Engineering of phase matching for mid-infrared coherent anti-Stokes Raman wavelength conversion with orthogonally polarized pump and Stokes waves in silicon-on-sapphire waveguides

Abstract

The conversion efficiency of mid-infrared wavelength conversion based on coherent anti-Stokes Raman scattering with TE-polarized pump and TM-polarized Stokes waves is theoretically investigated in silicon-on-sapphire (SOS) waveguides. The peak conversion efficiency of -10 dB is obtained when the linear propagation loss is 1 dB/cm at Δk=0; however, it is reduced to -13.6 dB when the linear propagation loss is 2 dB/cm. The phase matching for wavelength conversion with orthogonally polarized pump and Stokes waves can be realized by engineering the birefringence in SOS waveguides, because proper phase mismatch induced by birefringence together with material dispersion-induced phase mismatch can counteract the large phase mismatch induced by waveguide dispersion. Moreover, compared with the phase matching for identically polarized pump and Stokes waves, the phase matching for orthogonally polarized pump and Stokes waves can be realized in a SOS waveguide with much smaller cross section, which reduces the power requirement for optical systems.