Semiconductor Laser Reflector Layout for Uniform Beam Intensity

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Solution Overview

Problem

Existing semiconductor laser devices face issues with dispersion in reflectance due to varying laser-light incident angles, leading to potential degradation in communication quality and reduced light output.

Innovation Solution

The semiconductor laser device employs two-stage reflective surfaces with specific inclination angles, where one reflective surface is formed by a dielectric multi-layer film on a photodiode, and the secondary reflective surface is set to angles less and more than 45 degrees relative to the beam center, respectively, to minimize dispersion in reflectance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single reflective surface is used to reflect laser light, then the structure is simple, but dispersion in reflectance occurs due to varying incident angles, degrading communication quality

Engineering Contradiction:

Improvereflective surface structureVSAvoidcommunication quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single reflective surface is divided into two separate reflective surfaces with different inclination angles. The first reflective surface reflects light within a certain angular range, while the second reflective surface reflects light in another angular range, collectively covering the full spread angle of the laser beam. This segmentation eliminates reflectance dispersion and maintains communication quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the reflective system are assigned different inclination angles tailored to specific incident angle ranges. The first reflective surface has an inclination angle optimized for central beam components, while the second reflective surface has an inclination angle optimized for peripheral beam components. This local optimization ensures uniform reflectance across the entire beam profile.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If a 45-degree inclined reflective surface is used to bend light perpendicular to the stem top face, then the light path is controlled, but dispersion in incident angle causes deformation in intensity distribution

Engineering Contradiction:

Improvelight path controlVSAvoidintensity distribution uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The single 45-degree reflective surface is segmented into two reflective surfaces with different inclination angles. Each surface is responsible for reflecting light within a specific angular subset, ensuring that all incident angles within the spread angle are reflected with uniform intensity. This maintains the bent light path while eliminating intensity distribution deformation.

Inventive Principle:

Principle #1Segmentation

3Volume of moving object

If the photodiode is positioned on the rear-end side of the laser chip, then the structure is compact, but the forward-to-rearward output ratio becomes unstable, reducing control accuracy

Engineering Contradiction:

Improvedevice compactnessVSAvoidoutput control accuracy

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

Instead of positioning the photodiode on the rear-end side to monitor backward output, the invention positions the photodiode to monitor forward output by reflecting forward-emitted light onto the photodiode surface. This inversion of the monitoring approach provides stable forward-to-rearward output ratio measurement, enabling accurate control while maintaining device compactness.

Inventive Principle:

Principle #13The other way round (Inversion)

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 reduces dispersion in reflectance, ensuring uniform intensity distribution of laser light and maintaining high communication quality while minimizing light output reduction.

Implementation Method 1

a reflective surface for reflecting laser light incident from the semiconductor laser light source toward the emission port; and a secondary reflective surface for reflecting laser light incident from the semiconductor laser light source toward the emission port

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

one of said reflective surface and said secondary reflective surface is constituted by a dielectric multi-layer film that is formed on a photodiode

Methodology Applied

Scientific EffectDielectric multi-layer film reflection: Dielectric Mirror

Data Source

PatentUS12424816B2Semiconductor laser device

Publication Date: 2025.09.23 MITSUBISHI ELECTRIC CORP

AI summary

A semiconductor laser device disclosed in this application is characterized; wherein one of the reflective surface and the secondary reflective surface is constituted by a dielectric multi-layer film that is formed on a PD chip for measuring a light quantity of the laser light; and wherein an inclination angle of the reflective surface is set to a value obtained by subtraction of a value that is less than an inclination angle of beam center, from 45 degrees, while an inclination angle of the secondary reflective surface is set to a value obtained by subtraction of a value that is more than the inclination angle of beam center, from 45 degrees.