VCSEL Array Microlenses for High-Frequency Thermal Management
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Solution Overview
Problem
Existing VCSEL arrays face challenges in achieving high frequency modulation and high power output due to heating complexities, parasitic impedances, and frequency response limitations, which hinder their performance in applications requiring both high power and high frequency.
Innovation Solution
The design incorporates a monolithic array of VCSELs with minimized common p-contact area, increased distance between contact pads, and a raised heat sink structure, eliminating wire bonds and reducing parasitic impedance, while using microlenses to focus light efficiently without external optics, thereby enhancing heat dissipation and frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If VCSELs are arrayed to increase output power, then power output is improved, but heating complexities and frequency response deteriorate
Solution Approach 1:
The patent divides the common p-contact into multiple separate contact regions, each serving individual VCSELs or small groups of VCSELs. This segmentation reduces the total area of the common p-contact, thereby reducing parasitic impedance and improving frequency response while maintaining high power output capability through the distributed contact structure.
Solution Approach 2:
The patent introduces a raised heat sink structure that extends vertically from the substrate, creating a three-dimensional heat dissipation pathway. This vertical dimension provides enhanced thermal management by conducting heat away from the VCSEL array through the raised portion, which has improved thermal coupling to the substrate, thereby reducing operating temperature and maintaining frequency response at elevated power levels.
2Power
If VCSELs are arrayed to increase output power, then power output is improved, but parasitic impedance increases
Solution Approach 1:
The patent segments the common p-contact into multiple smaller contact regions distributed across the VCSEL array. This segmentation reduces the total contact area and the associated parasitic impedance by distributing the current path across multiple independent contact points, thereby reducing inductance and resistance effects that would otherwise limit high-frequency performance.
Solution Approach 2:
The patent introduces an intermediate raised heat sink structure that serves as a thermal and electrical mediator between the VCSEL array and the substrate. This raised structure provides improved thermal conduction pathways and reduces parasitic impedance by creating optimized electrical contact paths while maintaining mechanical support, thereby enabling high power output with reduced parasitic effects.
3Power
If VCSELs are arrayed to increase output power, then power output is improved, but frequency response decreases
Solution Approach 1:
The patent segments the common p-contact into multiple smaller contact regions, which reduces the total contact area and associated parasitic inductance and resistance. This segmentation allows for faster current modulation and improved frequency response by reducing the time constant of the electrical circuit, enabling the array to operate at higher frequencies while maintaining high power output.
Solution Approach 2:
The patent introduces a vertical dimension through the raised heat sink structure, which provides improved thermal management pathways. By enhancing heat dissipation in the vertical direction, the operating temperature of the VCSELs is reduced, which maintains the semiconductor material properties and carrier mobility at levels that support high-frequency operation, thereby preserving frequency response at elevated power levels.
4Illumination intensity
If external optics are used to focus light, then light focusing is improved, but device complexity increases
Solution Approach 1:
The patent integrates microlenses directly onto the VCSEL array substrate, merging the optical focusing function with the electrical and thermal management functions in a single integrated structure. This integration eliminates the need for separate external optics, reducing device complexity while maintaining effective light focusing capability for applications such as LIDAR and free-space communication.
Solution Approach 2:
The patent designs the VCSEL array substrate to serve multiple functions simultaneously: electrical contact, thermal management, and optical focusing. The raised heat sink structure and integrated microlenses enable the substrate to perform thermal conduction, mechanical support, and light focusing in a single component, thereby reducing the number of separate components needed and simplifying the overall device architecture while maintaining high illumination intensity at the focal point.
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 results in improved heat management, reduced parasitic impedance, and increased frequency response, enabling high-speed, high-power operation with superior reliability and cost efficiency, suitable for applications like LIDAR and free-space communication.
Implementation Method 1
a microlens array having a pitch that is slightly smaller than the pitch between the VCSELs
Implementation Method 2
a raised heat sink structure, eliminating wire bonds and reducing parasitic impedance
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A VCSEL array device formed of a monolithic array of raised VCSELs on an electrical contact and raised inactive regions connected to the electrical contact. The VCSELs can be spaced symmetrically or asymmetrically, in a manner to improve power or speed, or in phase and in parallel. The raised VCSELs and raised inactive regions are positioned between the electrical contact and an electrical waveguide. The VCSELs may be separated into subarrays and each VCSEL may be covered with an integrated or bonded microlens for directing light without external lenses. The microlenses may be offset to collect or collimate light and may be shaped to form various lens profiles.