Wavelength-Dependent Emission Mirror for InGaN Laser Stability
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Solution Overview
Problem
Semiconductor laser elements emitting light in the green region with wavelengths of 500 nm or more suffer from low light emitting efficiency due to the instability of InGaN layers, leading to deviations in emission wavelength and increased threshold current variations.
Innovation Solution
A semiconductor laser element is manufactured with a nitride semiconductor structure and mirrors having specific reflectance properties, where the emission-side mirror's reflectance increases with wavelength, reducing threshold current deviations and improving yield, and the reflection-side mirror maintains high reflectance across a range of wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the composition ratio of In in the InGaN layer is increased to achieve longer emission wavelength, then the emission wavelength increases, but the actual uptake amount of In becomes unstable and the emission wavelength deviates from target value
Solution Approach 1:
The patent changes the reflectance parameter of the emission-side mirror to compensate for wavelength deviations caused by In composition variations. By adjusting the mirror's optical parameter (reflectance) rather than the semiconductor layer composition, the system achieves wavelength control without suffering from the instability of In uptake
Solution Approach 2:
The patent implements a feedback mechanism where the reflectance of the emission-side mirror is specifically designed to increase with wavelength in the range of λo±X nm. This creates a self-correcting system where wavelength deviations automatically trigger reflectance changes that counteract the deviation, stabilizing the threshold current
2Length of moving object
If the emission wavelength is increased in the green region, then the light emitting efficiency decreases, but the reflectance of conventional emission-side mirrors remains almost unchanged
Solution Approach 1:
The patent fundamentally changes the reflectance parameter of the emission-side mirror from a constant value to a wavelength-dependent value that increases with wavelength. This parameter change compensates for the decreasing light emitting efficiency at longer wavelengths by reducing threshold current variations
Solution Approach 2:
The patent converts the harmful effect of decreasing light emitting efficiency at longer wavelengths into a benefit by designing the mirror reflectance to increase with wavelength. This creates a compensating mechanism where the mirror's wavelength-dependent reflectance counteracts the efficiency loss, transforming the problem into a solution
3Power
If a high reflectance mirror is used for the reflection-side mirror, then the optical output is improved, but the threshold current increases due to lower light emitting efficiency
Solution Approach 1:
The patent changes the reflectance parameter of the emission-side mirror to be wavelength-dependent, which compensates for efficiency losses and stabilizes threshold current while maintaining high optical output through the high reflectance of the reflection-side mirror
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 solution reduces variations in threshold current and enhances the stability of semiconductor laser elements by adjusting the reflectance of the emission-side mirror in response to wavelength changes, improving light emitting efficiency and optical output, especially in green light emission.
Implementation Method 1
forming an emission-side mirror on the light emission-side surface, the emission-side mirror having a reflectance that is lower than that of the reflection-side mirror and increases in accordance with an increase in wavelength
Data Source
AI summary
A method of manufacturing a semiconductor laser element includes: providing a nitride semiconductor structure with a target emission wavelength λo, the nitride semiconductor structure having a light emission-side surface and a light reflection-side surface; forming an emission-side mirror on the light emission-side surface; and forming a reflection-side mirror on the light reflection-side surface. The semiconductor laser element has an actual wavelength λa, which is 500 nm or more and is in a range of λo±X nm (5≤X≤15). A reflectance of the emission-side mirror is lower than a reflectance of the reflection-side mirror and increases in accordance with an increase in wavelength in a range of λo±X nm.