19 ps switching of a bistable laser diode with 30 fJ optical pulses

19-ps optical switch-on of a bistable laser diode with only 30-fJ input coupled optical energy at a repetition rate of 500 MHz is reported. The bistable laser was an inhomogeneously pumped three-section Fabry-Periot laser diode. The switch-off time was 94 ps, probably limited by the duration of the electrical reset pulse. Longer turn-on delay times were recorded when switching with less input energy     

Long-wavelength multiple-quantum-well voltage-controlled bistablelaser diodes

We have investigated static and dynamic characteristics of a multiple-quantum-well (MQW) voltage-controlled bistable laser diode at 1.5 μm. Using the quantum confined Stark effect, the absorption coefficient and the absorption band edge of the saturable absorption region are controlled by applied voltage, resulting in easy change of the hysteresis width and the threshold current. Applied voltage from below the current injection regime to the saturable absorption region, typically the reverse bias voltage, allows faster turn-off switching speed due to the carrier sweep-out by the applied electric field, MQW bistable lasers with InGaAs-InP, InGaAs-InGaAsP and InGaAs-InAlAs systems and several kinds of well numbers were fabricated and their threshold current and switching characteristics are compared. A hysteresis width change of about 20 mA was obtained by changing the applied voltage of about 1 V in each case, Less than 100 ps turn-on switching time with injection light of 1-mW peak intensity was obtained. The device can be switched-on by injection light with about 50 nm bandwidth, and the minimum input light switching intensity of less than 10 μW is achieved around the absorption peak wavelength of the saturable absorber. The InGaAs-InAIAs system has the advantage of low voltage bias at the saturable absorber, because the absorption edge is sharper than other materials due to its high conduction band offset. It has a turn-off switching time of less than 100 ps at the applied voltage height of 2.0 V. And also, memory operation with the repetition rate of 2 GHz has been achieved using input light and the applied voltage     

Temperature dependence of bistable InGaAsP/InP lasers

An increase of hysteresis current width in bistable lasers with two or three sections was observed at higher temperatures. A rate equation analysis was performed where both carrier density dependence on lifetime and the bleaching of saturable absorption by the spontaneous emission were taken into account. We show that the increased loss of injected carriers due to Auger recombination process causes the increase in the hysteresis width. A small-signal stability analysis for the switch-off point revealed that increased coupling between carriers in the gain and absorption regions, through the absorption of superradiant emission, has the effect of raising the switch-off point to higher current levels. It was shown experimentally that, without changing the temperature, the current hysteresis width can be controlled by adjusting the current distribution in three sections.     

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     

非均匀分布反馈半导体光放大器的动态双稳特性

分布反馈半导体光放大器(DFB-SOAs)具有较低的双稳上跳阈值，因而在光学信息处理方面有一定的应用前景。引入空间相移、啁啾等非均匀性后，其双稳特性可得到进一步改善。由于系统的传输速率受到脉冲下降沿形变及开启延时的限制，因此对其动态双稳特性的研究很有必要。从耦合模方程及载流子速率方程出发，数值分析了相移、啁啾分布反馈半导体光放大器的动态双稳特性。结果表明，相移使出射脉冲下降沿的形变及开启延迟随初始失谐量的减小呈现先恶化后缓和的趋势，引入啁啾可明显抑制脉冲下降沿的形变，但是增加了开启延迟所需的功率过载量。     

Set and reset operation dependence on input light intensity of a side-light-injection MQW bistable laser

Dynamic set and reset operations of a side-light-injection MQW bistable laser are achieved using absorption saturation and gain quenching. As input light intensity increases, the turn-on and turn-off times decrease. The turn-on time is 200 ps when the input light peak intensity is 1 mW and the turn-off time is 2 ns when the input light peak intensity is 2100 mW.<>     

声光调Q DPL脉冲宽度空间分布的研究

研究了在声光调Q二极管泵浦固体激光器（DPL）中,光斑不同部位的脉冲宽度的空间分布.由多模振荡引起脉冲宽度在空间分布的不均匀,导致脉冲宽度的展宽.以声光调Q DPL为例进行分析,通过数值计算,得出了在一定的泵浦速率和重复率下,TEM00模与TEM01模两种模式的脉冲建立时间及脉冲宽度的空间分布与上能级反转粒子数的关系.由计算结果得出：若调节二极管泵浦固体激光器中抽运光的空间分布能够使TEM00模和TEM01模在脉宽接近时同时起振,对低阶模和高阶模进行模式合成,从而减小由于多模振荡引起的脉冲宽度的展宽.该结果有助于调Q DPL的脉宽压缩和模式合成.     

