Semiconductor Laser Device Parasitic Capacitance Reduction
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Solution Overview
Problem
Conventional semiconductor laser devices with integrated electro-absorption modulators suffer from parasitic capacitance issues, leading to degraded high-frequency characteristics and optical losses due to the presence of n-type InP hole-trapping layers and level differences between laser and modulator sections.
Innovation Solution
The semiconductor laser device integrates a p-type cladding layer that covers the semi-insulative burying layers and mesa stripes in both the laser and modulator sections, eliminating parasitic capacitance and minimizing optical losses by forming the laser and modulator sections on the same semiconductor substrate with optimized mesa stripe configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If n-type InP hole-trapping layers are added to prevent hole injection and improve laser efficiency, then laser efficiency is improved, but parasitic capacitance increases and high-frequency characteristics are degraded
Solution Approach 1:
The patent divides the device into two distinct sections with different layer configurations: the laser section includes n-type InP hole-trapping layers for improved laser efficiency, while the modulator section omits these layers to reduce parasitic capacitance and maintain high-frequency characteristics. This segmentation allows each section to be optimized for its specific function without compromising the other.
2Reliability
If mesa stripe width is narrowed to reduce parasitic capacitance, then high-frequency characteristics are improved, but optical loss increases and light-output efficiency is degraded
Solution Approach 1:
The patent applies segmentation by creating distinct structural configurations for the laser section and modulator section. The modulator section is designed without n-type InP hole-trapping layers, which reduces parasitic capacitance without requiring mesa stripe narrowing, thereby maintaining both high-frequency characteristics and adequate optical coupling.
3Productivity
If different layer structures are used in laser and modulator sections, then specific performance requirements are met, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning different layer structures to different sections of the device based on their specific functional requirements. The laser section has n-type InP hole-trapping layers for efficient light generation, while the modulator section lacks these layers to minimize parasitic capacitance. This localized differentiation optimizes performance while maintaining a relatively simple overall structure that can be fabricated using standard semiconductor processing techniques.
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 enhances light-output efficiency by reducing parasitic capacitance and optical losses, thereby improving high-frequency characteristics and maintaining excellent light-distribution profiles without the need for narrowing mesa stripes.
Implementation Method 1
the n-type InP hole-trapping layers (n-type burying layers) in the modulator section induce parasitic capacitances at their interfaces with the overlying p-type InP cladding layer (p-type cladding layer), so that the high-frequency characteristic is degraded
Data Source
AI summary
A semiconductor laser device includes a laser section and a modulator section. The laser section has: a first mesa stripe which is formed on a semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the first mesa stripe and are formed on the semiconductor substrate; n-type burying layers formed on respective surfaces of the semi-insulative burying layers; and a p-type cladding layer which covers surfaces of the n-type burying layers and the first mesa stripe. The modulator section has: a second mesa stripe which is formed on the semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the second mesa stripe and are formed on the semiconductor substrate; and a p-type cladding layer which covers surfaces of the semi-insulative burying layers and the second mesa stripe.