Off-Normal VCSEL-PIC Coupling via Grating-Coupled Waveguides

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Solution Overview

Problem

The integration of vertical cavity surface emitting lasers (VCSELs) with photonic integrated circuits (PICs) for applications like near-eye displays and 3D sensing has low efficiency due to 90-degree coupling of laser beams into waveguides, leading to higher power consumption and reduced performance.

Innovation Solution

An off-normal bottom-emitting VCSEL is integrated with a PIC using a grating coupler, where the output facet is processed to emit light at an angle, allowing efficient coupling into the waveguide through a grating coupler, which also reduces back-reflection and enhances laser stability, and can include features like diffractive optical elements or metasurfaces for beam control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a vertical cavity surface emitting laser (VCSEL) is integrated with a photonic integrated circuit (PIC) using 90-degree coupling, then the integration is straightforward, but the coupling efficiency is low

Engineering Contradiction:

Improveintegration easeVSAvoidcoupling efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent changes the coupling angle parameter from 90 degrees to an oblique angle (e.g., 45 degrees) to improve coupling efficiency. This parameter modification allows better mode matching between the VCSEL beam and the waveguide, thereby increasing coupling efficiency while maintaining integration feasibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a grating coupler as an intermediary element between the VCSEL and the waveguide. This grating coupler acts as a mediator that transforms the oblique VCSEL beam into a form that can be efficiently coupled into the waveguide, resolving the contradiction between integration ease and coupling efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If a vertical cavity surface emitting laser (VCSEL) is integrated with a photonic integrated circuit (PIC), then the laser source is integrated, but power consumption increases due to low coupling efficiency

Engineering Contradiction:

Improveintegration capabilityVSAvoidpower consumption

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

By changing the coupling angle from 90 degrees to an oblique angle and introducing a grating coupler, the patent improves coupling efficiency. This reduces the amount of optical power lost during coupling, thereby reducing the overall power consumption of the integrated laser system while maintaining integration capability

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a vertical cavity surface emitting laser (VCSEL) is integrated with a photonic integrated circuit (PIC) using 90-degree coupling, then the integration structure is simple, but the laser stability is reduced

Engineering Contradiction:

Improveintegration structure complexityVSAvoidlaser stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The grating coupler serves as an intermediary that not only improves coupling efficiency but also reduces back-reflection into the VCSEL cavity. By minimizing back-reflection, the grating coupler enhances laser stability while adding only moderate complexity to the integration structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the simple 90-degree mechanical coupling approach with an oblique angle coupling combined with a grating coupler. This substitution improves laser stability by reducing back-reflection effects, accepting increased structural complexity as a trade-off for enhanced reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 increases the efficiency of light coupling into the PIC, reduces power consumption, and enhances the stability of the laser, enabling higher brightness and reduced complexity in integration processes.

Implementation Method 1

efficient coupling of light to a waveguide within a photonic integrated circuit (PIC) via a grating coupler

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the output facet is processed to emit light at an angle, allowing efficient coupling into the waveguide through a grating coupler, which also reduces back-reflection

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS20240019646A1Vertical cavity surface emitting laser (VCSEL) integration on a photonic integrated circuit (PIC)

Publication Date: 2024.01.18 META PLATFORMS TECHNOLOGIES LLC

AI summary

An off-normal bottom-emitting vertical cavity surface emitting laser (VCSEL) is integrated with a photonic integrated circuit (PIC) for incident light from the VCSEL to efficiently couple to a waveguide via a grating coupler in the PIC. Diffraction of the light by the grating coupler is in a direction that is aligned with an input of the waveguide such that most or all of the light enters the waveguide. The off-normal VCSEL output is achieved by arranging an output facet at a bottom surface of the VCSEL with decentered micro-lenses, micro-prisms, gratings, diffractive optical elements, and/or metasurfaces. The diffractive optical elements or metasurfaces may also be used for beam divergence mitigation and/or polarization control.