High TM Mode Transmission by Subwavelength-Gratings-Modified-Slab Ridge Waveguide

In this paper, we proposed an effective strategy for general high TM-mode transmission ridge waveguide. By introducing the subwavelength gratings into slab region, we reduced the equivalent medium index of local slab and suppressed the TE-TM polarization conversion strength. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TM}_0$</tex> mode, the maximum broadband transmission improvement is over 17.8dB in theory. In the wavelength range of 1500-1600nm, the minimum loss is below 0.05dB, and the max transmission improvement above 19dB is realized near the wavelength of 1530nm. That method is meaningful for overcoming the limitation of bound states in the continuum and expanding diverse ridge waveguide devices for TM polarization modes.