Photolytic fabrication of phase gratings on silver halide crystals

Diffraction phase gratings are formed on samples of crystalline silver halide by exposing them through a mask to 353-nm laser light followed by chemical processing. The exposure and photographic development processes generate metallic silver strips on the sample surface. The fixing process removes the silver strips, leaving grooves on the surface as deep as 1.1 μm. Gratings of 100-μm period are thus formed. The groove depth is determined by optical methods and is confirmed by atomic force microscopy. This method can be used to form diffractive optical elements on IR transmitting fibers and waveguides as well as on crystals.