Graphene Plasmonic Phase Modulator for THz Bandwidth

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Solution Overview

Problem

Current THz communication systems face limitations due to low modulation depth and symbol error rates caused by sub-GHz modulation bandwidths and low modulation depths in existing modulators, which hinder the use of the Terahertz band for high-data-rate wireless communications.

Innovation Solution

A graphene-based plasmonic phase modulator is developed, utilizing a conductive layer, a dielectric layer, and a plasmonic layer conductive to surface plasmon polariton waves, with a voltage signal source to modulate the propagation speed of SPP waves, enhancing modulation depth and symbol distinguishability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional modulators are used to control THz waves, then the device structure is simple, but the modulation bandwidth is sub-GHz and modulation depth is low

Engineering Contradiction:

Improvemodulation bandwidthVSAvoiddevice structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs a composite structure combining graphene plasmonic layer with dielectric and metal layers. The graphene layer provides high-frequency conductivity for THz operation, while the dielectric and metal layers provide structural support and electromagnetic field confinement. This composite approach enables sub-GHz modulation bandwidth while maintaining practical device complexity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent dynamically changes the electrical conductivity parameter of the graphene layer by applying voltage signals. This parameter change enables the graphene to modulate the propagation characteristics of SPP waves, achieving high modulation bandwidth and depth. The conductivity of graphene can be tuned over a wide range through gate voltage control

Inventive Principle:

Principle #35Parameter changes

2Reliability

If graphene-based amplitude modulators are used, then electrical conductivity is excellent, but modulation depth is low making symbols difficult to distinguish

Engineering Contradiction:

Improvesymbol distinguishabilityVSAvoidmodulation depth

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent replaces amplitude modulation with phase modulation of SPP waves. Instead of varying the amplitude of THz waves directly, the invention modulates the propagation phase by controlling the electrical conductivity of graphene. This phase modulation approach provides deeper modulation and better symbol distinguishability while maintaining the excellent electrical conductivity advantage of graphene

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces SPP waves as an intermediary between the electrical control signal and the THz wave modulation. The SPP waves propagate along the graphene-dielectric interface and their phase is controlled by the graphene conductivity. This intermediary mechanism enables efficient transfer of modulation information with high depth and reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If higher frequency bands are used to increase bandwidth, then transmission bandwidth increases, but available communication bandwidth decreases due to limited spectrum

Engineering Contradiction:

Improvewireless data rateVSAvoidavailable bandwidth

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent operates in the THz frequency band (0.1-10 THz) which provides extremely large transmission bandwidths ranging from almost 10 THz for short distances to multiple transmission windows for longer distances. By changing the operating frequency parameter to THz range, the system achieves Tbps wireless data rates despite limited available communication spectrum at lower frequencies

Inventive Principle:

Principle #35Parameter changes

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 modulator achieves improved symbol error rates and spectral efficiency, enabling practical THz-band communication systems by modulating the phase of THz waves effectively, thus supporting higher data rates.

Implementation Method 1

A plasmonic layer is disposed on the dielectric layer, the plasmonic layer being conductive to surface plasmon polariton (SPP) waves

Methodology Applied

Scientific EffectSurface plasmon polariton (SPP):

Implementation Method 2

A voltage signal source is operatively connected between the conductive layer and the plasmonic layer for modulating a propagation speed of an SPP wave propagating on the plasmonic layer

Methodology Applied

Scientific EffectElectrical conductivity modulation: Conduction (electrical)

Data Source

PatentUS10996379B2Plasmonic phase modulator and method of modulating an SPP wave

Publication Date: 2021.05.04 RES FOUND THE CITY UNIV OF NEW YORK

AI summary

A plasmonic phase modulator is provided. The modulator has a conductive layer, and a dielectric layer disposed on the conductive layer. A plasmonic layer is disposed on the dielectric layer. A plasmonic layer is disposed on the dielectric layer. The plasmonic layer is conductive to surface plasmon polariton (SPP) waves. The plasmonic layer may be, for example, a graphene sheet. A voltage signal source is operatively connected between the conductive layer and the plasmonic layer for modulating a propagation speed of an SPP wave propagating on the plasmonic layer.