Semiconductor Optical Element Segmented Current Injection
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Solution Overview
Problem
Current semiconductor lasers face challenges in increasing speed and reducing power consumption for high-speed optical communication, as the relaxation oscillation frequency is limited by the trade-off between carrier density and optical differential gain, leading to decreased optical confinement and increased mirror loss.
Innovation Solution
A semiconductor optical element with a multiple quantum well layer and an upper mesa structure, where the current injection structure has a narrower width than the mesa structure, and an insulating film covers the mesa structure, enhancing optical confinement and reducing leakage current, thereby increasing the relaxation oscillation frequency and optical gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If carrier density is increased to increase optical gain, then optical gain increases, but optical differential gain decreases and relaxation oscillation frequency decreases
Solution Approach 1:
The patent divides the current injection structure into multiple regions with different widths: a first region with width W1 over the quantum well layer, and second and third regions with smaller widths W2 and W3 over the cladding layers. This segmentation allows concentrated current injection at the center (first region) to increase optical gain, while the narrower outer regions reduce mirror loss and improve optical confinement, thereby resolving the contradiction between optical gain and relaxation oscillation frequency
Solution Approach 2:
The patent applies different structural characteristics to different locations: the central first region has larger width for high current density and optical gain, while the outer second and third regions have smaller widths for reduced mirror loss. This local differentiation optimizes both optical gain and relaxation oscillation frequency simultaneously
2Speed
If optical confinement is improved to increase speed, then relaxation oscillation frequency increases, but mirror loss increases
Solution Approach 1:
The segmented current injection structure with regions of different widths enables the outer regions (second and third regions with widths W2 and W3 smaller than W1) to provide enhanced optical confinement through their narrower geometry, which increases the fraction of optical power confined in the active region. This segmentation simultaneously manages mirror loss by controlling the lateral confinement characteristics
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 configuration results in a semiconductor laser with improved high-speed response, increased optical confinement, and high reliability, achieving higher relaxation oscillation frequencies and extended lifetime while maintaining low power consumption.
Implementation Method 1
enhancing optical confinement and reducing leakage current
Implementation Method 2
a lower structure that includes a multiple quantum well layer
Implementation Method 3
a semiconductor laser that can output light having a wavelength suitable for optical fibers
Data Source
AI summary
A semiconductor optical element is configured to emit or absorb light and includes a lower structure that includes a multiple quantum well layer; an upper mesa structure that is disposed on the lower structure; a current injection structure that is disposed on the upper mesa structure, when seen from an optical axis of the emitted or absorbed light, a width of a portion of the current injection structure in contact with the upper mesa structure is smaller than a width of the upper mesa structure, the portion of the current injection structure in contact with the upper mesa structure consisting of InP, and an average refractive index of the upper mesa structure is higher than a refractive index of the InP forming the current injection structure; and an insulating film covering both side surfaces of the upper mesa structure and a part of an upper surface of the upper mesa structure.