Graphene Josephson Junction Single Photon Detector

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Solution Overview

Problem

There is a gap in detector technology for low-energy photons, particularly those with wavelengths of 1 micron or more, as existing single-photon detectors are inadequate for such low-energy electromagnetic radiation.

Innovation Solution

A graphene-based single-photon detector is developed, utilizing a waveguide or transmission line coupled to a graphene sheet, where absorbed photons heat the graphene sheet, causing a decrease in the critical current of a Josephson junction, resulting in a voltage pulse detectable by a pulse detector.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If existing single-photon detector designs are used, then high-energy photons can be detected, but low-energy photons (wavelengths of 1 micron or more) cannot be detected

Engineering Contradiction:

Improvedetector wavelength rangeVSAvoiddetection capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the material parameter of the detector from traditional superconducting materials to graphene, which has different optical and electrical properties suitable for low-energy photon detection. The graphene sheet's unique electronic structure allows it to respond to infrared and longer wavelength photons that conventional detectors cannot detect

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure combining graphene sheet with superconducting materials (forming a Josephson junction). This composite approach leverages the advantages of both materials: graphene's sensitivity to low-energy photons and superconducting materials' ability to generate detectable electrical signals, thereby achieving both extended wavelength range and reliable detection

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If a graphene sheet is used to detect low-energy photons, then detection capability for infrared and longer wavelengths is achieved, but the mechanism for converting photon absorption into detectable signals becomes more complex

Engineering Contradiction:

Improvelow-energy photon detectionVSAvoidsignal conversion mechanism

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a Josephson junction as an intermediary mechanism between the graphene sheet and the detection circuit. The junction converts the subtle thermal and electrical changes in graphene caused by photon absorption into amplified voltage pulses that can be easily detected, simplifying the overall signal readout while maintaining sensitivity to low-energy photons

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 effectively detects single photons of infrared or longer wavelength electromagnetic radiation, addressing the lack of detectors for low-energy photons by converting photon absorption into measurable electrical signals.

Implementation Method 1

a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet

Methodology Applied

Scientific EffectEvanescent waves:

Implementation Method 2

A photon absorbed by the graphene sheet heats the graphene sheet

Methodology Applied

Scientific EffectPhoton absorption: Absorption (EM radiation)

Implementation Method 3

Part of the graphene sheet is part of the Josephson junction as the weak link, and a constant bias current is driven through the Josephson junction; an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 4

a Josephson junction adjacent or including the graphene sheet, the Josephson junction having a gap coupled to electrons of the graphene sheet

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Data Source

PatentUS9799817B2Josephson junction readout for graphene-based single photon detector

Publication Date: 2017.10.24 RTX BBN TECH INC

AI summary

A detector for detecting single photons of infrared radiation or longer wavelength electromagnetic radiation. In one embodiment a waveguide configured to transmit infrared radiation is arranged to be adjacent a graphene sheet and configured so that evanescent waves from the waveguide overlap the graphene sheet. In other embodiments a transmission line or antenna is coupled to the graphene sheet and guides longer-wavelength photons to the graphene sheet. A photon absorbed by the graphene sheet heats the graphene sheet. Part of the graphene sheet is part of the Josephson junction as the weak link, and a constant bias current is driven through the Josephson junction; an increase in the temperature of the graphene sheet results in a decrease in the critical current of the Josephson junction and a voltage pulse in the voltage across the Josephson junction. The voltage pulse is detected by the pulse detector.