YBCO高温超导微带线的非平衡光响应及其恢复时长

研究了在波长为0.68μm的连续激光辐照下,钇钡铜氧(YBCO)高温超导(HTS)微带线的非平衡光响应特性,并从超导体机制探索和光响应超导器件研制两个角度对实验现象进行讨论。实验观察到高温超导微带线的非平衡光响应阈值,当功率小于15 mW时,以辐射热效应为主;当功率大于15 mW时,出现非平衡光响应。该阈值的发现,是对Zeldov的“热效应”与“光子效应”同时存在理论的进一步完善,并设想了一种新型的高温超导衰减器;研究了高温超导微带线非平衡光响应的恢复时长,当激光功率为45 mW时,恢复时长约为3.5 s,分析了该时长存在的机制及其对光响应超导器件二次激光激励的影响。     

高功率光纤熔融器件设计综述

近年来,高功率光纤激光发展迅猛,基于光纤熔融器件的全光纤激光系统可以更好地发挥出光纤激光所固有的体积小、质量轻、稳定性和可靠性高等优势。高功率条件下,器件局部发热可能给器件带来灾难性的故障。决定器件高功率承受能力的不是传输功率,而是器件处理光功率损耗的能力。本文详细分析了单模器件和多模器件中的损耗产生机制,指出了低损耗设计的实现方法。减小器件封装的热阻也可以提高器件的功率耐受能力,文中对封装的设计给出了实用的建议。     

激光停照后探测器继续升温现象的实验研究

文章针对探测器组件,研究了响应波段内、外激光辐照停止后,组件内探测器的热恢复过程.实验发现激光辐照停止后,组件内探测器存在继续升温的新现象.研究表明,此现象是器件整体结构所致,Ge窗口或滤光片对激光能量的吸收是导致温升的直接原因.实验还测量了不同激光功率、不同辐照时间下探测器继续升温的时间,结果表明继续升温时间随辐照时间的加长而减小,随激光功率的提高而增大.     

红外焦平面器件对不同波长激光辐照的响应特性研究

为了有效地干扰红外焦平面探测器,需要研究在不同波长激光的辐照下该探测器的响应情况。本文采用四种波长的激光进行辐照实验。研究结果表明,探测器像元很容易达到饱和状态,器件的响应与光谱响应曲线基本吻合。结果验证了干扰效果与光谱响应曲线之间的关系,为中红外激光干扰提供了实验依据。最后对红外焦平面器件对波段内激光的响应机制进行了简要分析。     

基于CTIA的PV-HgCdTe线阵近红外激光响应特性

使用超连续谱激光辐照PV 型线阵HgCdTe 探测器,探测到了线阵器件输出信号随光照强度变化的全过程,发现了被辐照单元过饱和降压、低压稳定输出的反常响应规律;同时,未被辐照单元也存在响应。在总结实验响应规律的基础上,给出了各不同响应阶段功率阈值范围,并分别对辐照单元出现的过饱和降压、低压稳定输出等异常现象及未被辐照单元存在的整体降压反常响应现象进行了深入研究。研究认为采用CDS 相关双采样电路使器件的基底信号在强光下存在光响应是造成辐照单元异常响应的主要原因;而器件内部公共P 级结构、电路共用Vref 电压结构是导致未被辐照单元反常响应输出的主要因素。     

基于碲化铋纳米片的全光可控调Q光纤激光器

通过光学自组装方法制备了碲化铋可饱和吸收器件,并获得了该器件的非线性光学响应特性。将可饱和吸收体引入掺铒光纤激光器中,在抽运功率为170mW时,获得中心波长为1564.94nm,脉冲宽度为2.91μs的激光输出。通过外加连续光对非线性吸收器件进行调制,实现了脉冲持续时间和重复频率可调控的调Q光纤激光输出。     

SiC及其功率器件的激光制孔研究进展

SiC作为第三代半导体材料的典型代表,因具有优异的物化性能,在功率器件领域具有极大的应用前景.文章简要介绍了激光制孔的基本原理,综述了 SiC的长脉冲与超短脉冲激光制孔研究进展,对比了长脉冲与超短脉冲激光的加工特点,分析了不同脉冲宽度下SiC的制孔效果.同时,介绍了 GaN/SiC,AlGaN/GaN/SiC等SiC功率器件的激光制孔研究现状.最后,指出了 SiC及其功率器件激光制孔面临的挑战,并展望了未来的发展方向.     

