Semiconductor Laser Layer Structure for Narrower Horizontal Divergence

Solution Overview

Problem

The application of conventional semiconductor laser devices with a ridge shape to broad area types results in widened beam divergence angles and reduced coupling efficiency with optical components due to multimode oscillation in the horizontal direction.

Innovation Solution

A semiconductor laser device structure is designed with specific refractive index and thickness relationships between conductivity type cladding layers and optical guide layers, allowing a first-order or higher-order mode in the lamination direction perpendicular to the optical axis, and incorporating a low refractive index layer to satisfy the condition v2 > v1, reducing the number of modes in the horizontal direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a ridge shape structure is applied to broad area type semiconductor laser device, then the oscillation efficiency is improved, but the beam divergence angle in horizontal direction is widened and coupling efficiency with optical component is reduced

Engineering Contradiction:

Improveoscillation efficiencyVSAvoidbeam divergence angle

Core Design Contradiction:

Loss of energyVSShape

Solution Approach 1:

The patent applies local quality by creating asymmetric refractive index distribution in the vertical direction through selective doping. The n-type cladding layer has higher refractive index than the p-type cladding layer, creating a localized refractive index gradient that confines light in the vertical direction without affecting horizontal propagation, thus reducing horizontal divergence angle while maintaining oscillation efficiency

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by intentionally creating different refractive indices between n-type and p-type cladding layers through controlled doping concentrations. This asymmetric structure causes light to be confined more strongly in the vertical direction, allowing the beam to maintain a narrower horizontal divergence angle while still achieving high oscillation efficiency through the ridge waveguide structure

Inventive Principle:

Principle #4Asymmetry

2Loss of energy

If a ridge shape structure is applied to broad area type semiconductor laser device, then the oscillation efficiency is improved, but the coupling efficiency with optical component is reduced

Engineering Contradiction:

Improveoscillation efficiencyVSAvoidcoupling efficiency with optical component

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies local quality by creating asymmetric refractive index distribution in the vertical direction through selective doping. The n-type cladding layer has higher refractive index than the p-type cladding layer, creating a localized refractive index gradient that confines light in the vertical direction without affecting horizontal propagation, thus reducing horizontal divergence angle while maintaining oscillation efficiency

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by intentionally creating different refractive indices between n-type and p-type cladding layers through controlled doping concentrations. This asymmetric structure causes light to be confined more strongly in the vertical direction, allowing the beam to maintain a narrower horizontal divergence angle while still achieving high oscillation efficiency through the ridge waveguide structure

Inventive Principle:

Principle #4Asymmetry

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 structure narrows the horizontal divergence angle and enhances coupling efficiency with optical components by limiting the number of modes in the horizontal direction, thereby improving performance.

Implementation Method 1

a first conductivity type low refractive index layer having a thickness of d1 and a refractive index n1 lower than nc1 is provided between the first conductivity type side optical guide layer and the first conductivity type cladding layer or inside the first conductivity type cladding layer

Methodology Applied

Scientific EffectOptical waveguide mode confinement: Waveguide (optics)

Implementation Method 2

a relationship is satisfied

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS12542426B2Semiconductor laser device

Publication Date: 2026.02.03 MITSUBISHI ELECTRIC CORP

AI summary

A semiconductor laser device includes a first conductivity type cladding layer having a refractive index nc1, a first conductivity type side optical guide layer, an active layer, a second conductivity type side optical guide layer, and a second conductivity type cladding layer of nc2 laminated in order on a first conductivity type semiconductor substrate, wherein an oscillation wavelength is λ, a first conductivity type low refractive index layer of n1 lower than nc1 having a thickness of d1 is provided between the first conductivity type side optical guide layer and the first conductivity type cladding layer, a second conductivity type low refractive index layer of n2 lower than nc2 having a thickness of d2 is provided between the second conductivity type side optical guide layer and the second conductivity type cladding layer, and a condition of a normalization frequency v2>v1 is satisfied.