Demonstration of a 100mJ OPO/OPA for future lidar applications and LIDT testing of optical components for MERLIN

In the field of atmospheric research, LIDAR is a powerful technology that can measure gas or aerosol concentrations, wind speed or temperature profiles remotely. To conduct such measurements globally, spaceborne systems are advantageous. Pulse energies in the 100 mJ range are required to achieve highly accurate, longitudinal resolved measurements. Measuring concentrations of specific gases, such as CH₄ or CO₂, requires output wavelengths in the IRB, which can be addressed by optical parametric frequency conversion. An OPO/OPA frequency conversion setup was designed and built as a demonstration module to address the 1.6 μm range. The pump laser is an Nd:YAG-MOPA system, consisting of a stable oscillator and two subsequent Innoslab-based amplifier stages that deliver up to 500 mJ of output pulse energy at 100 Hz repetition frequency. The OPO is inherited from the OPO design for the CH₄ lidar instrument on the French-German climate satellite MERLIN. In order to address the 100 mJ regime, the OPO output beam is amplified in a subsequent multistage OPA. With KTP as nonlinear medium, the OPO/OPA delivered more than 100 mJ of output energy at 1645 nm from 450 mJ of the pump energy and a pump pulse duration of 30 ns. This corresponds to a quantum conversion efficiency of about 25 %. Besides demonstrating optical performance for future lidar systems, this laser will be part of a LIDT test facility, which will be used to qualify optical components especially for the MERLIN mission.