Cavity-resonator-integrated guided-mode resonance filter consisting of curved gratings

An integration of a cavity resonator was recently proposed to miniaturise a guided-mode resonance filter for application to a small-diameter beam launched from an optical fibre or waveguide end. Its operation principle has been demonstrated with a one-dimensional configuration so far, but a two-dimensional configuration is necessary for practical applications. A grating coupler and a pair of distributed Bragg reflectors of curved gratings were designed for a guided wave propagating with divergence due to diffraction. The cavity-resonator-integrated guided-mode resonance filter of 10 μm aperture was fabricated on a SiO₂ based waveguide. A narrowband reflection spectrum of 0.2 nm full width at half maximum was demonstrated experimentally.