Picosecond pulses from mode-locked dye lasers

Picosecond pulses have been generated in laser pumped (15 psec) and flashlamp pumped (6 psec) mode-locked dye lasers. Two-photon fluorescence and streak camera measurements are described.     

Direct measurement of pulse broadening in the second harmonic of mode-locked Nd: glass laser

Direct measurement of pulse broadening in the second harmonic of a mode-locked Nd: glass laser has been made using a high-speed streak camera. Recorded pulsewidths varied from 3.8 psec to greater than 15 psec.     

Direct linear measurement of ultrashort light pulses with a picosecond streak camera

The durations of ultra-short (4–7 psec) laser pulses have been directly measured with an image tube streak camera designed for time resolution in the picosecond region. The camera was calibrated with simultaneously recorded two photon fluorescence pulse profiles and it is shown that a time resolution limit of ≈1 psec should be possible with this system.     

Picosecond time-resolved photoluminescence studies of exciton-magnetic polaron complexes in Cd1−xMnxSe

The evolution of magnetic polarons in Cd_1?xMn_xSe was examined using time-resolved photoluminescence spectra of excitons at cryogenic temperatures. Sample with manganese concentration x = 0.05, 0.10 and 0.20 were studied using a streak camera, with a system resolution of 80 psec. The formation of magnetic polarons was observed to have a large effect on the exciton lifetime, and to be strongly dependent on temperature and manganese concentration.     

强场下的Li-like氖复合机制X光激光的数值模拟

论述了隧道电离和阈上电离加热过程。并把此二过程加到一个non-LTE平均原子模型,用此模型来研究强场下光致电离类锂氖复合机制X射线激光。计算结果表明,当驱动激光脉冲为100fs、波长为0.248μm、功率密度为2×10¹⁷Wcm^-2,氖气的密度为10^-3gcm^-3时,类锂氖精细结构跃迁3d_5/2→2p_3/2(λ=98Å)的最大增益系数约为100cm^-1,其维持时间约为1.5ps。     

Picosecond time-resolved luminescence of hydrogenated amorphous silicon-carbon

Photoluminescence decay curves and time-resolved luminescence spectra of amorphous Si_0.15C_0.85 : H films are measure. The decay curves are nearly exponential with a time-constant of about 200 psec at room temperature. The peak of the emission spectrum is shifted from 440 nm immediately after the excitation to 490 nm at 400 psec after the excitation.     

Polymethine IR laser dyes for passive mode-locking of ruby lasers

Several polymethine IR laser dyes, in addition to the well known DDI and cryptocyanine, are found to be suitable for mode-locking of ruby lasers. While with DDI pulses as short as 12 psec are obtained these new mode-lockers generate pulses in the 40 to 100 psec range, presumably due to their longer recovery time of the ground-state absorption.     

Photoisomer generation and absorption relaxation in the mode-locking dye 3,3'-diethyloxadicarbocyanine iodide

A quantum efficiency of ≈ 0.01 for the generation of the photoisomer of DODCI has been obtained. The establishment of equilibrium concentrations for the two forms of the dye in mode-locked rhodamine dye lasers has been confirmed. The measured saturable absorber recovery times of ≈ 200–250 psec are shown to be consistent with an excited state lifetime of ≈ 300 psec, in agreement with fluorescence measurements.     

10 μm detection system with 40 picosecond resolution

A 10 μm detection system with a temporal resolution of ? 40 psec has been used to investigate the output of a multi-atmosphere CO₂ laser. Mode-locking, by means of p-type germanium, has permitted the observation of pulses as short as ? 75 psec.     

Direct observation of the relaxation time of the symmetric molecular CO2-3 vibration of calcite

The relaxation of the internal A_1g-mode of the CO^2-₃ group (? = 1086 cm^-1) is investigated with picosecond pulses. The measured decay times are 4.4 psec and 8.7 psec at 295 K and 90 K, respectively. Our values are in agreement with spontaneous Raman data. Possible relaxation processes are discussed.     

Measurements of exciton absorption with pico-second light pulses produced by a self-phase modulation technique

Time-resolved absorption spectra of the A exciton in CdSe are measured by using pico-second white-light pulses produced by a self-phase modulation technique. The absorption peak of the n = 1 A exciton shifts to the high-energy side due to the high-density effect. The magnitude of the shift reaches a maximum at 20 psec after the pulse excitation, which is considered to indicate that the time constant for the formation of the n = 1 excitons by band-to-band excitation is about 20 psec.     

