Temporary gratings on germanium

Diffraction gratings have been formed on the surface of germanium using two beams from a ruby laser inclined at an angle to each other. Grating spacings from 2 to 20 μm have been formed that appear to be present only during the illumination and no visible damage is observed. Subsequent illumination with a single beam produces no observable diffracted beams. Permanent gratings in damaged areas can be produced with more intense beams. The intensity of a diffracted order appears to depend on the product of the intensities of the incident beams. Several applications of the temporary grating are suggested.