Tapered Waveguide Polarization Converter for Bandwidth
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Solution Overview
Problem
Prior-art polarization mode converters have a small process tolerance and high defect rate due to their sensitivity to waveguide width variations, leading to reduced signal quality and limited operating bandwidth.
Innovation Solution
The proposed polarization mode converter employs tapered waveguides with varying widths and heights, allowing for gradual changes in waveguide structure to accommodate different wavelengths, thereby enhancing process tolerance and operating bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional waveguides with fixed width and height are used for polarization mode conversion, then the device structure is simple, but the process tolerance is small and defect rate is high
Solution Approach 1:
The waveguide width and height are changed from fixed parameters to gradually varying parameters along the propagation direction. The first waveguide has width w1 and height h1, while the second waveguide has width w2 and height h2, where w1≠w2 and h1≠h2. This parameter variation enables adiabatic mode conversion while providing tolerance to manufacturing variations.
Solution Approach 2:
The waveguide dimensions are made dynamic along the propagation direction rather than static. The gradual transition from dimensions (w1, h1) to (w2, h2) creates a dynamic structure that adapts to different polarization modes, improving process tolerance while maintaining relatively simple fabrication.
2Device complexity
If conventional waveguides with fixed width and height are used for polarization mode conversion, then the device structure is simple, but the operating bandwidth is limited
Solution Approach 1:
By varying the waveguide width and height parameters along the propagation direction, the device can accommodate a broader range of wavelengths. The gradual dimensional change from (w1, h1) to (w2, h2) creates multiple resonance conditions that expand the operating bandwidth while keeping the overall structure relatively simple.
3Ease of manufacture
If conventional waveguides are used, then manufacturing is easy, but coupling efficiency is reduced and losses increase
Solution Approach 1:
The gradual variation of waveguide dimensions from (w1, h1) to (w2, h2) enables adiabatic mode conversion, which minimizes optical losses by avoiding abrupt discontinuities. This approach maintains ease of manufacture through standard lithography processes while significantly reducing coupling losses compared to sharp transitions.
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 design improves the coupling efficiency and reduces losses, enabling a high process tolerance, simple structure, and large operating bandwidth, effectively addressing the limitations of prior-art converters.
Implementation Method 1
a first waveguide portion, a polarization rotation portion, and a second waveguide portion, an effective refractive index of a TE mode having the highest effective refractive index in an eigen mode of waveguide light on a sectional surface of the first waveguide portion is higher than an effective refractive index of a TM mode having the highest effective refractive index, an effective refractive index of the TM mode having the highest effective refractive index on a sectional surface of the second waveguide portion is higher than an effective refractive index of the TE mode having the highest effective refractive index
Implementation Method 2
effective refractive indices are different in a transverse electric wave (TE) mode and a transverse magnetic wave (TM) mode in the PIC chip because of restrictions such as a birefringent effect or a waveguide size
Data Source
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AI summary
A polarization mode converter is provided and includes a rectangular waveguide (101), a first tapered waveguide (102), and a second tapered waveguide (103). A height of the rectangular waveguide (101) is a first height H1. A side of the first tapered waveguide (102) is connected to the rectangular waveguide (101). A width of the first tapered waveguide (102) changes gradually. A height of the first tapered waveguide (102) is a second height H2, and the second height H2 is less than the first height H1. The second tapered waveguide (103) is unconnected to the rectangular waveguide (101), and the second tapered waveguide (103) is unconnected to the first tapered waveguide (102). A width of the second tapered waveguide (103) changes gradually. A height of the second tapered waveguide (103) is the first height H1. A distance between a first end of the second tapered waveguide (103) and the rectangular waveguide (101) is a first distance, a distance between a second end of the second tapered waveguide (103) and the rectangular waveguide (101) is a second distance, and the second distance is greater than the first distance. The first tapered waveguide (102) is located between the rectangular waveguide (101) and the second tapered waveguide (103).