Mode-Selective Laser Facets for High-Power Beam Quality

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Solution Overview

Problem

Laser diodes with large cross-sectional areas often support multiple spatial modes, leading to poor beam quality due to inefficient mode selection in existing facet designs, which hinder the preferential reflection of desired waveguide modes while minimizing reflection in other modes.

Innovation Solution

The use of computational inverse design tools to optimize the structure of laser facets, employing a loss function that rewards high reflectivity for desired modes and penalizes other modes, while considering manufacturing constraints and material availability, using a finite-difference time domain method to determine optimal refractive indices and structural parameters for improved beam quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If laser diodes use large cross-sectional areas to support multiple spatial modes, then the device can achieve higher power output, but the beam quality deteriorates due to inefficient mode selection

Engineering Contradiction:

Improvepower outputVSAvoidbeam quality

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The patent applies local quality by designing facets with spatially varying properties - different regions of the facet have different reflectivity characteristics tailored to specific modes. The computational inverse design optimizes the facet structure to create local variations in optical properties that selectively enhance desired modes while suppressing unwanted modes, thereby achieving both high power output and good beam quality simultaneously.

Inventive Principle:

Principle #3Local quality

2Device complexity

If conventional facet designs are used in laser diodes, then the device structure remains simple, but mode selection efficiency deteriorates leading to poor beam quality

Engineering Contradiction:

Improvefacet structure complexityVSAvoidbeam quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent employs preliminary action through computational inverse design that pre-calculates and optimizes the facet structure before manufacturing. The loss function is defined in advance to encode desired mode selection characteristics, and the computational algorithm预先 determines the optimal facet geometry that will achieve the target beam quality, avoiding the need for complex iterative adjustments during manufacturing.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If computational inverse design tools are used to optimize facet structures for mode selectivity, then beam quality improves, but the design and manufacturing complexity increases

Engineering Contradiction:

Improvebeam qualityVSAvoiddesign complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces traditional mechanical/optical trial-and-error design methods with computational algorithms. The inverse design tool uses numerical optimization to automatically determine the optimal facet structure, substituting complex manual design processes with automated computational procedures. This reduces the actual manufacturing complexity even though the design phase involves advanced computational methods.

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 results in laser diodes with enhanced beam quality output by preferentially reflecting desired waveguide modes and minimizing reflection in undesired modes, effectively addressing the issue of multiple spatial modes and improving manufacturing feasibility and cost-effectiveness.

Implementation Method 1

using a time domain finite difference method for solving Maxwell's equations, for example, the tool can find solutions (i.e., facet structures) that give a high amount of reflectance for the desired light mode while minimizing reflectance for all other light modes

Methodology Applied

Scientific EffectMaxwell's equations:

Implementation Method 2

using a time domain finite difference method for solving Maxwell's equations

Methodology Applied

Scientific EffectFinite-difference time domain method:

Implementation Method 3

The two ends of the semiconductor crystal can be cleaved to form relatively smooth, parallel facets that serve to recirculate the photons propagating in the waveguide mode. Photons emitted into a mode of the waveguide can travel along the waveguide and be reflected several times from each end of the laser diode

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11804691B2Systems and methods for designing optical devices having mode selective facets

Publication Date: 2023.10.31 X DEVELOPMENT LLC

AI summary

Methods for designing a mode-selective optical device including one or more optical interfaces defining an optical cavity include: defining a loss function within a simulation space encompassing the optical device, the loss function corresponding to an electromagnetic field having an operative wavelength within the optical device resulting from an interaction between an input electromagnetic field at the operative wavelength and the one or more optical interfaces of the optical device; defining an initial structure for each of the one or more optical interfaces, each initial structure being defined using a plurality of voxels; determining values for at least one structural parameter and/or at least one functional parameter of the one or more optical interfaces by solving Maxwell's equations; and defining a final structure of the one or more optical interfaces based on the values for the one or more structural and/or functional parameters.