以半导体激光器为光源的准直研究

对半导体激光器的准直装置、温度变化对准直精度的影响、温度控制方法作了论述。试验表明,采用半导体激光器作准直光源,准直的稳定性可达到1×10~(-6)。     

半导体激光器在实时测温系统中的应用

该论文介绍了一种利用半导体激光器InGaAs I作光源 ,使用钽酸锂热释电探测器作光接收器件 ,以单片机为核心实现的中、高温度实时测量系统。该系统主要由光发射与接收系统、信号放大与处理系统及显示系统三部分组成。     

钢球表面缺陷检测用双光路光源稳定控制技术研究

半导体激光器作为光源产生器件进行钢球表面缺陷检测时，由于其自身的材质和结构，输出光功率受注入电流和温度变化的影响很大，光源很容易产生波动，这对检测结果产生了较大的干扰，影响钢球表面缺陷检测的准确率。本文设计了一种用于钢球表面质量检测的小功率半导体激光器功率稳定系统。通过上位机对单片机烧录程序实现对半导体激光器发光功率的自动控制，系统设计有光功率反馈模块、温度控制模块和光隔离模块，可以有效的消除电流浪涌现象、温度变化和反射光干扰等因素对激光器输出功率的影响，保证激光器发出恒定功率的稳定光。最后对1310 nm的激光器进行了测试，该系统将光功率的不稳定度从9.37%降低到1.42%，为后续的钢球表面缺陷检测奠定了良好的基础。     

分立型半导体激光器线阵温度场分析

目的　研究半导体激光器线阵的温度场分布 ,为设计冷却方案提供理论依据 .方法　用分离变量法推导简化后系统的温度场分布函数 ,获得理论最高温度所在位置 ;建立合理的有限元模型 ,在 ANSYS系统上进行数值仿真 .结果　得到系统稳定后的温度场分布图 ,确定了半导体激光器线阵在整个工作时间内的最高温度及其所在位置 .结论　根据简化后的数学模型 ,用有限元法得到的温度场分布与用分离变量法进行的理论分析得到的结论相一致 .     

半导体激光器在尺寸测量系统中的应用

本文介绍的尺寸测量系统采用半导体激光器作光源,可对非回转体类零件的位置尺寸进行非接触在线测量,并可根据测量结果实时输出反馈控制信号,对生产过程实现闭环控制和在线检测.本文最后还给出了实验结果和误差分析,根据数据对比可知,该测量系统的测量误差≤±4μm.     

DWT—702型控温仪的故障分析与维修（二例）

一、ＤＷＴ - 70 2型控温仪控温原理ＤＷＴ - 70 2是一种精密温度自动控制装置 ,它的控温精度可高达 12 50± 0 5℃。在计量部门 ,一般用它对热电偶检定炉进行温度控制 ,其工作原理如图 1所示。　　被控热电偶检定炉炉温由热电偶测量 ,由毫伏定值器给定 ,当热电偶测得的热电势 (炉内温度 )与定值器输出的毫伏值 (给定温度 )有偏差时 ,经微伏放大器将其放大送入ＰＩＤ调节器运算后 ,输出的直流信号经可控硅触发器 ,输出的脉冲信号控制可控硅执行器的导通角度 ,改变炉丝加热功率 ,进而消除偏差值 ,实现恒温。若热电偶测量值高于给定值 ,ＰＩ…     

基于光学放大的微小角度在线测量

由于自准直仪角度系统体积庞大,一些被检仪器的内部无法安装该系统。本文提出了一种利用光学放大测量微小角度的装置。该装置主要由激光器、反射镜、位置探测器、信号放大器和数据采集系统构成,具有精度高、体积小、速度快、低成本和通用性强等优势,故可广泛应用于各行各业的微小角度的在线检测。     

Design of a rail-to-rail operational amplifier for implantable neural signal regeneration systems

为满足治疗中枢神经损伤的植入式神经信号再生系统的低压低功耗要求,设计了该微电子系统的中间级放大和激励的核心电路——恒跨导轨到轨运算放大器.根据系统满摆幅和低功耗的特点,在电路设计中采用了工作在亚阈值区的电流开关跨导控制电路作为输入级,改进的前馈AB类放大器作为输出级.芯片采用中芯国际0.18μm 1P6MCMOS工艺设计完成.仿真和测试结果表明,芯片实现了满摆幅动态范围,跨导恒定,可用于对探测得到的微弱神经信号的放大和激励,满足神经信号再生系统的要求.此芯片电路功耗和体积都很小,满足生物体植入式器件的要求.     

