热膨胀机制产生窄带激光声信号的方法研究

为压缩激光声信号的带宽,基于热膨胀激光致声理论提出了一种采用高重频激光脉冲串产生窄带声信号的方法(重频法),推导了最优重复频率的计算过程,并通过实验测量对重频法进行了验证。以声信号在中心频率处的功率谱密度为参考标准,将重频法与长脉冲法产生窄带声信号的性能进行了比较。理论分析与实验结果表明,激光器在最优重复频率下产生的声信号窄带特性最好;最优重复频率与激光波长、光束半径以及观测角有关;激光脉冲数大于10时,重频法的性能优于长脉冲法;脉冲数为100时,在中心频率处重频法的功率谱密度比长脉冲法高9.3dB。     

氮化镓基发光二极管的发光光谱和功率特性

用直流和脉冲电流的方法研究了氮化镓基紫色和蓝色发光二极管的发光光谱和功率特性.结果表明，紫色发光二极管的发光中心波长在直流情况下随电流的增加发生红移，在脉冲情况下随电流的增加发生蓝移；蓝色发光二极管的发光中心波长在直流和脉冲情况下都发生蓝移.两种发光二极管的功率在直流情况下会发生饱和，并随电流的进一步增加而急剧减小，以上现象可能是由于热效应和量子阱中的压电效应引起的.     

Enhancing the output power of GaN-based LEDs grown on wet-etched patterned sapphire substrates

GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57/spl deg/ against {0001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme.     

InGaAsP/InP 1.3-µm wavelength surface-emitting LED's for high-speed short-haul optical communication systems

Performance and reliability for InGaAsP/InP 1.3-µm wavelength high-speed surface-emitting DH light emitting diodes (LED's) have been investigated. High-speed and high-radiance performances were obtained by the optimal design of both structural parameters and LED driving circuit. Rise and fall times were both 350 ps and peak optical power coupled to a 50-µm core 0.20 NA graded-index fiber at the 100-mA pulse current was - 15.8 dBm with 6-dB optical ON/OFF ratio. A 2-Gbit/s non-return-to-zero (NRZ) pulse transmission over a 500-m span was carried out, Feasibility of using surface-emitting LED's in a high-speed optical communication system has been confirmed. Accelerated aging tests on high-speed LED's were carried out. The half-power lifetimes have been estimated to be more than 1 × 10⁸h at 50°C ambient temperature.     

Fabrication and property analysis of AIGalnP red light LED with high bright

The LED with DBR and enhancing transmission film was grown by MOCVD. At 20 mA DC injection current, the LED peak wavelength was 623 nm, the light intensity was 200 mcd, and the output light power was 2.14 mW. The light intensity and output light power have been improved than traditional LED.     

宽反射角DBR红光发光二极管

对用于提高AlGaInP红光发光二极管出光效率的传统DBR进行了分析,用MOCVD生长了包含对垂直入射光反射的DBR和对斜入射光反射的DBR复合在一起的红光LED,在20 mA注入电流下,LED的峰值波长为630 nm,轴向光强达到137 mcd,输出光功率为2.32 mW.与常规的LED相比,光强和输出光功率有很大的提高.     

Narrow spectral width surface emitting LED for long wavelength multiplexing applications

We discuss a novel surface emitting InGaAsP LED with a relatively narrow spectrum obtained by the integral growth of a 2.6 μm thick semiconductor absorbing, or filtering, layer on a conventional double heterostructure device. The full width at half maximum for the filtered LED with peakpower atlambda_{0} = 1.29 mum isDeltalambda = 850Å (63 meV),compared with an unfiltered LED half width ofDeltalambda = 1300Å (97 meV). Half width measurements were made at a drive current density of 10 kA/cm². The optimization of the filtered LED is considered, and it is found that a substantial reduction of the power in the short wavelength spectral tail can be obtained without significantly decreasing the total LED output power. For these reasons, the filtered LED has potential applications for low cost wavelength division multiplexing systems where a low overlap of spectral output between adjacent wavelength channels is required. In addition, the narrow spectrum may prove useful in moderate bit rate (> 100 Mbits/s) multimode transmission systems where the output from broad spectrum, conventional surface emitting LED's leads to unacceptably high levels of signal dispersion.     

多功能光源调制驱动系统

为满足医学光疗、医学检测上对LED光源高稳定性和高精度且需具有多种发光模式的需求,利用DDS技术,研制了一种多功能光源调制驱动器.以ARM stm32和FPGA作为控制器,控制恒流源提供恒流信号的方法,实现提供可分时切换的双频正弦、正弦、方波等多种模式驱动信号的功能.实验结果表明：不同功率的LED均能在各种驱动模式下正常发光,稳定性好,精度高,满足多功能光源驱动装置的要求.     

