Excitation efficiency of working transitions in copper-vapor lasers

The conditions under which the influence of the discharge circuitry inductance on the efficiency of pulsed-periodic copper-vapor lasers is weak are determined. It is shown that for efficient pumping of the lasing transitions of Cu atom in these lasers it is advisable to form an excitation pulse having steep edges of the voltage applied to the discharge tube with the duration spanning the pumping period and termination of the lasing process providing, at the same time, the conditions for aperiodic behavior of the discharge during the excitation pulse. Such a pumping pulse can be formed due to a partial discharge of the storage capacitor in the laser discharge circuit. It is also shown that under such conditions of excitation the efficiency of copper-vapor laser (CVL) with respect to the energy pumped into the active element can reach 10%.     

4.7-W, 255-nm source based on second-harmonic generation of a copper-vapor laser in cesium lithium borate

We have generated 4.7 W of UV (255-nm) radiation with wall plug efficiency of 0.12% by frequency doubling the green (511-nm) output of a kinetically enhanced medium-scale copper-vapor laser (CVL) in cesium lithium borate (CLBO). Frequency doubling in beta -barium borate produced 3.9 W of UV radiation with wall plug efficiency of 0.1%. We found that conversion was better with CLBO because of the reduced constraints on CVL beam quality, less UV absorption, and smaller UV walk-off.     

Investigation of a copper-vapor laser pumped by trains of damped sine pulses

A copper-vapor laser the lasing medium of which is pumped by damped sine voltage pulses is studied experimentally. It is shown that this laser can operate at megahertz lasing pulse repetition rates. Each current pulse in a train of damped sine excitation pulses generates a lasing pulse. The time between lasing pulses is no more than 224 ns, which corresponds to a lasing pulse repetition rate of more than 4.5 MHz. According to estimates, the use of the megahertz sine voltage to excite the copper-vapor laser may raise the specific power of laser radiation by at least an order of magnitude at an efficiency of ≈15%.     

铜蒸汽激光器(CVL)的光脉冲改善及其特性研究

本文通过分析铜蒸汽激光器的工作原理,改善了CVL光脉冲形状并缩短了光脉冲宽度,测量了CVL光脉冲的晃动并证实CVL光脉冲晃动主要由闸流管引起.     

Temporal dynamics of high repetition rate pulsed single longitudinal mode dye laser

Theoretical and experimental studies of temporal dynamics of grazing incidence grating (GIG) cavity, single-mode dye laser pumped by high repetition rate copper vapour laser (CVL) are presented. Spectral chirp of the dye laser as they evolve in the cavity due to transient phase dynamics of the amplifier gain medium is studied. Effect of grating efficiency, focal spot size, pump power and other cavity parameters on the temporal behaviour of narrow band dye laser such as build-up time, pulse shape and pulse width is studied using the four level dye laser rate equation and photon evolution equation. These results are compared with experimental observations of GIG single-mode dye laser cavity. The effect of pulse stretching of CVL pump pulse on the temporal dynamics of the dye laser is studied.     

Study of gain dynamics and temporal jitter effects in copper vapor laser oscillator-amplifier chain

Effect of temporal jitter on the performance of copper vapor laser (CVL) master oscillator power amplifier (MOPA) chain using Monte-Carlo techniques was studied. The MOPA chain comprised an oscillator and five amplification stages. Amplification of CVL signal in each amplifier stage was modeled using rate equation based optical model. The effect of temporal jitter on the pulse energy stability in CVL MOPA chain was estimated for various jitter values. Our studies show that the pulse energy spread and the pulse energy instability increases with increase in jitter which in turn depends on the gain pulse width and the jitter considered. Pulse to pulse gain variation in CVL MOPA chain was studied along with temporal jitter. The acceptable tolerance limit on temporal jitter is ±4 ns for a pulse energy stability of 5% of CVL MOPA chain.     

