Rotated SWG Waveguide for Polarization Control
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Solution Overview
Problem
Existing integrated optics devices face challenges in efficiently controlling birefringence for polarization-independent or polarization-selective operations, leading to increased manufacturing complexity and inefficiencies.
Innovation Solution
A single mode waveguide with a sub-wavelength grating (SWG) structure rotated at a specific angle with respect to the propagation direction of light, allowing for controlled birefringence properties without requiring multiple etch depths or additional materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional materials or multiple layers are incorporated to control birefringence, then polarization control is improved, but manufacturing complexity increases significantly
Solution Approach 1:
The patent changes the geometric parameters of the waveguide structure by introducing a tilted interface at a specific angle (e.g., 45 degrees) relative to the propagation direction. This parameter change modifies the effective refractive index for TE and TM modes differently, enabling polarization control without adding materials or layers. The tilted interface angle is optimized to achieve desired polarization splitting or independent mode control.
Solution Approach 2:
The patent introduces asymmetry in the waveguide structure through the tilted interface, which breaks the symmetry between TE and TM mode confinement. This asymmetric geometry causes different effective indices for the two polarizations, enabling polarization-selective operation. The asymmetry is achieved purely through geometric modification of the existing waveguide structure.
2Reliability
If sub-wavelength diffraction gratings or photonic crystals are used for polarization splitting, then polarization separation is improved, but manufacturing precision requirements increase due to sensitivity to deviations
Solution Approach 1:
The patent modifies the waveguide geometry by introducing a tilted interface with a specific angle parameter. This parameter change creates polarization-dependent effective indices that are less sensitive to manufacturing variations compared to sub-wavelength gratings. The tilted interface approach provides robust polarization splitting with relaxed tolerances.
3Device complexity
If multimode interference couplers are used for polarization splitting, then device simplicity is improved, but efficiency decreases and device size increases due to small propagation constant differences
Solution Approach 1:
The patent changes the waveguide structure from a continuous multimode waveguide to one with a tilted interface. This parameter change increases the difference in propagation constants between TE and TM modes, enabling efficient polarization splitting in a compact length. The tilted interface creates stronger polarization-dependent confinement, improving splitting efficiency while maintaining a reasonable device footprint.
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 approach enables compact, efficient, and low-loss polarization control with a large bandwidth, while maintaining manufacturing simplicity by allowing single-exposure manufacturing systems.
Implementation Method 1
the birefringence and anisotropy of the SWG structure are not controllable during design, but rather are a consequence of the geometric parameters thereof
Data Source
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AI summary
The invention relates to a waveguide and a polarisation splitter based on said waveguide, in which a rotation of an angle greater than zero is applied to a plurality of sections of a core material and a plurality of sections of a covering material, thereby achieving an independent control of the refractive indices of a zero-order transverse electric mode and a zero-order transverse magnetic mode. This document also describes a manufacturing method of said waveguide which allows the birefringence of the light that passes through the waveguide.