VCSEL Array Variable Spacing for Thermal Uniformity
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Solution Overview
Problem
Vertical-emitting laser arrays with uniform spacing suffer from thermal runaway and non-uniform optical power due to temperature differences between emitters, leading to reduced performance and increased chip costs.
Innovation Solution
Implementing a VCSEL array with variable spacing between emitters, where the distance between adjacent emitters varies based on their distance from the center of the array, reducing temperature and optical power non-uniformity without increasing the physical footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform spacing is used between VCSELs, then manufacturing is simplified, but temperature non-uniformity and optical power non-uniformity increase
Solution Approach 1:
The patent applies local quality by varying the spacing between VCSELs based on their position in the array. Specifically, VCSELs closer to the center have smaller spacing while those at the edges have larger spacing. This non-uniform spacing distribution compensates for the inherent temperature differences in the array, with closer spacing in cooler central regions and larger spacing in hotter edge regions, thereby achieving more uniform temperature and optical power across the entire array.
2Device complexity
If uniform spacing is used between VCSELs, then device structure is simplified, but thermal runaway threshold decreases
Solution Approach 1:
The patent implements local quality through position-dependent spacing where the distance between adjacent VCSELs varies according to their location. VCSELs at the array edges, which experience higher temperatures and greater thermal stress, are spaced farther apart to reduce thermal coupling and prevent thermal runaway. Central VCSELs maintain smaller spacing as they operate in cooler conditions. This localized spacing optimization raises the overall thermal runaway threshold of the array.
3Reliability
If variable spacing is implemented, then temperature uniformity improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the spacing parameter based on VCSEL position. The spacing between adjacent VCSELs is defined as a function of their distance from the array center, creating a graded distribution pattern. This controlled parameter variation achieves temperature uniformity while maintaining manufacturability, as the spacing changes follow a predictable pattern that can be incorporated into standard fabrication processes rather than requiring arbitrary precise positioning.
Data Source
AI summary
In some implementations, a VCSEL array may include a plurality of VCSELs that each operates concurrently and emits light at a same wavelength. A first distance between a first pair of adjacent VCSELs, of the plurality of VCSELs, may be different from a second distance between a second pair of adjacent VCSELs of the plurality of VCSELs. The first pair of adjacent VCSELs may be located closer to a center of the VCSEL array than the second pair of adjacent VCSELs. At least one of temperature non-uniformity or optical power non-uniformity among the plurality of VCSELs may be reduced as compared to another VCSEL array, with a same physical footprint as the VCSEL array, comprising uniformly spaced VCSELs.