慢流CO_2激光器最佳冷却条件的实验研究

螺旋水冷慢流CO_2激光器件比普通慢流器件输出激光功率高16%。瓷管慢流器件气、水逆流较气、水顺流运用激光功率高7.6%。给出了最佳冷却条件。     

高灵敏度的量子效应探测器的建模和微光探测

针对新型量子点-量子阱光电探测器在不同的辐照功率和器件偏压下的电特性测试,采用曲线拟合的方法,得到不同辐照光功率下的I-V、C-V之间的函数关系,应用Verilog-A语言建立等效电路模型,然后利用电路模拟软件进行验证,为读出电路的设计提供准确的便于和读出电路一起模拟仿真的探测器模型。针对这种探测器低温下具有的暗电流小、灵敏度高、光电转换效率高等优点,设计了电容反馈互阻放大器(CTIA)和相关双采样(CDS)结构的读出电路。芯片集成后和2×8阵列的量子效应探测器封装在陶瓷基板上,低温下(77 K)采用633 nm He-Ne激光聚焦照射探测器,测试得到探测器的微光响应电压。实验结果表明,当器件在50 pW光功率、29.3μs的积分时间、偏压约-3.1 V时,读出电路与探测器对接后12个像元有响应电压;增大光功率至500 pW时,16个像元都有响应;读出电路与探测器对接后平均响应电压为18 mV,平均电压响应率达到3.6×107 V/W。     

高响应度InGaAs PIN光电探测器的研制

分析了影响探测器响应度的各因素,在此基础上设计了InGaAs/InP PIN探测器的外延材料结构并优化了增透膜厚度和p-InP区欧姆接触电极图形的设计,以达到提高响应度的目的。采用MOCVD技术和闭管扩散等工艺制备了器件并测量了其响应度。结果显示,器件的光谱响应范围为1000~1600nm,在1500nm激光的辐照下,5V反向偏压时器件的响应度可达0.95A/W以上。     

Measurement of intrinsic frequency response of semiconductor lasersusing optical modulation

For the first time, optical modulation is used to determine the intrinsic frequency response of a laser diode. It is shown that the shape of the measured frequency response agrees very well with the predicted intrinsic response of semiconductor laser. As anticipated, the measured frequency response lacks the frequency rolloff that occurs with direct RF current modulation. The resonant frequencies measured are shown to be proportional to the square root of the probe laser bias power and the damping rates are found to be linear in power, in agreement with expectations     

两相两重斩波变换的半导体激光器电源研究

为了提高传统线性半导体激光器电源的电能转换效率、输出电流的动态响应以及对负载电压的自适应能力,采用两相两重斩波变换技术,设计了一种半导体激光器用2kW直流驱动电源。测试并分析了该电源在激光系统中的静态特性、动态特性以及两相两重斩波变换电流源的效率。结果表明,电源对负载电压自适应能力强,具有较好的矩形输出特性;直接驱动激光二极管模块时,该电流源的电能转换效率高达93%,输出电流0A~100A的上升、下降时间仅为0.5ms,电流纹波系数小于0.03%。     

用于半导体激光器冷却囚禁原子的声光晶体驱动器及其性能测量

为满足半导体激光器应用于激光冷却囚禁原子的需要,本文设计了输出功率和频率可由外部信号控制的声光晶体驱动器,其输出功率可由0W变至2W,频率由54MHz变至120MHz.提出了F-P腔和声光晶体双通过装置联用来测量其频率动态特性的一种方法,对驱动器的频率和功率动态性能进行了测量.     

