Semiconductor Laser Asymmetric Light Guide
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Solution Overview
Problem
Conventional semiconductor laser devices with asymmetric structures achieve reduced threshold current and improved slope efficiency but face limitations in enhancing power conversion efficiency during high output power.
Innovation Solution
A semiconductor laser device with a light guide layer structure that includes a first conductivity type cladding layer, a light guide layer, a second conductivity type cladding layer, and a first conductivity type low-refractive-index layer, where the active layer is positioned closer to the second conductivity type cladding layer than the center of the light guide layer, and the layer thickness is optimized to allow high-order modes, reducing light confinement and operating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the active layer is disposed at a position where light confinement increases (asymmetric structure), then threshold current is reduced and slope efficiency is improved, but power conversion efficiency during high output power is limited
Solution Approach 1:
The patent employs an asymmetric light guide layer structure where the active layer is positioned closer to the second conductivity type cladding layer than to the center of the light guide layer. This asymmetric positioning optimizes the balance between light confinement and carrier distribution, enabling improved power conversion efficiency during high output power operation while maintaining reduced threshold current characteristics.
2Illumination intensity
If a low-refractive-index layer is inserted to expand light intensity distribution, then far-field pattern is narrowed, but when light guide layer is thick, light intensity is conversely narrowed and FFP expands
Solution Approach 1:
The patent introduces a low-refractive-index layer positioned between the first conductivity type cladding layer and the light guide layer. This layer creates localized refractive index variations that expand the light intensity distribution in the crystal growing direction without adversely affecting the far-field pattern, even when the light guide layer has a thickness that would normally permit high-order modes.
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 increases slope efficiency and reduces operating current during high output power, thereby improving power conversion efficiency compared to symmetric and conventional asymmetric structures.
Implementation Method 1
a first conductivity type low-refractive-index layer formed between the first conductivity type cladding layer and the light guide layer and having a refractive index which is lower than a refractive index of the first conductivity type cladding layer
Data Source
AI summary
An active layer is provided on a side closer to the second conductivity type cladding layer than a center of the light guide layer in the light guide layer. A first conductivity type low-refractive-index layer is formed between the first conductivity type cladding layer and the light guide layer and has a refractive index which is lower than a refractive index of the first conductivity type cladding layer. A layer thickness d of the light guide layer is a value at which a high-order mode equal to or higher than a first-order mode is permissible in a crystal growing direction by satisfying2πλng2-nc2d2≧π2.The active layer is disposed at a position where a light confinement of the active layer becomes smaller compared to a case in which the active layer is disposed at a center of the light guide layer while there is not the first conductivity type low-refractive-index layer.