Optical study of the laser beam propagation on Nd:YAG crystal slab for space LIDAR missions

Abstract

The present paper reports on the development of a simulation and modeling tool which allows to estimate the propagation effects on a laser beam passing through a laser-diode-pumped Nd:YAG slab amplifier. This in-house research work is motivated by current ESA spaceborne LIDAR programs (ADM, Earth Care) as a mean to provide understanding of the LIDAR beam pointing stability as results of thermal and mechanical stresses. A dynamic model has been generated that can simulate the optical characteristics of the laser beam propagation, as a result of the various thermal and mechanical processes occurring inside the laser Pumping Unit and the thermal lensing occurring along the crystal slab. The simulation results and their comparison with actual laboratory tests are being presented and discussed. The model developed is based on the Finite Element Model (FEM) methodology, where the slab as an active element is "broken" down into interdependent segments, each simulated as being heated by an individual LD source. The light beam is propagated along the slab using dynamically varying boundary conditions, to the next so to account for the cumulated thermal and mechanical loads.

The present paper reports on the development of a simulation and modeling tool which allows to estimate the propagation effects on a laser beam passing through a laser-diode-pumped Nd:YAG slab amplifier. This in-house research work is motivated by current ESA spaceborne LIDAR programs (ADM, Earth Care) as a mean to provide understanding of the LIDAR beam pointing stability as results of thermal and mechanical stresses. A dynamic model has been generated that can simulate the optical characteristics of the laser beam propagation, as a result of the various thermal and mechanical processes occurring inside the laser Pumping Unit and the thermal lensing occurring along the crystal slab. The simulation results and their comparison with actual laboratory tests are being presented and discussed. The model developed is based on the Finite Element Model (FEM) methodology, where the slab as an active element is "broken" down into interdependent segments, each simulated as being heated by an individual LD source. The light beam is propagated along the slab using dynamically varying boundary conditions, to the next so to account for the cumulated thermal and mechanical loads.