An Nd:YAG-MOPA system consisting of a stable oscillator and two subsequent Innoslab-based amplifier stages has been designed and built as a technology demonstrator for future lidar applications. Overall, the authors demonstrate that it generates more than 500 mJ of pulse energy at a 1064 nm wavelength and 100 Hz pulse repetition frequency at about 30 ns pulse duration in the single longitudinal mode. Seeded with 75 mJ pulses, the second amplifier stage achieved an optical efficiency (extracted energy to pump energy) of more than 23% while preserving excellent beam quality. To address the 500 mJ regime while retaining the basic system properties, an established Innoslab design was scaled geometrically.

In the field of atmospheric research lidar is a powerful technology to measure remotely different parameters like gas or aerosol concentrations, wind speed or temperature profiles. For global coverage, spaceborne systems are advantageous. To achieve highly accurate measurements over long distances high pulse energies are required. A Nd:YAG-MOPA system consisting of a stable oscillator and two subsequent InnoSlab-based amplifier stages was designed and built as a breadboard demonstrator. Overall, more than 500 mJ of pulse energy at 100 Hz pulse repetition frequency at about 30 ns pulse duration in single longitudinal mode were demonstrated. When seeded with 75 mJ pulses, the 2nd amplifier stage achieved an optical efficiency (pump energy to extracted energy) of more than 23 % at excellent beam quality. Recently, different MOPA systems comprising a single InnoSlab amplifier stage in the 100 mJ regime were designed and built for current and future airborne and spaceborne lidar missions. Amplification factors of about 10 at optical efficiencies of about 23 % were achieved. In order to address the 500 mJ regime the established InnoSlab design was scaled geometrically in a straight forward way. Hereby, the basic design properties like stored energy densities, fluences and thermal load densities were retained. The InnoSlab concept has demonstrated the potential to fulfill the strong requirements of spaceborne instruments concerning high efficiency at low optical loads, excellent beam quality at low system complexity. Therefore, it was chosen as baseline concept for the MERLIN mission, currently in phase B

We present a theoretical and experimental analysis of a pulsed 1645 nm optical parametric oscillator (OPO) to prove the feasibility of such a device for a spaceborne laser transmitter in an integrated path differential absorption (IPDA) lidar system. The investigation is part of the French-German satellite mission MERLIN (Methane Remote Sensing Lidar Mission). As an effective greenhouse gas, methane plays an important role for the global climate. The architecture of the OPO is based on a conceptual design developed by DLR, consisting of two KTA crystals in a four-mirror-cavity. Using numerical simulations, we studied the performance of such a setup with KTP and investigated means to optimize the optical design by increasing the efficiency of the OPO and decreasing the fluence on the optical components. For the experimental testing of the OPO, we used the INNOSlab-based ESA pre-development model ATLAS as pump laser at 1064 nm. The OPO obtained 9.2 mJ pulse energy at 1645 nm from 31.5 mJ of the pump and a pump pulse duration of 42 ns. This corresponds to an optical/optical efficiency of 29%. After the pump pulse was reduced to 24 ns, a similar OPO performance could be obtained by adapting the pump beam radius. In recent experiments with optimized optical design the OPO obtained 12.5 mJ pulse energy at 1645 nm from 32.0 mJ of the pump, corresponding to an optical/optical efficiency of 39%. Two different methods were applied to study the laser damage thresholds of the optical elements used

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 CH 4 or CO 2 , 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 CH 4 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. © The Authors.Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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