An Ultralow Noise and Narrow Linewidth λ/4-Shifted DFB Er-Doped Fiber Laser With a Ring Cavity Configuration

We report a polarization-maintaining lambda/4-shifted distributed feedback (DFB) Er-doped fiber laser with a ring cavity configuration. The ring cavity suppressed the self-pulsation of the stand-alone Er-doped DFB fiber laser. The laser with a 57-m-long ring cavity achieved single-longitudinal-mode operation, a linewidth as narrow as 6 kHz, and relaxation-oscillation-free noise characteristics.     

Degradation mechanisms of GaAs PHEMTs in high humidity conditions

We have studied the degradation mechanisms of AlGaAs/InGaAs pseudomorphic HEMTs (PHEMTs) under high humidity conditions (85 °C, 85% relative humidity). The degraded samples under high humidity conditions show a decrease in maximum drain current (I_max) and a positive shift in threshold voltage (V_th). Cross-sectional transmission electron microscopy (TEM) images from the deteriorated devices reveal an existence of damaged recess surface region and a peeling of a passivation film (SiN_x). The secondary ion mass spectrometry (SIMS) depth profile at the interface between the passivation film and AlGaAs surface also indicates the diffusion of gallium (Ga), arsenic (As) and aluminum (Al) into the passivation film. The degradation of PHEMTs arises from mainly two mechanisms: (1) the positive shift in V_th due to stress change under the gate caused by the peeling of passivation films, and (2) the decrease in I_max due to the net carrier concentration reduction of the AlGaAs carrier supply layer caused by the combination of surface degradation at the AlGaAs recess regions and diffusion of Ga, As and Al at the interface between the passivation film and AlGaAs surface. A special treatment just prior to the deposition of SiN_x films on the devices effectively suppresses the degradation of PHEMTs under high humidity conditions without degradation of the high frequency performance.     

大屏幕液晶电视图像画质的改善

描述了大屏幕液晶电视图像画质的改善。在屏幕尺寸上已经超过C R T的液晶电视,即使屏幕尺寸达到60英寸,也可以实现全屏100%亮度的高水准。另一方面,高亮度和大尺寸屏幕使液晶电视在图像画质方面存在的问题变得更加明显,因此应当对它们加以解决。例如可见轮廓、动画模糊以及M PEG压缩引起的图像压缩失真及其补偿算法都将在本文中描述。     

Mode-Hop-Free, Optical Frequency Tunable 40-GHz Mode-Locked Fiber Laser

We have successfully achieved a mode-hop-free, optical frequency tunable 3-ps 40-GHz mode-locked fiber laser by installing an optical etalon in a 6.8-m laser cavity. The laser frequency was continuously tuned over 1 GHz without mode hopping by tuning the etalon peak frequency. The oscillation wavelength was also tuned over 1535-1560 nm by tuning an optical bandpass filter installed in the laser cavity.     

Development of a 1 MV field-emission transmission electron microscope

We developed a 1 MV field-emission transmission electron microscope. This paper reports details and specifications of the instrument. The microscope was designed to obtain a bright and coherent electron beam by using the field emission gun equipped with a pre-accelerating magnetic lens and the high-voltage power supply with high stability (0.5 ppm min(-1)). Using this microscope, the brightness of 1.8 x 10(10) A cm(-2) sr(-1) and the lattice resolution of 49.8 pm were attained.     

Field electron emission of multiwalled carbon nanotubes and carbon nanofibers grown from Camphor

Vertically aligned carbon nanofibers (CNF) and multiwalled carbon nanotubes (MWCN) were synthesized from camphor by catalytic thermal chemical vapor deposition on Co and Co/Fe thin films (for CNF) and on silicon substrates using a mixture of camphor and ferrocene (for MWCN). CNF and MWCN were studied by scanning and transmission electron microscopy, visible Raman spectroscopy, X-ray diffraction in order to get insight into the microstructure and morphology of these materials. Field electron emission study indicates turn-on field of about 1.52, 2.3 and 4.3 V/μm for MWCN, Co/CNF and Co/Fe/CNF films, respectively; and threshold field of about 2.48, 3.1 and 6 V/μm, respectively. Our study indicates a better performance for field electron emission compared with some of the earlier published reports which might be due to higher aspect ratio, good graphitization and suitable density.     

Asymmetric Half-Wave Plate Configuration of PLC Mach–Zehnder Interferometer for Polarization Insensitive DQPSK Demodulator

We propose a novel polarization dependent frequency shift (PDf) reduction method for fabricating a silica-based PLC DQPSK demodulator incorporating an asymmetrically positioned half-wave plate, and demonstrate error-free 43-Gbit/s demodulation for any incident SOP. The PDf has a detrimental effect on the demodulation performance of a DQPSK signal, and it is degraded by various kinds of PLC fabrication errors. In this paper, we focus on the polarization crosstalk in the coupler, which is one of the main causes of PDf. To eliminate such PDf, we controlled both the position of the half-wave plate in the MZI and the polarization of the propagated light. We describe the principle of this PDf reduction method in detail and provide a theoretical and experimental discussion. In addition, we describe a compact DQPSK demodulator composed of a single MZI based DQPSK demodulator with a 90-degree optical hybrid. This demodulator configuration can reduce the receiver's footprint. Finally we achieved a compact DQPSK demodulator with a low PDf of less than 0.10 GHz in the L-band.     

Remarkable improvement in emission efficiency of ZnCdSe/Zn(S)Se LEDs by thermal annealing

Thermal annealing effects on optical and electrical characteristics for p-type and n-type II–VI compound layers (ZnSe, ZnSSe, and MgZnSSe) and on the emission efficiency of ZnCdSe/Zn(S)Se 6 quantum well (QW) light emitting diodes (LEDs) grown by molecular beam epitaxy were investigated. It was clarified that serious degradation of optical and electrical characteristics was not observed up to an annealing temperature of 400°C. In the case of p-MgZnSSe, the maximum permitted annealing temperature was lower than that of Zn(S)Se. The light output of the ZnCdSe/Zn(S)Se multi QW LEDs was enhanced by a factor of three at optimum thermal annealing conditions. The study suggests that this thermal effect for LEDs was produced by the improved crystal quality of ZnCdSe QWs by thermal annealing.     

A 1.6 Gbyte/s data transfer rate 8 Mb embedded DRAM

An 8 Mb embedded DRAM has been developed. The salient feature of this embedded DRAM is page fault tolerance. Accessing across different pages can be performed using a minimum column cycle. This feature is achieved by placing a data latch and a transfer gate between the bit line sense amplifier and the column select gate. This DRAM can be reconfigured as separated 2 Mb units when it is embedded as a macro cell of an ASIC library     

Plastic module of laser diode and photodiode mounted on planarlightwave circuit for access network

Low-cost plastic packaging of laser diodes and photodiodes mounted on planar lightwave circuit (PLC) platform are developed and its reliability is confirmed under various environmental and endurance tests. The high performance of the module is maintained under reliability tests, such as high-humidity high-temperature tests (85°C, 85%RH) and temperature cycling tests (-40°C/85°C). No laser diodes show any device characteristics change during environmental tests and their stability has very little dependence on current bias. Although the photodiodes show an increase in leakage current under high-temperature high-humidity tests and the rate of leakage current increase is proportional to the square root of bias voltage, the increase is negligible for system use. These plastic modules can be applied to actual access networks and other fiber-optic networks