Fabrication of broadband, high-efficiency, metal-multilayer-dielectric gratings

Fabrication procedures and testing results of broadband, high-efficiency, metal-multilayer-dielectric gratings (MMDG) for high power laser pulse compression applications are reported. Gratings of 1740 line/mm line density to operate at 53 degrees incident angle and TE polarization were engraved in the top three layers of metal-multilayer-dielectric substrates. The groove depth was controlled to be between 310 nm and 320 nm by monitoring the diffraction efficiency of grating at—1st-order in Littrow mounting using a He–Ne laser with a wavelength of 632.8 nm. The duty cycles of masks was controlled with a range from 0.14 to 0.17 and the duty cycles of MMDGs was controlled with a range from 0.15 to 0.19. The bandwidth of a fabricated MMDG at a level of diffraction efficiency higher than 90% was 169 nm and the peak value was 95.1% at wavelength of 810 nm.