眼科准分子激光实时监控能量计

利用激光感生热电电压(LITV)效应制成了激光功率/能量计,它不仅能测量和记录每个脉冲的能量值及实时施加的脉冲总能量等信息,也能记录每个入射脉冲的响应波形,实现了对激光能量的实时监控。用此功率/能量计对248 nm准分子激光器进行模拟实验。测量结果表明,在1~50 Hz重复频率下,激光器输出能量的相对标准偏差在8.6%~10.7%。在模拟屈光手术设置参数下,对193 nm准分子激光器进行测量,表明此激光器输出能量的相对标准偏差在8.3%。将这种激光功率/能量计用于激光近视眼科手术中,对提高激光的切削质量和手术质量有重要意义。     

Ten-to-twenty gigabit-per-second modulation performance of1.5-μm distributed feedback lasers for frequency-shift-keying systems

The frequency modulation (FM) and amplitude modulation (AM) responses of a 1.5-μm distributed feedback (DFB) laser were measured to 15 GHz. At 9-mW output power, the magnitude of the FM response was flat out to 12 GHz, and there was a 15-25-ps delay between the FM and AM responses. Computer simulation techniques indicate that the measured FM response is adequate to produce good eye patterns for frequency-shift-keying modulation at data rates up to 20 Gb/s. The high-speed frequency-shift-keying modulation capability of this 1.5-μm DFB laser was experimentally confirmed at 11 Gb/s     

Efficient diffraction-limited beam combining of semiconductor laserdiode arrays using photorefractive BaTiO3

Beam combining of 820-nm-wavelength laser diodes using two-wave mixing in BaTiO₃ is reported. Energy transfer efficiencies up to 80% were obtained with an index-guided diode. Efficient beam combining of two injection-locked laser arrays was demonstrated. Nearly 100 mW power in a diffraction-limited beam was obtained on the combined beam. Crystal response time of the order of a few seconds was measured     

窄线宽低噪声可调谐非平面环形激光器

针对空间相干光通信和探测等应用,对非平面环形激光器的线宽、噪声和调谐特性进行了系统的实验研究。单频输出功率达到752mW,光光效率42%,斜率效率54%。采用延时自外差拍频法测试了激光线宽,其随泵浦功率的增加而增大,输出功率小于200 mW 时,线宽小于1 kHz,在最高输出功率下线宽为2.3 kHz。激光强度噪声主要由弛豫振荡引起,相对强度噪声（RIN）随着泵浦功率的提高而降低。在1.78W 泵浦功率下,RIN 达到-93 dB/Hz。采用温度和压电两种方式进行了激光调谐。温度调谐范围达到62 GHz。压电调谐范围达到130MHz,响应带宽100 kHz。     

Characterisation of frequency response of 1.5 ?m InGaAsP DFB laser diode and InGaAs PIN photodiode by heterodyne measurement technique

The frequency response of an InGaAs PIN photodiode and the ratio of the frequency modulation (FM) index to the intensity modulation (IM) index of a 1.5 ?m InGaAsP vapour-phase-transported DFB laser diode have been measured by an optical heterodyne measurement technique. From the response of the photodiode to the laser radiation beat frequency, a 20 GHz detector bandwidth is determined. The ratio of the FM and IM indices at 3 mW laser output power per facet decreases from 60 at 100 MHz modulation frequency to 3.3 above 2 GHz.     

Response of photovoltaic cells to pulsed laser illumination

Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe₂, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current versus bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC “ringing”, and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components     

用注入锁模法改善DFB激光器的频率响应

验证了通过注入锁模方法,分布反馈(DFB)半导体激光器的频率响应可以得到明显的改善.实验中通过一个环形器,将主激光器的输出光注入到从激光器.测量了从激光器在有注入光和没有注入光时的光谱和频率响应.发现在不同的注入光强度和波长下,激光器的调制带宽和弛豫振荡峰频率会发生变化.通过适当选择注入光的强度和波长,频率响应可以得到改善.激光器频率响应的改善可以用两个模式的拍频来解释,一个模式是从激光器的主模,另一个是主激光器的模式,该模式与从激光器的边带重合.该理论与实验结果符合得很好.