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.

Mirror-based polarization-insensitive broadband vertical optical coupling for Si waveguide

“…In our previous works, we integrated the mirrors into SiO x or SiON optical waveguides and evaluated their coupling characteristics. 8,9) With efficient optical coupling characteristics, the integrated mirrors demonstrated perfect vertical optical coupling and high compatibility with wavelength-division multiplexing (WDM) and polarization diversity, which are difficult to achieve with popular grating couplers. [10][11][12][13][14][15][16][17][18][19] The coupling loss penalty of the mirrors was approximately 0.3 dB and the wavelengthand polarization-dependent losses were less than 0.6 and 0.2 dB, respectively.…”

“…8) The mirror angle was controlled with an error of less than ±1°over a wide range of more than 20°; thus, the controllability of mirror angle was sufficiently high for practical use. 9) However, our previous works were performed using only SiO x or SiON optical waveguides; Si photonic wire waveguides were not included. In this paper, to present the practical coupling characteristics for Si photonics applications, we demonstrate a complete mirror-based vertical optical coupling including the Si photonic wire waveguide and evaluate its coupling characteristics.…”