Rib Waveguide Polarization Beam Splitter for Low Loss
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Solution Overview
Problem
Silicon waveguides used in coherent receivers for DP-QPSK systems face challenges in productivity due to sensitivity to waveguide width, rib height, and core thickness, leading to high propagation loss and manufacturing complexity, particularly in achieving a polarization beam splitting function.
Innovation Solution
A polarization beam splitter is designed using a combination of rib waveguides for demultiplexing and multiplexing, and channel waveguides for guiding light, forming a Mach-Zehnder interferometer structure to achieve high productivity and reduce propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a channel waveguide is used to achieve small bend radius, then the bend radius is reduced to several μm, but the propagation loss increases to 2 to 3 dB/cm
Solution Approach 1:
The waveguide structure transitions from a uniform channel waveguide to a rib waveguide with varying cross-sectional dimensions. The rib waveguide has a core region with different refractive index characteristics compared to the surrounding clad, creating local quality variations that enable both tight bending and low loss by optimizing the light confinement in specific regions.
Solution Approach 2:
The invention changes the geometric parameters of the waveguide from a simple channel structure to a rib structure with specific height and width dimensions. By adjusting the rib height to be smaller than the core thickness and the rib width to be larger than the core width, the effective refractive index and mode confinement are optimized, allowing small bend radii while maintaining low propagation loss.
2Loss of energy
If a rib waveguide is used to reduce propagation loss, then the propagation loss is reduced to 0.5 to 1.0 dB/cm, but the bend radius increases to about 200 μm
Solution Approach 1:
The invention optimizes the rib waveguide parameters by setting the rib height to be smaller than the core thickness and the rib width to be larger than the core width. This parameter configuration creates an optimal balance between light confinement and mode field distribution, enabling the waveguide to achieve both low propagation loss and small bend radius that neither traditional channel nor conventional rib waveguides can achieve alone.
3Manufacturing precision
If silicon waveguide parameters (width, rib height, core thickness) are precisely controlled to achieve polarization beam splitting, then the beam splitting function is achieved, but the manufacturing complexity and sensitivity to parameters increase
Solution Approach 1:
The rib waveguide structure serves multiple functions simultaneously: it provides the polarization beam splitting function through its anisotropic geometry, enables low-loss propagation through optimized light confinement, and achieves compact bending through enhanced mode confinement. This multi-functionality reduces the need for additional specialized structures and simplifies the overall device design.
Solution Approach 2:
By changing the fundamental geometric parameters of the waveguide (rib height smaller than core thickness, rib width larger than core width), the invention creates a structure where the polarization beam splitting function is achieved through the inherent geometric anisotropy rather than requiring precise control of multiple independent parameters, thereby reducing manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the productivity of coherent receivers by reducing propagation loss and manufacturing errors, allowing for smaller bend radii and more efficient production of polarization beam splitters, while maintaining low insertion loss.
Implementation Method 1
A polarization beam splitter includes: a demultiplexer that is formed of a rib waveguide and demultiplexes input light into first input light and second input light
Implementation Method 2
The channel waveguide can be formed with an extremely small bend radius of about several μm, while the roughness of waveguide side walls is easily felt and the waveguide has a large propagation loss of 2 to 3 dB/cm
Implementation Method 3
A polarization beam splitter is designed using a combination of rib waveguides for demultiplexing and multiplexing, and channel waveguides for guiding light, forming a Mach-Zehnder interferometer structure
Data Source
AI summary
Provided are a polarization beam splitter and an optical device with high productivity. A polarization beam splitter (PBS) according to an exemplary embodiment of the present invention includes: a demultiplexer (11) that is formed of a rib waveguide (50) and demultiplexes input light into first input light and second input light; a multiplexer (14) that is formed of the rib waveguide (50) and multiplexes the first input light and the second input light that are obtained by demultiplexing the input light by the demultiplexer (11); a first arm waveguide (12) that is formed of a channel waveguide (51) and guides the first input light to the multiplexer (11); and a second arm waveguide (13) that is formed of the channel waveguide (51), generates a phase difference in the first input light propagating through the first arm waveguide, and guides the second input light to the multiplexer (14).