窄线宽外腔半导体激光器研究进展

窄线宽外腔半导体激光器具有结构简单、可调谐、噪声低等优势,广泛应用于量子精密测量、光通信、激光雷达等领域。 根据外腔选频器件的不同,本文主要介绍光栅型激光器、干涉滤光型激光器、波导型激光器和法拉第激光器四类外腔半导体激 光器,分析各类激光器的基本结构与选频机制、介绍各自的优缺点以及国内外研究进展。 其中,前三类激光器采用非量子器件 进行频率选择,而法拉第激光器利用共振法拉第旋光效应选频,输出波长直接对应原子跃迁谱线,对激光二极管的电流与温度 变化具有良好的鲁棒性。 随后介绍外腔半导体激光器的应用情况,尤其是在精密测量领域中的典型应用。 最后总结并展望窄 线宽外腔半导体激光器的未来发展方向。     

A high frequency sensor for optical beam deflection atomic force microscopy

We demonstrate a novel electronic readout for quadrant photodiode based optical beam deflection setups. In our readout, the signals used to calculate the deflections remain as currents, instead of undergoing an immediate conversion to voltages. Bipolar current mirrors are used to perform all mathematical operations at the transistor level, including the signal normalizing division. This method has numerous advantages, leading to significantly simpler designs that avoid large voltage swings and parasitic capacitances. The bandwidth of our readout is solely limited by the capacitance of the quadrant photodiode junctions, making the effective bandwidth a function of the intensity of photocurrents and thus the applied power of the beam deflection laser. Using commercially available components and laser intensities of 1-4 mW we achieved a 3 dB bandwidth of 20 MHz with deflection sensitivities of up to 0.5-1 V/nm and deflection noise levels below 4.5 fm/Hz. Atomic resolution imaging of muscovite mica using FM-AFM in water demonstrates the sensitivity of this novel readout.     

A linear,wide-range absolute temperature thermometer using a novel p–n diode sensing technique

We describe a novel application arising from earlier observations that under several different constant currents the p–n diode exhibits different diode voltages at the same temperature. Firstly, we show by theory, simulation and experiment that this voltage difference increases linearly with temperature. Secondly, we show that the approach allows direct measurement of absolute temperatures. These two facts have, to the best of our knowledge, not been reported before. The approach alleviates complexity issues typically associated with p–n diode thermal sensors by reducing conditioning circuits and eliminating delicate voltage references and calibration. In the test application the current through the diode is switched between two values by a micro-controller. The buffered diode voltage is fed into the analog to digital converter (ADC) of the microcontroller to facilitate direct temperature readout on an appropriate device with a minimum of programming. Finally, the performance of the prototype against two standards is shown to validate the present approach.     

电压源换流器直流侧短路故障特性分析

电压源换流器直流侧发生故障时,其故障电压电流变化迅速,对系统造成了严重威胁。针对这一问题,从电力电子层面深入分析了电压源换流器直流侧短路故障中最为严重的两极短路故障过程。将故障过程分为3个阶段,推导了电容放电阶段直流电压、电流表达式,分析了不控整流初始阶段存在的两种情况,对不控整流稳态阶段提出了采用开关函数计算短路电流的方法。最后通过PSCAD/EMTDC环境下±10 kV直流线路两极短路故障模型的仿真计算,对理论分析进行了验证。研究结果表明,两极短路故障后电路的响应情况与短路阻抗大小相关,短路阻抗较小时需要直流断路器在极短的时间内切除故障,短路阻抗较大时则可以利用交流侧的保护装置对直流侧电压、电流进行动态监测,实现直流侧短路故障的后备保护。     

Application of a diffraction grating and position sensitive detectors to the measurement of error motion and angular indexing of an indexing table

