Grating Cover Layer Refractive Index Control for Semiconductor Laser Efficiency
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Solution Overview
Problem
Existing semiconductor lasers with diffraction gratings face challenges in achieving high laser output efficiency and temperature characteristics due to limitations in the refractive index difference and grating depth, particularly when reducing the size of the resonator length.
Innovation Solution
A grating layer with a projection-recess structure is designed using a group III-V semiconductor, where the cover layer has a different refractive index than the base layer, allowing for increased refractive index difference and coupling coefficient, achieved by varying the Al compositional ratio in the AlGaAs material to enhance the effective refractive index difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the resonator length is reduced to miniaturize the semiconductor laser, then the device size is decreased, but the laser output efficiency deteriorates due to insufficient refractive index difference and grating depth
Solution Approach 1:
The grating cover layer is designed with spatially varying compositional ratios: a first region with higher Al composition (lower refractive index) and a second region with lower Al composition (higher refractive index). This local differentiation creates enhanced refractive index contrast at the grating interface, improving light coupling efficiency and compensating for the reduced resonator length.
Solution Approach 2:
The patent varies the compositional parameters of the AlGaAs material system to optimize optical performance. By adjusting the Al composition ratio in different regions of the grating cover layer, the refractive index is precisely controlled to maximize the coupling coefficient between the waveguide and grating, thereby maintaining high laser output efficiency in a miniaturized device.
2Loss of energy
If the Al compositional ratio is increased to enhance the refractive index difference, then the coupling coefficient is improved, but the material composition uniformity becomes more difficult to control
Solution Approach 1:
The grating cover layer is segmented into distinct regions with different Al compositional ratios. This segmentation allows independent optimization of each region's composition to achieve the desired refractive index profile, while the overall structure maintains manufacturability through systematic composition control rather than requiring precise control of a single uniform composition.
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 results in a semiconductor laser with improved laser output efficiency and reliability, capable of emitting a laser beam with a shorter wavelength when combined with a second harmonic generation element, such as a green laser operating in the 530 nm range.
Implementation Method 1
the grating cover layer includes a first region which is disposed over recessed portions of the grating base layer and which has a compositional ratio of a group III-V semiconductor having a first refractive index, and a second region which is disposed over projecting portions of the grating base layer and which has a compositional ratio of a group III-V semiconductor having a second refractive index that is smaller than the first refractive index
Implementation Method 2
A laser beam is oscillated by utilizing recombination light emission of carriers injected into the active layer
Implementation Method 3
A laser beam is oscillated by utilizing recombination light emission of carriers injected into the active layer and optical resonance using cleaved end faces, a diffraction grating, or the like
Implementation Method 4
A laser beam is oscillated by utilizing recombination light emission of carriers injected into the active layer and optical resonance using cleaved end faces, a diffraction grating, or the like
Data Source
AI summary
An optical semiconductor element includes: a grating base layer including a projection-recess structure disposed over a substrate; and a grating cover layer including a group III-V semiconductor having three or more elements, wherein the grating cover layer includes a first region which is disposed over recessed portions of the grating base layer and which has a compositional ratio of a group III-V semiconductor having a first refractive index, and a second region which is disposed over projecting portions of the grating base layer and which has a compositional ratio of a group III-V semiconductor having a second refractive index that is smaller than the first refractive index, wherein the grating base layer includes a group III-V semiconductor having a third refractive index that is smaller than the first refractive index.