Spatial phase modulating masks and production processes thereof, and processes for the formation of phase-shifted diffraction gratings

摘要

Spatial phase modulating transparent masks comprising two or more portions having two different optical paths and their production processes are disclosed. The transparent masks are particularly useful as an exposure mask in the production of phase-shifted, distributed feedback (DFB) semiconductor lasers for a single-mode operation. A process for the formation of phase-shifted diffraction gratings or corrugations (23) which comprises exposing a substrate (12), through the above transparent mask (11), to exposure radiation (15, 16) is also disclosed. According to the present invention, the phase-shifted diffraction gratings can be easily and directly produced with a high accuracy and reliability.