Tunable Echelle Grating Mux/Demuxes for Bidirectional Low-Power Tuning

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Solution Overview

Problem

Echelle grating mux/demuxes in photonic integrated circuits are sensitive to changes in effective refractive index, leading to power loss and back reflections, which existing tunable solutions require high power consumption and can only adjust refractive index in a single direction.

Innovation Solution

The implementation of a tunable echelle grating mux/demux with a monotonic refractive index gradient generated by heaters or force applicators, allowing adjustment in both increasing and decreasing directions to correct peak transmission wavelength shifts efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If existing tunable solutions are used to adjust refractive index, then peak transmission wavelength shifts can be corrected, but power consumption is high and adjustment is limited to a single direction

Engineering Contradiction:

Improvetuning direction rangeVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The free propagation region is divided into multiple segments with different refractive indices by introducing a monotonic refractive index gradient. This segmentation allows the system to achieve bidirectional tuning capability by selectively activating different gradient configurations, thereby improving adaptability without requiring high power consumption for uniform refractive index adjustment across the entire region.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of uniformly adjusting the refractive index across the entire free propagation region (which consumes high power), the patent applies local quality changes by creating a monotonic refractive index gradient that varies spatially. This allows precise local control of light propagation characteristics, enabling bidirectional wavelength tuning with reduced power consumption by only adjusting the necessary gradient magnitude and direction.

Inventive Principle:

Principle #3Local quality

2Productivity

If existing tunable solutions are used, then some wavelength shifts can be corrected, but the system lacks efficiency under typical operating conditions

Engineering Contradiction:

Improvetuning efficiencyVSAvoidbidirectional adjustment capability

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic refractive index control by applying a monotonic gradient that can be adjusted in magnitude and direction. This dynamic configuration allows the system to efficiently respond to different operating conditions and correct wavelength shifts in both directions, significantly improving tuning efficiency and productivity compared to static or unidirectional tuning mechanisms.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the refractive index parameter spatially by introducing a monotonic gradient across the free propagation region. By controlling the gradient magnitude and direction, the system can efficiently adjust peak transmission wavelengths in both increasing and decreasing directions, thereby improving productivity while maintaining bidirectional adaptability under typical operating conditions.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If a monotonic refractive index gradient is applied, then power consumption is reduced and bidirectional tuning is enabled, but the system complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidgrating structure complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical or multi-component tuning mechanisms with a refractive index gradient field approach. By using a monotonic gradient in the free propagation region, the system achieves bidirectional tuning with reduced power consumption without requiring additional mechanical moving parts or complex structural modifications, thereby managing device complexity effectively.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 reduces power consumption and enables precise tuning of peak transmission wavelengths, correcting shifts in both directions, optimizing performance under typical operating conditions.

Implementation Method 1

a first heater positioned to generate a first monotonic temperature gradient across the free propagation region

Methodology Applied

Scientific EffectTemperature gradient: Temperature Gradient

Implementation Method 2

generate a monotonic refractive index gradient across the free propagation region

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

an echelle grating positioned to redirect light received from the one or more input waveguides to the one or more output waveguides

Methodology Applied

Scientific EffectDiffraction grating: Diffraction Grating

Data Source

PatentUS20250216628A1Gradient-based tunable echelle grating mux/demuxes

Publication Date: 2025.07.03 APPLE INC

AI summary

Embodiments are directed to photonic integrated circuits that include a tunable echelle grating mux/demuxes. The tunable echelle grating mux/demuxes are configured to, during operation, selectively generate a monotonic refractive index gradient across a free propagation region in order to adjust the peak transmission wavelength(s) of one or more channels of the echelle grating mux/demux. The tunable echelle grating mux/demuxes described herein may tune these peak transmission wavelengths in a power efficient manner as compared to conventional tunable echelle grating mux/demuxes.