Segmented VCSEL Array Wiring for Thermal Runaway Prevention
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Solution Overview
Problem
VCSEL arrays face thermal-induced failures due to overheating, particularly in the central area of two-dimensional arrays, which leads to reduced power output, increased thresholds, and catastrophic device failure, as excessive heat generation and poor thermal conductivity exacerbate defect propagation and thermal runaway.
Innovation Solution
The VCSEL array is divided into separate areas with distinct metal layer connections, allowing for independent control of electrical currents to prevent overheating by reducing or turning off VCSELs in the central or high-density areas, while maintaining unchanged currents in surrounding areas, thereby managing temperature distribution and preventing thermal destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If VCSELs are operated in continuous-wave mode to achieve stable laser output, then power output is maintained, but thermal accumulation occurs causing overheating and device failure
Solution Approach 1:
The patent applies periodic pulsed operation instead of continuous-wave operation. VCSELs are activated in alternating patterns where some emitters are turned on while others are turned off or operated at reduced power, creating periodic cycles of high and low power states that prevent thermal accumulation while maintaining average output stability
Solution Approach 2:
The VCSEL array is segmented into multiple independent emitter groups that can be controlled separately. This segmentation allows different regions of the array to operate at different power levels or be activated at different times, distributing thermal load across the device and preventing localized overheating
2Power
If VCSEL density is increased in the central area to maximize array output, then power output is improved, but thermal runaway is accelerated due to heat accumulation
Solution Approach 1:
The patent implements local quality control by assigning different operational characteristics to different regions of the VCSEL array. The central area with higher VCSEL density is operated with reduced power or different pulsed patterns compared to peripheral areas, allowing each region to operate within safe thermal limits while contributing to overall array output
Solution Approach 2:
The system dynamically adjusts the operational state of VCSELs based on real-time thermal conditions and usage patterns. Emitters are selectively activated or deactivated during operation to balance power distribution and thermal load, preventing any single region from experiencing thermal runaway while maintaining total array output
3Device complexity
If common electrical connection is used for all VCSELs to simplify control, then device complexity is reduced, but thermal management capability is lost
Solution Approach 1:
The electrical connection system is segmented into multiple independent control groups rather than using a single common connection. Each group can be controlled independently with different current levels or activation patterns, enabling regional thermal management while maintaining relatively simple control circuitry for each group
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 solution effectively prevents thermal runaway and catastrophic failures by reducing heat generation in overheated areas, enhancing the reliability and operational longevity of VCSEL arrays by allowing for separate control of VCSELs in different regions, thus maintaining uniform power output and preventing thermal destruction.
Implementation Method 1
Each VCSEL structure emits a laser beam when being powered on
Implementation Method 2
The first metal layer portion electrically connects VCSEL structures in a predetermined central part of the area. The second metal layer portion electrically connects VCSEL structures in the surrounding part of the area
Implementation Method 3
Self-heating in a VCSEL is caused by the excessive heat and the accumulation of heat inside the laser cavity. The doped semiconductor distributed Bragg reflectors (DBRs) have high series resistance and are the main reason for the excessive heat generated
Implementation Method 4
VCSELs also exhibit large thermal impedances because they are small and the DBRs have poor thermal conductivity
Data Source
AI summary
A VCSEL array is divided into at least a first area and a second area. The first area is surrounded by the second area. The first area would experience higher temperature than the second area after VCSELs in the first and second areas are turned on for a given time period. VCSELs in the first area are electrically connected to a first metal layer portion. VCSELs in the second area are electrically connected to a second metal layer portion. The first and second metal layer portions are electrically insulated from each other.