Grating Structure for High-Power Single-Mode Laser Operation

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Solution Overview

Problem

Many single-mode lasers do not provide high optical powers due to limitations such as spatial hole burning, spectral hole burning, catastrophic optical damage, carrier leakage, and self-heating, while high-power lasers often operate in multimode, supporting undesirable higher order transverse modes.

Innovation Solution

The design of a laser with a wide ridge waveguide and a grating structure that preferentially couples to the fundamental optical mode over higher order transverse modes, using a grating width that enhances the coupling coefficient for the fundamental mode while suppressing higher order modes through tailored grating architectures and confinement reduction layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the laser operates in high-power mode, then optical power output is improved, but the laser tends to support multiple transverse modes including higher order modes

Engineering Contradiction:

Improveoptical power outputVSAvoidsingle-mode operation

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The grating structure is positioned specifically within the ridge waveguide region to provide localized coupling that preferentially affects the fundamental mode. The grating's spatial location and dimensions are optimized to create different coupling conditions for different modes, allowing high-power operation while maintaining single-mode selectivity through localized structural modification.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the coupling parameter between the grating structure and optical modes by adjusting the grating width, period, and depth. These parameter modifications create a coupling coefficient that is higher for the fundamental mode than for higher order modes, enabling the system to achieve both high power output and single-mode operation simultaneously.

Inventive Principle:

Principle #35Parameter changes

2Power

If a wide ridge waveguide is used to increase power handling, then optical power capacity is improved, but coupling to higher order transverse modes increases

Engineering Contradiction:

Improvepower handling capacityVSAvoidhigher order mode generation

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The grating structure is embedded locally within the wide ridge waveguide region, creating a localized coupling mechanism that selectively interacts with the fundamental mode. This local modification allows the wide ridge to maintain its high power handling capacity while the grating provides mode-selective coupling to suppress higher order modes.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The grating structure acts as an intermediary element between the wide ridge waveguide and the optical modes. It mediates the coupling process by providing a mechanism that preferentially couples to the fundamental mode while leaving higher order modes uncoupled, thus enabling the wide ridge to handle high power without generating harmful higher order modes.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If grating width is increased to enhance coupling to fundamental mode, then coupling coefficient to fundamental mode is improved, but coupling to higher order modes also increases

Engineering Contradiction:

Improvecoupling efficiency to fundamental modeVSAvoidcoupling to higher order modes

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The grating width, period, and depth are optimized to specific parameter ranges that create a coupling coefficient profile where the fundamental mode experiences maximum coupling while higher order modes experience minimal coupling. This parameter optimization creates a selective coupling regime that improves fundamental mode coupling without proportionally increasing higher order mode coupling.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The grating structure is designed with dimensions that provide excessive coupling strength for the fundamental mode relative to higher order modes. By making the grating coupling for the fundamental mode sufficiently strong, the system achieves reliable single-mode operation even though the grating physically extends across the ridge width where it could potentially couple to higher order modes.

Inventive Principle:

Principle #16Partial or excessive action

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 high-power single-mode operation by suppressing higher order transverse modes, allowing for increased optical power output while maintaining single-mode performance.

Implementation Method 1

at least one grating structure, wherein a coupling coefficient of the at least one grating structure to the fundamental optical mode is greater than a coupling coefficient of the at least one grating structure to at least one higher order transverse optical mode

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS11152764B1Gratings for high power single mode laser

Publication Date: 2021.10.19 FREEDOM PHOTONICS LLC

AI summary

An optical device is provided that includes a waveguide layer and at least one grating structure. A coupling coefficient of the at least one grating structure to a fundamental optical mode supported by the waveguide layer is greater than a coupling coefficient of the at least one grating structure to at least one higher order transverse optical mode supported by the waveguide layer.