Abstract
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 IR-B, 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 methane remote-sensing lidar mission (MERLIN). To address the 100-mJ regime, the OPO output beam is amplified in a subsequent multistage OPA. With potassium titanyl phosphate 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%. In addition to demonstrating optical performance for future lidar systems, this laser will be part of a laser-induced damage thresholds test facility, which will be used to qualify optical components especially for the MERLIN.
Highlights
Methane is one of the most important anthropogenic greenhouse gases in the atmosphere.[1]
A preliminary design of the laser transmitter was developed at Fraunhofer Institute for Laser Technology (ILT) and is currently in the detailed design review phase
The concept is based on an Nd:YAG-MOPA system, consisting of a injection-seeded stable oscillator and a subsequent Innoslab-based amplifier
Summary
Methane is one of the most important anthropogenic greenhouse gases in the atmosphere.[1] Within the scope of a German–French cooperation, methane remote-sensing lidar mission (MERLIN) was initiated, which employs an integrated path differential absorption lidar system.[2] A preliminary design of the laser transmitter was developed at Fraunhofer Institute for Laser Technology (ILT) and is currently in the detailed design review phase. Since the MERLIN mission lasts 3 years, it requires a very stable and robust optomechanical and optical design of the laser transmitter. Optical-parametric oscillator (OPO)/optical-parametric amplifier (OPA) converters can deliver pulse energies up to 50 mJ, while satisfying the other requirements for lidar measurements.[9] Here, an OPO/OPA converter was designed and set up to demonstrate the scalability to the 100 mJ regime. Elsen et al.: Demonstration of a 100-mJ OPO/OPA for future lidar applications and laser-induced damage.
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