Investigation of laser damage of grating waveguide structures submitted to sub-picosecond pulses

Grating waveguide structures (GWS) are reflective diffractive optical elements that operate based on the combination of sub-wavelength gratings (periodic microstructures) integrated with planar waveguides. They can be used for high-power laser applications for pulse compression, spectral stabilization, wavelength multiplexing, as well as polarization shaping. In this work, we investigate the laser-damage resistance of GWS based on Ta2O5/SiO2 multilayers at pulse durations of 500 fs and wavelength of 1030 nm. We particularly study the influence of the material of the multilayer sequence, the designed grating structure, and the operational conditions (angle of incidence and polarization of the laser beam) on the laser-damage resistance of the GWS. Comparison of measurements to simulation of the electric-field distribution in the structure reveals a good correlation between laser-induced damage threshold (LIDT) values and electric-field enhancement in the structure. Based on this work, an optimized design has been defined to increase the LIDT of the GWS. An improvement of the LIDT of a factor 2 has been obtained.