Single-Chip Series-Connected VCSEL Array Design
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Solution Overview
Problem
Current VCSEL arrays face limitations in scaling optical power due to aperture size constraints and additive bulk capacitance in parallel configurations, which can lead to impedance mismatch with high current pulsed driver circuits, and tiling multiple chips for series connections increases costs and complexity.
Innovation Solution
A series-connected VCSEL array design on a single semiconductor die with electrically separate conductive regions and metallization patterns for serial connection, allowing for flip-chip bonding and reduced parasitic inductance, enabling higher optical power output without the need for tiling multiple chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple VCSELs are connected in parallel on a single substrate, then the optical output power is increased, but the additive bulk capacitance limits the modulation bandwidth and causes impedance mismatch with driver circuits
Solution Approach 1:
The patent divides the VCSEL array into multiple electrically independent regions on a single substrate, with each region containing VCSELs that can be independently controlled. This segmentation allows the array to achieve high optical power output while maintaining low capacitance per region, thus preserving modulation bandwidth and impedance matching characteristics.
2Power
If multiple chips are tiled on a common sub-mount to achieve series connection, then the optical power is enhanced, but the design complexity and manufacturing costs increase
Solution Approach 1:
The patent merges multiple electrically independent VCSEL regions onto a single substrate, creating a unified device that achieves series connection functionality without requiring multiple separate chips. This integration eliminates the need for complex tiling arrangements, reduces manufacturing steps, and simplifies packaging while maintaining the high optical power output of series-connected VCSELs.
3Power
If multiple chips are tiled for series connection, then the optical power output is increased, but the alignment accuracy between micro-lenses deteriorates
Solution Approach 1:
By integrating all VCSEL regions on a single substrate, the patent ensures that all micro-lenses and other optical components are fabricated in the same manufacturing run, guaranteeing consistent alignment accuracy across the entire device. This eliminates the alignment errors that would accumulate when tiling multiple separately fabricated chips.
4Power
If the aperture size of a single VCSEL is increased to achieve higher power, then the optical output power is improved, but current spreading losses and modal properties limit further scaling
Solution Approach 1:
The patent segments the high-power VCSEL array into multiple smaller, electrically independent regions, each operating at optimal aperture sizes that minimize current spreading losses. By connecting these regions in series, the system achieves high total optical power output while each individual VCSEL operates in its optimal efficiency range, avoiding the energy losses associated with oversized single VCSELs.
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 design enhances optical power output while reducing manufacturing and packaging costs, allowing for optimal matching of drive circuitry and micro-optics, and improving frequency response and thermal performance.
Implementation Method 1
Vertical-cavity surface-emitting lasers (VCSELs) are used in a variety of communication technologies
Implementation Method 2
a conductive cathode layer, the conductive cathode layer including a plurality of electrically separate conductive regions
Data Source
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AI summary
Methods, devices and systems are described for enabling a series-connected, single chip vertical-cavity surface-emitting laser (VCSEL) array. In one aspect, the single chip includes one or more non-conductive regions one the conductive layer to produce a plurality of electrically separate conductive regions. Each electrically separate region may have a plurality of VCSEL elements, including an anode region and a cathode region connected in series. The chip is connected to a sub-mount with a metallization pattern, which connects each electrically separate region on the conductive layer in series. In one aspect, the metallization pattern connects the anode region of a first electrically separate region to the cathode region of a second electrically separate region. The metallization pattern may also comprise cuts that maintain electrical separation between the anode and cathode regions on each conductive layer region, and that align with the etched regions.