Mode-Conversion Light Recycling in Waveguides

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Solution Overview

Problem

Conventional light recycling methods using resonators are limited by narrow bandwidth and inefficiency due to resonance, requiring long lengths and high power consumption, which restricts their application in integrated photonics.

Innovation Solution

Implementing mode conversion within a waveguide to recycle light by converting modes after each pass, utilizing high index contrast waveguides to avoid interference and achieve broadband operation, allowing for multiple passes without cross-talk and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If conventional resonators (micro-rings, micro-disks, Fabry-Perot cavities) are used for light recycling, then light can circulate multiple round trips, but the operational bandwidth is narrowed due to resonance constraints

Engineering Contradiction:

Improvenumber of recycling round tripsVSAvoidbandwidth

Core Design Contradiction:

Duration of action of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental operating parameter from resonance-based light recycling to mode-conversion-based light recycling. By utilizing mode converters that transform light between different spatial modes (e.g., TE0 to TE1) rather than relying on resonant cavities, the system achieves broadband operation while maintaining multiple round trips. This parameter change resolves the contradiction by decoupling the number of recycling rounds from bandwidth constraints.

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If light recycling is implemented using conventional resonators, then the required waveguide length is reduced, but power consumption increases due to the need for high quality factor resonance

Engineering Contradiction:

Improvewaveguide lengthVSAvoidpower consumption

Core Design Contradiction:

Length of stationary objectVSUse of energy by moving object

Solution Approach 1:

The patent substitutes the mechanical resonance system (conventional resonators requiring high Q-factors and precise frequency matching) with an optical mode-conversion system. The mode converters use evanescent field coupling between waveguides of different widths to achieve mode transformation without requiring high-quality-factor resonance, thereby reducing power consumption while maintaining compact waveguide lengths.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If mode conversion is used for light recycling, then broadband operation is achieved, but device complexity increases due to the need for mode converters at waveguide ends

Engineering Contradiction:

ImprovebandwidthVSAvoidstructure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the light recycling function into distinct mode converter modules positioned at the ends of the waveguide. Each mode converter is an independent component that performs mode transformation, allowing the system to maintain broadband operation while managing complexity through modular design. This segmentation enables independent optimization of each mode converter and simplifies the overall system architecture.

Inventive Principle:

Principle #1Segmentation

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 a seven-fold increase in phase shift in compact integrated interferometers, enhances sensing signals, and reduces power consumption, making it suitable for applications requiring long phase shifts, such as depletion-type phase shifters.

Implementation Method 1

an optical mode in a single-mode waveguide can be evanescently coupled to a specific spatial mode in an adjacent multimode waveguide

Methodology Applied

Scientific EffectEvanescent coupling:

Implementation Method 2

converting the mode of the light to a different mode at the second end of the bus waveguide

Methodology Applied

Scientific EffectMode conversion:

Implementation Method 3

light makes multiple passes through the same waveguide by converting the mode to a different mode after each pass and rerouting the light back into the same waveguide

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS11256031B2Resonance-free light recycling in waveguides

Publication Date: 2022.02.22 THE TRUSTEES OF COLUMBIA UNIV IN THE CITY OF NEW YORK

AI summary

Light recycling within a waveguide is achieved by mode conversion instead of resonance. A structure is provided in in which light makes multiple passes through the same waveguide by converting the mode to a different mode after each pass and rerouting the light back into the same waveguide. The structure includes a bus waveguide and at least one mode converter device disposed at or adjacent each of two opposing ends of the bus waveguide, wherein each mode converter devices is configured to receive light having a receiving mode along a first direction and to cause light having a different mode from the receiving mode to propagate in a second direction opposite the first direction.