Novel ring interferometer for frequency stabilization of semiconductor lasers

A novel type of ring interferometer is proposed which is used as a reference for frequency stabilization of semiconductor lasers. This interferometer is fabricated by precisely polishing a block of synthesized quartz into the shape of an equilateral prism with multilayer dielectric films on each side. This interferometer has the advantage of drastic reduction of optical feedback to semiconductor lasers. The alignment of the optical axis of the interferometer is relatively easy compared with a conventional ring interferometer. The frequency fluctuation of an AlGaAs semiconductor laser is reduced to <1 MHz using this interferometer.