Composite Cavity Laser with Dual-Semiconductor Waveguides for High Power
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Solution Overview
Problem
Current vertical-cavity surface-emitting lasers (VCSELs) face limitations in achieving high optical power and efficiency due to thermal management and optical loss issues, particularly in maintaining reliability at high power levels and integrating semiconductor materials with differing bandgaps effectively.
Innovation Solution
A composite cavity laser (CCL) is developed, comprising an upper narrow bandgap semiconductor structure with a distributed Bragg reflector and a lower wide bandgap semiconductor structure, coupled via a vertical grating or evanescent tapered coupler, which enhances thermal conductivity and reduces optical loss by guiding lasing light through a lower refractive index waveguide for efficient output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a traditional VCSEL cavity structure is used, then the device is simple to fabricate, but thermal management and optical loss issues limit high optical power and efficiency
Solution Approach 1:
The laser cavity is segmented into two separate semiconductor structures with different bandgaps. The first structure (narrower bandgap) provides gain and distributed mirrors, while the second structure (wider bandgap) provides a low-loss waveguide and better thermal conductivity, allowing each segment to optimize for its specific function and resolve the contradiction between power and reliability
Solution Approach 2:
The patent uses composite semiconductor materials with different bandgaps (e.g., GaAs/InP combination) to create a cavity that combines the optical gain properties of narrow bandgap materials with the thermal and optical loss properties of wide bandgap materials, enabling simultaneous achievement of high optical power and reliability
2Loss of energy
If semiconductor materials with differing bandgaps are integrated, then thermal conductivity and optical loss are improved, but fabrication complexity increases
Solution Approach 1:
By segmenting the cavity into two separate structures that can be fabricated independently and then coupled, the patent reduces fabrication complexity compared to attempting to grow a single complex heterostructure, while still achieving the benefits of different bandgap materials for reduced optical loss
Solution Approach 2:
A coupler structure acts as an intermediary to connect the two semiconductor structures with different bandgaps, enabling efficient optical coupling between them while simplifying the overall fabrication process compared to direct integration methods
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
The CCL achieves improved thermal management, higher optical power, and reduced optical damage, enabling efficient light coupling and enhanced reliability at high power levels with lower loss and better thermal removal, while integrating materials with differing bandgaps for improved performance.
Implementation Method 1
Each mirror stack includes a number of epitaxial layers of alternating refractive index values (e.g., alternating between 'high' and 'low' refractive index values). As light passes from a layer of one index of refraction to another, a portion of the light is reflected, creating a diffractive Bragg reflector (DBR) structure.
Implementation Method 2
coupled via a vertical grating or evanescent tapered coupler, which enhances thermal conductivity and reduces optical loss by guiding lasing light
Implementation Method 3
coupled via a vertical grating or evanescent tapered coupler
Data Source
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AI summary
A laser may include a lower semiconductor structure and an upper semiconductor structure. The lower semiconductor structure may include a lower waveguide along a top side of the lower semiconductor structure. The upper semiconductor structure may include an upper waveguide along a bottom side of the upper semiconductor structure. The upper semiconductor structure may be positioned over the top side of the lower semiconductor structure such that a first portion of the upper waveguide vertically overlaps a second portion of the lower waveguide. A coupler between the upper waveguide and the lower waveguide may couple optical energy of the upper waveguide to the lower waveguide. The lower waveguide may comprise semiconductor material having a wider bandgap than semiconductor material of the upper waveguide.