Method of two-pulse frequency regulation of copper-vapor laser parameters

A method for a wide-range control of the laser action parameters of a metal-vapor laser on self-limited transitions without violation of the heating regime is described. The method is based on the formation of an additional control pulse with each of the excitation pulses without laser action, and the regulation is realized by variation of the delay between the pulses. The method was tested with a copper-vapor laser. It is shown that the control of the lasing parameters is realized by changing the prepulse population of the metastable level of the active medium.     

铜蒸气激光器计算机辅助设计

在已有的各种输出功率、激励条件参数和实际模拟程序基础上,对铜蒸气激光器计算机辅助设计进行改进,获得了适合于宽广参数条件下的模拟程序及实用曲线组。可在一定的激光输出功率条件下确定器件的激活体积;当口径选定后,可得铜蒸气激光器对应的电功率输入密度、激励电场、最佳重复频率和放电管壁温度值。     

Operational efficiency increase in copper vapor laser due to the replacement of vacuum jacket Brewster windows with flat windows

The vacuum integrity of the discharge tube of a copper vapor laser (CVL) is normally protected by Brewster angled windows. In an attempt to increase the operating efficiency of the CVL, flat windows were used to replace the Brewster windows. Experimental data confirm that the overall efficiency of the CVL does increase when such windows are used. The experimental results are discussed in terms of a computer model found in the literature. The cause of the efficiency increase appears due to a double optical cavity set up by the flat windows. However, the variation of the efficiency due to changes in the pulse repetition frequency (PRF) and buffer gas pressure are less well understood.     

铜蒸气激光器计算机辅助设计

 在已有的各种输出功率、激励条件参数和实际模拟程序基础上,对铜蒸气激光器计算机辅助设计进行改进,获得了适合于宽广参数条件下的模拟程序及实用曲线组。可在一定的激光输出功率条件下确定器件的激活体积;当口径选定后,可得铜蒸气激光器对应的电功率输入密度、激励电场、最佳重复频率和放电管壁温度值。     

Modulation enhancement of a laser diode in an external cavity

The influence of Zn-atom additive on ‘pure’ copper vapor laser output characteristics is studied. The laser pulse width, energy and power are found to increase under the diffusion of zinc atoms from a zinc-containing reservoir into the discharge of the copper-vapor laser at temperatures above 500°C. Additional absorption experiments and calculations are consistent with the conclusion that not only optical resonant pumping by the 213.9-nm Zn I line, but also other processes, should be taken into account to explain the effects of additive influence.     

Studies on a Laser Driven Photoemissive High-Brightness Electron Source and Novel Photocathodes

A laser driven photoemissive high-brightness electron source at Peking University is reported.Through a DC accelerating gap of 100kV voltage,the device is capable of delivering high-brightness electron beam of 35—100ps pulse duration when irradiated with a mode-locked YAG laser.The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON.The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given.The proposed laser driven superconducting RF gun is also discussed.     

An experimental study and theoretical analysis of the mode characteristics of a narrow line-width,pulsed dye laser oscillator at different pump powers

This paper presents an experimental study and theoretical analysis on the effect of pump power on the divergence, pointing, line-width and wavelength stability of a narrow line-width, high repetition rate dye laser oscillator. The dye laser oscillator, based on the hybrid multiple-prism grazing-incidence grating cavity, was pumped by copper vapor laser (CVL). The dye laser mode characteristics were studied at CVL average pump powers of 2, 4 and 8 W. The single pulse dye laser divergence/pointing stability was studied by far-field intensity distributions. The line-width and wavelength stability were studied using a high resolution wave-meter. The experimental results were theoretically analyzed in terms of dye laser mode structure drift induced by beam pointing instability, beam divergence and thermally induced optical path length fluctuation. A comprehensive theoretical treatment on pointing stability of dye laser beam and its influence in the dye laser wavelength stability is presented. The theoretical and experimental trends were found to be in good agreement.     

