Two-port calibration of test fixtures with OSL method.

The open-short-load (OSL) method is very simple and widely used, for one-port test fixture calibration. In this paper, this method. is extended to the two-port calibration of test fixtures for the first time. The problem of phase uncertainty arising in this application has been solved. The comparison between our results and those obtained with the short-open-load-thru (SOLT) method shows that the method established is accurate enough for practical applications.

Real-time far distance micro-vibration measurement using an external cavity semiconductor laser interferometer with a feedback control system

An external cavity semiconductor laser interferometer used to measure far distance micro-vibration in real time is proposed. In the interferometer, a single longitudinal mode and excellent coherent characteristic grating external cavity semiconductor laser is constructed and acted as a light source and a phase compensator. Its coherent length exceeds 200 meters. The angle between normal and incidence beam of the far object is allowed to change in definite range during the measurement with this interferometer, and this makes the far distance interference measurement easier and more convenient. Also, it is not required to keep the amplitudes of the first and second harmonic components equal, and then the dynamic range is increased. A feedback control system is used to compensate the phase disturbance between the two interference beams introduced by environmental vibration.

Analysis of equilateral triangle semiconductor microlasers with rough sidewalls

The mode frequencies and quality factors are calculated for the equilateral triangle semiconductor microlasers with sinusoidal and random Gaussian sidewalls. The results show that the modes can still have high Q-factors.

A novel polarization-insensitive semiconductor optical amplifier structure with large 3dB bandwidth

A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure. which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm. 65nm has been obtained in die experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed, The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.

1.5 mu m DFB integrated with vertical tapered spotsize converter fabricated by selective MOVPE

1.5 mu m DFB LD butt-joint integrated with vertical tapered spotsize converter was fabricated by LP-MOVPE. The vertical far field angle (FWHM) was decreased from 34degrees to 10degrees the threshold currents was as low as 19.8mA, the output power was 9.6mw at 100mA without HR coating and the SMSR was 35.8dB. The 1-dBm misalignment tolerance was 3.2 mu m, while the counterpart of the device without SSC was 2.2 mu m.

Strained MQW electro-absorption modulators with high extinction ratio and low capacitance

We fabricate an electro-absorption modulator for optical network system using a new strategy, the improved modulation properties of the strained InGaAs/InAlAs MQW show it's polarization independent, high extinction ratio (> 40dB) and low capacitance (C <0.6pF) which can achieve an ultra-high frequency(> 10GHz). The device is be used in 10Gbps optical time division multiplex (OTDM) system as a signal generator.

Eigenmode confinement in semiconductor microcavity lasers with an equilateral triangle resonator

We analyze the mode behaviors for semiconductor lasers with an equilateral triangle resonator by deriving the mode field distribution and the eigenvalue equation. The eigenvalue equation shows that the longitudinal mode wavelength interval is equivalent to that of a Fabry-Perot cavity with the cavity length of 1.5a, where a is the side length of the equilateral triangle resonator. The transverse waveguiding is equivalent to as a strip waveguide with the width of root 3a/ 2, and the number of transverse modes supported by the resonator is limited by the total reflection condition on the sides of the equilateral triangle. Semiconductor microcavity laser with an equilateral triangle resonator is suitable to realize single mode operation, and the mode wavelength can be adjusted by changing the side length.

High efficiency, low vertical divergence angle 980nnn Al-free active region lasers with novel large optical cavity and asymmetrical cladding layers

980nm InGaAs/InGaAsP/AlGaAs strained quantum well lasers,vitta novel large optical cavity and asymmetrical claddings was fabricated bg MOCVD. Very high differential quantum efficiency elf 90% (1.15W/A) and low vertical divergence angle of 24 degrees at long cavity length were obtained for 100 mu m stripe lasers. The differential quantum efficiency is up to 94% (1.20) at cavity length of 500 mu m.

Wavelength tunable electroabsorption modulated DFB baser with thin film heater

　

High quality hydrogenated amorphous silicon films with significantly improved stability

High quality hydrogenated amorphous silicon (a-Si:H) films have been prepared by a simple "uninterrupted growth/annealing" plasma enhanced chemical vapor deposition (PECVD) technique, combined with a subtle boron-compensated doping. These a-Si:H films possess a high photosensitivity over 10(6), and exhibit no degradation in photoconductivity and a low light-induced defect density after prolonged illumination. The central idea is to control the growth conditions adjacent to the critical point of phase transition from amorphous to crystalline state, and yet to locate the Fermi level close to the midgap. Our results show that the improved stability and photosensitivity of a-Si:H films prepared by this method can be mainly attributed to the formation of a more robust network structure and reduction in the precursors density of light-induced metastable defects.