In this paper, two systems for the measurement of the error motion and angular indexing of a rotary indexing table have been developed. A laser diode, a laser holder and a position sensitive detector (PSD) are integrated as a simple measuring device for the measurement of the rotary error without using a precision reference artifact (a cylinder or a sphere), multiple probes or error separation methods. The laser diode is assembled in the laser holder and fixed on the rotary table. The PSD is set up above the laser holder to detect the position of an incident laser beam from the laser diode. When the rotary table rotates, the rotary error changes the direction of the incident beam and also the position of the spot on the PSD. For the measurement of the angular indexing, a reflective diffraction grating and two PSDs are integrated as a high-resolution angle measuring device without using an autocollimator or a laser interferometer system. The diffraction grating is set at the center of the rotary table and reflects an incident laser beam into several diffractive rays. Two PSDs were set up for detecting the positions of ±1st-order diffraction rays. A simple algebraic method is used to solve the angular indexing through an optical analysis. The experimental results showed the feasibility of the proposed test devices.     

低噪声半导体激光器驱动电源的研制

根据半导体激光器的工作特性,研制了一台低噪声、高稳定度半导体激光器的驱动电流源。该电流源特点具有慢启动电路和过流保护电路,提高了半导体激光器抗冲击能力和工作稳定性。     

宽禁带电力电子器件研发新进展

碳化硅和氮化镓是最有发展前途的半导体材料,可用于电力半导体器件的制造。与硅半导体电力电子器件相比,其优点是：标定阻断电压较高,功率损耗较低,工作温度较高,因此给这种器件增加了与硅器件竞争的活力。至于其发展水平,SiC肖特基二极管的标定阻断电压达1．2kV、电流20A,并已投入生产;SiC大功率二极管的研制水平,标定阻断电压达12．3kV,正向电流密度达100A／km^2。预期在数年内,SiC与GaN器件将在因节能而著称的电力电子设备中得到广泛采用。     

Effect of operating parameters on the threshold voltages and impedance response of non-insulated rolling element bearings under the action of electrical currents

In the present work, the effects of operating parameters on the threshold voltages and impedance response of non-insulated rolling element bearings under the influence of varying levels of electrical currents have been studied. The voltage-current relationships in the bearings have been established.Investigations reveal that first and second threshold voltages appear under the influence of electrical currents in the bearings, depending on the lubricant resistivity, oil film thickness, bearing conditions and the operating parameters. The detected threshold voltages are primarily responsible for momentary flow of current and the further increase in current intensity with a slight change in potential drop across the bearings. The impedance of the bearings becomes negligible as the current intensity across the bearing increases. However, the impedance is more affected by the speed and film thickness than by the load on the bearings.This paper highlights the mechanism of the process of failure of the bearings, using lubricants with different characteristics. The investigations show that the experimentally evaluated threshold voltage coefficients of the bearings, using high resistivity lubricants, increase with speed and are independent of the loads on the bearings. This behaviour of the threshold coefficients of the bearings is used to predict the threshold voltages at different parameters of operation. However, bearings using low resistivity lubricants do not display the threshold voltage phenomenon.The investigation may also be used to determine the safe levels of potential drop across the bearing elements, to avoid damage of the bearings under different operating parameters and also to assess the film thickness by the measured impedance and current intensity response of the bearings.     

基于TDLAS烟道气在线检测系统的降噪技术

可调谐激光光谱（TDLAS）技术利用激光管的波长扫描实现痕量气体吸收曲线的二次谐波检测,具有响应时间短、检测灵敏度高、精度高等优点。但实际应用条件分析结果表明,烟道气在线检测中存在外界环境和系统本身引入的噪声。为了实现TDLAS检测方法的高精度、高灵敏度等优势,本文提出在检测系统中加入温度反馈,以减少高温环境带来的干扰,设计并采用双光路扣除背景,消除颗粒物及背景吸收干扰以及采用对激光管驱动电流进行高频调制来抑制系统噪声等3条主要的降噪途径。理论分析表明,这些措施可以降低环境干扰及系统噪声影响,有效提高检测精度。     

