VCSEL Cathode Finger Bridging for Uniform Optical Output

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Solution Overview

Problem

Vertical cavity surface emitting lasers (VCSELs) experience optical output delays and power differences due to long current paths through cathode electrodes, leading to increased rise times and uneven optical power outputs.

Innovation Solution

The implementation of a VCSEL device with multiple cathode electrodes and interconnects, including bridging traces and conductive pads, to distribute current more evenly across the VCSELs, reducing optical output delays and achieving uniform power outputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single cathode electrode is used to connect multiple VCSELs, then the device complexity is reduced, but the optical output uniformity and rise time performance deteriorate due to long current paths

Engineering Contradiction:

Improvecathode electrode structureVSAvoidoptical output uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The cathode electrode is segmented into multiple fingers that are distributed across the VCSEL array. Each finger connects to a subset of VCSELs, creating shorter and more uniform current paths. This segmentation resolves the contradiction by maintaining structural simplicity while achieving uniform optical output across all VCSELs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cathode electrode structure transitions from a single-point connection to a distributed multi-finger configuration across the substrate surface. This dimensional expansion allows current to be delivered to multiple locations simultaneously, reducing path length variations and improving optical output uniformity without significantly increasing device complexity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If a single cathode electrode connects all VCSELs, then the interconnect structure is simplified, but the optical output rise time increases due to long current paths

Engineering Contradiction:

Improveinterconnect structureVSAvoidoptical output rise time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The interconnect structure is segmented into multiple cathode electrode fingers, each serving a localized group of VCSELs. This creates parallel current paths that are shorter in length, reducing the time for current to reach all VCSELs simultaneously and thereby decreasing optical output rise time while maintaining interconnect simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multiple cathode electrode fingers enable continuous and simultaneous current delivery to all VCSELs across the array. This continuous action ensures that all lasers receive current at the same time, minimizing rise time variations and maintaining efficient operation without complex timing control.

Inventive Principle:

Principle #20Continuity of useful action

3Device complexity

If a single cathode electrode is used, then the electrical connection structure is simplified, but the power output uniformity across VCSELs deteriorates

Engineering Contradiction:

Improveelectrical connection structureVSAvoidpower output uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The electrical connection structure is segmented into multiple cathode electrode fingers distributed across the VCSEL array. Each finger provides a dedicated current path to nearby VCSELs, ensuring that all lasers receive comparable current levels. This segmentation achieves uniform power output across the array while keeping the overall connection structure relatively simple.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each cathode electrode finger is locally optimized to connect to specific VCSELs in its vicinity, creating localized current distribution zones. This local quality approach ensures that each VCSEL receives appropriate current for uniform power output, while the collective arrangement of all fingers maintains overall structural simplicity.

Inventive Principle:

Principle #3Local quality

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 configuration results in reduced optical output rise times, more uniform power outputs, and improved reliability of electrical connections between the VCSEL device and the carrier.

Implementation Method 1

a bridge element that electrically connects a first finger of the multiple cathode electrode fingers and a second finger of the multiple cathode electrode fingers

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20240396297A1Electrode bridging in an emitter assembly

Publication Date: 2024.11.28 WELLS FARGO BANK NA

AI summary

In some implementations, an emitter assembly includes a vertical cavity surface emitting laser (VCSEL) device. The VCSEL device may include a substrate. The VCSEL device may include a plurality of VCSELs on the substrate. The VCSEL device may include at least one anode layer on the substrate and electrically connected to the plurality of VCSELs. The VCSEL device may include a cathode electrode over at least a portion of multiple VCSELs, of the plurality of VCSELs, and electrically connected to the multiple VCSELs. The cathode electrode may include multiple cathode electrode fingers. The emitter assembly may include a bridge element that electrically connects a first finger of the multiple cathode electrode fingers and a second finger of the multiple cathode electrode fingers.