Multi-Junction VCSEL Contacts for Optical Power Control

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Solution Overview

Problem

Vertical-cavity surface-emitting lasers (VCSELs) face limitations in meeting multiple optical power specifications across varying conditions, such as temperature changes, leading to thermal runaway and performance degradation, making them unsuitable for high-power applications like ToF and LIDAR due to fixed drive current or voltage requirements.

Innovation Solution

Implementing a multi-junction VCSEL structure with epitaxial layers and sets of contacts that allow independent current control to specific active layers, enabling variable optical output power in constant current mode and switching between modes to accommodate different power requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a VCSEL operates at high drive current to meet high-power specifications, then optical output power is improved, but thermal runaway and performance degradation occur

Engineering Contradiction:

Improveoptical output powerVSAvoidperformance stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The VCSEL is divided into multiple independently addressable active layers (first active layer, second active layer) with separate electrical contacts. This allows the total drive current to be segmented and distributed across multiple layers, enabling high optical output power while maintaining lower current density in each individual layer, thus preventing thermal runaway and performance degradation.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If a VCSEL uses fixed drive current or voltage, then manufacturing is simplified, but the device cannot meet multiple optical power specifications across varying conditions

Engineering Contradiction:

Improveoptical power specification rangeVSAvoidelectrical contact structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The electrical contact structure is segmented into multiple independent contacts (first anode contact, second anode contact, cathode contact) that can be selectively combined to form different current paths. This segmentation enables the VCSEL to adapt to multiple optical power specifications by activating different active layers through different contact combinations, while the underlying epitaxial structure remains manufacturable using standard processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The VCSEL transitions from a fixed drive current/voltage configuration to a dynamic configuration where the drive current can be dynamically distributed among multiple active layers. The selective activation of different active layers through different contact combinations allows the device to adapt its optical output to varying application requirements, achieving multiple power specifications with a single device structure.

Inventive Principle:

Principle #15Dynamics

3Productivity

If multiple VCSELs are arranged in an emitter array on a common substrate, then productivity is improved, but thermal management and performance uniformity become problematic

Engineering Contradiction:

Improveemitter array densityVSAvoidperformance uniformity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Each VCSEL in the emitter array is segmented into multiple independently addressable active layers with separate electrical contacts. This allows for selective activation of specific active layers in specific VCSELs within the array, enabling localized thermal management and performance optimization. VCSELs experiencing thermal issues can operate with fewer active layers while others operate at full capacity, maintaining overall array productivity and performance uniformity.

Inventive Principle:

Principle #1Segmentation

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 approach allows VCSELs to operate across a range of temperatures with improved performance, extended lifespan, and suitability for diverse applications by controlling optical output power, reducing thermal issues and enhancing reliability.

Implementation Method 1

a tunnel junction therebetween

Methodology Applied

Scientific EffectQuantum tunneling:

Data Source

PatentUS20230420918A1Vertical cavity surface emitting laser with active layer-specific addressability

Publication Date: 2023.12.28 WELLS FARGO BANK NA

AI summary

A vertical cavity surface emitting laser (VCSEL) may include an epitaxial structure that includes a first active layer, a second active layer, and a tunnel junction therebetween. The VCSEL may include a set of contacts that are electrically connected to the epitaxial structure. The set of contacts may include three or more contacts, and the set of contacts may be electrically separated from each other on the VCSEL. At least one contact, of the set of contacts, may be electrically connected to the epitaxial structure at a depth between the first active layer and the second active layer.