Optical Transmission Device With Butt-Joined Waveguides
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Solution Overview
Problem
The optical transmission device disclosed in Patent Document 1 faces issues with optical coupling loss between III-V gain medium material and silicon waveguide, resulting in poor laser efficiency due to its complex structure and lack of resonator structure in the III-V gain medium material.
Innovation Solution
An optical transmission device with a semiconductor laser array and modulator array hybrid integrated, where the laser waveguide and modulator waveguide are butt-joined with a distance of 10 μm or less, utilizing distributed feedback semiconductor lasers on an n-InP substrate and Mach-Zehnder modulators on a silicon substrate, eliminating the need for lenses and simplifying the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a III-V gain medium material is bonded to a silicon waveguide with a reflector structure, then an optical resonator can be formed, but the laser efficiency deteriorates due to optical coupling loss between different materials
Solution Approach 1:
The patent applies homogeneity by forming the resonator structure entirely within the III-V semiconductor layer using a distributed feedback (DFB) mechanism. The grating structure is created in the same material layer as the gain medium, eliminating the need for bonding III-V material to silicon waveguides. This homogeneous structure removes the optical coupling loss that occurs at material interfaces, thereby improving laser efficiency while maintaining the necessary resonator functionality.
2Reliability
If a resonator structure is provided in the silicon waveguide, then the laser can operate, but the structure becomes complicated with bonding requirements between different substrates
Solution Approach 1:
The patent segments the laser structure into independent distributed feedback regions within the III-V semiconductor layer. Instead of requiring a complex bonded structure with silicon waveguides and external reflectors, the resonator function is segmented into periodic grating structures formed directly in the gain medium layer. This segmentation approach simplifies the overall device structure by eliminating the need for heterogeneous bonding while maintaining laser operation capability.
Solution Approach 2:
The patent extracts the resonator function from the silicon waveguide structure and relocates it entirely within the III-V semiconductor layer. By taking out the resonator requirement from the silicon substrate and implementing it through DFB gratings in the III-V material, the invention eliminates complex bonding requirements and simplifies the device structure while preserving essential laser operation.
3Productivity
If hybrid integration of semiconductor laser array and modulator array is performed, then transmission capacity increases, but manufacturing complexity increases due to bonding requirements
Solution Approach 1:
The patent merges the laser array and modulator array fabrication processes by forming both structures on the same III-V semiconductor substrate. The distributed feedback laser structures and modulator structures are created in the same material system using compatible fabrication techniques, eliminating the need for separate substrate bonding steps. This merging approach maintains high transmission capacity through array integration while significantly reducing manufacturing complexity.
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 achieves high laser efficiency and simplifies the structure, reducing optical coupling loss and manufacturing costs while maintaining high reliability and frequency response characteristics.
Implementation Method 1
a laser structure in which a III-V semiconductor (III-V gain medium material) as a gain medium material is bonded to a waveguide (silicon waveguide) made of a silicon-based material and a reflector structure (optical resonator with reflector pair) is formed in the waveguide made of the silicon-based material
Implementation Method 2
a modulator structure in which a silicon-based material as a core material is bonded to a cladding material and an optical resonator is formed in the silicon-based material
Data Source
AI summary
An optical transmission device includes a semiconductor laser chip in which a semiconductor laser array having a plurality of distributed feedback semiconductor lasers formed on a first semiconductor substrate is formed, a semiconductor waveguide chip in which a semiconductor modulator array formed on a second semiconductor substrate and having the same number of semiconductor modulators as the semiconductor lasers is formed. In the optical transmission device, a waveguide and a waveguide are butt-joined such that a distance between an end face of the waveguide on a side to the semiconductor modulator array in each of the semiconductor lasers of the semiconductor laser array and an end face of the waveguide on a side to the semiconductor laser array in each of the semiconductor modulators of the semiconductor modulator array is 10 μm or less.