Sub-ps laser damage resistance of optical coatings for reflective components

Since the early years of laser research, laser damage resistance of optical components has been extensively studied. The research dealing with laser-induced damage threshold (LIDT) remains still very active thanks to the complexity of the involved physical mechanisms and numerous breakthroughs in the field of lasers and their applications. The laser damage studies are important for proper handling of optical components in laser systems and for the research on damage initiation, material processing comprising ablation and laser machining. The emerging scientific fields and industrial applications require optical elements that tune the polarization, wavelength, or pulse duration of emitted ultrashort pulses. Key elements that can control the light properties are diffraction gratings. For high power use, a design based on the combination of a planar waveguide and sub-wavelength grating, called grating waveguide structures (GWS), is very promising. [1] Within the MSCA GREAT project [2] , an established network of scientific institutions designs, fabricates, characterizes and implements the GWS into laser systems. Our role is to develop and implement robust laser damage metrology to investigate the power handling capabilities of GWS. An essential part of the characterization of such complex structures is the laser damage study of particular materials used in high reflective (HR) mirrors, see Fig. 1a ). In this work, high-index dielectric coatings of HfO 2 , Nb 2 O 5 and Y 2 O 3 were tested by near-infrared sub-ps pulses, see Fig. 1b ).