毫微微秒(10~(-15)秒)激光技术

本文简要评述了毫微微秒激光技术的发展,论述了获得、测量毫微微秒激光脉冲的新机理、新方法及毫微微秒激光技术的新应用。     

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。     

超短光脉冲测量用的条纹照相机

微微秒以及更短的亚微微秒激光脉冲可以以高的时间分辨率研究光和物质相互作用。目前已在物理、化学、生物物理、生物化学、核聚变等研究中被采用。同时,也就迫切要求发展微微秒时间分辨率的新的测量技术。现在,最佳     

锁模FA(II)色心激光器产生的可调谐红外微微秒脉冲

演示同步泵浦FA(II)色心锁模激光器。在氮净化气氛中加长腔长已使脉冲宽度短到75微微秒。脉冲相位延迟与腔长和泵功率的关系是16微微秒·微米-1和0.5微微秒·亳瓦-1。     

170微微秒热电探测器

设计和测试了响应时间不到200微微秒的LiTaO_3热电探测器。探测器元件敷有光谱响应平坦的快速热吸收的黑色涂层,并与-13千兆赫带宽Tektronix S-4取样头在阻抗上匹配。用峰值功率在54千瓦时脉冲为100微微秒的Q开关模锁Nd:YAG激光源测量了在1.06微米时的响应。所测量的上升时间为170±30％微微秒,比元件的50微微秒的时间常数长。     

染料分子微微秒吸收恢复时间的测量

本文介绍了测量染料分子微微秒吸收恢复时间的一种改进型实验装置。利用此装置测量得隐花菁染料分子的吸收恢复时间τ_α为16±3微微秒。由简化的二能级模型推算得隐花菁分子激发高能级的弛豫时间τ为21±4微微秒。     

硅片激光退火后熔融的新进展

硅片上脉冲激光退火实验的新进展使得能够测量时间分辨率为熔点前后30微微秒的反射率，这些进展带来了显而易见的迹象：晶格过热、熔化和蒸发可在20微微秒脉冲内产生。哈佛大学的布隆伯根(N. Bloemberger)等在为第三届微微秒现象专题会议准备的报告中报导了这些结果。     

行波氮激光抽运的短腔染料激光器

描述一台可调谐染料激光器，用300微微秒脉冲的行波氮激光抽运，在短染料腔中获得50微微秒脉宽的脉冲。     

波长可调的大功率微微秒脉冲放大系统

由于微微秒(亚微微秒)脉冲的研究，在光谱领域的时间分辨率迅速提高，在各种各样的应用中，大功率且波长可调的微微秒(亚微微秒)脉冲的重要性增大起来。要求大功率的，通常当然是非线性现象的实验。特别是在采用相干的共振激发的实验中，由于非线性现象跟脉冲面积(光电场与脉冲宽度的 乘积)成正比，所以，脉冲宽度一旦变窄，与脉冲宽度的平方成反比的入射光强度就必须增大。     

高重复频率磷玻璃锁模激光器

高重复频率磷玻璃微微秒激光器已获得运转,重复率达10赫,脉宽24微微秒,谱宽0.84埃,序列能量～6毫焦耳。     

亚毫微秒GaAlAs双异质结激光器

当双异质结连续激光器加上大于阈值的阶跃脉冲时,激光器的光脉冲前沿便产生张驰振荡,振荡频率f_r为:f_r=1/(2π)[1/τ_(ph)τ_s(I/I_(th)-1)-I~2/(4τ_s~2I_(th)~2)]~(1/2)式中I为注入激光器的峰值电流;I_(th)为阈值电流;τ_(ph)为光子寿命;τ_s为载流子自发复合寿命.当I/I_(th)=2,τ_s=2毫微秒,τ_(ph)=1.2微微秒时,f_r=4千兆周;当I/I_(th)更大时,f_r更高.我们用一个峰值电流     

Amplification of a low-power picosecond Nd:YVO/sub 4/ laser by a diode-laser side-pumped grazing-incidence slab amplifier

An optimized diode-laser side-pumped grazing-incidence Nd:YVO/sub 4/ amplifier was used to increase the power of a 50-mW 150-MHz continuous-wave (CW)-pumped mode-locked oscillator up to 6.1 W in single pass, with 22% optical-to-optical efficiency, or up to 8.4 W in double pass, with 30% efficiency. Both beam quality (M/sup 2/<1.4 from TEM/sub 00/ seed pulses) and pulse duration (7.5 ps from 6.9 ps) were preserved. Single- or double-pass small-signal gain greater than 40 dB was achieved. These experimental results have been corroborated by a numerical model analysis of the amplifier.     

