Bottom-Emitting VCSEL Array Layout for Optical Power Uniformity
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Solution Overview
Problem
Bottom-emitting VCSEL arrays face optical power uniformity issues due to lateral separation of electrical contacts, leading to resistance gradients and non-uniform optical power distribution, making them unsuitable for accurate detection and sensing applications.
Innovation Solution
A VCSEL array design with a metal layer on the bottom side of the substrate, featuring openings for light emission, reduces lateral voltage gradients and enhances optical power uniformity by allowing lateral current flow through the metal layer, thereby improving chip performance without increasing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electrical contacts are laterally separated in bottom-emitting VCSEL arrays, then device complexity is reduced, but optical power uniformity deteriorates due to resistance gradients
Solution Approach 1:
The patent introduces a bottom side metal layer on the substrate, adding a new dimensional pathway for current flow. Instead of relying solely on lateral current flow at the top surface, electrons can now travel through the substrate thickness dimension via the bottom metal layer, effectively creating a three-dimensional current distribution that reduces lateral voltage gradients and improves optical power uniformity across the emitter array
Solution Approach 2:
The bottom side metal layer acts as an intermediary conductive path between the laterally separated electrical contacts. By providing this intermediate current flow pathway through the substrate, the patent mediates the resistance gradient issue caused by lateral contact separation, enabling uniform current distribution without requiring complex contact configurations
2Manufacturing precision
If lateral current flow path is extended to improve uniformity, then optical power uniformity improves, but device complexity increases
Solution Approach 1:
Rather than extending the lateral current path which would increase device footprint and complexity, the patent extends the current path in the vertical dimension by adding a bottom metal layer. This allows current to flow laterally at the bottom surface while maintaining a compact device structure, achieving uniformity without increasing lateral dimensions or overall complexity
Solution Approach 2:
Instead of providing current flow pathways only at the top surface where contacts are located, the patent inverts the approach by adding a conductive layer at the bottom surface of the substrate. This inverted current path configuration allows electrons to enter from top contacts, flow through the active regions, and exit through the bottom metal layer, creating symmetric current distribution that improves uniformity without complicating the contact structure
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 solution achieves improved optical power uniformity across the emitter array, enabling more accurate optical detection and sensing applications with reduced complexity, and allows for the generation of light spots for three-dimensional sensing.
Implementation Method 1
a metal layer disposed on a bottom side of the substrate, where the metal layer is electrically connected to the second electrical contact, and where the metal layer includes one or more openings for light emission
Data Source
AI summary
In some implementations, an emitter array may include a substrate, an epitaxial structure on the substrate, a plurality of bottom-emitting emitters defined in the epitaxial structure, a first electrical contact positioned at a top side of the epitaxial structure, a second electrical contact positioned at the top side of the epitaxial structure, and a metal layer disposed on a bottom side of the substrate. The metal layer may be electrically connected to the second electrical contact. The metal layer may include one or more openings for light emission of the plurality of bottom-emitting emitters.