Raman converter for efficient generation of NIR laser radiation

• Applicants: Professor Dr. Hans J. Eichler; Dr. Andreas Fix
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2008 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 73561751

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.

• DFG Programme: Research Grants
• Participating Person: Dr. Thomas Riesbeck