Amplification of picosecond 10 µm pulses in multiatmosphere CO2lasers

Picosecond pulses, generated by semiconductor switching (2-40 ps), have been regeneratively amplified to an energy density of ∼1.5 J/cm²in a multiatmosphere CO2laser. The characteristics of the amplified pulses have been investigated as a function of wavelength, pulse duration, and the pressure in the gain medium. Using a high-power pulse compression technique, 10 μm pulses as short as 600 fs have been obtained.     

Electronically tuned synchronously pumped dye laser

We have demonstrated electronically tunable pulses as short as 1.3 ps with a tuning rate of 150 Å/kV using a synchronously pumped rhodamine dye laser. Electronically tunable transform limited pulses of 5 ps duration have also been produced.     

用横向行波泵浦产生超短染料ASE脉冲

用λ=337.1nm、脉宽为700ps的氮激光器作泵浦光源。在横向行波泵浦装置情况下,对Rh6G、RhB和C311三种染料溶液,分别获得45、55和45ps ASE脉冲输出。     

1.5 /spl mu/m GaInNAs semiconductor saturable absorber for passively modelocked solid-state lasers

Fully self-starting and passively modelocking of a 1.5 /spl mu/m solid-state laser with a GaInNAs semiconductor saturable absorber mirror (SESAM) has been demonstrated for the first time. A saturation fluence of 20 /spl mu/J/cm/sup 2/, a modulation depth of 0.39% and a fast temporal decay of 18 ps were measured. These well-suited nonlinear optical SESAM parameters allowed for self-starting and passive modelocking of a diode-pumped Er:Yb:glass laser at 1.534 /spl mu/m with a pulse duration of 5 ps at 61 MHz.     

Picosecond soliton pulse-duration-selectable source based onadiabatic compression in Raman amplifier

Raman amplified 10 ps soliton pulses generated directly from an electroabsorption modulator based source have been adiabatically compressed in a Raman fibre amplifier, giving pulse duration tunable sources of 10-1 ps at 10 GHz and average powers up to 650 mW, dependent on the magnitude of the amplification     

Diode-End-Pumped Passively CW Mode-Locked Nd:YLF Laser by the LT-In$_0.25$Ga$_0.75$As Absorber

We have demonstrated a self-staring passively continuous-wave mode-locked diode end-pumped Nd:YLF laser with a semiconductor saturable absorber mirror of single-quantum-well (In$_0.25$Ga$_0.75$As) grown by metal–organic chemical-vapor deposition technique at low temperature. The saturable absorber was used as nonlinear absorber and output coupler simultaneously. Stable pulse duration of 3 ps has been achieved at the repetition rate of 98 MHz. The average output power was 530 mW at 1053 nm under the incident pump power of 10 W, corresponding to the peak power of 1.8 kW and pulse energy of 5.4 nJ.     

Subnanosecond multi-gigawatt CO2 laser

A semiconductor switching technique has been utilized to produce 30-300 ps variable duration CO₂ laser pulses of 0.5-MW peak power. Eight passes through a 1.2-m long, UV-preionized, 3-atm TE CO₂ amplifier raise the output laser peak power to the 10¹⁰ W level. Sampling the amplifier gain in linear and saturated regimes using CO₂ laser radiation ranging from CW to 30 ps pulse length permits comparison with computer modeling of picosecond CO₂ pulse amplification. The potential for further peak power scaling of picosecond molecular lasers is discussed     

Sub-nanosecond coherent pulse generation at millimetre-wave frequencies

Described is a simple method to produce sub-nanosecond phase coherent pulses with rise times and fall times of at least 80 ps at power levels in excess of 200 mW at 94 GHz. The duration and timing of these pulses are controlled by fast input logic, and pulses as short as 110 ps have been achieved. The technique is easily extended to both higher and lower frequencies, and produces pulses with an infinite extinction ratio suitable for amplification to higher power levels