Cooling rate in diode laser bonding

Diode laser die bonding parameters were measured for the cases of slow cool and rapid cool die bonding processes. The thermal strain, solder composition and structure, thermal impedance, and bond strength of InP based diode lasers bonded to AlN chip carriers using pre-deposited Au-Sn solder were examined. Relative to the rapid cool process, the slow cool process was found on average: to induce greater strain in the laser chips; to exhibit a larger thermal impedance in the die bonds; to produce a rougher solder structure; and, to promote alloying of the solder material and chip carrier metallization.     

All-optical synchronisation with frequency division using selfpulsating laser diode

All optical synchronisation with frequency division is demonstrated for the first time using a twin section selfpulsating laser diode. Frequency division ratios of 1:2 and 1:3 are achieved. The range of frequencies over which synchronisation is maintained is also investigated and is found to decrease with increasing division ratio.<>     

CO2分子的近红外可调谐二极管激光吸收光谱高灵敏探测

利用近红外可调谐半导体二极管激光用直接吸收光谱技术和波长调制光谱技术初步观测了CO2在1.31 m附近的吸收.从实验结果可以看出,在4.5torr压力下,可探测最小吸收线强度为3.769×10-27μcm-1/(molecule·cm-2),相应的信噪比是16.8.     

Wavelet-denoising technique in near-infrared methane detection based on tunable diode laser absorption spectroscopy

A novel wavelet denoising （WD） assisted wavelength modulation technique is proposed for improving near-infrared de- tection performance on methane concentration based on tunable diode laser absorption spectroscopy （TDLAS）. Due to the ability of multi-level analytical resolutions both in time- and frequency-domains, the noise contained in the differen- tial signal is greatly suppressed. Sensor mechanical part, optical part and electrical part are integrated, and a portable detection device is finally developed. Theory and formulations of the WD-assisted wavelength modulation technique are presented, and experiments are carried out to prove the normal function on the extraction of the second harmonic （2j） signal from severely polluted differential signal by using the technique. By virtue of WD＇s suppression on noises, the sensing characteristics on CH4 concentration are improved, and the limit of detection （LOD） is decreased from 4× 10-6 （without WD processing） to 10-6. The proposed technique can also be used for the measurement on the concentration of other gases with corresponding near-infrared distributed feedback lasers.     

Enhanced damping of laser diode relaxation oscillations fromrevised rate equations

The standard rate equations are incomplete when the optical cavity conductance depends on the optical frequency at the operating point. Corrected rate equations are given in the paper, that involve an action of frequency back on the amplitude. The number of relaxation oscillations is found to be much smaller than that calculated from standard rate equations when the optical wave is weakly index guided, as in CSP lasers. The revision of the rate equations proposed in the paper may affect most laser characteristics     

基于法布里-珀罗激光器的超高重复频率光脉冲生成技术

本文提出了一种新的基于双模自注入锁定DC电流驱动的法布里-珀罗半导体激光器(FP-LD)来生成超高重复频率,高功率光脉冲的简单方法。传统的基于注入锁定增益开关调制的FP-LD产生光脉冲方法,存在输出脉冲重复率低(通常小于10GHz)、啁啾大和低输出功率的缺点。文章提出的方案中,通过一个带直流偏置的FP-LD与两个均匀光纤布拉格光栅(FBG)相连,来实现双模自注入锁定输出。该输出信号再进入一根长的、高度非线性的光纤(HNLF)中,通过自相位调制和反常色散之间的相互作用可获得高频光脉冲。实验结果,在FP-LD相邻的两个纵模同时注入锁定时,可获得了重复频率为139.6GHz宽度为1.6ps和时间带宽积为0.34的孤子光脉冲,峰值功率为120mW。我们还观察到当改变光栅的应力,可选择相间隔的两个纵模同时注入锁定,重复频率为279.2GHz的光脉冲序列,由于该脉冲序列的四波混频增益较139.6GHz序列低,因此四波混频效应不明显。该方案结构简单,成本低廉。     

A laser diode model based on temperature dependent rate equations

Terms are included in the model to account for the variation in the laser's differential gain coefficient and transparency carrier density with temperature. The model shows good agreement with DC experimental results and is useful for the design of the control circuitry of laser diode-based optical transmitters operating over a wide range of temperatures. This is particularly important when noncooled lasers are used. The model can easily be extended to investigate transient behavior of the laser with change in temperature     

用于频分复用相干光纤通信的半导体激光器稳频系统

本文以Fabry-Perot干涉仪为鉴频器,并利用其众多梳状透过峰,实现了若干半导体激光器的稳频,相对频率稳定度可达10~(-11)量级(τ=10s)。还实现了数个激光器对一主激光器的频率跟踪。     

半导体激光器特性测试中温度控制技术的研究

温度特性是影响半导体激光器(LD)特性测试准确性的重要因素,对LD温度控制技术的研究有着重要的意义.在分析了LD的温度特性的基础上,提出了一种高稳定温度控制的设计方案,并从几个方面讨论了保证LD高稳定温度控制和保证温度信号检测、传输精度的方法.实验结果表明,在10℃～40℃范围内温度稳定度为±0.01℃,在25℃时稳定度达到士0.005℃,从而为LD的准确测试提供了有效的保证.此系统稍加改动即能广泛应用于各类LD的控温系统.     