基于AVR单片机的激光电源闭环控制系统设计

为使激光器稳定输出,采取控制驱动电流和温度的设计方案,基于AVR单片机设计一种半导体激光器驱动电源控制系统。采用负反馈原理和闭环控制思想分别实现对驱动电流和温度的控制,从而完成高性能半导体激光器的研制。采用AVR作为主控制芯片,以模数、数模等转换芯片作为其外部扩展电路。为保护激光器和其他易损元件,整个驱动电路具有抗电冲击和过流保护等多种功能。通过实验证明:该系统能使激光驱动电路1 h内偏差为0.02%,稳定性良好,温度控制偏差为±0.005℃。该电源控制系统可靠性高,可移植性强,具有较好的应用前景。     

半导体激光器特性自动测量系统

随着激光技术的广泛应用 ,尤其是光通信的迅猛发展 ,半导体激光器在工业和科研领域发挥着越来越大的作用 ,因此半导体激光器特性的自动测量具有非常重要的实用意义。文章介绍了一种计算机控制的半导体激光器参数采集和计算系统 ,能够自动完成半导体激光器的功率电流曲线、电压电流曲线、激光阈值、外量子效率的测量工作。其主要优点在于 :测量时间短、精度高 ,该系统适合用于大批量生产和使用半导体激光器的单位应用。     

Wavelength tuning in optically mode-locked semiconductor fiber ring lasers with linearly chirped fiber Bragg gratings

We demonstrate wavelength tuning in single-wavelength and multiwavelength semiconductor fiber ring lasers that are mode locked with an optically injected control signal. A semiconductor optical amplifier is used to provide gain as well as to function as an optically controlled mode-locking element. Linearly chirped fiber Bragg gratings--single or superimposed--are used to define the lasing wavelengths as well as to provide wavelength tunability and allow for multiwavelength operation. We obtain pulses of tens of picoseconds in duration when we inject a sinusoidal optical control signal into the laser cavity, and we can tune the lasing wavelength(s) over the reflection bandwidth(s) of the grating(s) by simply changing the frequency of the injected control signal.     

Wavelength control of tunable dense wavelength-division multiplexing sources by use of a Fabry-Perot etalon and a semiconductor optoelectronic diode

A high-resolution tunable-wavelength controller is achieved by use of an etalon for control of wavelength drift and a semiconductor optical diode (SOD) for channel recognition. The etalon provides a stable wavelength reference, and the SOD can detect mode-hopping and incomplete-tuning problems in tuning a laser. With the help of a Fabry-Perot etalon as a precise wavelength reference, the usual concern with the temperature stability of a SOD can be relaxed at least tenfold compared with wavelength control with a single SOD. We demonstrate the feasibility of monitoring tunable lasers by using a Fabry-Perot laser diode (FPLD) or a semiconductor optical amplifier (SOA). The induced voltage of the FPLD and that of the SOA are modeled with analytic expressions that can help to optimize the operation of a SOD sensor.     

An Allan variance real-time processing system for frequencystability measurements of semiconductor lasers

A real-time frequency stability measurement system for semiconductor lasers was developed. Since the frequency of the input signal is measured successively without clearing the counter, measurements of the Allan variance made with this system are more accurate than those made with conventional instruments. The Allan variance can be measured for integration times τ from 1 μs to 10000 s, and the number N of measured frequencies averaged over the integration time τ can be arbitrarily selected up to N=707 for each integration time. The highest measurable frequency was 90 MHz. It was demonstrated experimentally that this system can be used for measurements of the frequency stability of semiconductor lasers     

SOA-based multi-wavelength source

A simple fiber laser configuration based on a semiconductor optical amplifier (SOA) is proposed for obtaining multi-wavelength oscillation at room temperature, in which a Sagnac loop mirror is used as the wavelength selective component. The SOA has a flat gain of approximately 23dB within a bandwidth of 12 nm at a small input signal power. The loop mirror was constructed using a 3dB coupler and polarization maintaining fiber (PMF). The output spectrum of the proposed laser can be adjusted by controlling the bias current of the SOA and is quite stable at room temperature. At a bias current of 150 mA, six lines are obtained with at least ?40 dBm output power and 25dB signal-to-noise ratio (SNR). The channel spacing and number of lines is determined by the length of polarization maintaining fiber (PMF) used in the loop mirror. The channel spacing of the proposed laser is 1.49 nm with a PMF 3 m. The multi-wavelength comb output can also be tuned by adjusting the operating temperature of the SOA. The multi-wavelength laser has the advantage of a simple configuration, stability at room temperature, a broad wavelength band, and no need for optical pump lasers.     

