Edge-Emitting Laser Diode Facet Tapering Against COMD
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Solution Overview
Problem
Edge-emitting semiconductor laser diodes suffer from high failure rates due to thermal stresses and strains at the facets, leading to catastrophic optical mirror damage (COMD), which are exacerbated by high power densities and luminous and non-luminous recombination in the active layer near the facets.
Innovation Solution
The semiconductor layer sequence is designed with reduced active layer volume fraction and thickness near the facets, tapering the active layer towards the facets, and incorporating passivation layers and mirrors to reduce power density and thermal stress, while avoiding interfacial defects and fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the active layer is positioned close to the facets to maximize light emission, then the light extraction efficiency is improved, but thermal stress and strain at the facets increase leading to catastrophic optical mirror damage
Solution Approach 1:
The patent applies local quality by creating distinct regions within the semiconductor layer sequence: a first region with higher active layer volume fraction for efficient light generation, and a second region near the facets with reduced active layer volume fraction to minimize thermal stress. This spatial variation in active layer distribution allows simultaneous optimization of light extraction efficiency and reliability by assigning different functional characteristics to different locations within the device structure.
2Productivity
If high power density is used to increase output power, then the productivity is improved, but thermal stress and luminous/non-luminous recombination at the facets worsen causing COMD
Solution Approach 1:
The patent implements local quality by spatially differentiating the active layer volume fraction across the semiconductor layer sequence. The first region maintains high active layer content to support high power density and high output power production, while the second region near the facets reduces active layer content to specifically address and mitigate thermal stress and recombination effects. This localized structural modification allows the device to operate at high power densities without suffering from facet-related degradation.
3Illumination intensity
If the active layer thickness is increased to improve light generation, then the light emission intensity is improved, but the thermal stress and strain near the facets increase leading to higher failure rates
Solution Approach 1:
The patent applies local quality by varying the active layer thickness and volume fraction across different regions of the semiconductor layer sequence. In the first region, the active layer has greater volume fraction to maximize light emission intensity, while in the second region near the facets, the active layer volume fraction is reduced to minimize thermal stress accumulation. This regional differentiation allows the device to achieve high light emission intensity while maintaining reliability by protecting the facet regions from excessive thermal stress.
4Reliability
If the active layer volume fraction is reduced near the facets to lower thermal stress, then the reliability is improved, but the light emission efficiency in those regions decreases
Solution Approach 1:
The patent resolves this contradiction by applying local quality - recognizing that different regions of the device have different functional requirements. The first region is optimized for light emission efficiency with high active layer volume fraction, while the second region near the facets is optimized for stress reduction with lower active layer volume fraction. The overall device performance is improved because the facet region, which would otherwise be a failure point, is protected while the main emission region maintains high efficiency.
Solution Approach 2:
The patent applies segmentation by dividing the semiconductor layer sequence into distinct functional regions: a first region for primary light generation with high active layer content, and a second region near the facets with reduced active layer content for stress management. This segmentation allows each region to be independently optimized for its specific function, with the transition between regions being gradual to avoid abrupt changes in optical and mechanical properties.
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 design significantly reduces the failure rate of the semiconductor laser diode by minimizing thermal stress and strain, enhancing stability and reliability through controlled power density and improved light propagation.
Implementation Method 1
The active layer serves to generate electromagnetic radiation
Implementation Method 2
a portion of the light is reflected at the facets. A laser resonator is thus formed between the facets
Data Source
AI summary
In an embodiment, an edge-emitting semiconductor laser diode includes a growth substrate, a semiconductor layer sequence located on the growth substrate, the semiconductor layer sequence having an active layer and an etch stop layer and two facets located opposite each other, wherein the facets bound the semiconductor layer sequence in a lateral direction, wherein the semiconductor layer sequence includes two edge regions adjoining the facets and a central region directly adjoining both edge regions, wherein, within each of the edge regions, a volume fraction of the active layer in the semiconductor layer sequence is smaller than in the central region, wherein the active layer is spaced apart from one facet, wherein a distance of the active layer to the facet varies along a direction parallel to this facet, and wherein the etch stop layer is arranged between the growth substrate and the active layer.