Dual-Wavelength Semiconductor Laser End Face Window Structure
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Solution Overview
Problem
Monolithic dual-wavelength semiconductor laser devices face challenges in maximizing characteristics of each laser element due to issues like carrier overflow, impurity diffusion, and contamination, which affect stability and power output, particularly at high temperatures and high power operations.
Innovation Solution
The semiconductor laser device is structured such that the lower end of the end face window structure of the first laser element is positioned higher than that of the second laser element, with specific layer formations and impurity diffusion control to prevent impurity pileup and contamination, allowing for optimized wavelength shift and reduced light absorption, thereby enhancing output and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impurity diffusion is excessively conducted in the AlGaInP-based cladding layer to form end face window structure, then COD degradation is suppressed, but wavelength shift amount is reduced and impurity pileup occurs in the active layer
Solution Approach 1:
The patent divides the cladding layer into two distinct segments: an AlGaInP-based cladding layer and an AlGaAs-based cladding layer. The AlGaInP layer is positioned closer to the active layer to provide wavelength shift through controlled impurity diffusion, while the AlGaAs layer is positioned closer to the end face to suppress COD degradation. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between wavelength shift and COD suppression.
Solution Approach 2:
Different regions of the cladding structure are assigned different material compositions and impurity concentrations tailored to their specific functions. The AlGaInP-based cladding layer has impurities diffused to create wavelength shift in the gain region, while the AlGaAs-based cladding layer has impurities diffused to create the end face window structure. This local quality approach ensures that each region has the optimal properties for its intended purpose, resolving the contradiction between wavelength shift and COD suppression.
2Power
If higher power operation is implemented, then output power is improved, but carrier overflow in the active layer increases and stability at high temperature deteriorates
Solution Approach 1:
The patent introduces an AlGaAs-based cladding layer as an intermediary between the AlGaInP-based cladding layer and the end face. This intermediary layer serves multiple functions: it prevents direct contact between the highly doped end face window structure and the active layer, thereby preventing carrier overflow; it provides thermal management to maintain stability at high temperatures; and it allows the system to operate at higher power levels without sacrificing reliability.
3Device complexity
If monolithic dual-wavelength structure is used, then manufacturing complexity is reduced, but it becomes difficult to maximize characteristics of each laser element
Solution Approach 1:
The patent employs parameter changes by varying the material composition (AlGaInP vs. AlGaAs), impurity concentration, and layer thickness in different regions of the monolithic structure. These parameter variations allow each laser element (infrared and red) to be optimized for its specific wavelength and performance characteristics while maintaining a single integrated manufacturing process. The dual-cladding layer structure enables independent optimization of parameters for each wavelength without requiring separate devices.
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 effectively suppresses COD degradation, improves output power, and ensures stable operation at high temperatures and high power levels, while also simplifying the manufacturing process and reducing costs by standardizing process conditions for both infrared and red laser elements.
Implementation Method 1
In formation of the end face window structure, impurities are diffused in an active layer near the light emitting end face of a laser element for equalization of the composition, whereby an effective bandgap near the end face is widened.
Implementation Method 2
Light absorption near the end face is thus suppressed by the end face window structure. Accordingly, a negative chain reaction of heat generation near the end face due to light absorption, reduction in bandgap due to the heat generation, and further light absorption due to the reduction in bandgap can be prevented
Data Source
AI summary
A semiconductor laser device includes a first semiconductor laser element and a second semiconductor laser element. The first semiconductor laser element has a first end face window structure that is a region including first impurities formed near an end face, and the second semiconductor laser element has a second end face window structure that is a region including second impurities formed near an end face. The distance from a lower end of a first active layer to a lower end of the first end face window structure is shorter than the distance from a lower end of a second active layer to a lower end of the second end face window structure.