Compact and broadband silicon-based transverse electric-pass power splitter using triple-guide directional couplers with hybrid plasmonic waveguides and subwavelength gratings

Abstract

A compact and broadband transverse electric (TE)-pass power splitter using triple-guide directional couplers (TGDCs) is proposed and analyzed in detail, where the TGDCs are formed by two outside subwavelength grating (SWG) waveguides and a central strip waveguide with segmented hybrid plasmonic waveguides (HPWs) on its top. For input transverse magnetic (TM) mode, it is transmitted along the central strip waveguide, gradually transferred from the strip waveguide into the horizontal slots formed by strip waveguide and HPWs, and finally radiated into the claddings since the HPWs are segmented. As to the TE mode, by choosing suitable structural parameters, phase-matching condition is only satisfied for TE mode so that it is evenly coupled from the central waveguide into the outside SWG waveguides, effectively preventing the coupling of the residual TM mode in the TGDC. Consequently, a TE-pass power splitter is realized. Moreover, efficient transitions between the SWG and strip waveguides are used at the end of the outside SWG waveguides. Results show that, with the number of the segments of the HPWs being 6, a compact device of ∼9 μm in length is achieved with an insertion loss (IL) of 0.56 dB (TE), an extinction ratio (ER) of 23.74 dB, and a reflection loss of −30.6 dB (−4.94 dB) for TE (TM) mode at 1.55 μm. Also, the bandwidth is up to 150 nm when ER > 15 dB and IL < 0.9 dB. In addition, fabrication tolerances to the key structural parameters are investigated and field evolution through the present device is also presented.