Ridge Semiconductor Laser Layout for Narrow Beam Divergence
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Solution Overview
Problem
Conventional ridge-type broad-area semiconductor laser devices with real refractive index distribution face issues such as varying horizontal beam divergence angles due to small gain differences among modes, lack of near-field pattern peaks, and reduced reliability due to proton implantation-induced crystal defects, leading to decreased power conversion efficiency and reliability.
Innovation Solution
A semiconductor laser device design with a ridge region composed of an inner region and outer regions, where current non-injection structures are provided in the outer regions to enhance the gain in low-order modes, narrowing the horizontal beam divergence angle and reducing loss, while avoiding the proton implantation region to minimize crystal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If current non-injection structures are provided in ridge outer regions, then gain in low-order modes is enhanced and horizontal beam divergence angle is narrowed, but device complexity increases
Solution Approach 1:
The ridge region is segmented into an inner region and outer regions, with current non-injection structures selectively provided in the outer regions. This segmentation allows differential current control across the ridge width, enhancing low-order mode gain while maintaining structural manageability through clear spatial division.
Solution Approach 2:
Current non-injection structures are applied locally to the ridge outer regions rather than uniformly across the entire ridge. This local quality approach modifies the refractive index distribution specifically where needed to enhance low-order modes, avoiding unnecessary complexity in the inner region where current injection is desired.
2Reliability
If proton implantation is performed to create high resistance regions, then current confinement is improved, but crystal defects increase and reliability decreases
Solution Approach 1:
The invention converts the harmful effect of proton implantation-induced crystal defects into a beneficial current confinement mechanism. By strategically positioning current non-injection structures in ridge outer regions, the design utilizes the high resistance property while minimizing the impact of crystal defects on overall device reliability through spatial separation from the active region.
Solution Approach 2:
The harmful crystal defects are effectively extracted or isolated from the critical active region by placing current non-injection structures only in the ridge outer regions. This extraction approach separates the functional benefit (current confinement) from the harmful effect (crystal defects), protecting the active region from defect-induced reliability issues.
3Use of energy by moving object
If current non-injection width is reduced to suppress loss increase, then power conversion efficiency is improved, but mode selectivity decreases
Solution Approach 1:
The invention addresses the trade-off by operating in the spatial dimension of ridge width distribution. By controlling the width and position of current non-injection structures in the horizontal dimension, the design achieves both adequate mode selectivity and acceptable power conversion efficiency, resolving the contradiction through dimensional optimization.
Solution Approach 2:
The invention optimizes the width parameter of current non-injection structures to balance mode selectivity and power conversion efficiency. By carefully selecting the width parameter within specific ranges, the design achieves sufficient mode discrimination while minimizing loss and maintaining acceptable power conversion efficiency.
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 achieves higher gain in low-order modes, narrows the horizontal beam divergence angle, and improves efficiency and reliability by ensuring current primarily flows in the ridge inner region, while minimizing the impact of proton implantation-induced defects.
Implementation Method 1
a ridge region in which the laser beam is guided between the front end surface and the rear end surface, the ridge region having a width of 2W
Implementation Method 2
a first-conductivity-type cladding layer, a first-conductivity-type-side optical guide layer, an active layer, a second-conductivity-type-side optical guide layer, a second-conductivity-type cladding layer, which are laminated above the first-conductivity-type semiconductor substrate
Data Source
AI summary
A semiconductor laser device of the present disclosure includes: a first-conductivity-type cladding layer, a first-conductivity-type-side optical guide layer, an active layer, a second-conductivity-type-side optical guide layer, a second-conductivity-type cladding layer, and a second-conductivity-type contact layer laminated above a semiconductor substrate; a resonator having a front end surface and a rear end surface; and a ridge region for guiding a laser beam between the front and rear end surfaces. The ridge region is composed of a ridge inner region in which an effective refractive index is nai, and ridge outer regions which are provided on both sides of the ridge inner region and in which an effective refractive index is nao, the ridge outer regions having current non-injection structures. A ridge outer region width Wo is greater than a distance from a lower end of each current non-injection structure to the active layer.