Physics behind 100J/10Hz laser for new scientific applications

The most serious problem limiting the efficient high power operation of solid-state lasers is the thermal effect which results from various physical phenomena such as quantum defects, non-unity quantum efficiency, concentration quenching, upconversion, and others. In addition, a high average power solid state laser typically needs a way to defeat the naturally occurring transverse gain that can lead to losses from amplified spontaneous emission (ASE) and/or parasitic oscillation. The benefits of cryogenic cooling to mitigate thermal effects and ASE in Yb:YAG lasers have been well documented. The goal of HiLASE Project is to design and build a cryogenic gas-cooled 100 J / 10 Hz Yb:YAG laser amplifier that is scalable to the kJ regime. The multi-slab architecture developed within the HiLASE project is a simple configuration for energy scaling, as it yields uniform absorption along the laser propagation axis and it spreads the absorbed power over a large volume. Finite element methods (FEM) have been used to predict temperature distribution, mechanical stresses, optical path difference and birefringence. Our detail study demonstrates that cryogenic helium gas cooling and the proper choice of the slab and cladding parameters will be able to provide safe operation of kW class amplifiers with minimal optical distortions. Recent experimental results obtained at STFC/RAL laboratory (U.K.) on the cryogenically-cooled 10 J / 10 Hz pre-amplifier agree very well with our model predictions. With the demonstration of the 100 J laser system expected to be completed by May 2015, the HiLASE center will host the world’s highest pulse energy short pulse (2-10 ns) diode-pumped solid-state laser operating at 10 Hz. This will open a new set of scientific and high-tech applications, including Laser Shock Peening, Laser Induced Damage Threshold measurements, and Warm Dense Matter experiments.

Antonio Lucianetti obtained his PhD from the Institute of Applied Physics, Bern University, Switzerland in 1999. Later, he worked as a Post-doctoral Researcher at Max-Born-Institut (Germany) and at Lawrence Livermore National Laboratory (USA). In the US, he also worked as Research Scientist and Local Run Coordinator in the LIGO (Laser Interferometer Gravitational Wave Observatory) project before moving back to Europe at Ecole Polytechnique (France). In 2011, he joined HiLASE Project at the Institute of Physics ASCR.