二极管泵浦的声光Q开关高重频Nd:YAG激光器研究

采用光纤耦合输出的连续激光二极管端面泵浦声光Q开关Nd:YAG激光器，在重复频率1kHz时，获得最窄脉宽5.5ns，最大峰值功率76kW；在重复频率20kHz时，最大平均功率4W（脉宽16ns），斜效率达33.4％。并对实验结果进行了讨论。     

半导体泵浦被动调Q高重频Nd:YAG激光器

从被动调Q固体激光器的速率方程出发,分析给出了Cr4+:YAG被动Q开关Nd:YAG激光脉冲的峰值功率、脉冲能量、脉宽及重频等相关参量表达式.以此为基础,进行了光纤耦合输出的连续半导体激光纵向泵浦被动Q开关Nd:YAG激光器实验研究,采用不同参数Cr4+:YAG晶体作为被动Q开关,获得了不同参数的高重频脉冲激光输出.     

Stability of two modes in DFB laser diode under high data rate modulation

Using a DFB-LD with two longitudinal modes in the 1.55 ?m region, the mode stability was examined experimentally. It is found that these modes are very stable under direct modulation at least up to around 300 Mbit/s and there is no power penalty due to mode partition noise in 97 km single-mode-fibre transmission at 280 Mbit/s.     

Analysis of diode laser properties

An analytic model of diode lasers applicable to both the lasing and the nonlasing states is described. For these homogeneously broadened devices, spectral envelope widths for TE00and TM00modes are related to power in each modal family and are shown to depend critically on spontaneous emission coupling into the transverse modes. Thus, lasers with real-refractive index waveguiding (and associated weak spontaneous emission coupling) operate single longitudinal mode above threshold, whereas gain-guided devices run multimode. After connecting gain and spontaneous emission, a charge conservation equation, containing optical power in the form of a stimulated emission term, pumping current, spontaneous emission, and spectral width, is derived. These equations are then demonstrated to suffice for determination of the completeLversusIcharacteristic. For lasers in which both charge and mode confinement exist, such as the buried heterostructure (BH) and channelled-substrate narrow stripe (CNS) types, it is shown that both TM00power and spectral envelope width approach limiting values at threshold, whereas TE00mode power grows in conjunction with TE00spectral envelope narrowing.     

Efficiency of Nd laser materials with laser diode pumping

For pulsed laser-diode-pumped lasers, where efficiency is the most important issue, the choice of the Nd laser material makes a significant difference. The absorption efficiency, storage efficiency, and extraction efficiency for Nd:YAG, Nd:YLF, Nd:GSGG, Nd:BEL, Nd:YVO₄ , and Nd:glass are calculated. The materials are then compared under the assumption of equal quantum efficiency and damage threshold. Nd:YLF is found to be the best candidate for the application discussed here     

Switching characteristics of laser diode switch

Switching characteristics for laser diode switches controlled by the forward injection current have been studied. Pumping rate dependences for the internal gain and for the extinction ratio, defined as the ratio of output signal power to total power, were analyzed numerically and experimentally. They were in good agreement. Turn-on response time is determined mainly by the space-charge capacitance and was seen typically to be ten times the carrier lifetime. The fall time was almost equal to the carrier lifetime. A method to reduce turn-on response time by preshaping the drive pulse is also analyzed. The turn-on response time could be reduced to about 1 ns.     

半导体激光器列阵器件光束复合研究

文中针对半导体激光器列阵的波长复合和偏振复合技术开展了设计和实验研究。首先利用半导体材料波长易调节的特点,设计了AlGaInAs/GaAs/AlGaAs压应变量子阱结构,得到了760nm、800nm、860nm、930nm、976nm五个波长激射的半导体列阵激光器,同时设计了四个短波通滤波片参数,开展了半导体列阵激光器的多波长光束复合技术的实验研究;其次利用1/2波片和偏振复合棱镜将两束不同偏振状态的光束进行了复合,并设计了光束聚焦系统。最终实现了5个波长,10条半导体激光器列阵的光束复合,得到了196W的激光功率输出,总体效率为76%,其中,波长复合效率可以达到92.4%,输出聚焦光斑尺寸为144μm×1 330μm,聚焦光功率密度达到1.02×105W/cm2,与单条半导体激光器列阵相比,合束光的光功率密度提高了4.3倍。     

多功能半导体激光器驱动电源的研制

研制了一种单片机控制的连续半导体激光器(LD)驱动电源。LD可以工作于自动电流控制(ACC)模式、自动功率控制(APC)模式和自动电压控制(AVC)模式。LD的电流可实现0～2A连续可调,满量程精度在±0.1%以内;对LD的温度可以实现精确的控制,采用了比例积分(PI)控制技术,并结合积分分离的思想,使温度控制快速而有效,控制精度为±0.1℃;采取了软启动控制、短路开关和限幅保护的措施,有效地保证了LD的安全。实验表明:该电源具有智能化程度高、抗干扰能力强、稳定度高和使用方便的优点。     

半导体激光在加工中的应用

由于半导体激光器在光电转换效率、输出功率、使用寿命等方面的优势,在工业加工领域具有广泛的应用前景,是目前国际上激光加工技术领域研究的热点之一.文中介绍了半导体激光加工技术的优点,现状及发展趋势.     

二极管激光器运行特性的研究

对输出功率为50W的激光二极管的运行特性进行了测试,研究了冷却水温对激光二极管输出功率的影响,以及工作电流和冷却水温对激光二极管中心波长漂移的影响,为二极管泵浦固体激光器的设计提供有益参考.     

新型的半导体激光器保护电路

根据半导体激光器的特性,设计了一套新型的保护电路系统,利用有效的滤波电路、防浪涌保护电路、慢启动电路、过流过压保护电路及精密温控电路,较大地改进了半导体激光器电源的可靠性,提高了半导体激光器的输出稳定性,延长了激光器的使用寿命。该保护系统具有性能可靠、结构简单、成本低廉等优点。