Polarization Rotation Beam Splitter Fabrication

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Solution Overview

Problem

Existing polarization rotation beam splitters (PRBS) face challenges in fabrication due to stringent requirements for the splitting ratio and gap in the y-splitter/combiner, which affect the supported modes, leading to difficulties in manufacturing and performance.

Innovation Solution

A PRBS design incorporating a waveguide, combiner, and polarization rotator that allows for arbitrary splitting ratios and gaps, rotating combined modes by greater than zero degrees and less than ninety degrees, resulting in orthogonal output modes that are not purely TE0 and TM0, thereby simplifying fabrication and improving performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If tight tolerances are used for the y-splitter/combiner splitting ratio and gap, then the desired TE0 and TE1 modes are achieved, but fabrication becomes challenging

Engineering Contradiction:

Improvemode support precisionVSAvoidfabrication difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the polarization rotation approach from rotating only TE1 mode to rotating both TE0 and TE1 modes by different angles. This parameter change in the polarization rotation mechanism allows the system to achieve orthogonal output modes without requiring tight tolerances on the y-splitter/combiner geometry, thereby resolving the contradiction between manufacturing precision and ease of manufacture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent separates the functions of mode combination and polarization rotation into distinct components: the y-splitter/combiner handles mode combination with relaxed tolerances, while a dedicated polarization rotator handles the polarization transformation. This segmentation allows each component to be optimized independently, reducing overall fabrication difficulty

Inventive Principle:

Principle #1Segmentation

2Reliability

If the PRBS rotates only TE1 mode to TM0 mode, then orthogonal modes are achieved, but fabrication tolerances become stringent

Engineering Contradiction:

Improveorthogonal mode outputVSAvoidsplitting ratio tolerance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the polarization rotation parameters by rotating both TE0 and TE1 modes by different angles (θ0 and θ1) rather than rotating only TE1 by 90 degrees. This parameter change provides flexibility to achieve orthogonal output modes while accommodating broader manufacturing tolerances for the splitting ratio and gap dimensions

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If arbitrary splitting ratios and gaps are used, then fabrication is simplified, but the output modes may not be purely TE0 and TM0

Engineering Contradiction:

Improvefabrication simplicityVSAvoidmode purity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent introduces a polarization rotator as an intermediary component between the y-splitter/combiner and the output. This intermediary takes the combined modes (which may not be purely TE0 and TE1 due to arbitrary splitting ratios) and transforms them into orthogonal output modes, thereby decoupling the fabrication simplicity from mode purity requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The design enables improved manufacturability and performance by allowing for looser tolerances in the splitting ratio and gap, while maintaining orthogonal polarization states suitable for applications like dual polarization in-phase and quadrature IQ modulators.

Implementation Method 1

The polarization rotator is coupled with the combiner and is configured to rotate a first polarization of the combined output corresponding to a first combined mode and to rotate a second polarization of the combined output corresponding to a second combined mode

Methodology Applied

Scientific EffectPolarization rotation: Birefringence

Data Source

PatentUS20250208353A1Polarization rotation beam splitter usable with lithium containing optical devices and dual polarization IQ modulation

Publication Date: 2025.06.26 HYPERLIGHT CORP

AI summary

A polarization rotation splitter/combiner (PRBS) is described. The PRBS includes a waveguide, a combiner, and a polarization rotator. The waveguide includes a first channel and a second channel. The combiner is configured to combine a first beam for the first channel and a second beam for the second channel to a combined output having combined mode. The polarization rotator is coupled with the combiner and is configured to rotate a first polarization of the combined output corresponding to a first combined mode and to rotate a second polarization of the combined output corresponding to a second combined mode. The polarization rotator providing an output having orthogonal output modes. Thus, both of the orthogonal output modes are rotated greater than zero degrees and less than ninety degrees relative to the combined modes.