Transverse-Coupled VCSEL Bandwidth Enhancement

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Solution Overview

Problem

Conventional Vertical-Cavity Surface-Emitting Lasers (VCSELs) are limited by relaxation-oscillation-frequency, restricting their bandwidth and preventing their use in applications beyond 50 GBaud due to inherent design limitations.

Innovation Solution

The integration of multiple short feedback cavities with the main cavity, each coupled separately, induces carrier-photon resonance while avoiding photon-photon resonance effects, enhancing modulation bandwidth without peaky structures in the frequency response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional VCSEL design is used, then device simplicity is maintained, but bandwidth is limited to below 50 GBaud due to relaxation-oscillation-frequency

Engineering Contradiction:

ImprovebandwidthVSAvoiddevice structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The single cavity is segmented into multiple cavities (first cavity, second cavity, third cavity) coupled in series. This segmentation allows the system to achieve enhanced bandwidth through the combined effect of multiple resonant modes while avoiding the relaxation-oscillation-frequency limitation of conventional single-cavity VCSELs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extends the resonant cavity structure into the lateral dimension by coupling multiple cavities side-by-side rather than stacking them vertically. This lateral arrangement enables the system to achieve higher bandwidth by utilizing transverse electromagnetic modes without increasing the vertical device complexity significantly.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If multiple feedback cavities are integrated to enhance bandwidth, then modulation bandwidth increases, but photon-photon resonance effects create peaky structures in frequency response

Engineering Contradiction:

Improvemodulation bandwidthVSAvoidfrequency response uniformity

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

Each cavity in the coupled-cavity structure has locally optimized dimensions and refractive index properties. The first, second, and third cavities can have different lengths and refractive indices, allowing each to contribute differently to the overall frequency response. This local differentiation smooths out the peaky structures that would arise from identical cavities experiencing strong photon-photon resonance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The coupled-cavity structure employs asymmetric design where cavities have different physical dimensions and refractive indices. This asymmetry breaks the degeneracy of resonant modes and distributes the frequency response more uniformly, preventing the formation of sharp peaks that would result from symmetric, identical cavity configurations.

Inventive Principle:

Principle #4Asymmetry

3Productivity

If conventional single cavity design is used, then manufacturing is simple, but relaxation-oscillation-frequency limits the achievable bandwidth

Engineering Contradiction:

Improvedata rate capabilityVSAvoidcavity structure fabrication

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

Multiple cavities are merged into a single integrated VCSEL structure with unified fabrication processes. The coupled cavities share common fabrication steps including epitaxial growth, lithography, and etching, allowing the complex multi-cavity structure to be manufactured using standard VCSEL fabrication techniques without requiring significantly more complex manufacturing processes.

Inventive Principle:

Principle #5Merging (Combining)

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 achieves significant bandwidth enhancement while maintaining a well-behaved modulation frequency response, supporting higher data rates without the undesirable effects of strong photon-photon resonance.

Implementation Method 1

Methodology Applied

Scientific EffectCarrier-photon resonance: Resonance

Implementation Method 2

VCSELs are comprised of an active region (or cavity region) sandwiched between two distributed Bragg reflector (DBR) structures that include multiple pairs of alternating low and high refractive index material to generate high reflectance at the desired emission wavelength

Methodology Applied

Scientific EffectBragg reflection: Bragg Diffraction

Data Source

PatentUS10658815B1Optical devices with transverse-coupled-cavity

Publication Date: 2020.05.19 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

A light-emitting device is provided. The light-emitting device can include a main cavity formed within an epitaxial structure that is configured to generate light in response to having an electrical current provided thereto. The light-emitting device can also include a plurality of feedback cavities also formed within the epitaxial structure, where each of the plurality of feedback cavities are transversely-coupled with the main cavity to receive light from the main cavity and reflect at least some feedback light back into the main cavity. The light-emitting device may provide enhanced modulation bandwidth or ultra-high speed communication capabilities.