Low-loss gratings for next-generation gravitational wave detectors

By combining electron beam lithography with coating processes, very shallow gratings with diffraction efficiencies between 0.02% and 7% have been realized. Advantages and disadvantages of different layout concepts for such gratings, their fabrication regime and measurements of their scattering will be discussed. The application of such gratings as coupling components to a reflective Fabry-Perot cavity resulted in a finesse of more than 400.