高功率脉冲染料激光放大器物理设计

从理论研究出发,用激光增益理论得到了在平衡状态下忽略染料分子激发态吸收时,高功率脉冲梁料激光放大器物理设计的简单方法,同时以铜蒸气激光器双侧抽运的平均输出功率52.5W的脉冲染料激光放大器为例,对其物理尺寸进行了模拟设计。     

530-mW 7-kHz cerium LiCAF laser pumped by the sum-frequency-mixed output of a copper-vapor laser

We report, for what we believe to be the first time, a Ce:LiCAF laser pumped by ultraviolet radiation obtained by sum-frequency mixing of the green and the yellow output from a copper-vapor laser. The 7-kHz pulse repetition frequency free-lasing Ce:LiCAF laser yielded a maximum output power of 530 mW, with a slope efficiency of 32%, from a pump power of 1.9 W. With a single prism tunability from 280.5 to 316 nm was achieved.     

超短电子脉冲在聚焦强激光场中的三维有质动力散射

采用三维测试粒子模拟(test-padicle simulation)的方法，研究了聚焦的飞秒脉冲强激光与超短电子束进行有质动力的散射过程.详细讨论了超短电子束经过不同激光延迟下有质动力散射的空间分布特征和能谱特征.提出了通过测量电子束的空间分布和能谱分布实现对超短脉冲电子束的脉冲宽度测量的方法. 关键词： 有质动力散射 聚焦的飞激光 飞秒电子束     

一维氦原子非依次电离的经典模拟

利用经典系综理论研究了强超短激光脉冲作用下的（一维）氦原子的非依次电离过程．通过对先后电离的两个电子的平均库仑势能和距核的平均距离的动力学模拟发现：在脉冲长度不变的条件下,长波长和高强度的超短激光脉冲更有助于非依次电离的发生． 关键词：     

Generator on the basis of reversely switched dynistors forming pump pulses for a copper-vapor laser

A generator designed on the basis of reversely switched dynistors and forming pump pulses for a coppervapor laser is described. The operation of the circuit is considered in detail. Its main components are a low-voltage high-current switch operating on the basis of a reversely switched dynistor (RSD), a step-up pulse transformer, and a system for magnetic compression of pulses. It is shown that a RSD makes it possible to increase the efficiency and decrease the dimensions of the generator in comparison with thyristor systems. Pulses of electric current through the active element of a copper-vapor laser with a 40-ns leading edge and a repetition rate of 8 kHz are formed. Laser radiation with an output power of 2 W is obtained.     

Fast etching and metallization of SiC ceramics with copper-vapor-laser radiation

The etching of polycrystalline SiC is studied with the help of radiation of a copper-vapor laser either in air or under the layer of a liquid (H₂O, DMSO). The etching rate in air is as high as 0.24 m/pulse, in DMSO 0.07 gm/pulse at an energy density of 16 J/cm². The etched surface is characterized with Scanning Electron Microscopy (SEM) and X-ray diffractometry. Etching of SiC ceramics in air revealed the partial amorphization of SiC and the formation of microcrystals of elementary Si with an average size of 300 Å. The etched surface of SiC ceramics takes on the ability to reduce Cu from a corresponding electroless plating solution. The adherence of the deposit is as high as 30 N/mm² and is a function of the scanning velocity of the laser beam.     

激光等离子体相互作用的数值模拟

 基于激光等离子体相互作用的复杂物理过程的数学模型，采用PIC方法分别研究了P极化和S极化非均匀短脉冲强激光入射均匀分布的稠密等离子体时引起的空泡、成丝等物理现象。模拟了激光脉冲在真空中的3维传播形貌。由3维密度分布图发现：激光产生的巨大的有质动力向两侧推动粒子，形成等离子体密度通道；当激光脉冲入射等离子体区域后，纵向加速的电子速度峰值出现在电流峰值处。