We report on significant improvements of the performance of thick diffraction gratings for cold neutrons. The basis material for the production of holographic gratings by optical means is photosensitized deuterated poly(methy1 methacrylate) (D-PMMA). The properties of these gratings now approach those of perfect monochromator crystals for neutrons of shorter wavelength: for cold neutrons with 1.0nm wavelength the gratings exhibit a reflectivity in the percent range which makes them suitable for a wide range of applications in neutron optics.