Pulse propagation through multimode fibres

To evaluate their communication potential, measurements have been made on multimode glass fibres. Detector limited pulses of 180 psec risetime from a Ga-As laser were transmitted through various lengths of fibre. After a 120 m length the risetime was still not greater than 450 psec. Measurements with a mode locked He-Ne laser, done on shorter lengths of fibre, agreed with the above results.     

软X射线皮秒变象管扫描相机

软X射线皮秒变象管扫描相机技术是一种用变象管扫描相机测量X射线脉冲而能达到皮秒时间分辨率和一维微米级空间分辨率的技术。X射线扫描相机是研究伴有X射线辐射的一切高速瞬变过程的极为重要的测量工具。例如在激光核聚变的研究中,加热压缩期间靶球发生内爆过程中高温高密度等离子体的光谱辐射主要为软X射线,对这些软X射线的研究,可以获得有关等离子体的电子温度、电子能量分布、各种不稳定性的形态及这些参量随时间变化的资料。     

Silex-I飞秒激光装置X射线探测系统时间特性北大核心CSCD

在Silex-Ⅰ飞秒激光装置上,利用32fs、800nm的激光辐照平面金靶,产生小于1ps的X射线脉冲,作为δ脉冲X射线源,研究XRD探测器的时间响应特性,并且探索X射线条纹相机时间分辨和分幅相机曝光时间的X射线标定方法。实验给出了XRD探测器的时间响应特性。解决了条纹相机和分幅相机触发晃动问题,给出了条纹相机时间分辨和分幅相机曝光时间的X射线标定方法,初步给出条纹相机时间分辨和分幅相机曝光时间。     

Production of single subnanosecond multi-line 10.6 μm laser pulses by fast optical gating

An electro-optic shutter, activated by a pulse generator switched with a laser triggered spark gap having a risetime of 120 psec, has been used to produce optical pulses of variable duration, as short as 600 psec, from the output of a uv photo-preionized CO₂ laser, which simultaneously oscillates on several rotational transitions.     

一种用于Z箍缩实验的软X射线成像系统

基于塑料闪烁体转换和光学条纹相机的方法建立了一套用于Z箍缩实验中的软X射线条纹图像诊断系统,解决了以往实验中使用的X射线条纹相机易被电磁环境干扰以及相机电极部件易被实验产生的高速粒子损伤的问题.诊断系统的光谱响应范围主要集中在0.2—10 keV,系统的空间分辨率经过理论评估小于120μm,通过标定闪烁体对X射线的时间...     

Time-resolved spectra of spontaneous luminescence from high density electron-hole plasma in CdS

Pico-second time-resolved spectra of the spontaneous luminescence from high density electron-hole plasma in CdS are measured at 4.2 K suppressing the stimulation effect. It is found that after the pulse excitation hot carriers are cooled rapidly for the first 100 psec, and that therafter up to the 400 psec delay time the shape of spectra hardly changes but the spectral width depends on excitation density. Although it seems as if some kind of state like electron-hole liquid is formed, one cannot easily regard that state as the condensed electron-hole drop state.     

门控MCP软X射线皮秒多分幅相机

 介绍了用于等离子体诊断的门控MCP软X射线皮秒多分幅相机结构、工作原理、性能指标、关键技术以及在激光等离子体诊断中获得的典型结果。     

Suppression of fast-ions from a laser-produced plasma

Fast-ion emission occurs when a target is irradiated with single 25 psec pulses from a Nd: YAG/glass laser but is suppressed when the same target is irradiated with a mode-locked pulse train at the same intensity. Possible explanations for this effect are given.     

透射式X射线光阴极的M带平响应设计

获取高时空分辨的M带X射线辐射能流信息是黑腔物理研究的重要内容之一,条纹相机平响应存在谱响应耦合、谱改造元件结构设计等问题。通过对条纹相机和透射式X射线光阴极谱响应特性的研究,提出组合滤片调制法以实现条纹相机M带带通平响应。计算表明,在M带能区内谱灵敏度不平整度仅为2.7%,带通效果良好。