Ultracompact silicon-based TE-pass power divider for 1.55/2 μm dual-wavelength

An ultracompact transverse electric (TE)-pass/transverse magnetic (TM)-stop power divider using subwavelength gratings (SWGs) and hybrid plasmonic waveguides (HPWs) for 1.55  /  2  μm is proposed and analyzed, where SWGs are, respectively, embedded in a partially etched taper within the input waveguide to form an SWG transition and input taper/output inverse tapers in the bottom layer to construct an SWG coupler, and a silicon nitride layer with a metal cap is placed right above the bottom SWG coupler to form an augmented silicon nitride-guiding HPW. For both wavelengths of 1.55 and 2  μm, the injected TE mode is transmitted from the input waveguide to the bottom SWG coupler by the SWG transition and further undergoes a strong coupling from the bottom input taper into two adjacent inverse tapers due to the cutoff condition. As to the input TM mode, it is transferred into the eigenmode that is strongly confined in the silicon nitride layer of the HPW and is greatly absorbed by metals. Consequently, both power dividing and polarization handling for a dual-wavelength operation are achieved in the proposed single device simultaneously with a compact length of 5.2  μm. Results show an extinction ratio (ER) of 22.44  /  19.87  dB for TM mode and an insertion loss (IL) of 0.25  /  0.57  dB for TE mode are obtained at 1.55  /  2  μm; its bandwidth of IL     18  /  17  dB exceeds 290  /  260  nm around the wavelength of 1.55  /  2  μm. In addition, the fabrication tolerances and mode-field evolutions are also given.