用有限元方法计算X光源场发射阴极电流

针对场致发射阵列建立了有效的三维有限元模型来分析单个尖锥的发射电流.考虑到场致发射阵列的周期性和尖锥的轴对称性,仅对一个尖锥单元的1/4进行分析.对模型的表面施加电压边界条件,计算得到尖锥表面电场强度分布,电场强度在尖锥顶点最强,场发射电流在此处也最强.由Fowler-Nordheim函数可得到尖锥表面的场致发射电流密度分布,对整个尖锥表面进行积分后得到了单个尖锥的场致发射电流约为7μA.计算了在100V门电压下不同顶端半径的场致发射电流.结果显示,场发射对顶端半径有很强的依赖性.计算了100个顶端半径为8nm的尖锥在不同门电压下的总场致发射电流,发射电流与开启电压与实际测量值符合得很好.     

Laser, fiber optic, and CCD array sensing systems

Lasers and fiber optics have recently been accepted in industry for sensing as well as for communications. Charge-coupled devices (CCD) and charge-injection devices (CID) are important new solid-state image sensors for fast display inputs to computers. The sensors may be coupled in a sensor fusion system by optical fibers to bring to the plant floor the advantages of intrinsic safety and immunity to radio frequency, electromagnetic, and optical noise. These new developments in sensing by lasers, fiber optics, and CCD arrays may be applied singly or in combination. For example, improved Raman spectroscopy employs a hostile environment fiber optic probe interface, an infrared laser diode to avoid fluorescence, and a CCD array detector for better sensitivity. We will examine recent developments that will help us with rapid, accurate real-time information for better monitoring and control.     

A Simple Driver for Dynamic Or Static Operation of a Laser Diode Intracavity Spectrophotometer

ABSTRACT

Modulated operation of the recently described method of laser diode intracavity absorption spectrometry is discussed. A simple driver circuit which can be used for cw or modulated operation of laser diodes is described. Development of a modulated near infrared laser diode intracavity spectrophotometer for absorption measurements is also provided. This modulated operation mode was compared to cw mode as to sensitivity, noise, ease of operation and detection limit. This modulated driver was implemented using an inexpensive 3 mW 750 nm laser diode and an IR3C02A driver circuit. Advantages of modulated laser diodes in spectroscopic applications are also presented.     

A linear photodetector with noiseless sensitivity adjustment

The sensitivity of linear charge-coupled devices can be adjusted by using controlling voltages on a constant aperture. It is shown that, in the case of devices of traditional design, this adjustment can be accompanied by generation of a correlated (geometric) noise, which essentially deteriorates the resolution capability. A device free of these drawbacks is described.     

一种有源谐波抑制的18脉波整流器仿真

为消除大功率整流系统的谐波污染,提出了一种有源谐波抑制的18脉波整流器.整流器的3个二极管整流桥的输出分别与3个boost变流器级联.与传统的三相有源功率因数校正技术不同的是,18脉波整流桥通过控制其输出电流(即boost变流器输入电流)近似三角波来使交流侧的输入电流近似正弦波.分析了整流器的输入输出电流特性,并对有源谐波抑制的电流调制策略进行了详细的研究.利用 Matlab/Simulink进行了仿真验证,结果表明,所提出的电路拓扑能够获得正弦输入电流,电能质量明显改善,证明了理论分析的正确性.     

Wide-Range Inductive Sensors of Currents with Nanosecond Rise Times for Measuring Parameters of High-Current Pulses (Review)

The design and characteristics of inductive current sensors (modernized Rogovski coils) and inductive sensors on their basis (in the form of a part of a tore) with shielded coils for measuring the parameters of pulse currents in conductors with diameters of up to 1.7 m and electron beam currents of 10–2000 kA with durations of 10–100 ns in a self-integration mode. The Rogovski coils and sensors have current rise times of nanosecond duration and improved noise immunity and mechanical strength. Methods for the calibration of Rogovski coils for determining their transient response and amplitude sensitivity are presented. Specific features of the certification of large-diameter devices are pointed out, and a new method for certifying such sensors is expounded. The sensors are used in experimental investigations and the refinement of units of high-current linear induction accelerators as well is in the starting and adjustment work with a high-power LIA-30 electron accelerator with water-insulated radial lines in the inductors of accelerating modules and for monitoring its parameters (40 MeV, 100 kA, 20 ns). Such sensors are applicable for recording pulse current characteristics in other electrophysical facilities.     

