Continuous-wave mid-infrared laser sources based on difference frequency generation

We report on recent developments of widely tunable, continuous-wave (CW) laser sources based on difference-frequency generation (DFG) in nonlinear optical materials. The state-of-the-art of CW DFG technology will be reviewed. Applications of the DFG-based laser source to high-resolution molecular spectroscopy and trace gas detection will be presented. New development trends of DFG will be discussed. To cite this article: W. Chen et al., C. R. Physique 8 (2007).     

Difference frequency generation laser based spectrometers

Tunable mid‐infrared laser sources are the key to precision optical trace gas detection. Difference‐frequency generation (DFG) based laser sources are among a few practical laser sources that have demonstrated ultra‐high detection sensitivities during real‐world applications when combined with appropriate signal enhancing and noise reduction spectroscopic techniques. This article will discuss the technical approaches, illustrate application examples of DFG sources, and offer perspectives to competing technologies.     

Widely-tunable mid-infrared frequency comb source based on difference frequency generation

We report on a mid-IR frequency comb source of unprecedented tunability covering the entire 3-10 μm molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman-shifted solitons generated in a highly nonlinear suspended-core fiber with the same source. Average powers up to 1.5 mW were achieved at the 4.7 μm wavelength.     

差频产生中红外飞秒激光脉冲的研究进展

中红外飞秒激光脉冲在科研、民用及军事等方面都有重要的应用,文章回顾了产生中红外飞秒激光脉冲的几种方法,结合差频法产生中红外飞秒脉冲的优点,详细介绍了差频产生中红外飞秒激光脉冲的研究进展,最后进行了总结和展望.     

4.5MW小型化全固态腔倒空飞秒掺钛蓝宝石激光器

研制了国内首台腔倒空克尔透镜自锁模掺钛蓝宝石激光器,该激光采用二极管抽运的全固态连续波532nm激光抽运.在5.4W的抽运功率下,获得了峰值功率大于4.5MW、脉宽小于18fs的稳定锁模脉冲,其重复频率可低至20kHz,所占尺寸约53.5cm×20.5cm.据知,此结果是迄今重复率最低、结构最紧凑的声光腔倒空飞秒激光器件 关键词： 掺钛蓝宝石 腔倒空 飞秒脉冲 克尔透镜锁模     

Ti:Sapphire Pumped 10 at-% Yb:YAG Thin Chip with 320 mW CW laser output of 1.053 μm

We have developed an efficient room-temperature 10 at-% Yb:YAG thin chip (7 mm×7 mm×1 mm) laser operating at 1.053 μm pumped by a Ti-sapphire laser operating at 940 nm. 320 mW of output power was obtained for an absorbed pump power of 791 mW. The slope efficiency was 54%, and extrapolated threshold power was 203 mW.     

无展宽器的高重复率钛宝石啁啾飞秒脉冲再生放大器的研究

通过优化放大腔结构参数和采用高光束质量的泵浦激光,依靠放大器腔内各个元件的色散展宽种子脉冲, 用钛宝石作为增益介质, 在低泵浦能量下, 实现了高光束质量,高稳定的中等能量的高重复率飞秒脉冲再生放大. 将钛宝石晶体离焦放置,有效的避免了光学损伤. 在1.1 mJ的绿光泵浦下, 获得了2 ps, 120 μJ, 重复频率为1 KHz, 光谱带宽7.8 nm的放大脉冲, 用石英棱镜对压缩可得到130 fs的激光脉冲.     

差频可调谐太赫兹技术的新进展

太赫兹技术在最近30年来得到快速发展, 并在医学、生物、农业、材料、安检、通信、天文等领域得到广泛应用. 从太赫兹源的频谱特性可以分为窄带(单频)太赫兹源和宽带太赫兹源. 从频谱技术方面来说, 相干的宽带和窄带太赫兹谱是一种互补性关系, 具有各自的技术特点和应用范围. 宽带太赫兹谱可以用于快速获取较宽频谱范围的分子振转谱, 实现混合特征谱的快速检测或成像. 窄带太赫兹源具有很好的光谱灵敏度和分辨率, 适用于太赫兹抽运-探测、分子振转能级谱精细结构分辨 以及太赫兹远程探测和成像. 因此研制具有可调谐的高峰值功率的窄带太赫兹源是适用于探测和识别分子振转能级指纹谱的应用需求, 而差频技术是获得高功率和宽调谐窄带太赫兹源最重要的技术之一. 为了突出该技术的最新进展, 本综述引证论文仅仅限于近5 年来基于差频技术产生太赫兹波的研究进展, 分为光学激光差频源和量子级联激光器差频源两大部分. 对于光学激光差频源, 分别对目前文献报道的各种双波长差频源和太赫兹产生用的非线性晶体进行分类介绍, 并给出所采用的技术和实验结果; 对于量子级联激光器差频源, 分别介绍了量子级联激光器中的差频产生技术和波长调谐技术的最新进展. 量子级联激光器差频太赫兹源是目前实现量子级联激光器在太赫兹波段室温运转的惟一技术, 是实现小型化、窄带宽调谐和室温运转太赫兹源的新发展领域, 值得关注.     

Membrane device for holding biomolecule samples for terahertz spectroscopy

A device for holding biomolecule samples on a membrane allows scanning using terahertz frequency waves. Such scanning has previously been difficult due to the strong attenuation of terahertz frequency waves by water. Several types of biomolecules were scanned using terahertz time domain spectroscopy (TDS), and the data showed clear differences in transmittance among the samples. This membrane device is a promising aid for research on biomolecules using terahertz waves.     

