Silicon-on-insulator based electro-optic variable optical attenuator with a series structure

An electro-optic variable optical attenuator in silicon-on-insulator is designed and fabricated. A series Structure is used to improve the device efficiency Compared to the attenuator in the single p-i-n diode Structure in the same modulating length, the attenuation range of the device in the series structure improves 2-3 times in the same injecting current density, while the insertion loss is not affected. The maximum dynamic attenuation of the device is greater than 30 dB. The response frequency is obtained to be about 2 MHz.

The effect of proton radiation on a superlumine scent diode (SLD)

The effect of proton radiation on a superluminescent diode (SLD) was studied, and the radiation damage from different energies was compared. The results reveal that the optical power degradation is greater from 350 KeV protons than from 1 MeV protons. Analysis of SLD characteristics after irradiation shows that the main effect of radiation is damage within the active region. At the same time, the results also show that quantum-well (QW) SLDs are far less sensitive to radiation than double-heterojunction (DH) SLDs. (C) 2007 Elsevier B.V. All rights reserved.

Design of a fibre-optic disc accelerometer: theory and experiment

Mechanical principles of fibre-optic disc accelerometers (FODA) different from those assumed in previous calculation methods are presented. An FODA with a high sensitivity of 82 rad/ g and a resonance frequency of 360 Hz is designed and tested. In this system, the minimum measurable demodulation phase of the phase-generated carrier (PGC) is 10(-5) rad, and the minimum acceleration reaches 120 ng theoretically. This kind of FODA, with its high responsivity, all-optic-fibre configuration, small size, light weight and stiff shell housing, ensures effective performance in practice.

Submicrosecond rearrangeable nonblocking silicon-on-insulator thermo-optic 4 X 4 switch matrix

A rearrangeable nonblocking silicon-on-insulator-based thermo-optic 4 X 4 switch matrix is designed and fabricated. A spot-size converter is integrated to reduce the insertion loss, and a new driving circuit is designed to improve the response speed. The insertion loss is less than 10 dB, and the response time is 950 us. (c) 2007 Optical Society of America

Analysis of temperature dependence of silicon-on-insulator thermo-optic attenuator

The temperature dependence of silicon-on-insulator thermo-optic attenuators is analysed, which originates from the temperature dependence of characteristics of multimode interference. The attenuator depth and power consumption are independent of temperature while the insertion loss depends on the temperature heavily. The variation of the insertion loss decreases from 4.3 dB to 1 dB as the temperature increases from 273 K to 343 K.

Electro-optic coefficients of Si0.75Ge0.25/Si/Si0.5Ge0.5 asymmetric superlattice measured by polarization-maintaining fiber-optic Mach-Zehnder interferometer

Ten-period 5.5 nm Si0.75Ge0.25/10.3 nm Si/2.5 nm Si0.5Ge0.5 trilayer asymmetric superlattice was prepared on Si (001) substrate by ultrahigh vacuum chemical vapor deposition at 500 degrees C. The stability of Mach-Zehnder interferometer was improved by utilizing polarization-maintaining fibers. According to the electro-optic responses of the superlattice with the light polarization along [110] and [-110], respectively, both electro-optic coefficients gamma(13) and gamma(63) of such asymmetric superlattice were measured. gamma(13) and gamma(63) are 2.4x10(-11) and 1.3x10(-11) cm/V, respectively, with the incident light wavelength at 1.55 mu m. (c) 2006 American Institute of Physics.

SOI-based 16x16 thermo-optic waveguide switch matrix

A 16 x 16 thermo-optic wavelenght switch matrix has been designed and febricated on silicon-on-insulator wafer. For reducing device lenght, blocking switch matrix configuration is chosen. The building block of a matix is a 2 x 2 cell with Mach-Zehnder interferometer configuration, where a multi-mode interferometer serves as splitters/combiners. Spot size converters and isolating grooves are integrated on the same chip to reduce loss and power consumption. Average power consumption of the switch cell is 220 mW. The switching time of a switch cell is less than 3 mu s.

Study on the stacking faults in hexagonal GaN grown by epitaxy lateral overgrowth with synchrotron radiation

By means of low temperature photoluminescence and synchrotron radiation X-ray diffraction, existence of stacking faults has been determined in epitaxy lateral overgrowth GaN by metalorganic chemical vapor deposition.

