Terahertz Light Modulator Using Tunable Conductive Layer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current light modulators for terahertz radiation lack efficiency, broadband capability, and suffer from limited frequency range, high voltage requirements, and inefficient transmission in their off state, particularly due to reliance on resonance phenomena.

Innovation Solution

A light modulator using a prism with a tunable conductive layer that undergoes total internal reflection, where the conductivity of the layer can be dynamically controlled to modulate the intensity and phase of terahertz radiation, utilizing materials like graphene and incorporating metamaterials for enhanced control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If resonance-based modulator structures are used, then modulation depth can be achieved, but frequency range is limited and transmission loss is high

Engineering Contradiction:

Improvemodulation depthVSAvoidfrequency range

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental operating principle from resonance-based to total internal reflection (TIR) based modulation. By controlling the conductivity of the graphene layer, the device modulates TIR conditions dynamically, enabling broadband operation across multiple octaves while maintaining high modulation depth. This parameter change resolves the contradiction by decoupling modulation performance from frequency-specific resonance conditions.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If resonance-based modulator structures are used, then modulation depth can be achieved, but transmission loss is high in off state

Engineering Contradiction:

Improvemodulation depthVSAvoidtransmission loss

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent converts the typically lossy resonance absorption into a beneficial mechanism by using TIR. When the graphene layer conductivity is low, TIR conditions are maintained with minimal loss. When conductivity increases, the modulated TIR effect achieves modulation depth without the continuous energy loss associated with resonance absorption. This transforms the potential harm of conductive layer absorption into a controllable modulation mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Illumination intensity

If high voltage is applied to achieve modulation, then modulation depth improves, but device complexity and power consumption increase

Engineering Contradiction:

Improvemodulation depthVSAvoidvoltage requirements

Core Design Contradiction:

Illumination intensityVSPower

Solution Approach 1:

The patent exploits the unique property of graphene where low carrier concentrations (achieved with low gate voltages) enhance TIR conditions for effective modulation. This is opposite to conventional absorptive modulators that require high carrier densities and high voltages. By changing the operational parameter regime to low-voltage, low-carrier-concentration operation, the device achieves high modulation depth with minimal power consumption.

Inventive Principle:

Principle #35Parameter changes

4Measurement precision

If conventional modulator designs are used, then specific frequency modulation is achieved, but broadband capability is limited

Engineering Contradiction:

Improvefrequency selectivityVSAvoidbroadband operation

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal modulator based on TIR principles that can operate across a broad frequency spectrum. The graphene layer's ability to control conductivity dynamically allows the same device structure to effectively modulate different frequency ranges by adjusting the carrier concentration, achieving multi-functionality without requiring frequency-specific resonant structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution provides improved modulation efficiency, broadband operation, and flexible frequency control, enabling high modulation depth and reduced voltage requirements, while maintaining low loss in the off state.

Implementation Method 1

A light modulator using a prism with a tunable conductive layer that undergoes total internal reflection

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

The tunable conductive layer can absorb a portion of the reflected light beam, attenuating the beam

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Data Source

PatentUS10197793B2Light modulator using total internal reflection at an interface with a tunable conductive layer

Publication Date: 2019.02.05 THE CHINESE UNIV OF HONG KONG OFFICE OF RES KNOWLEDGE TRANSFER SERVICES

AI summary

A light modulator (e.g., for terahertz radiation) may be constructed using a prism in which light undergoes total internal reflection (TIR) at one surface. A tunable conductive layer is disposed on the TIR surface. The tunable conductive layer can have a conductivity that is dynamically controllable, e.g., by applying a voltage across the tunable conductive layer or by optically pumping the tunable conductive layer. The tunable conductive layer can absorb a portion of the reflected light beam, attenuating the beam, with the attenuation being a function of the electrical conductivity of the tunable conductive layer. The phase of the reflected light beam can also be altered as a function of electrical conductivity of the tunable conductive layer.