Generation of Stable Near－infrared and Violet Femtosecond Pulses from a Self－mode－locked Ti：Sapphire Laser

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基于光纤激光器的中红外差频多波长激光产生

针对由YDFL和EDFL作为基频光源的QPM-DFG激光系统,利用PPMgLN晶体的色散关系及其温度特性,有效拓宽了QPM波长接受带宽.模拟结果表明,当采用1550和1060 nm波段的EDFL和YDFL分别作为DFG的信号和抽运光源时,对于相同的中红外波段,满足QPM条件所允许的抽运光波长变化范围远大于信号光波长变化范围.当固定信号光波长为1560 nm时,对于给定的晶体温度,1060 nm波段抽运光的QPM接受带宽超过17 nm,对应于中红外差频光带宽可约180 nm.采用多波长YDFL作为抽运源,单 关键词： 差频产生 准相位匹配 多波长中红外 光纤激光器     

脉冲钛宝石激光器的双波长运转

报道了脉冲钛宝石激光器的双波长可调谐运转，双汉总能量达到４１．８ｍＪ，调谐范围大于１００ｎｍ并且研究了双波长运转时的竞争效应，增益损耗的影响，时域特性等。     

低功率泵浦Ti：Al2O3自锁模激光器

本文报道了低功率泵浦的Ｔｉ：Ａｌ２Ｏ３激光器实现了稳定的自锁模运转，锁模脉冲宽度为１８０ｆｓ。分析了激光器的结构及工作特性。     

低重复频率激光放大系统中再生腔的结构性能及实验研究

本文从高斯光束的理论出发,充分考虑到放大介质的克尔非线性效应的影响,引入了一个与之相应的非线性传输矩阵,对低重复率的钛宝石激光放大系统中的再生腔的结构性能进行了分析研究。并以此为根据,在实验上设计了激光放大再生腔,实现了TEM_oo模激光振荡,并得到了腔倒空脉冲。     

Compact tunable mid-infrared laser source by difference frequency generation of two diode-lasers

Two continuous-wave single mode diode-lasers (Hitachi HL 7851G and Toshiba TOLD 9150) are applied as signal and pump sources for difference frequency generation (DFG) in an AgGaS2 crystal with a length of 30 mm. For 90° type I phase matching tunable mid-infrared laser radiation around 5 µm is obtained with an output power of up toP _DFG = 0.2 µW while the diode lasers are operated with powers of 30 and 50 mW at the center wavelengths 682 and 791 nm, respectively. The performance of the diode-laser-DFG system is shown as the absorption spectrum of CO for the P(28) rotational line around 2023 cm^–1 is probed in a 10cm long cell and in the exhaust of an engine.This research was supported by the Technologiestiftung Schleswig-Holstein under contract 94-35i.     

提高灯泵钛宝石激光器效率的技术途径

介绍了几种提高灯泵钛宝石激光器效率的技术途径,包括脉冲氙灯参数的选取,放电电流的优化,泵浦腔几何结构的设计,光学谐振腔参数的优化和输出耦合镜最佳透过率的选取。通过以上各项技术的完善,激光效率得到明显提高,从０．５％到２％［１］。     

Recent Developments in Modulation Spectroscopy for Trace Gas Detection Using Tunable Diode Lasers

Abstract

The need for higher sensitive detection technology for trace gas samples, either in the laboratory setup or in the atmospheric remote sensing has been a goal for several decades. The development of the tunable diode laser has propelled the progress of trace detection technology, and modulation technology enables the improvement of the detection sensitivity. As a result, the detection of 10^?7 or 10^?8 absorbance is possible for some applications, and modulation technology has been applied to the ultraviolet as well as mid-infra red wavelength range. In this review, recent progress of tunable diode lasers and diode laser-based modulation technologies are presented. Wavelength modulation, frequency modulation, and two-tone frequency modulation techniques are mainly described along with the actual application of the techniques. In addition, the state-of-the-art of diode laser development which can be adopted for the trace detection is presented.     

A cw AgGaS2 difference frequency spectrometer with diode lasers as pump sources

2 and two diode lasers as pump sources and experiments with this setup are presented. In contrast to the majority of known applications of the difference frequency mixing with solid state or gas lasers, we apply two single mode diode lasers with emission wavelengths of 690 nm and 805 nm, respectively. By fixing the emission wavelength of one diode laser and tuning the wavelength of the second laser, by changing temperature or excitation current, we can cover typically 0.87 cm^-1 (FWHM) in good agreement with recently published data and theory. With an input power of 20 mW and 6 mW we achieved an output power in the nW-range. To demonstrate the capabilities of the spectrometer we scanned CO and OCS absorption lines near 2107 cm^-1. From these experiments we deduce an overall signal-to-noise ratio of 1000:1 and a spectral resolution better than 30 MHz. With such parameters a trace gas detection of CO at sub-ppm level will be possible. Received: 19 August 1996/Revised version: 5 November 1996     

预脉冲灯泵钛宝石可调谐激光器

利用预脉冲技术,可减小氙灯放电初始阻抗,使主放电电流脉冲前沿变陡,脉冲包络变窄,峰值变高,泵浦能量集中,有利于灯泵钛宝石激光输出。试验证明,在低能量（４７Ｊ）注入时,电光转换效率提高１８％,输出９５０ｍＪ;在高能量（１１６Ｊ）注入时,效率提高５％,输出能量１８１０ｍＪ。该激光器可调谐范围为６９５～９４０ｎｍ。