Increasing input power dynamic range of SOA by shifting thetransparent wavelength of tunable optical filter

Gain-saturation-induced self-phase modulation (SPM) leading to pulse distortion in a semiconductor optical amplifier (SOA) is overcome by shifting a tunable optical filter (TOF). A recovered or broadened pulse can be obtained after filtering the amplified pulse in the SOA even if the short pulse is only 2-3 ps long. The input power dynamic range (IPDR) can be strongly increased by shifting the TOF and the direction of the shifted transparent wavelength is different for 10 Gb/s return-to-zero (RZ) or nonreturn-to-zero (NRZ) signals. The transparent wavelength of the TOF should be shifted to a longer wavelength for RZ signals and to a shorter for NRZ signals. 80-Gb/s optical time division multiplexing (OTDM) signal amplification in the SOA is demonstrated for the first time. We also demonstrate that a large IPDR for the 80-Gb/s OTDM signal can be obtained by shifting the TOF     

一种新型皮秒脉冲激光器

一种新型皮秒脉冲激光器由序列脉冲激光的产生、单脉冲激光的选取、放大和倍频等部分组成,激光器工作物质选用Nd∶YAG晶体,用两个格兰棱镜分别作为起偏器和检偏器,激光器的振荡级利用被动锁模染料产生的锁模序列脉冲激光,经过单脉冲选择器选取出其中的一个单脉冲激光,再经激光器放大部分的放大和倍频晶体的倍频后,激光器最终输出能量为120mJ,脉冲宽度为100ps,波长为532nm的单脉冲激光,其功率约为1.2×109W,功率密度约为4.2×109W/cm2,系统的外触发同步精度优于2μs。     

Integration of 1024 InGaAsP/InP optoelectronic bistable switches

A photonic parallel memory (PPM), which is an array of 32×32 optoelectronic bistable switches, is discussed. The switch consists of a heterojunction phototransistor (HPT) and a light-emitting diode (LED). Optical positive feedback from LED to HPT is the cause of bistability. The PPM can be written in and read out with 1-kb parallel optical signals. The PPM has been fabricated and memory operation has been demonstrated as expected. Dissipation current for a single switch and the input optical power necessary to turn on the switch were 600 μA and 20 μW, respectively. A light pulse with a width of 5 ns was able to turn on the switch, and the product of turn-on power and pulsewidth for the short pulse region was 1.5 pJ     

Micro-LED蓝宝石衬底AlN上GaN激光剥离研究

为了比较分析纳秒激光和皮秒激光剥离微型发光二极管(micro-LED)时AlN上GaN的热传导效果, 采用了改进的实时紫外光吸收和热传导的激光剥离理论模型进行计算分析的方法, 取得了在不同的激光波长、激光脉冲宽度、激光能量密度下的紫外波段光辐照时和停止辐照后GaN材料热场分布等数据, 并获得了适合micro-LED器件剥离的所用纳秒激光和皮秒激光的阈值条件。结果表明, 激光脉宽、激光波长、激光能量密度是实现激光剥离工艺的关键因素; 较适合的激光波长为209 nm~365 nm的紫外波段; 皮秒激光的剥离效果优于纳米激光, 且激光的脉冲宽度越短, 激光的波长越短, 剥离所需激光脉冲阈值能量也越低, 则对LED芯片区域的热影响也越小。该研究可为开发新型激光剥离设备和相关工艺应用提供重要参考。     

Optical phase conjugation of multiwavelength signals in adispersion-shifted fiber

Optical phase conjugation (OPC) of multiwavelength signals in a dispersion-shifted fiber (DSF), which can be used for dispersion compensation in the wavelength division multiplexing communication system, is theoretically studied. The multiwavelength phase-conjugate signals are generated by four-wave mixing (FWM) in the dispersion-shifted fiber. There are the pulse-shape distortion and the induced frequency chirping in the phase-conjugate signals owing to pump depletion and the cross-phase modulation among the signals and phase-conjugate signals, respectively. The FWM among the pump wave, signals, and phase-conjugate signals causes unequal conversion efficiencies for the multiwavelength signals and enhances the induced frequency chirping in the phase-conjugate signals. The induced frequency chirping may deteriorate the restoration of the pulse shape. Both the pulse-shape distortion and induced frequency chirping increase with the signal and pump powers. The formula for the induced frequency chirping that is only caused by the signals through cross-phase modulation is derived. The requirement of the signal power in the dispersion-shifted fiber for the restoration of the pulse shape by the optical phase conjugation is estimated and numerically verified     

