Ultracompact and high efficient silicon-based polarization splitter-rotator using a partially-etched subwavelength grating coupler

Abstract

On-chip polarization manipulation is pivotal for silicon-on-insulator material platform to realize polarization-transparent circuits and polarization-division-multiplexing transmissions, where polarization splitters and rotators are fundamental components. In this work, we propose an ultracompact and high efficient silicon-based polarization splitter-rotator (PSR) using a partially-etched subwavelength grating (SWG) coupler. The proposed PSR consists of a taper-integrated SWG coupler combined with a partially-etched waveguide between the input and output strip waveguides to make the input transverse-electric (TE) mode couple and convert to the output transverse-magnetic (TM) mode at the cross port while the input TM mode confine well in the strip waveguide during propagation and directly output from the bar port with nearly neglected coupling. Moreover, to better separate input polarizations, an additional tapered waveguide extended from the partially-etched waveguide is also added. From results, an ultracompact PSR of only 8.2 μm in length is achieved, which is so far the reported shortest one. The polarization conversion loss and efficiency are 0.12 dB and 98.52%, respectively, together with the crosstalk and reflection loss of −31.41/−22.43 dB and −34.74/−33.13 dB for input TE/TM mode at wavelength of 1.55 μm. These attributes make the present device suitable for constructing on-chip compact photonic integrated circuits with polarization-independence.

Subwavelength-Grating Metamaterial Structures for Silicon Photonic Devices

“…In [39] a very compact PBS based on mode evolution was presented, with promising simulation results. In a further refinement [40], the same authors proposed a compact PSR based on a Reproduced with permission from [37].) similar approach.…”

Design of narrowband Bragg spectral filters in subwavelength grating metamaterial waveguides

“…Not only that most of such devices can be fabricated in single lithographic step but clever utilization of specific dispersion properties of SWG waveguides also allows for designing ultra-broadband devices. Among numerous applications of SWG technique, let us mention highly efficient fiber-chip couplers [1][2][3][4][5][6], broadband directional couplers [7] and multimode interference (MMI) couplers [8], polarization mode splitters [9][10][11], wavelength-division [2] and modedivision [12] multiplexers, optical delay lines [13], evanescent field sensors [14,15] and suspended membrane waveguides for mid-infrared applications [16]. Principles of operation and further applications of SWG devices have been recently reviewed in [17,18].…”

Disorder effects in subwavelength grating metamaterial waveguides

“…Since the first experimental demonstration of an optical waveguide with a subwavelength periodic core [4], these structures, also called subwavelength gratings (SWGs), have found many applications in integrated optics, for example as highly efficient fiber-chip couplers [3][4][5][6][7][8][9], low-loss waveguide crossings, evanescent field sensors [10,11], broadband directional couplers [12] and multimode interference (MMI) [13] couplers, polarization beam splitters [14][15][16], wavelength division [4] and mode division [17] multiplexers, delay lines [18], Fourier-transform spectrometers [19] and suspended (membrane) waveguides for mid-infrared applications [20]. Exhaustive reviews of SWG fundamentals and applications can be found in [21,22].…”