Buried Mesa Semiconductor Laser With High-Index Layer for Optical Coupling
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Solution Overview
Problem
Semiconductor lasers with buried heterostructures face issues with optical coupling efficiency due to large spread angles of far field patterns and decreased optical confinement coefficients, leading to reduced power output and reliability.
Innovation Solution
Incorporating a high refractive index layer beneath the mesa structure that expands light distribution, combined with a semi-insulating buried layer and specific cladding layers, to broaden the higher-order transverse-mode cut-off width and reduce the spread angle of the far field pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the optical confinement coefficient to the mesa structure is increased, then power output is improved, but the spread angle of the far field pattern becomes large, leading to decreased optical coupling tolerance
Solution Approach 1:
The patent introduces a high refractive index layer in the vertical dimension beneath the mesa structure to control light distribution. This dimensional addition allows independent optimization of optical confinement (affecting power output) and far field pattern spread (affecting coupling tolerance) by manipulating refractive index profiles at different vertical positions, thereby resolving the contradiction between power output and optical coupling tolerance.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a high refractive index layer with specifically controlled thickness and position beneath the mesa structure. This parameter change allows the optical confinement coefficient to be optimized for power output while simultaneously controlling the far field pattern spread angle to maintain optical coupling tolerance, thus resolving the technical contradiction.
2Reliability
If the mesa width is broadened, then current density of the multi-quantum well is reduced, but the higher-order transverse-mode appears, leading to decreased optical coupling efficiency
Solution Approach 1:
The patent applies local quality by creating a high refractive index layer with specific spatial distribution beneath the mesa structure. This localized refractive index modification allows the mesa width to be broadened for reduced current density and improved reliability, while the high refractive index region locally confines the optical mode to prevent higher-order transverse-mode appearance, thereby maintaining optical coupling efficiency.
3Power
If the n-InGaAsP guide layer is disposed to fill the diffraction grating, then optical properties are improved, but design flexibility of the guide layer is reduced
Solution Approach 1:
The patent segments the waveguide structure by separating the diffraction grating filling function from the optical confinement function. The high refractive index layer beneath the mesa structure handles optical confinement independently, while the guide layer can be optimized for diffraction grating compatibility without being constrained by optical confinement requirements, thus improving design flexibility while maintaining optical 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
Improves optical coupling efficiency and reliability by increasing the area of the near field pattern and reducing the spread angle of the far field pattern, allowing for higher power output and better tolerance in optical coupling.
Implementation Method 1
The high refractive index layer with the high refractive index expands distribution of light. Thus, the higher-order transverse-mode cut-off width becomes larger, the area of the NFP becomes larger, and the spread angle of the FFP becomes smaller
Implementation Method 2
a diffraction grating layer at least partially constituting a diffraction grating capable of diffracting the light oscillating in the multi-quantum well layer
Data Source
AI summary
A semiconductor laser includes: a multi-quantum well layer in a mesa structure; a buried layer comprising a semi-insulating semiconductor, the buried layer being in contact with each of both sides of the mesa structure; a first cladding layer with a first conductivity type, the first cladding layer having a lower refractive index than the multi-quantum well layer; a high refractive index layer configured to not absorb light oscillating in the multi-quantum well layer, the high refractive index layer having a higher refractive index than the first cladding layer; a diffraction grating layer at least partially constituting a diffraction grating capable of diffracting the light oscillating in the multi-quantum well layer, the diffraction grating layer not contacting the high refractive index layer; a substrate with the first conductivity type; and a second cladding layer with a second conductivity type above the multi-quantum well layer.