Monolithic Series-Connected Laser Diode Array for LiDAR
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Solution Overview
Problem
Conventional laser-diode arrays face challenges with high current requirements, leading to bulky and expensive power supplies, and complex packaging methods, which hinder miniaturization and introduce parasitic electrical issues, especially in high-power applications like LiDAR.
Innovation Solution
A monolithic series-connected laser-diode array is fabricated with conductive regions located outside the laser cavities, allowing for optical decoupling and higher doping levels without optical absorption, enabling efficient lateral electrical conduction and reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly doped conductive regions are placed within the laser cavity to enable lateral electrical conduction, then electrical conductivity is improved, but dopant-induced absorption degrades laser performance
Solution Approach 1:
The conductive region is extracted from the laser cavity and positioned adjacent to it instead. This separation removes the harmful dopant-induced absorption from the optical path while maintaining electrical conductivity for lateral current flow. The conductive region is formed in the substrate next to the laser cavity, enabling series connection without degrading laser performance.
2Power
If conventional wire bonding is used to connect laser diodes in series, then current requirements are reduced, but device complexity and parasitic electrical issues increase
Solution Approach 1:
The electrical connection function is merged into the substrate structure itself through conductive regions and traces. Instead of separate wire bonds connecting individual laser diodes, the substrate provides integrated conductive pathways that electrically connect multiple laser diodes in series, simplifying the overall device structure and reducing parasitic effects.
Solution Approach 2:
The mechanical wire bonding process is replaced with a monolithic integrated circuit approach using conductive traces in the substrate. This substitution eliminates the need for external wire bonds and complex packaging, reducing device complexity and parasitic electrical issues while maintaining series connection functionality.
3Power
If external electrical connections are used to realize series connections, then current requirements are reduced, but parasitic electrical issues limit high-frequency operation
Solution Approach 1:
External electrical connections are replaced with monolithic conductive traces integrated into the substrate. This substitution creates shorter, more direct electrical pathways with fewer interfaces and connections, reducing parasitic inductance and capacitance that limit high-frequency operation, thereby improving reliability for high-frequency applications.
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 approach reduces the complexity and cost of laser-diode arrays, enhances performance by avoiding dopant-induced absorption, and allows for thinner conductive regions with lower resistance, making them suitable for various applications including LiDAR and medical imaging.
Implementation Method 1
enabling efficient lateral electrical conduction and reduced resistance
Implementation Method 2
dopant-induced absorption in the conduction region impairs the optical mode that develops within the laser cavity
Data Source
AI summary
A monolithic series-connected laser-diode array is presented, where the array is formed on a non-conductive substrate that includes a plurality of discrete electrically conductive regions. Each laser diode of the array is disposed on a different conductive region such that the laser cavity of each laser diode is optically isolated from its respective conductive region, thereby avoiding optical loss in the laser cavity due to interaction with the highly doped conductive material. Each conductive region is configured to extend past the lateral extent of its respective laser-diode structure. Electrical connection between adjacent laser diodes of the array is made by forming a conductive trace that extends from the top contact of one of the laser diodes to the conductive region on which the other laser diode is disposed.