Integrated Photonic Device for Wavelength-Stable Laser Oscillation and Simultaneous Input Coupling

A guided-mode-resonance device for both narrow-band retroreflection and waveguide input coupling was designed and fabricated for operation wavelength of 1550 nm. It consists of a focusing grating coupler (FGC) integrated in a waveguide cavity resonator constructed by a pair of distributed Bragg reflectors (DBRs) on a reflection substrate. The size of the FGC was 31 × 20 μm
²
. The device was used as a laser mirror of an external cavity laser. The oscillation wavelength was fixed to the retroreflection wavelength, and the laser power was coupled to a waveguide. The coupled power depends on the length of one DBR. The optimal length for the maximum coupling was also discussed theoretically and experimentally.