快速光闸

一种开关时间为5微微秒——比最好的 克尔盒商品快1,000倍-——的光闸已由美帝贝耳电话实验室研制成功。     

微微秒克尔光闸原理及应用

微微秒克尔盒光闸开关首先由Duquay和Hansen研制成功。这一装置具有微微秒时间分辨率,广泛应用于微微秒过程的测量上,对于具有微微秒时间尺度的快速物理过程的研究,提供一有力的工具。本文就超快速微微秒克尔光闸的原理、优点和装置的时间分辨率极限,做了详细的评论;并且对于光闸的几种改进措施,例如,阶梯技术,微微秒取样示波器,多通道取样探测器列阵等方面,都做了评述。为了说明清楚起见,文中多次列举实例加以阐述。光闸技术是微微秒光谱学中三大测量技术之一。本文较全面介绍了超快速微微秒光闸技术及其应用的可能性。     

同步泵浦可调谐染料激光器输出特性的研究

用微微秒Kerr光闸测定脉冲宽度的方法,研究了同步泵浦可调谐染料激光器的输出脉冲宽度以及输出能量和激光器的腔长匹配等因素的依赖关系。 被研究的是采用被动锁模Nd:YAG激光器TEM_(oo)模脉冲列倍频光同步泵浦若丹明6G染料激光器。锁模Nd:YAG激光器输出的脉冲列之单脉冲能量为1毫焦耳,脉宽为40微微秒(用微微秒Kerr光闸测定),经KDP倍频,倍频效率为40％。染料激光器由曲率半径3米的全反射镜、反射率为75～80％的平面输出镜、染料池和ZF_560°角棱镜组成。染料池厚5毫米,充以浓度为1×10~(-4)克分子的若丹明乙醇溶液,按布儒斯特角放置。转动全反射镜进行调谐。     

新型晶体β-BaB_2O_4的超短光脉冲倍频

本文分析了群速度失配,脉冲线宽对超短光脉冲倍频的影响。用光栅取样,克尔光闸,硅靶摄象系统组成的微微秒脉宽测量装置测量了新型晶体β-BaB_2O_4倍频Nd~(3+):YAG锁模光脉冲的谐波脉宽和倍频效率,并与ADP,LN晶体相应数据作了比较。实测数据和预计结果基本一致。实验表明β-BaB_2O_4晶体是一种优异的超短光脉冲倍频材料。     

超高速硅开关

能够产生微微秒光脉冲的锁模振荡器进展很快,现在已经得到了稳定性和重复性很好的微微秒脉冲(功率稳定度±3％)。随着微微秒激光器的发展,现在正在研制能产生与这种光脉冲同步的各种超高速电脉冲开关元件。以前常用激光触发火花隙做开关元件。最近则研制并应用了触发管、雪崩晶体管和介质开关等。激光触发火花隙和触发管     

微微秒克尔光闸

微微秒光闸是研究在微微秒时间范围内发生的超快物理过程动力学的有力工具,它是基于强的超短激光脉冲与克尔介质相互作用,产生非线性极化的原理做成的。强的线偏振光脉冲,可使克尔介质极化率主轴平行于光场E的方向,形成类似于单轴晶体的双折射性质,通称交流光克尔效应。把装有克尔介质的盒,放在两个正交放置的偏振器中间,超短光脉冲线偏振方向与起偏器和检偏器分别成45°角。当无开关脉冲存在时,光闸对于讯号光脉冲透过为零,当开关脉冲存在     

激光器中产生长度可变的亚毫微秒脉冲

本文叙述Q突变激光器输出脉冲的改进了的整形系统。采用这个系统,已经产生半峰值宽度小于250微微秒的光脉冲。由于采用了附加光路,使最初的Q开关和最终成形脉冲之间的峰值强度只有较小程度的降低。激光触发火花隙被用作产生上升时间小于180微微秒的控制电脉冲。本文叙述光孔径为5毫米和电上升时间为74微微秒的普克尔盒的设计。     

几种毫微秒脉冲产生的方法

近代无线电技术、核物理以及其他一些科学技术领域中,很广泛地应用了毫微秒脉冲.例如:高速数字电子计算机、高分辨率的雷达、精密时间的测量、二极管开关时间的测量等,脉冲都须从微秒过渡到毫微秒数量级.毫微秒脉冲的频谱伸至数千兆赫,已达微波范围.因此,有些在微秒级脉冲电路中可以忽略的参数,在毫微秒脉冲电路中却成为有决定性的因素了.原有的微秒脉冲电路加以改进后,一般只能获得小电流,上升时间为10～20毫微秒的脉冲,显然是不能满足要     

亚微微秒锁模光脉冲用于光导纤维的研究

亚微微秒锁模光脉冲和非线性相关测量相结合,开辟了一个精密测量的新技术。将它用于光导纤维的研究,得到15微米空间分辨率的后向散射及2.5微微秒/米的光色散。     

用双光子光电导探测器测量微微秒光脉冲

已研制成了能够测量锁模钕玻璃激光器的微微秒光脉冲宽度的光探测器。探测器由7片在空间彼此分开的CdS0.5Se.5晶体构成。当用1.06微米光照射时,CdS0.5Se0.5晶体显示出双光子电导性。使7通道峰值检波器和显示系统与双光子探测器相连,即可用来记录单个微微秒脉冲。用在激光上,由所测的相关曲线给出对比度为2.8:1的10微微秒的脉冲。     