Fabrication of thermo-optic switch in silicon-on-insulator

Silicon-on-insulator technology has been used to fabricate 2 x 2 thermo-optic switches. The switch shows crosstalk of -23.4 dB and extinction ratio of 18.1 dB in the bar-state. The switching speed is less than 30 mus and the power consumption is about 420 mW The measured excess loss is 1.8 dB. These merits make the switch more attractive for applications in wavelength division multiplexing.

Multimode-interference-type thermo-optic variable optical attenuator with a response frequency of 10 kHz

A thermo-optic variable optical attenuator based on a multimode interference coupler principle is fabricated. The propagation loss of the fabricated device is 1.6 to 3.8 dB at the wavelength range 1510 to 1610 nm, which is very near the calculated value (1.2 dB) by the finite difference beam propagation method. The maximum power consumption is 363 mW and the dynamic attenuation range is 0 to 26 dB. The response frequency of the fabricated attenuator is about 10 kHz. (C) 2003 Society of Photo-Optical Instrumentation Engineers.

Calculation of the hourly and daily radiation incident on three step tracking planes

Mathematical formulas for estimating the hourly and daily radiation incident on planes of azimuth three step tracking and hour angle three step tracking have been derived in this paper. Based on the hourly solar radiation data of an average day in each month at Er-Lian-Hao-Te city, the hourly and monthly radiation received by planes of these two kinds of tracking have been calculated. The results show that in this district, one axis azimuth three step tracking and hour angle three step tracking could, respectively, obtain 66.5% and 63.3% higher radiation than that on the horizontal surface all year. Moreover, a two axis azimuth three step tracking plane could receive 72% more radiation than the horizontal surface. (C) 2002 Elsevier Science Ltd. All rights reserved.

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.

Longitudinal optic phonon-plasmon coupling in delta-doped metamorphic InAlAs/InGaAs high-electron-mobility transistor structures on GaAs substrates

InAlAs/InGaAs metamorphic high-electron-mobility transistor structures with different spacer layers on GaAs substrates are characterized by Raman measurements. The influence of In0.52Al0.48As spacer thickness on longitudinal optic phonon-plasmon coupling is investigated. It is found that the intensity of GaAs-like longitudinal optic phonon, which couples with collective intersubband transitions of two-dimensional electron gas, is strongly affected by the different subband energy spacings, subband electron concentrations, and wave function distributions, which are determined by different spacer thicknesses. (C) 2001 American Institute of Physics.

Anisotropic radiation pattern from InGaAlP quantum well mesa-like microdisks

To overcome the isotropic directional emission of an ideal circular microdisk, two kinds of cylindrical mesa-like InGaAlP single quantum well (SQW) microdisks emitting at a visible red wavelength of 0.66 mu m have been fabricated. An anisotropic luminescence pattern was revealed by the microscopic fluorescence (FL) image. FL intensity, preferentially enhanced with twofold symmetry, appeared at the circumference of the InGaAlP SQW microdisks. Our results demonstrated that anisotropic radiation can be achieved by geometry shaping of the disks on the top view two-dimensional boundary slightly deformed from circular shape and/or on the side-view cross-section of the circular mesa by wet etching anisotropic undercut. (C) 2000 Elsevier Science Ltd. All rights reserved.

Simple reflection technique for measuring the linear electro-optic coefficient of the polymer thin films

The simple reflection technique is usually used to measure the linear electro-optic (EO) coefficient (Pockels coefficient) in the development of EO polymer thin films. But there are some problems in some articles in the determination of the phase shift between the s and p light modes of a laser beam waveguided into the polymer film while a modulating voltage is applied across the electrodes, and different expressions for the linear EO coefficient measured have been given in these articles. In our research, more accurate expression of the linear EO coefficient was deduced by suitable considering the phase shift between the s and p light modes. The linear EO coefficients of several polymer thin films were measured by reflection technique, and the results of the Linear EO coefficient calculated by different expressions were compared. The limit of the simple reflection technique for measuring the linear EO coefficient of the polymer thin films was discussed.