Raman converter for efficient generation of NIR laser radiation

本课题的总体目标是研制一种适用于高脉冲的拉曼变频器。特别是，我们专注于受激拉曼散射（SRS）转换Nd：YAG激光波长，例如1064 nm到波长约为1570至1613 nm的CO2-detection.Current脉冲激光雷达系统的CO2测量的发展是由Koch等人2004年和Gibert等人2006年。他们报告了在2 µm发射波长下使用外差检测系统进行的测试测量。Ismail等人在2006年开发了一种2 µm的直接检测系统。Spiers等人2002年（2 µm，外差检测）和Krainak等人2003年（1.57 µm，直接检测）描述了基于连续波激光器的系统。Bufton等人（1983）和Sugimoto等人（1993）描述了早期方法。所提到的系统中没有一个已经证明了所需的准确性。拉曼激光器有望获得所需的高转换效率、光谱特性和光束质量。CO2-DIAL激光发射机的要求汇总见表1。这些要求是IPM、UNIBAS和DLR为计算后向散射信号特性而开发的端到端模拟器的结果（Di Girolamo等人，2004 a/B，Bauer等人，2004，Summa等人，2004，Houweling等人，2003，DLR 2005，IPSL 2005）。该项目将扩展我们以前与德国和俄罗斯的合作，在第一步中，将根据转换效率和高脉冲能量操作来选择和表征合适的拉曼晶体。利用这些晶体，我们将建立拉曼激光器，以在固定频率下产生稳定的窄带激光发射。受激拉曼散射（SRS）允许高能量率从泵浦光束转移到低能量种子光束。这种方法的优点是，光谱和空间特性由种子激光器提供，对泵浦激光器的要求较低。

The general subject of this proposal is the development of a Raman frequency converter (FC) for high pulse. In particular we focus on stimulated Raman scattering (SRS) to convert Nd:YAG-laser wavelengths, e.g. 1064 nm into wavelengths at about 1570 to 1613 nm for CO2-detection.Current developments of pulsed lidar systems for CO2 measurements are described by Koch et al. 2004 and Gibert et al. 2006. They report on test measurements with systems at 2 µm emission wavelength with heterodyne detection. Ismail et al. 2006 developed a 2 µm system with direct detection. Systems based on continuous wave lasers are described by Spiers et al. 2002 (2 µm, heterodyne detection), and Krainak et al. 2003 (1.57 µm, direct detection). Early approaches are described by Bufton et al. 1983 and Sugimoto et al. 1993. None of the systems mentioned has demonstrated the required accuracy yet. Hence the development of new systems is necessary.Raman Lasers are promising to obtain the required high conversion efficiency, spectral properties and beam quality. A summary of requirements for a CO2-DIAL laser transmitter is given in Table 1. These requirements are the result from end-to-end simulators developed at IPM, UNIBAS and DLR to calculate the backscattered signal properties (Di Girolamo at al. 2004a/b, Bauer et al. 2004, Summa et al. 2004, Houweling et al. 2003, DLR 2005, IPSL 2005).The project will extend our previous German Russian cooperation, where a large variety of new nonlinear crystals have been produced and checked for SRS.In a first step selection and characterization of suitable Raman crystals will be made with respect to conversion efficiency and high pulse energy operation. With these crystals Raman lasers will be built up to create stable narrow-band laser emission at fixed frequencies.In parallel, a second promising method will be investigated. Stimulated Raman scattering (SRS) allows the transfer of high energy rates from a pump beam into a low energy seed beam. This method has the advantage that the spectral and spatial properties are given by the seed laser and the requirements for the pump laser are lower.