基于半导体光放大器的新型全光逻辑与门

为了实现基于半导体光放大器的全光逻辑与门,采用了在半导体光放大器构成的马赫-曾德尔干涉仪的基础上,注入外部连续光的方法。以半导体光放大器速率方程为基础,对设计方案进行了理论分析和仿真验证,取得了不同重复周期、不同脉冲宽度的光脉冲序列经过全光逻辑与门操作后的输出数据。结果表明,该方案能对传输速率为10Gbit/s或以下的信号进行正确与运算,同时,外光注入可以有效提高半导体光放大器信号处理速度。这一结果对基于半导体光放大器的全光逻辑的设计是有帮助的。     

Dynamic internal testing of CMOS circuits using hot luminescence

Subnanosecond pulses of hot electron luminescence are shown to be generated coincident with logic state switching of individual devices in CMOS circuits. These pulses are used to directly observe 90 ps gate delays in a ring oscillator as well as the logic switching and gate delays of a counter. By use of a detector with both space- and time-resolution, the dynamics of all the gates of the circuit are simultaneously measured. This noninvasive technique can be extended to smaller device size, as well as probing from the backside of the wafer. The optical emission may provide an alternative to electron beam testing for measuring the dynamics of high-speed CMOS circuits     

Picosecond optical sampling

A 10-channel optical-sampling technique has been developed to give oscilloscope displays of picosecond laser pulses in a single shot. Pulses with durations of 10-30 ps and powers ranging down to ∼ 1 W have been displayed with this technique. An ultrafast optical gate and a 10-channel multibeam splitter are used to cut out in one laser shot ten samples centered at 4.1-ps intervals from the leading to the lagging edge of the pulse. The ten optical samples are then spaced out at 10-ns intervals by means of an optical fiber array, detected by a fast photomultiplier, and displayed on a real-time oscilloscope. The envelope of the sample pulses represents a display of the laser pulse. This technique could substitute for picosecond streak cameras in certain applications.     

Optical pulse compression in 1.5 μm wavelength region usinglarge-positive-dispersion fibre and grating pair

Optical pulse compression at 1.5 μm has been conducted. 20 ps (FWHM) optical pulses from a Tl:KCl-colour-centre laser were compressed into pedestal-free 1.2 ps pulses using a large-positive-dispersion fibre and a grating pair. In addition, 280 fs pulses were obtained from the resultant 1.2 ps through the soliton compression effect in a negative-dispersion fibre     

Simple picosecond pulse generation scheme for injection lasers

A simple scheme is reported for generating picosecond optical pulses from injection lasers based on short electrical pulse excitation. An integrated step recovery diode impulse-train generator (`comb? generator) which gives 50 ps 25 V electrical pulses at 200 to 500 MHz rates is used to drive the injection lasers. Optical pulses as short as 40 ps are generated by the corresponding electrical drive pulses.     

14 Gbit/s optical signal encoding for ? = 1.32 ?m with double pulse drive of a Ti:LiNbO3 waveguide modulator

Optical pulses with time separation corresponding to bit rates of ~ 14 Gbit/s (NRZ) have been produced at ? = 1.32 ?m with a Ti: LiNbO3 broadband travelling-wave directional coupler modulator driven by closely spaced, narrow electrical drive pulses. Resolvable optical pulses with as little as 100 ps separation have been generated.     

Optical Pulse Characterization in a Regeneratively Mode-Locked Fiber Ring Laser

We characterize optical pulses generated using a regeneratively mode-locked fiber ring laser (RML-FRL) in terms of pulsewidth and pulse noise. These results are then compared with pulses obtained from a conventional active harmonically mode-locked fiber ring laser (ML-FRL). We establish that under the same operating conditions, optical pulses from the RML-FRL are shorter by more than 8% and exhibit a 15-dB improvement in phase noise compared to those obtained from ML-FRL. In addition, over a frequency range 100 Hz–100 kHz, a reduced amplitude noise of 0.3% and rms timing jitter of 0.26 ps have been estimated for the RML-FRL pulses compared to 0.6% and 0.38 ps, respectively, for the pulses in the ML-FRL. Relaxation oscillations are also completely eliminated in the RML-FRL.     

131 ps optical modulation in semiconductor multiple quantum wells (MQW's)

A new optical modulator has been fabricated which uses the recently discovered electroabsorption effect in MQW's. Optical pulses 131 ps long were generated when the device was driven with 122 ps electrical pulses. The input-output characteristics of the device show that it has low insertion loss with reasonable modulation depth and drive voltage.     

Picosecond pulses (2 ps) from hybrid mode-locked AlGaAs QW lasers with integrated active waveguide cavities

Single ultrashort optical pulses (2 ps with 17.6 GHz repetition rate) have been generated with hybrid mode-locked monolithic GaAs/AlGaAs lasers at lambda =856 nm. Instead of an external cavity, long active waveguides were used as resonators with a roundtrip frequency of 5.9 GHz. Increasing the pump current in the waveguide far above transparency led to 10 ps pulses with a high peak power of 110 mW.<>