Photonic Crystal Surface-Emitting Laser for Low Divergence and Threshold

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Solution Overview

Problem

Conventional lasers have large divergence angles and high threshold currents, which limit their performance in applications such as medicine and optical communication.

Innovation Solution

A photonic crystal surface-emitting laser is designed with an index matching layer that is electrically insulating and has a refractive index identical to the active layer, surrounded by a photonic crystal structure, which reduces the divergence angle and threshold current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional laser structure is used, then device complexity is low, but divergence angle is large and threshold current is high

Engineering Contradiction:

Improvelaser structure complexityVSAvoiddivergence angle

Core Design Contradiction:

Device complexityVSShape

Solution Approach 1:

The laser structure is segmented into multiple functional layers including n-type cladding layer, active layer, index matching layer, and photonic crystal structure with periodic holes. This segmentation allows each layer to perform specific functions that collectively reduce the divergence angle while maintaining manageable device complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The index matching layer is positioned specifically around the active layer with its refractive index matched to the active layer, creating local optical quality improvement. The photonic crystal structure is positioned over the active layer to provide localized control of light emission, reducing divergence angle without requiring complex modifications throughout the entire device

Inventive Principle:

Principle #3Local quality

2Device complexity

If conventional laser structure is used, then device complexity is low, but threshold current is high

Engineering Contradiction:

Improvelaser structure complexityVSAvoidthreshold current

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The refractive index parameter of the index matching layer is specifically matched to the active layer parameter, creating optimal optical conditions. The photonic crystal structure introduces periodic geometric parameters that control light emission characteristics, reducing threshold current through parameter optimization rather than complex structural changes

Inventive Principle:

Principle #35Parameter changes

3Shape

If index matching layer with matched refractive index is added, then divergence angle is reduced, but device complexity increases

Engineering Contradiction:

Improvedivergence angleVSAvoidlaser structure complexity

Core Design Contradiction:

ShapeVSDevice complexity

Solution Approach 1:

The index matching layer acts as an intermediary between the active layer and the photonic crystal structure, with its refractive index matched to the active layer. This intermediary layer facilitates efficient optical coupling and reduces divergence angle without requiring complex integration of the photonic crystal structure directly with the active layer

Inventive Principle:

Principle #24Intermediary (Mediator)

4Use of energy by moving object

If photonic crystal structure is added, then threshold current is reduced, but device complexity increases

Engineering Contradiction:

Improvethreshold currentVSAvoidlaser structure complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The photonic crystal structure serves multiple functions: it acts as a distributed feedback mechanism for lasing, provides optical confinement, and controls the emission pattern. This multi-functionality reduces threshold current without requiring additional separate components, thereby limiting the increase in device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design results in a laser with a smaller divergence angle and lower threshold current, enhancing its performance and efficiency in various applications.

Implementation Method 1

an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

The photonic crystal structure is disposed over the active layer and the index matching layer

Methodology Applied

Scientific EffectPhotonic crystal effect: Photonic Crystal

Data Source

PatentUS12088063B2Photonic crystal surface-emitting laser

Publication Date: 2024.09.10 INTERFACE TECH (CHENGDU) CO LTD

AI summary

A photonic crystal surface-emitting laser includes a substrate, an n-type cladding layer, an active layer, an index matching layer and a photonic crystal structure. The n-type cladding layer is disposed over the substrate. The active layer is disposed over the n-type cladding layer. The index matching layer is disposed over the n-type cladding layer and is arranged around the active layer. The index matching layer is electrically insulating, and an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer. The photonic crystal structure is disposed over the active layer and the index matching layer.