Effect of high index buffer layer in PbSe clad waveguide to design a visible range polarizer

Abstract

Polarization properties of PbSe clad optical waveguide are exploited theoretically, in the visible range at λ = 0.6328 μm. Due to semiconducting nature, lead selenide (PbSe) supports lossy modes and showed oscillatory behavior in generated attenuation curves. It is observed that at different PbSe thicknesses, TM or TE guided modes may be selectively attenuated. High attenuation in waveguide modes mainly occurred due to the phase matching between lossy modes supported by PbSe cladding and lossless waveguide modes. It is proposed that by placing a high index buffer layer between PbSe cladding and waveguide, phase matching can be improved further. This property can be utilized to design highly efficient polarizers. Significant results are presented to show the effect of different buffer indices (1.55, 1.88 and 2.67). At the buffer index value 1.88, TE and TM pass polarizers can be designed with extinction ratios 501 dB and 316 dB respectively. Also, an extensively high attenuation loss of 243299 dBcm-1 can be achieved with buffer index 2.67 for TM mode polarization. Obtained results are well supported by generated field plots for the proposed polarizing structures.