Two-stage sub-wavelength grating silicon-based light polarization beam splitting rotator based on asymmetric coupling

Abstract

The invention discloses a two-stage sub-wavelength grating silicon-based light polarization beam splitting rotator based on asymmetric coupling. Silicon dioxide is used as a substrate, and air is usedas an upper cladding to break vertical symmetry; a polarization beam splitting rotator main body is formed by using a silicon waveguide; the silicon waveguide is divided into three parts: a waveguide1 is a primary coupling sub-wavelength grating waveguide, the characteristic size of the waveguide is equivalently expanded, and the manufacturing tolerance is further increased; the waveguide 2 is atwo-stage conical etching waveguide, the first-stage conical etching and the waveguide 1 complete phase matching to achieve polarization rotation, and the second-stage etching recovers the thicknessof the waveguide to participate in second-stage coupling; and the waveguide 3 is a secondary sub-wavelength grating waveguide and is used for carrying out secondary coupling filtering on the residualTM0 polarization mode. According to the polarization beam splitting rotator, multi-stage coupling is adopted, a multi-stage filtering structure achieves the high polarization extinction ratio and thelarge manufacturing tolerance under the compact structure, and the polarization beam splitting rotator has important application in optical communication and photoelectric signal processing.

Description

technical field [0001] The invention belongs to the fields of silicon-based photon integration, multi-dimensional multiplexing of optical signals, polarization mode conversion, etc., and in particular relates to a two-stage sub-wavelength grating silicon-based optical polarization beam splitter rotator based on asymmetric coupling. Background technique [0002] The silicon-based optical waveguide polarization processor device is an integrated polarization processing device based on the polarization characteristics of silicon materials. There are mainly two polarization modes of light in silicon-based optical waveguides, TE (transverse electric mode) and TM (transverse magnetic mode), and practical applications mainly focus on the fundamental modes of these two modes, namely TE 0 and TM 0 polarization mode (or quasi-TE 0 and quasi TM 0 polarization mode). The polarization beam splitter based on the asymmetric coupling structure mainly adopts the principle of phase matchin...

AI Technical Summary

Problems solved by technology

Most of the above papers are uniform waveguide single-stage coupling or multi-stage asymmetric coupling structure. Although asymmetric coupling has a simple structure, it is very sensitive to the waveguide width and coupling length, which makes the manufacturing tolerance of the device extremely small, so some people extend the structure size. For example, the polarization beam splitting rotator designed by Y Xiong et al. based on adiabatic tapered etching extends the manufacturing error to 50nm, but its structure size is close to 200μm, which is not conducive to compact system-on-chip integration (Y.Xiong, D.X.Xu , J.H.Schmid, P.Cheben, S.Janz, and W.N.Ye,"Fabrication tolerant and broadband polarization splitter and rotator based on a taper-etched directional coupler,"Opt.Express 22, 17458(2014))

Therefore, sub-wavelength gratings become a better choice for increasing the manufacturing tolerance in a compact structure. However, the current polarization beam splitting rotators based on sub-wavelength structures are rarely able to take into account the performance of extinction ratio. For example, W Yun et al. A polarization beam splitting rotator with a wavelength grating structure can only achieve an extinction ratio of 10dB within a bandwidth of 50nm (W.Yun, M.Ma, Y.Han, Z.Lu, and L.Chrostowski,"Ultra-compact sub- Wavelength grating polarization splitter-rotator for Silicon-on-Insulator platform,"IEEE Photonics J.PP,1(2016))

[0005] According to the above analysis, the current silicon-based optical polarization beam splitter rotator based on sub-wavelength gratings is difficult to take into account the key index of extinction ratio under the condition of large manufacturing tolerance, and the polarization extinction ratio is used to measure the performance of a polarization processing device. As well as important indicators of practicability, they directly affect the actual application value of the designed device

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