Two-stage Subwavelength Grating Silicon-Based Optical Polarization Beamsplitter Rotator Based on Asymmetric Coupling

Abstract

The invention discloses a two-stage sub-wavelength grating silicon-based light polarization beam splitter rotator based on asymmetric coupling, which uses silicon dioxide as the base and air as the upper cladding to break the vertical symmetry; uses silicon waveguides to form a polarization splitter The main body of the beam rotator; the silicon waveguide is divided into three parts: waveguide 1 is a first-stage coupling sub-wavelength grating waveguide, which equivalently widens the characteristic size of the waveguide, thereby increasing the manufacturing tolerance; waveguide 2 is a two-stage tapered etching waveguide, the first Phase matching with waveguide 1 is completed by stage tapered etching to achieve polarization rotation; second stage etching restores waveguide thickness to participate in secondary coupling; waveguide 3 is a secondary sub-wavelength grating waveguide, and the remaining TM 0 Polarized modes are filtered out by secondary coupling. The polarization beam splitting rotator of the present invention adopts a multi-stage coupling and multi-stage filtering structure to realize a high polarization extinction ratio and a large manufacturing tolerance under a compact structure, and has important applications 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...

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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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