Non-Resonant Multi-Pass Waveguide for Efficient Phase Tuning

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Solution Overview

Problem

Existing waveguides in photonic circuits face challenges in efficient phase tuning and modulation due to limitations in frequency and wavelength management, particularly in multi-mode environments, where resonant cavities introduce strong wavelength effects and require complex bends.

Innovation Solution

A non-resonant grating-based multi-mode multi-pass tunable waveguide that utilizes two-mode Bragg gratings to reflect optical signals into orthogonal modes, allowing multiple passes without resonant cavity effects, enhancing phase tuning efficiency and flexibility through thermal, electro-optic, or stress-optic effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If resonant cavities are used to achieve multiple passes through the waveguide, then the interaction length is increased, but strong wavelength effects and complex bends are introduced

Engineering Contradiction:

Improveinteraction lengthVSAvoidcomplex bends

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The patent extracts the resonant cavity component from the system and replaces it with non-resonant multi-pass architecture using directional couplers and gratings. This removes the wavelength-selective resonant effects while maintaining multiple passes through the waveguide, thereby reducing device complexity and eliminating the need for complex bends.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The waveguide is segmented into multiple sections with directional couplers and gratings that enable sequential passes through different segments. This segmentation allows the optical signal to traverse the waveguide multiple times without requiring a resonant cavity, thus achieving increased interaction length without complex bends.

Inventive Principle:

Principle #1Segmentation

2Productivity

If resonant cavities are used to achieve multiple passes, then phase tuning efficiency is enhanced, but wavelength selectivity and parasitic coupling increase

Engineering Contradiction:

Improvephase tuning efficiencyVSAvoidparasitic coupling

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potentially harmful parasitic coupling into a beneficial effect by using it for mode conversion between orthogonal polarizations. The directional couplers and gratings are designed to exploit coupling effects for constructive mode conversion rather than destructive interference, thereby maintaining phase tuning efficiency while eliminating parasitic issues.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Instead of using resonant cavities to achieve phase tuning, the patent inverts the approach by using non-resonant multi-pass architecture with directional couplers. This inversion eliminates wavelength selectivity constraints and parasitic coupling while maintaining or enhancing phase tuning efficiency through multiple interaction passes.

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If single-pass waveguides are used, then device complexity is reduced, but phase tuning efficiency and interaction length are limited

Engineering Contradiction:

Improvedevice simplicityVSAvoidphase tuning efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent merges multiple passes through the waveguide into a single integrated structure using directional couplers and gratings. This combining of multiple interaction opportunities into one compact device achieves high phase tuning efficiency without increasing overall device complexity, as the multi-pass architecture is seamlessly integrated into the waveguide structure.

Inventive Principle:

Principle #5Merging (Combining)

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 solution enables compact, efficient phase modulation and signal manipulation with reduced tuning requirements, achieving enhanced performance and flexibility in photonic circuits by maintaining orthogonal modes and preventing parasitic coupling.

Implementation Method 1

two-mode Bragg gratings to reflect optical signals into orthogonal modes

Methodology Applied

Scientific EffectBragg reflection: Bragg Diffraction

Implementation Method 2

enhancing phase tuning efficiency and flexibility through thermal, electro-optic, or stress-optic effects

Methodology Applied

Scientific EffectThermal effect: Heating

Implementation Method 3

enhancing phase tuning efficiency and flexibility through thermal, electro-optic, or stress-optic effects

Methodology Applied

Scientific EffectElectro-optic effect: Electro-Optic Effects

Implementation Method 4

enhancing phase tuning efficiency and flexibility through thermal, electro-optic, or stress-optic effects

Methodology Applied

Scientific EffectStress-optic effect: Photoelasticity

Data Source

PatentUS12487395B2Non-resonant grating based multi-mode multi-pass tunable waveguide

Publication Date: 2025.12.02 CISCO TECHNOLOGY INC

AI summary

Embodiments herein describe an electro-optic waveguide having a multi-mode multi-pass phase shifter (MMPS) tuner, one or more two-mode Bragg gratings, and one or more selective evanescent couplers. An input signal having a fundamental mode is reflected by the one or more Bragg gratings and tuned by the MMPS tuner. In this manner, the electro-optic waveguide isolates the higher order modes of the input signal. The one or more selective evanescent couplers capture an output signal having the highest order mode and reduces the mode of the output signal to the fundamental mode.