Quantum Dot Photon Source With Bragg Cavity for High Extraction

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Solution Overview

Problem

Existing photon sources struggle to efficiently emit single photons with controlled accuracy and high extraction efficiency over a broad wavelength range, limiting their applications in quantum LEDs, quantum key distribution, and quantum communication systems.

Innovation Solution

A photon source design incorporating a quantum dot within an optical cavity with a diffractive Bragg grating and planar reflection layer, featuring concentric reflective rings and semiconductor bridges, enhances Purcell factor and extraction efficiency by applying an electric field, allowing controlled photon emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a quantum dot is used as a photon source, then single photon emission capability is achieved, but extraction efficiency remains limited

Engineering Contradiction:

Improvesingle photon emission capabilityVSAvoidextraction efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The device is segmented into distinct functional layers: quantum dot layer for photon generation, photonic crystal layer for mode control, and distributed Bragg reflector for extraction enhancement. This segmentation allows each layer to be optimized independently for its specific function while working together to achieve high extraction efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The quantum dot is nested within the photonic crystal structure, which is in turn nested within the distributed Bragg reflector cavity. This nested configuration allows the quantum dot to benefit from both the mode confinement of the photonic crystal and the extraction enhancement of the DBR, achieving high extraction efficiency while maintaining single photon emission capability

Inventive Principle:

Principle #7Nested doll (Nesting)

2Device complexity

If conventional photon sources are used, then device simplicity is maintained, but wavelength range coverage is limited

Engineering Contradiction:

Improvedevice simplicityVSAvoidwavelength range coverage

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The photonic crystal structure utilizes changes in refractive index parameters through its periodic lattice design, and the DBR utilizes changes in layer thickness parameters, to achieve broadband operation. By adjusting these parameters, the device can be tuned to cover different wavelength ranges while maintaining a relatively simple overall structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The device employs composite material structures: the photonic crystal uses alternating high and low refractive index materials, and the DBR uses alternating semiconductor layers. These composite structures enable broadband operation across multiple wavelengths while keeping the device architecture manageable

Inventive Principle:

Principle #40Composite materials

3Productivity

If extraction efficiency is increased, then photon output is improved, but structural complexity increases

Engineering Contradiction:

Improveextraction efficiencyVSAvoidstructural complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The photonic crystal structure serves multiple functions simultaneously: it confines photons to vertical modes, defines the emission direction, and works with the DBR to enhance extraction. This multi-functionality reduces the need for additional separate components, achieving high extraction efficiency without proportionally increasing structural complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The photonic crystal acts as an intermediary between the quantum dot and the DBR. It converts the isotropic emission from the quantum dot into directional vertical modes that can be efficiently extracted by the DBR, enabling high extraction efficiency while maintaining a compact structure

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The design achieves a Purcell factor greater than 3 and photon extraction efficiency over 40% across a broad wavelength range, enabling efficient single photon emission for quantum communication and computing applications.

Implementation Method 1

an optical cavity, the optical cavity comprising: a diffractive Bragg grating 'DBG'

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 3

enhances Purcell factor and extraction efficiency

Methodology Applied

Scientific EffectPurcell effect:

Data Source

PatentUS12484339B2Photon source and method of fabricating a photon source

Publication Date: 2025.11.25 KK TOSHIBA

AI summary

A photon source comprising:a quantum dot; and an optical cavity,the optical cavity comprising:a diffractive Bragg grating “DBG”; anda planar reflection layer,the DBG comprising a plurality of concentric reflective rings surrounding a central disk and at least one conductive track extending from the central disk across the plurality of concentric rings, the quantum dot being provided within the central disk and the planar reflection layer being provided on one side of the DBG to cause light to be preferentially emitted from the opposing side of the DBG.