Nanometer edge profile measurement of diamond cutting tools by atomic force microscope with optical alignment sensor

This paper describes an atomic force microscope (AFM) based instrument for nanometer edge profile measurements of diamond cutting tools. The instrument is combined with an AFM unit and an optical sensor for alignment of the AFM probe tip with the top of the diamond cutting tool edge in the submicrometer range. In the optical sensor, a laser beam from a laser diode is focused to generate a small beam spot with a diameter of approximately 10 μm at the beam waist, and then received by a photodiode. The tool edge top and the AFM probe tip are brought to the center of the beam waist, respectively, through monitoring the variation of the photodiode output. To reduce the influence of the electronic noise on the photodiode output so that the positioning resolution can be improved, a modulation technique is employed that modulates the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements are carried out.     

808nm含铝半导体激光器的腔面镀膜

研究了高功率808nm量子阱脊型波导结构含铝半导体激光器在空气中解理时不同镀膜方法对输出激光功率的影响,讨论了半导体激光器的灾变性光学镜面损伤机理及其腔面钝化薄膜的选择特性。对半导体激光器管芯前后腔面不镀膜,前后腔面镀上反射膜和前后腔面先镀上钝化薄膜再镀腔面反射膜方法进行了对比,测试了半导体激光器的输出功率。结果表明,先镀上钝化薄膜的器件比只镀上腔面反射膜的器件输出的激光功率高36%。只镀腔面反射膜的半导体激光器器件在电流为5A时就失效了,而镀钝化膜的器件在电流为6A时仍未失效,说明镀钝化薄膜的器件能有效地防止灾变性光学损伤和灾变性光学镜面损伤。在半导体激光器芯片腔面镀上钝化薄膜是提高大功率半导体激光器输出功率的有效方法。     

激光加工用半导体激光器的光束变换

考虑不同的激光加工方式对激光功率密度和激光光斑尺寸的要求不同,研究了如何通过调整光路设计实现各种尺寸的聚焦光斑输出,使半导体激光器满足不同激光加工方式的需求.利用ZEMAX光学设计软件模拟半导体激光光路,包括光束整形、准直、聚焦等光束变换方式,实现了多种尺寸的光斑输出.实验中采用16个bar叠加而成的980 nm半导体激光叠阵,阈值电流为6.4A,最大工作电流为84.8A,最大输出功率为1 280 W,总的电-光转换效率为58.9％.准直后快轴的发散角小于4 mrad,慢轴的发散角小于20 mrad.通过实验对该激光叠阵进行光束整形和扩束准直、聚焦,最终实现了功率为1 031 W的激光输出,聚焦镜焦距为300 mm时的聚焦光斑尺寸达1.2 mm×1.5 mm,功率密度达3.8×104 W/cm2,可以用于金属的表面重熔、合金化、熔覆和热导型焊接.     

Application of a cylindrical diode as a load with vacuum insulation in high-voltage generators

Results of experimental tests of the possibility of using cylindrical diodes in the self-magnetic insulation mode as an equivalent load with a stable impedance of about units of ohms at voltages below 450 kV are given. The diode with a radial size of ～10 cm and an interelectrode gap of ～1.5 cm demonstrated a stable resistance of ～3 Ω within ～200 ns. The analyzed results show that the current of the self-magnetic insulation in the diode is determined by the limiting current.     

LD泵浦固体激光器驱动倍频输出系统调制噪声的研究

阐述了一具体实验现象 :LD泵浦掺钕矾酸钇固体激光器输出激光再驱动 ( KTP)倍频晶体产生倍频绿激光输出的系统 ,存在严重噪声 ,但可通过改变入射角 ,用对应的特定频率调制 ,使噪声降至很小