Two-stage asymmetric directional coupler-type optical polarization beam splitting rotator connected by u-shaped waveguide

Abstract

The invention discloses a U-shaped waveguide connected with two-stage asymmetric directional coupler-type optical polarization beam splitting rotator. Polarized effective refractive index conditions for waveguide 2 coupling; waveguide 2 is a U-shaped waveguide, which is divided into three sections in structure: the center of the first section is fully etched to form a gap to realize TM 0 Separation of polarization modes forms a first-stage asymmetric directional coupler with waveguide 1, the second section is a curved waveguide, which is used to fold the device to increase compactness, and the third section is a uniform waveguide, which is jointly formed with waveguide 3 The second-stage asymmetric directional coupler; the waveguide 3 is a tapered etched waveguide, and the etching direction is the same as that of the waveguide 1. The invention has the characteristics of compact structure, improved extinction ratio of the device, large manufacturing tolerance and the like. It plays an important role in optical polarization multiplexing and demultiplexing, polarization signal processing, optical communication and photoelectric signal processing.

Description

technical field [0001] The invention belongs to the fields of silicon-based photon integration and optical devices, optical polarization multiplexing and demultiplexing, and multi-dimensional multiplexing of optical signals, and in particular relates to a two-stage asymmetric directional coupler-type optical polarization beam splitting rotation based on U-shaped waveguide connection device. Background technique [0002] With the development of planar optical waveguide integrated device technology, the number of integrated devices has increased rapidly, and the integrated system has become more and more complex. On-chip polarization cannot be ignored. However, most planar optical waveguide devices have a strong polarization dependence, so it is very important to realize the separation and conversion of different polarization modes into the same polarization mode on the chip. The dimension of signal multiplexing and utilization; at the same time, the separated polarization mo...

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Problems solved by technology

Its disadvantages are: due to the use of other materials, the complexity of the process will be increased, and large losses may be introduced. At the same time, the performance of this device is low

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. , such as the polarization beam splitting rotator designed by Ding Y et al. based on adiabatic tapered etching, is no longer too sensitive to manufacturing errors, but its structure size is close to 240 μm, which is not conducive to compact system-on-chip integration (Ding Y, Liu L ,Peucheret C, et al.Fabrication tolerant polarization splitter and rotatorbased on a tapered directional coupler[J].Optics Express,2012,20(18):20021-20027.)

Therefore, subwavelength gratings have become a better choice to increase the manufacturing tolerance in a compact structure. However, the current polarization beam splitting rotators based on subwavelength structures are rarely able to increase the manufacturing tolerance while taking into account the extinction ratio performance. For example, the polarization beam splitting rotator based on the sub-wavelength grating structure designed by Xiong Y et al. can only achieve an extinction ratio of 10dB in the 100nm bandwidth range, and at the same time can only guarantee the insensitivity of the loss index to manufacturing errors. Compared with this indicator, the effect is not obvious (Xiong Y, Wangüemert-Pérez, J.Gonzalo, Xu D X, et al. Polarization splitter and rotator with subwavelength grating for enhanced fabrication tolerance [J]. Optics Letters, 39, 6931-6934 (2014 )

[0006] According to the above analysis, the polarization beam splitting rotator based on the asymmetric directional coupler structure is generally difficult to achieve the balance of the three indicators of compact structure, high overall performance and large manufacturing tolerance. This phenomenon has led to the current silicon-based Polarization beam splitting rotators based on photonic integration platforms are difficult to manufacture and apply on a large scale at low cost

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