The enhancement of spontaneous emission factor in selectively oxidized vertical cavity lasers with double oxide layers

The behaviors of lateral propagating modes in the aperture and the oxidized regions are investigated numerically for selectively oxidized vertical-cavity surface-emitting lasers (VCSELs). The results show that the lateral propagating modes in the oxidized region are greatly affected by the oxide layer due to its low index, the modes are divergence for the VCSELs with sufficient thick double oxide layers. So the coupling between the modes in the aperture and oxidized regions is very weak, and we can expect that the lateral spontaneous emission is greatly affected in this case. Ignoring the contribution of the lateral spontaneous emission, we calculate spontaneous emission factor by counting the total number of the guided modes in selectively oxidized VCSELs with double oxide layers. The results agree very well with the reported measurements and are inversely proportional to the lateral index step.

The diphasic nc-Si/a-Si : H thin film with improved medium-range order

A series of silicon film samples were prepared by plasma enhanced chemical vapor deposition (PECVD) near the threshold from amorphous to nanocrystalline state by adjusting the plasma parameters and properly increasing the reactions between the hydrogen plasma and the growing surface. The microstucture of the films was studied by micro-Raman and Fourier transform infrared (FTIR) spectroscopy. The influences of the hydrogen dilution ratio of silane (R-H = [H-2]/[SiH4]) and the substrate temperature (T-s) on the microstructural and photoelectronic properties of silicon films were investigated in detail. With the increase of RH from 10 to 100, a notable improvement in the medium-range order (MRO) of the films was observed, and then the phase transition from amorphous to nanocrystalline phase occurred, which lead to the formation of diatomic hydrogen complex, H-2* and their congeries. With the increase of T-s from 150 to 275 degreesC, both the short-range order and the medium range order of the silicon films are obviously improved. The photoconductivity spectra and the light induced changes of the films show that the diphasic nc-Si/a-Si:H films with fine medium-range order present a broader light spectral response range in the longer wavelength and a lower degradation upon illumination than conventional a-Si:H films. (C) 2004 Elsevier B.V. All rights reserved.

Strain relaxation of GeSi alloy with low dislocation density grown on low-temperature Si buffers

We have developed a low-temperature (LT) growth technique. Even with Ge fraction x upto 90%, the total thickness of fully relaxed GexSi1-x buffers can he reduced to 1.7 mu m with dislocation density lower than 5 x 10(6) cm(-2). The surface roughness is no more than 6 nm. The strain relaxation is quite inhomogeneous From the beginning. Stacking faults generate and form the mismatch dislocations in the interface of GeSi/LT-Si. (C) 1999 Elsevier Science B.V. All rights reserved.

Electronic and vibrational Raman scattering in resonance with yellow luminescence transitions in GaN on sapphire substrate

We analyze low-temperature Raman and photoluminescence spectra of MBE-grown GaN layers on sapphire. Strong and sharp Raman peaks are observed in the low frequency region. These peaks, which are enhanced by excitation in resonance with yellow luminescence transitions, are attributed to electronic transitions related to shallow donor levels in hexagonal GaN. It is proposed that a low frequency Raman peak at 11.7 meV is caused by a pseudo-local vibration mode related to defects involved in yellow luminescence transitions. The dependence of the photoluminescence spectra on temperature gives additional information about the residual impurities in these GaN layers.

High electrical-to-green efficiency high stability intracavity-frequency-doubled Nd:YAG-LBO QCW 532 nm laser with a straight cavity

An electrical-to-green efficiency of more than 10% was demonstrated by intracavity-frequency-doubling a Q-switched diode-side-pumped Nd:YAG laser with a type II lithium triborate (LBO) crystal in a straight plano-concave cavity. An average power of 69.2 W at 532 nm was generated when electrical input power was 666 W. The corresponding electrical-to-green conversion efficiency is 10.4%. To the best of our knowledge, this is the highest electrical-to-green efficiency of second harmonic generation laser systems with side-pumped laser modules, ever reported. At about 66 W of green output power, the power fluctuation over 4 hours was better than +/-0.86%.