory intragastric pH monitoring system, which is designed for prolonged ambulatory studies of Gastroesophageal Reflux Diseases. The whole system is composed of the gastric catheter with two pH sensors, a small data logger (Microdatalog), and a notebook PC. In this paper, the design of monitoring system hardware and software are described in detail. Clinical applications reveal good results.

Long-wavelength SiGe/Si MQW resonant-cavity-enhanced photodiodes (RCE-PD)

Si1-xGex/Si optoelectronic devices are promising for the monolithic integration with silicon-based microelectronics. SiGe/Si MQW RCE-PD (Resonant-Cavity-Enhanced photodiodes) with different structures were investigated in this work. Design and fabrication of top- and bottom-incident RCE-PD, such as growth of SiGe MQW (Multiple Quantum Wells) on Si and SOI (Si on insulator) wafers, bonding between SiGe epitaxial wafer and SOR (Surface Optical Reflector) consisting Of SiO2/Si DBR (Distributed Bragg Reflector) films on Si, and performances of RCE-PD, were presented. The responsivity of 44mA/W at 1.314 mum and the FWHM of 6nm were obtained at bias of 10V. The highest external quantum efficiency measured in the investigation is 4.2%.