Transverse electric and transverse magnetic mode selective filters in metal clad high index buffer layer optical waveguides: design and analysis

Theoretical attenuation characteristics of a metal clad four-layer thin film optical waveguide with a high index buffer are presented. Metal clad optical waveguides with a high index buffer layer possess a unique property which arises from the effect of periodic coupling between the lossless modes of a dielectric waveguide and the lossy modes supported by the high index buffer clad with metal. It is observed that both transverse electric (TE) and transverse magnetic (TM) pass polarizers can be produced using this structure. High extinction ratio polarizers for a high index dielectric buffer layer and a metallic overlayer for ion exchanged planar optical waveguides for λ = 0.6328 µm have been designed; this corresponds to the most commonly used He–Ne laser. Results are presented for As2S3 as a buffer layer and Al, Au and Ag as metal claddings. We have shown that a waveguide polarizer extinction coefficient as high as 800 dB can be obtained for both polarizations. An oscillatory behavior similar to that of semiconductor clad waveguides is observed for both TE and TM mode losses. The effect of the buffer thickness and index on the guided modes is also presented