Integrated Laser Modulator Structure for Scattered-Light Absorption
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Solution Overview
Problem
Existing optical semiconductor devices with integrated semiconductor laser and optical modulator sections face issues with leakage light, leading to decreased extinction ratios, especially during high-power operation, due to the difficulty in processing light-shielding films on the output end surface.
Innovation Solution
The optical semiconductor device incorporates a semiconductor laser section and an optical modulator section with a light absorption layer made of group III-V semiconductor compound crystal containing Bi, and scattered-light absorption layers facing either the lower or upper surface of the light absorption layer to absorb scattered light, reducing leakage and heat-induced pile-up phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-shielding film with an opening is formed on the output end surface of the optical modulator section to shield leakage light, then the extinction ratio is improved, but the processing difficulty and manufacturing complexity increase significantly
Solution Approach 1:
The patent extracts the light-shielding function from a separate film structure and integrates it into the optical modulator section's semiconductor layers. By forming the light-shielding function within the semiconductor stack itself (using the n-type InP lower cladding layer and p-type InP upper cladding layer as inherent shielding structures), the need for additional metal film deposition and patternning steps is eliminated, significantly reducing processing difficulty while maintaining extinction ratio performance
Solution Approach 2:
The patent merges the light-shielding function with the existing semiconductor laser and modulator structures. The n-type InP lower cladding layer and p-type InP upper cladding layer serve dual purposes: as optical confinement layers and as inherent light-shielding structures. This integration eliminates the need for separate light-shielding film processing steps
2Reliability
If the light absorption layer contains Bi to suppress hole pile-up, then the extinction ratio is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent changes the compositional parameter of the light absorption layer by incorporating Bi (bismuth) into the InGaAsP material system. This parameter change fundamentally alters the material's electrical properties, enabling efficient hole extraction that suppresses hole pile-up and maintains high extinction ratio during high-power operation. The Bi content is controlled within a specific range (0.1-5 at%) to achieve the desired effect while managing manufacturing precision
Solution Approach 2:
The patent uses composite material InGaAsPBi (a quaternary alloy containing Bi) for the light absorption layer. This composite material combines the advantages of InGaAsP (optical properties) with Bi (electrical properties for hole extraction), creating a material that simultaneously achieves high extinction ratio and efficient carrier management
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 maintains a high extinction ratio by effectively absorbing scattered light and utilizing heat generated by absorption to reduce the impact of hole pile-up, allowing operation without additional cooling mechanisms and simplifying manufacturing.
Implementation Method 1
a scattered-light absorption layer that faces either a lower surface or an upper surface of the light absorption layer... absorbs the scattered light other than the guided light guided by the optical absorption layer
Implementation Method 2
a light absorption layer configured to absorb the laser light incident from the active layer
Implementation Method 3
utilizing heat generated by absorption to reduce the impact of hole pile-up
Data Source
AI summary
An optical semiconductor device according to the present disclosure having a semiconductor laser section and an optical modulator section formed above a common semiconductor substrate, comprising: the semiconductor laser section including: a first-conductivity-type lower cladding layer; an active layer configured to emit laser light; and a second-conductivity-type upper cladding layer provided with a first-order diffraction grating, which are each made of a group III-V semiconductor compound crystal; and the optical modulator section including: a light absorption layer configured to absorb the laser light incident from the active layer, at least a part of the light absorption layer made of a group III-V semiconductor compound crystal containing Bi; and a scattered-light absorption layer that faces either a lower surface or an upper surface of the light absorption layer, or a pair of scattered-light absorption layers that face the lower surface and the upper surface of the light absorption layer, respectively.