Semiconductor Laser Device Asymmetric Dummy Elements
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Solution Overview
Problem
Multi-beam semiconductor laser devices face challenges in achieving uniform optical properties due to variations in shear strain and polarization angles caused by thermal stress during mounting, which existing methods fail to adequately address.
Innovation Solution
The solution involves intentionally displacing the central positions of metal layers with respect to light-emitting portions and controlling the ratio of contact areas between metal layers and solder to counteract shear strain, using materials with specific thermal expansion coefficients and wettability properties to reduce shear strain and polarization angle differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If junction-down mounting is used to efficiently dissipate heat, then heat dissipation is improved, but thermal stress causes variations in optical properties and polarization angles
Solution Approach 1:
The patent introduces asymmetric dummy laser elements with different structures (different numbers of quantum wells, different active layer thicknesses) from the actual laser elements. This asymmetry creates differential thermal stress distribution that compensates for the stress-induced polarization angle variations in the actual laser elements, thereby resolving the contradiction between heat dissipation efficiency and optical property uniformity.
Solution Approach 2:
The dummy laser elements act as intermediary structures that absorb and redistribute thermal stress. These dummy elements are positioned adjacent to the actual laser elements and serve as stress buffers, mediating the thermal stress between the substrate and the actual laser elements to maintain uniform optical properties while preserving efficient heat dissipation.
2Manufacturing precision
If thermal stress is reduced during mounting, then polarization angle uniformity is improved, but heat dissipation efficiency may be compromised
Solution Approach 1:
The asymmetric design of dummy laser elements creates a controlled thermal stress gradient that specifically targets polarization angle uniformity without interfering with the overall heat dissipation pathway. The dummy elements absorb lateral thermal stress while allowing vertical heat flow to continue efficiently to the heat sink.
Solution Approach 2:
The patent segments the laser element array into actual laser elements and dummy laser elements. This segmentation allows the dummy elements to specifically address polarization uniformity concerns while the actual elements maintain their light-emitting function and heat dissipation role, resolving the contradiction between these two requirements.
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 approach effectively reduces shear strain and polarization angle variations, leading to more uniform optical properties and improved performance in multi-beam semiconductor laser devices.
Implementation Method 1
When the temperature falls to ambient temperature after the solder bonding (after mounting), since the submount 6 contracts less than the substrate 11 (has a smaller linear expansion coefficient)
Implementation Method 2
A metal layer 10 for heat dissipation made of Au plating or the like is formed on each surface of the p type electrode 3
Implementation Method 3
The submount 6 has a function to relax the thermal stress caused by the difference in a linear expansion coefficient between the heat sink and the semiconductor laser element array 8
Data Source
AI summary
In a multi-beam semiconductor laser device, relative difference in shear strain applied to each of light-emitting portions of a laser chip mounted on a submount is suppressed, thereby reducing relative difference in polarization angle. A semiconductor laser element array mounted on a submount has a structure in which a semiconductor layer having two ridge portions is stacked on a substrate, and Au plating layers are formed on the surfaces of p type electrodes formed on the ridge portions. In each of the ridge portions, a central position of the Au plating layer in a width direction is intentionally displaced with respect to a central position of the underlying light-emitting portion in a width direction, so that shear strain is applied to each of the light-emitting portions at a stage before the semiconductor laser element array is mounted on the submount.