Silicon-on-sapphire (SOS) waveguide modal analysis for mid-infrared applications

Mid infrared photonics is a very promising field with many applications in various areas. Silicon-on-sapphire (SOS) is one of the proposed platforms for this region. This paper present a novel and rigorous modal analysis of the SOS strip waveguide in the mid-infrared range from λ = 2 to 6 μ m using finite element method solver. The analysis include fundamental and higher modes with both transverse-electric (TE) and transverse-magnetic (TM) polarization, where the dependence of these modes on the waveguide dimensions have been studied. Based on our modal analysis, a compact, wideband and easy to fabricate TE-pass and TM-pass integrated silicon waveguide polarizers have been designed. The different polarizer designs spans the whole mid-infrared transparency region of the SOS waveguide ( λ = 2–6 μ m). The TE-pass polarizer reaches 35.14 dB polarization extinction ratio while the TM-pass polarizer reaches 69.77 dB polarization extinction ratio with structure length of only 23 μ m.