Nd: GSAG laser for water vapor detection by LIDAR near 942 nm

摘要

For weather forecast, especially for civil protection from high-impact weather events, measuring the three-dimensional distribution of water vapour by DIAL techniques is a fundamental concern. Especially for development and evaluation of atmospheric models, knowledge of water vapour distribution is important. Suitable wavelengths for a water vapour DIAL are e.g. around 943 nm. This region can be reached with well established technologies such as the optical parametric oscillator (OPO) and the Ti: Sapphire laser. But these systems suffer from low efficiency and complex set-up. In contrast the NdrGSAG laser presented here can be directly pumped with 808 nm laser diodes. This supports the realisation of an efficient and compact laser system. Different oscillator and amplifier setups working at 943 nm were realised. An output energy of > 17 mJ in a 100 ns pulse with 10 Hz repetition rate was demonstrated. In a MOPA system a double pass gain of 1.5 and an output energy of > 18 mJ was achieved. The Nd: GSAG laser oscillator was successfully injection seeded with DFB laser diode from FBH-Berlin. Also the gain cross section in a Nd:GSAG laser crystal from 941-944 nm was measured. The FWHM of the homogeneous line is 2 nm with a peak stimulated emission cross section of 4.0·10~(-20)cm~2 at 942.7 nm.