Mirror-based surface optical input/output technology with precise and arbitrary coupling angle for silicon photonic application

Abstract

Mirror-based surface optical coupling is an attractive technology for the optical input/output of Si photonics. For the practical use of the mirrorbased surface optical coupling, we evaluated its coupling angle controllability. Different angular mirrors were integrated into 3 × 3-μm-square single-mode silicon oxynitride optical waveguides on Si substrates. Near- and far-field patterns of optical beams output from the mirrors were measured to evaluate the beam characteristics and coupling angles. We successfully controlled the coupling angle over a wide range of more than 20° without beam characteristic variation, and perfect vertical output, which is difficult to achieve using grating couplers, was successfully demonstrated. The coupling angle error was less than ±1°, which was sufficiently small to ignore additional coupling loss. The wavelength dependence of the coupling angle was also evaluated and found to be less than +0.5° over wide wavelength ranges of 1.26-1.36 and 1.52-1.62 μm.