Design of a Broadband Polarization Splitter Based on Anisotropy-Engineered Tilted Subwavelength Gratings

Abstract

Polarization management is of paramount importance in integrated optics, particularly for highly birefringent photonic platforms such as silicon-on-insulator. In this paper, we present a polarization beam splitter based on a multimode interference coupler incorporating tilted subwavelength gratings. The tilt provides accurate control of the structural anisotropy and enables independent selection of the beat length for two orthogonal polarization states. As a result, device length is reduced to less than 100 μm while simultaneously achieving broadband operation through subwavelength grating dispersion engineering. Insertion losses below 1 dB and an extinction ratio higher than 20 dB are demonstrated through three-dimensional FDTD simulation in a 131-nm bandwidth.

Silicon Photonic Platform for Passive Waveguide Devices: Materials, Fabrication, and Applications

“…[172] Several PBSs have been realized based on SWGs, [173][174][175] inverse design method, [176] and anisotropyengineered metamaterials. [177,178] The working bandwidth is limited for ADC-based PBSs, as the wavelength shift leads to variations in both the effective index and the coupling strength. A PBS was proposed and demonstrated through "effective MZIs [133] -1.1…”

Experimental demonstration of metamaterial anisotropy engineering for broadband on-chip polarization beam splitting

“…Tilting each individual segment of a SWG waveguide away from the transverse direction significantly modifies TE effective refractive index, whereas TM mode remains almost unaffected. This principle was leveraged in the theoretical design of an MMI polarization beam splitter [26], resulting in a compact device under 100 µm long. Tilted SWGs were also applied to a polarization-independent monomode waveguide [27], achieving a birefringence under 6.10 −3 in a 100-nm bandwidth around a central wavelength of 1550 nm.…”

An Ultracompact GRIN‐Lens‐Based Spot Size Converter using Subwavelength Grating Metamaterials

“…Uniform (non‐graded) SWGs have been used to demonstrate many high‐performance devices in the silicon‐on‐insulator (SOI) platform, including integrated biosensors, ultrabroadband waveguide couplers, and narrowband Bragg filters among others. The anisotropy of such uniform SWGs has recently been exploited to achieve advanced functionalities such as broadband behavior, control of evanescent fields, and high‐performance polarization handling . However, in graded‐index metamaterials, the advantages of this intrinsic anisotropy remain unexplored.…”