Suppression of self-pulsing behavior in erbium-doped fiber lasers with a semiconductor optical amplifier

We experimentally demonstrate that the stability of cw and mode-locked erbium-doped fiber ring lasers can be improved significantly with a semiconductor optical amplifier (SOA) inside the cavity. The fast saturable gain of the SOA suppresses significantly the self-pulsing that is due to ion pairs in the erbium-doped fiber, which acts as a saturable absorber. A linear stabilization analysis of the laser system agrees with our experimental results.     

An RF-powered, wireless CMOS temperature sensor

We present a wireless, fully integrated CMOS temperature sensor that recovers power from a radio frequency (RF) signal, and returns data as a frequency-modulated 2.3-GHz signal to a base station. Power is recovered from a 450-MHz incident signal with the help of a low-threshold, high-efficiency, voltage rectifier-multiplier circuit. This technique decreases the minimum incident RF power required, compared to state-of-the-art wirelessly powered telemetry systems. The rectifier-multiplier can collect energy from a base station placed up to 18 m away. To further increase the range from the base, the device collects energy in a low power standby/charging mode. A mode selector circuit monitors the amount stored energy and decides if the system is transmitting data or is in the standby/charging mode. A bootstrapped reference generates a complementary to absolute temperature (CTAT) voltage with an R-squared regression of 0.9995 to a linear fit. This reference is used as the temperature sensor of the system, controlling a low-power, integrated, voltage-controlled LC oscillator (VCO). The oscillation frequency of the VCO is modulated by ambient temperature changes. The modulated carrier is transmitted by a fully integrated power amplifier. A temperature sensitivity of 126 ppm//spl deg/C is achieved and the entire sensor consumes 1.1 mA while transmitting data.     

Travelling-wave Brewster-angled Stripe InGaAsP Laser Amplifier at 1·3 µm

Abstract

Optical amplification of a Brewster-angled stripe travelling-wave laser amplifier operating at 1·3 µm is described. An actively mode-locked external cavity semiconductor laser generating pulses of duration from 11 to 30 ps was used as a signal source. Maximum single-pass gain of 32 dB was attained for an input of ?24 dB m and a maximum output peak power of 25 dB m was measured for an input power of 8 dB m. Narrowing in the amplified pulse was observed on a synchroscan streak camera when the amplifier gain is too weak to sustain constant temporal amplification across the whole pulse     

Broader, flatter optical spectra of passively mode-locked semiconductor lasers for a wavelength-division multiplexing source

Using the time domain master equation for a complex electric-field pulse envelope, we find analytical results for the optical spectra of passively mode-locked semiconductor lasers. The analysis includes the effect of optical nonlinearity of semiconductor lasers, which is characterized by a slow saturable amplifier and absorber. Group velocity dispersion, bandwidth limiting, and self-phase modulation were considered as well. The FWHM of the spectrum profile was found to have a strong dependence on group velocity dispersion and self-phase modulation. For large absolute values of the chirp parameter, the optical spectra result in equispaced continuous wave frequencies, a large fraction of which have equal power.     

Numerical model of wavelength conversion through cross-gain modulation in semiconductor optical amplifiers

A steady-state numerical model of wavelength conversion through cross-gain modulation in semiconductor optical amplifiers is described, which includes the spatial variations of the carrier density, gain coefficient, differential gain, and internal loss. Of particular interest is the analytic gain coefficient model, which is applied to the semiconductor optical amplifier converter problem for the first time to our knowledge. The model is used to compare performances of upconverters and downconverters for cases of long and short device lengths, and in large and small signal regimes. Comparisons with results of other studies are presented.     

基于DS18B20温度传感器的半导体制冷装置研制

针对大空间半导体制冷装置设计问题,研制半导体制冷系统和温度监测系统。系统采用分布式DS18B20温度传感器,实现制冷装置温度的智能控制与调节,得到在不同电流下制冷片两端的温差及箱体内平均温度随制冷片工作时间的变化情况。试验结果表明:温度监测系统实时性好,控制精度高,为分析半导体制冷片制冷性能提供数据依据,为研制装甲车辆驾驶舱半导体制冷装置奠定理论与试验基础。