Broadband pulse compression gratings with measured 99.7% diffraction efficiency.

We present experimental investigations of grating mirrors with high diffraction efficiencies exceeding 99.7% in the -1st order for TE polarization at a wavelength of 1060 nm, and exceeding a diffraction efficiency of 99% in the wavelength range from 1025 nm to at least 1070 nm. The total efficiency of a four-pass compressor for chirped pulse amplification was >96%. The design, fabrication, and characterization of the fully dielectric grating mirrors are presented.