PRODUCTION OF CHIRPED-GRATING

摘要

PURPOSE:To perform chirped-grating at an irregular period with high accuracy by providing a mask on a base plate while leaving stripe-shaped apertures at irregular intervals in a grating pattern then disposing the base plate in a diffusing ion beam and etching the masking surface of the base plate. CONSTITUTION:A mask 12 is provided on the surface of a base plate 10 in the state of leaving parallel arranged slit apertures 11. The width W2 of the aperture 11 and the mask width between the adjacent apertures are made into a stripe shape expanding successively in one direction (y). An SiO2 film to be inscribed with grating grooves is provided over the entire surface of the plate 10 and is subjected to exposing and developing, whereby a prescribed pattern is obtd. The masked plate 10 is disposed within the range of an ion beam 13. The plate is disposed in such a way that the central axis 16 of the ion beam is included within the virtual perpendicular plane crossing the apertures 11 and the normal 12 of the base plate plane is inclined at a specified angle phi toward the side where the width of the apertures 11 is narrow. A grating 1 of an irregular period wherein the braze angle theta of a diffraction surface 2A decreases gradually in one direction can be formed on the masking surface of the plate 10.