A new bistable laser diode configuration for all optical switching

A new bistable laser diode configuration for all optical switching has been suggested and its equivalent circuit model is developed. For switching the device to the high state (set) a TE mode optical pulse is required, which is the oscillating mode of the laser, whereas a TM mode pulse is used to bring the output to a low state (reset). But the wavelength of the set and reset pulses are the same as that of the lasing wavelength of the device. The static and dynamic characteristics are studied by simulating the equivalent circuit model using the circuit simulation program PSPICE. It is found that as the carrier lifetime τ_a of the absorption section increases, the width of the optical pulse required for reset increases nonlinearly. The rise and fall times are found to be 0.15 and 0.16 ns, respectively, for a τ _a, of 3 ns     

Numerical study on a frequency-tunable actively mode-locked fiber laser

We have numerically presented an actively mode-locked fiber laser with tunable repetition rate based on phase modulator. By finely optimizing intra-cavity parameters, the ultrashort pulses with tunable repetitive frequency at giga hertz level can be easily generated due to the balance between dispersion and nonlinearity in the fiber laser cavity. When the pulse frequency is changed from 1.0 GHz to 4.2 GHz, the spectral width increases from ~15.65 nm to ~27.25 nm. In addition, the corresponding pulse duration decreases from ~81.59 ps to ~31.57 ps. Moreover, these output pulses with giga hertz repetitive rates and the picosecond widths can be further compressed by using the reasonable dispersion medium. For the pulse regime with repetition frequency at giga hertz level, the obtained smallest pulse duration is about ~62 fs based on chirp pulse compression. We hope that these simulation results can promote further research and application in the ultrashort pulse lasers with high repetition rate.     

可变偏振光注入垂直腔面发射激光器的频率诱导偏振双稳

为了探索垂直腔面发射激光器偏振敏感的双稳演 化规律,进一步拓展其在光信息处理领域方面的应 用,本文采用自旋反转模型,数值研究了可变偏振光注入下1 550 nm垂直腔面发射激光器频率诱导偏振双 稳的特性。研究结果表明:在可变偏振角度光注入下,通过沿不同路径扫描频率失谐,垂直 腔面发射激光 器的两个正交偏振分量可在负失谐和正失谐区域产生频率诱导的偏振双稳。对于一确定的注 入强度,注入 光偏振角度的增加可导致负失谐区域的偏振双稳宽度逐渐扩展,而正失谐区域双稳宽度无明 显的变化;给 定适当的注入光角度,较大的注入强度更易于在负失谐区域展宽偏振双稳宽度。此外,在注 入光偏振角度 和注入强度均一定时,不同偏置电流情况下激光器偏振分量的频率诱导双稳宽度存在较大差 异,系统可以 通过合理地调节注入光偏振角以及偏置电流等参量实现对频率诱导偏振双稳的灵活控制。     

重复频率可调的脉冲氩离子激光器

这里介绍的是一台脉冲放电、频率从50赫芝到200赫芝连续可调的氩离子激光器。它为超声全息提供一个可见的相干光源。它输出的可见光在蓝—绿光谱区域。最强的光谱线是4880埃和5145埃。该器件用国产GG-17料制成。放电毛细管和阴极泡用水冷却。放电管内径是6毫米,长度是860毫米。谐振腔总长为1200毫米。工作物质是氩气,并加入辅助气体He。输出光中可清楚地看到五条谱线。光脉冲宽度为6微秒。在最佳工作电流时功率可达30瓦至50瓦。加氦气比纯氩运转时的寿命长三倍左右。     

小型热传导冷却(Nd,Ce):YAG激光器热稳定性研究

在小型Cr4+:YAG被动调Q热传导冷却(Nd,Ce):YAG激光器中,采用定向反射器取代平行平面腔中的全反射镜,大大提高了器件的热稳定性,获得了重复频率5pps的激光输出,单脉冲激光能量输出20～25mJ,调Q激光脉宽15ns,束散3～5mrad,工作温度范围-40℃～+55℃,激光器总长度小于130mm。     

采用小孔等离子体开关实现TE CO2激光窄脉冲整形

典型的TE CO2激光脉冲,通常由高功率窄脉冲（100 ns）和低功率长拖尾部分（3~5 s）组成。采用一种简单的小孔等离子体开关技术可以实现对低功率长拖尾部分的有效吸收和散射,保留需要的高功率窄脉冲前沿部分,达到激光脉冲压缩和整形目的。详细研究了小孔位于不同离焦距离时整形激光脉冲波形的变化,获得了整形激光脉宽、能量与离焦距离的变化关系,实现了50~110 ns的窄脉冲CO2激光输出。进一步研究发现,小孔等离子体开关的使用寿命主要由激光脉冲能量、重复频率、整形脉冲宽度决定。通过该技术实现的窄脉冲CO2激光可以用于极紫外光刻等离子体光源、激光雷达等领域的研究。     

Optical bistability in a two-section InAs quantum-dot laser

Room temperature,continuous-wave bistable operation is achieved in two-section 1.24μm InAs quantum-dot (QD) lasers with integrated intracavity QD saturable absorbers(SA).It is found that the hysteresis width is narrowed with increasing reverse bias voltage,and broadened with increasing length of saturable absorber.This can be explained by the competition between QD absorption and electroabsorption in the SA section.In addition,a larger hysteresis width is realized than other reports so far,which can be a...     

