Narrow-band optical filter based on the Fabry-Perot interferometer with waveguide-grating mirrors

Two variants of the Fabry-Perot interferometer working as a narrow-band filter are analyzed. In the first variant, a waveguide-grating mirror is used instead of a highly reflecting multilayer mirror. In the second variant, both mirrors of the interferometer are waveguide-grating mirrors. It is demonstrated that a narrow (deltalambdasimilar to1 Angstrom) transmission line of the filter is related to a strong spectral dependence of the phase of the wave reflected from the waveguide-grating mirror. The filter transmittance and spectral width are substantially affected by the radiation losses in the waveguide mirrors. It is also demonstrated that narrowing of the reflection line of the waveguide mirror in the Fabry-Perot interferometer is possible even in the presence of losses in the waveguide mirrors.