单级PFC LED驱动电源的研究与设计

论述了单级功率因数校正(PFC)LED驱动电源的设计思想,分析了单级PFC恒压源AC/DC构建原理,给出了单级PFC恒压源产生相关问题的解决办法,重点设计了恒流源部分,给出了恒流驱动芯片BP2808工作原理和设计步骤,同时,设计了手动调光部分,运用自激多谐振荡器NE555产生固定频率且占空比为0.09%相似文献   

微型脉搏表中低功耗电路的设计

便携式测量仪器的设计通常需要考虑功耗问题,微型脉搏表的设计也是如此。文中介绍了微型脉搏表的工作流程,并给出了降低能耗的方法。通过脉冲驱动发光二极管发光、模拟开关控制放大器的工作状态,降低了电路的工作能耗。由于采用脉冲驱动二极管发光,就要解决单片机A／D转换电路的采样和脉冲驱动发光同步的问题,论文对脉冲驱动的模拟电路进行了特殊的改进－－将模拟电路放大的脉冲信号经过采样保持,进行平滑处理,最后在A／D芯片的输入端得到连续信号,解决了同步问题。经过实际使用,该系统在低功耗和易控制方面有着非常好的结果。     

基于注入锁定法布里-珀罗型激光二极管的超宽带信号产生技术

提出了一种基于三波长注入法布里-珀罗型激光二极管(FP-LD)产生超宽带(UWB)信号的方案。在FP-LD不同激射模式中注入一路信号光和两路直流探测光,实现多波长变换并得到两路反码输出和一路正码输出;再通过光纤进行色散走离,使不同波长信号之间产生时延,形成UWB脉冲,最后经过光电转换产生UWB信号。对所提出的UWB信号产生方案的原理进行分析,并对UWB信号的波形以及频谱特性进行了实验研究。在此基础上,进行了1.25Gb/s非归零码(NRZ)信号注入FP-LD产生差分编码UWB信号的实验。实验产生的UWB脉冲信号半峰全宽最小为83.3ps,10dB谱宽约为4.6GHz,其频宽比为107%。     

单光束双脉冲、双波长巨脉冲Cr:LiSAF激光器

为实现单光束、双波长、双脉冲Cr:LiSAF调Q激光输出,实验中创造性地采用高压方波驱动电光Q开关实现了双波长、双脉冲的Cr:LiSAF可调谐激光输出。获得了波长分别为890nm与900nm,脉冲能量分别为31mj与38mj,脉冲宽度分别为30ns和27ns,脉冲间隔82μs的单光束、双波长、双脉冲Cr:LiSAF调Q激光输出,双脉冲的不同轴度不大于0.15mrad。为差分吸收激光雷达系统所需单光束、双波长、双脉冲激光器的进一步研制奠定了良好的理论与实验基础。     

Repeated wavelength conversion of 10 Gb/s signals and convertedsignal gating using wavelength-tunable semiconductor lasers

Repeated wavelength conversion of 10 Gb/s pseudorandom nonreturn-to-zero signals is demonstrated using semiconductor lasers that can be tuned wavelength over a broad range. Error-free tunable wavelength conversion with a very low power penalty can be achieved in both first and second wavelength conversion over a broad wavelength range from 1.486-1.573 μm. The converted signal can be switched rapidly within this wavelength region. High-speed converted signal gating controlled by adjusting the bias current to the device active region is also demonstrated     

基于三波长SLA的全光解复用器

工作在三波长状态下的SLA作为非线性元件,在光环形镜中实现OTDM信号的解复用,模拟计算表明,在保持光束功率为1W时,SLA恢复时间小于10ps,可从OTDM复用信号中提取出任一路信号,在控制脉冲功率为900mW时,带宽可达100GHz。     

COTDR散射信号相关特性的研究

在基于相干光时域反射计的分布式光纤温度与应变传感原理的基础上,对不同频率入射光的后向瑞利散射信号在频域上的相关特性进行了分析。用后向瑞利散射的离散模型来说明后向瑞利散射信号在传感光纤中传播的原理,用MATLAB软件对COTDR(相干光时域反射)过程进行了仿真和分析,对不同脉冲宽度的入射信号的功率及相关特性进行了分析研究。结果表明,输入脉冲宽度与频域相关带宽成反比,即传感位置精度与温度或应变精度成反比。