Tunable Quantum Light Source With Barrier Regions

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Solution Overview

Problem

Existing photon emitters in quantum cryptography and computing face challenges in reliably producing single photons and entangled photon pairs, as applying an electric field to control emission wavelengths decreases efficiency due to carrier tunneling out of quantum dots before emission.

Innovation Solution

A semiconductor heterostructure photon source with a quantum well and barrier regions is designed to apply a tunable electric field, increasing tunneling time of carriers beyond radiative decay, allowing controlled emission from a single quantum dot while minimizing fine structure splitting for entangled photon production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If an electric field is applied across the quantum dot to tune the emission wavelength, then the tuning range is improved, but the emission efficiency decreases due to enhanced carrier tunneling

Engineering Contradiction:

Improveemission wavelength tuning rangeVSAvoidphoton emission efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The device is segmented into three distinct regions: a quantum well region containing the quantum dot, a first barrier region between the quantum well and first contact, and a second barrier region between the quantum well and second contact. This segmentation allows the electric field to be applied across the quantum dot for wavelength tuning while the barrier regions prevent carrier tunneling losses to the contacts, thus maintaining emission efficiency during tuning.

Inventive Principle:

Principle #1Segmentation

2Productivity

If the tunneling time of carriers is increased to prevent tunneling losses, then the emission efficiency is improved, but the carrier confinement becomes more difficult

Engineering Contradiction:

Improvephoton emission efficiencyVSAvoidcarrier confinement structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The barrier regions act as intermediary structures between the quantum well and the electrical contacts. These barrier regions have higher conduction band offsets that mediate the interaction between carriers and contacts, increasing the tunneling time and preventing carrier losses without requiring complex confinement structures. The barriers serve as a simple yet effective interface that solves the carrier confinement problem.

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

This configuration enhances emission efficiency and tuning range, enabling reliable production of single photons and entangled pairs with minimized fine structure splitting, improving quantum communication and computing applications.

Implementation Method 1

The emission wavelength may be tuned by applying an electric field across the quantum dot

Methodology Applied

Scientific EffectStark effect:

Implementation Method 2

an exciton is formed when there is a bound state between a small number of electrons in the conduction band and holes in the valence band, radiative decay occurring when one hole and one electron recombine resulting in the emission of a photon

Methodology Applied

Scientific EffectRadiative recombination:

Implementation Method 3

applying an electric field across the quantum dot causes the efficiency of the photon source to decrease since the applied field enhances tunneling of carriers out of the quantum dot before photon emission can occur

Methodology Applied

Scientific EffectTunneling:

Data Source

PatentUS9219191B2Tuneable quantum light source

Publication Date: 2015.12.22 KK TOSHIBA

AI summary

A photon source comprising a semiconductor heterostructure, said semiconductor heterostructure comprising a quantum well, a barrier region adjacent said quantum well and a quantum dot provided in said quantum well, the photon source further comprising electrical contacts and a power supply coupled to first and second electrical contacts configured to apply a tuneable electric field across said quantum dot to control the emission energy of said quantum dot, said electric field being tuneable across an operating range an wherein the tunneling time of carriers from said quantum dot to said first electrical contact and the tunneling time of carriers from said quantum dot to said second electrical contact are greater than the radiative decay time of an exciton in said quantum dot over said operating range for controlling the emission energy, said photon source being configured such that emission from a single quantum dot exits said photon source.