全固体1.3μm增益开关激光器的研究

增益开关和Q开关是获得脉冲激光运转的常用方法,对于在非线性光学研究、光通讯第二窗口装置检测、光纤传感等方面有着广泛应用前景的1.3μm波段全固体激光的脉冲产生,提出了使用增益开关的方法。首先在理论上使用速率方程对增益开关的运转进行分析,并就腔长对脉冲参数的影响进行了数值模拟。接着在实验上采用高频调制激光二极管供电电源的方法,使Nd:YVO4激光器工作在增益开关状态,即通过逐渐减小工作电源泵浦电流的脉冲宽度,使激光仅输出弛豫振荡的第一个脉冲,最后在泵浦电流脉冲宽度为5μs时,获得了平均功率80mW,光脉冲宽度200ns,频率200kHz,峰值功率2W,单脉冲能量0.4μJ的1.342μm激光的增益开关运转。     

The influence of microwave pulse repetition frequency on the thermal burnout effect of a PIN diode limiting-amplifying system

This paper analyzes the influence of the microwave pulse repetition frequency on the thermal burnout effect of a PIN diode limiting-amplifying system. Based on the study of the single-shot microwave pulse thermal burnout effect and by introducing a new assumption that the heat dissipation of the electric field energy and the nonequilibrium carrier energy during the microwave pulse intervals can be neglected, the theoretical thermal burnout model in our previous study is extended to be suitable for repetitive microwave pulses. The theoretical relationship among the pulse number, the pulse repetition frequency, the pulse width and the thermal burnout power threshold is obtained by theoretical derivation. Because the assumptions are introduced, the theoretical relationship requires that both the whole length of a repetitive microwave pulse and the pulse width in a cycle of a repetitive microwave pulse should be between 10 ns and 10 μs. The results obtained by the theoretical relationship are in good agreement with the simulation results obtained by our self-designed device-circuit joint simulator, which verifies the correctness of the theoretical analyses, modeling and derivation. By fitting at least two sets of simulation or experimental data, the theoretical relationship can be used to predict the thermal burnout power thresholds of PIN diode limiting-amplifying systems under microwave pulse injections with different pulse parameters. It can greatly reduce the simulation or experimental costs and could be helpful for the design of a radio frequency receiver.     

两段式双稳半导体激光器下跳阈值点的确定

对Ｋｕｚｎｅｔｓｏｖ采用的速率方程加以修正，考虑了俄歇效应的影响，我们流子寿命不再作为常数处理，而写成载流子浓度的函数。由此导出了两段式双稳半导体激光器下跳阈值点载流子浓度所满足的隐函数解析表达式。通过该解析表达式确定出了器件存在双稳的必要条件。进而讨论了俄歇复合系数、吸收区偏置电流和长度等对双稳特性的影响。     

Experimental characterization of the continuous switching regime in floating-body PD SOI MOSFETs

The floating body configuration in partially depleted (PD) SOI MOSFETs gives rise to the switch-on and switch-off transients of the drain current, that can strongly affect the performance of PD SOI circuits. In this work we present an experimental characterization of the impact of those transients on the current delivered under continuous switching operation. The on state current shows a frequency dependent behavior that changes with the bias region. For voltages below the kink where impact ionization is negligible, the current decreases increasing frequency, while for voltages above the kink, the current increases increasing frequency. Thus, circuit instabilities arise at low frequencies. At high frequencies, the transients vanish and the current capability of these devices, particularly in the kink region, can be fully exploited. However, the off state leakage current must also be taken into account.     

声光调Q DPL中衍射效率对激光输出特性的影响

对二极管泵浦固体激光器（DPL）声光调Q过程进行分析,得出了在一定的泵浦速率和重复率下,衍射效率对输出特性的影响。以四能级系统为例,通过对速率方程的数值求解,得到衍射效率与峰值功率、单脉冲能量、脉冲宽度、平均功率等主要输出参数的关系;得出衍射效率与泵浦速率和重复率相匹配时,才能充分利用上能级反转粒子数,而刚好满足匹配条件的衍射效率是可取到的最小值。实验结果与理论分析一致。     

Control of Stokes pulse duration in stimulated Raman scattering

The generation of long Stokes pulses by stimulated Raman scattering, which is made efficient by a short seed pulse at the Stokes frequency, is demonstrated both in experiments and in simulations for pump powers below the threshold power for unseeded scattering. It is observed that a second seed pulse with appropriate phase and intensity can extend, switch-off or briefly interrupt the Stokes pulse