Mesa-Structured Semiconductor Laser for Low-Capacitance Spot Conversion
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Solution Overview
Problem
Conventional embedded type semiconductor lasers with integrated spot size converters face challenges in high-speed modulation due to increased parasitic capacitance and mode disturbances, which deform the optical output signal and beam shape.
Innovation Solution
A semiconductor optical element with a mesa structure where the active layer is embedded, featuring a straight propagating section with uniform active layer width and a spot size converter section with weaker light confinement, resulting in a larger spot size at the emission facet, and a smaller average mesa width in the straight propagating section compared to the spot size converter section, reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the width of the mesa structure is enlarged to efficiently enlarge the spot size at the emission facet, then the spot size can be increased, but the electrode area is increased and parasitic capacitance is increased
Solution Approach 1:
The mesa structure is divided into two functional sections: a straight propagating section with a first width and a spot size converter section with a second width. This segmentation allows the spot size converter section to have a larger width for effective spot size enlargement, while the straight propagating section maintains a smaller width to minimize electrode area and parasitic capacitance.
Solution Approach 2:
Different sections of the mesa structure are assigned different width characteristics tailored to their specific functions. The spot size converter section has a larger width optimized for spot size conversion, while the straight propagating section has a smaller width optimized for low parasitic capacitance and high-speed modulation performance.
2Speed
If the width of the mesa structure is enlarged to reduce parasitic capacitance effects, then high-speed modulation can be achieved, but the spot size conversion efficiency is reduced
Solution Approach 1:
The mesa structure is divided into two functional sections: a straight propagating section with a first width and a spot size converter section with a second width. This segmentation allows the spot size converter section to have a larger width for effective spot size enlargement, while the straight propagating section maintains a smaller width to minimize electrode area and parasitic capacitance.
Solution Approach 2:
Different sections of the mesa structure are assigned different width characteristics tailored to their specific functions. The spot size converter section has a larger width optimized for spot size conversion, while the straight propagating section has a smaller width optimized for low parasitic capacitance and high-speed modulation performance.
3Speed
If a spot size converter section is formed using a different semiconductor waveguide, then high-speed modulation can be achieved, but waveguide mode disturbance occurs and beam shape is deformed
Solution Approach 1:
The active layer is formed as a homogeneous structure throughout both the straight propagating section and the spot size converter section. This homogeneity ensures consistent material properties and refractive index across the entire laser structure, preventing waveguide mode disturbance and maintaining stable beam shape, while still enabling high-speed modulation through the optimized mesa width configuration.
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
Enables high-speed modulation with reduced parasitic capacitance and a narrow emitted beam width, improving alignment with optical fibers and maintaining a stable beam shape by minimizing mode disturbances.
Implementation Method 1
light confinement in an active layer is gradually weakened, and a penetration of light in a semiconductor layer in which an active layer is embedded becomes greater
Implementation Method 2
the light is reflected at the facet mirrors repeatedly
Implementation Method 3
When a spot size of Near Field Pattern (NFP) in the vicinity of an emission facet is large, diffraction of an emitted light becomes small, therefore the width of a beam in Far Field Pattern (FFP) can be narrowed
Data Source
AI summary
A semiconductor optical element has a mesa structure in which an active layer is embedded, and comprises a straight propagating section and a spot size converter section being such that a light confinement in the active layer is weaker than that of the straight propagating section, wherein in a same plane parallel to a layer surface of the active layer, an average value of a width of the mesa structure of the straight propagating section is smaller than a value of the width of the mesa structure at the emission facet of the spot size converter section, and at a top part of the mesa structure, an electrode is formed so that an electric current is injected in the active layer across the entire length of the straight propagating section and the spot size converter section.