Semiconductor Laser Resonator Facet Depth Optimization

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Solution Overview

Problem

Existing semiconductor laser devices face issues with optical loss due to scattering of laser light at the resonator facet, leading to deteriorated optical output characteristics, as the near-field pattern and protruding portions are not adequately considered during dry etching, affecting both light output and far-field patterns.

Innovation Solution

The semiconductor laser device is designed with a resonator facet and a protruding portion having a stepped bottom surface, where the depth of the bottom surface is set to a specific depth or deeper, ensuring that the laser light is not hindered by the protruding portion, and a reflective coating film is optionally used on the rear facet to enhance reflectivity and reduce optical loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If dry etching is performed to form a resonator facet, then the resonator facet can be formed, but a protruding portion occurs that scatters laser light and increases optical loss

Engineering Contradiction:

Improveresonator facet formationVSAvoidoptical loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The harmful protruding portion is removed by performing additional etching or polishing steps after the initial dry etching, extracting the scattering element that causes optical loss while preserving the resonator facet structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The resonator facet surface is treated differently from other regions by applying anti-reflection coatings or performing selective polishing only at the facet location, reducing scattering locally without affecting the overall device structure

Inventive Principle:

Principle #3Local quality

2Shape

If the protruding portion is made deeper to improve far-field pattern, then the far-field pattern improves, but the optical loss increases due to light scattering

Engineering Contradiction:

Improvefar-field patternVSAvoidoptical loss

Core Design Contradiction:

ShapeVSLoss of energy

Solution Approach 1:

The depth and shape parameters of the resonator facet are optimized by varying etching conditions, polishing depth, or coating thickness to achieve the ideal balance between far-field pattern quality and optical loss minimization

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Multiple materials or processing steps are combined, such as combining dry etching with wet etching, or adding anti-reflection coating layers, to simultaneously achieve good far-field pattern and low optical loss

Inventive Principle:

Principle #40Composite materials

3Device complexity

If the resonator facet is formed without considering near-field pattern, then the manufacturing process is simpler, but a large amount of light is scattered and optical output characteristics deteriorate

Engineering Contradiction:

Improvemanufacturing process complexityVSAvoidoptical output

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The near-field pattern is calculated and analyzed before the actual resonator facet fabrication, allowing the facet shape and depth to be pre-optimized to minimize light scattering and maximize optical output

Inventive Principle:

Principle #10Preliminary 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 configuration effectively suppresses optical loss and ensures high light output and excellent far-field patterns by optimizing the depth of the bottom surface portion and using a reflective coating to manage laser radiation, thereby improving the overall performance of the semiconductor laser device.

Implementation Method 1

a resonator facet portion (7a, 10a) containing an end portion of the active layer (3)

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

a protruding portion (7b, 10b) protruding in a resonator length direction beyond the resonator facet portion (7a, 10a) by a predetermined protrusion amount (X) and having a stepped bottom surface portion (7c, 10c) that faces a side of the resonator facet portion (7a, 10a)

Methodology Applied

Scientific EffectLight blocking and redirection: Absorption (EM radiation)

Data Source

PatentUS11211769B2Semiconductor laser device

Publication Date: 2021.12.28 MITSUBISHI ELECTRIC CORP

AI summary

A front facet of the semiconductor laser device includes a resonator facet portion containing an end of an active layer, and a protruding portion which protrudes beyond the resonator facet portion in a resonator length direction by a predetermined protrusion amount and has a stepped bottom surface portion. The resonator facet portion and the stepped bottom surface portion are connected to each other to form a corner portion. The distance from a thickness center position of the active layer to the stepped bottom surface portion is defined by a bottom surface portion depth. The bottom surface portion depth is set to be equal to a predetermined specific depth or deeper than the specific depth.