Semiconductor Laser End Face Window Structure for COD Resistance
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Solution Overview
Problem
Semiconductor laser elements with end face window structures face challenges in increasing catastrophic optical damage (COD) levels while maintaining thermal saturation and long-term reliability, as increasing the well layer thickness leads to deteriorated temperature characteristics and reliability issues.
Innovation Solution
A semiconductor laser device with an end face window structure, featuring a well layer with a P-side second barrier layer having a higher Al composition ratio than the P-side first barrier layer, and a band gap energy greater than that of the first barrier layer, allowing for increased COD levels without compromising temperature characteristics or long-term reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the well layer thickness is increased to increase thermal saturation level, then thermal saturation level is improved, but temperature characteristics deteriorate and long-term reliability decreases
Solution Approach 1:
The patent applies local quality by creating different Al composition ratios in different barrier layers (P-side first barrier layer with lower Al composition, P-side second barrier layer with higher Al composition). This allows each barrier layer to have optimized properties: the first barrier layer maintains good temperature characteristics, while the second barrier layer provides enhanced reliability and COD level, resolving the contradiction between thermal saturation and reliability.
2Strength
If a window region is formed in end face portion to increase COD level, then COD level is improved, but the effect is blocked when well layer thickness is increased
Solution Approach 1:
The patent segments the barrier layer into multiple distinct layers (P-side first barrier layer and P-side second barrier layer) with different Al composition ratios. This segmentation allows the window region to maintain its COD-enhancing effect while the increased well layer thickness provides thermal saturation, as each barrier layer performs its specific function independently without interfering with the other.
3Strength
If a window region is formed in end face portion to increase COD level, then COD level is improved, but temperature characteristics deteriorate
Solution Approach 1:
The patent uses local quality by assigning different Al composition ratios to different barrier layers. The P-side first barrier layer with lower Al composition maintains good temperature characteristics, while the P-side second barrier layer with higher Al composition enhances COD level. This localized differentiation resolves the contradiction between temperature characteristics and COD level.
Data Source
AI summary
A semiconductor laser device includes an N-type cladding layer, an active layer, and a P-type cladding layer. The active layer includes a well layer, a P-side first barrier layer above the well layer, and a P-side second barrier layer above the P-side first barrier layer. The P-side second barrier layer has an AI composition ratio higher than an AI composition ratio of the P-side first barrier layer. The P-side second barrier layer has band gap energy greater than band gap energy of the P-side first barrier layer. The semiconductor laser device has an end face window structure in which band gap energy of a portion of the well layer in a vicinity of an end face that emits the laser light is greater than band gap energy of a central portion of the well layer in a resonator length direction.