Ultracompact and broadband silicon-based TE-pass 1 × 2 power splitter using subwavelength grating couplers and hybrid plasmonic gratings.

Abstract

An ultracompact TE-pass 1 × 2 power splitter, using subwavelength grating (SWG) couplers and hybrid plasmonic gratings (HPGs), is proposed and analyzed in detail. As the input strip waveguide is tapered to a narrow wire, where TE mode is cutoff, the launched TE-mode can be evenly divided with high efficiency with the help of the SWG couplers, which are placed between the central silicon wire and two nearby output branches. The injected TM-mode will be perfectly reflected by the carefully designed HPG, whose periodically varied metal layer is located above the bottom strip and SWG waveguides. Consequently, a single device combining both the functions of polarization selection and power division can be realized. This is valuable for highly dense integrated circuits. Results show that, with a period number of 4 in HPG, the present device is only ~6.2-μm-long with an extinction ratio (ER) and an insertion loss (IL) of 25.4 and 0.53 dB at 1.55 μm, respectively, and its bandwidth of ER > 20 dB is ~180 nm with the IL < 0.8 dB, showing a broadband property. Besides, fabrication tolerances to the key dimensions are analyzed and modal field evolution through the device is also presented.