Smith-Purcell THz Source With Mirror Redirection and Frequency Tuning

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Solution Overview

Problem

Existing coherent electromagnetic source technologies in the THz range are either expensive and bulky, or compact but not tunable, lacking flexibility in frequency adjustment.

Innovation Solution

A compact, economical device using an electrically conductive diffraction grating with external walls, an electron beam, and a mirror to generate and redirect coherent Smith-Purcell electromagnetic radiation, allowing frequency variation by interchangeable mirrors and gratings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If gyrotron equipment is used to generate high-power THz radiation, then power level exceeds one watt, but the equipment is expensive and bulky

Engineering Contradiction:
Improvepower levelVSAvoidequipment size and cost
Core Design Contradiction:
PowerVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical gyrotron system with a Smith-Purcell radiation mechanism using a diffraction grating and electron beam, eliminating the need for complex superconducting magnets and cryostats while maintaining high power output

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using a periodic diffraction grating structure with specific geometry (period, depth, width) and controlling electron beam parameters (energy, current, transverse size) to optimize radiation efficiency and power output

Inventive Principle:
Principle #35Parameter changes

2Device complexity

If quantum cascade lasers are used to generate THz radiation, then the device is compact, but the emitted power does not exceed 1 mW and the frequency is not tunable

Engineering Contradiction:
Improvedevice compactnessVSAvoidemitted power
Core Design Contradiction:
Device complexityVSPower

Solution Approach 1:

The patent combines the compactness of laser technology with the high power capability of free-electron radiation by integrating a diffraction grating structure with an electron beam source, achieving both compact size and high power output

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces dynamic tunability by allowing adjustment of the electron beam energy and diffraction grating parameters, enabling continuous frequency tuning while maintaining high power output, unlike fixed-frequency quantum cascade lasers

Inventive Principle:
Principle #15Dynamics

3Device complexity

If quantum cascade lasers are used to generate THz radiation, then the device is compact, but the frequency is not tunable

Engineering Contradiction:
Improvedevice compactnessVSAvoidfrequency tunability
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamic tunability by allowing adjustment of the electron beam energy and diffraction grating parameters, enabling continuous frequency tuning while maintaining high power output, unlike fixed-frequency quantum cascade lasers

Inventive Principle:
Principle #15Dynamics

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 device achieves high-power, tunable, and highly directional electromagnetic radiation in the THz range, optimizing compactness and cost-effectiveness.

Implementation Method 1

an electron beam configured to interact with the diffraction grating so as to generate coherent Smith-Purcell electromagnetic radiation

Methodology Applied
Scientific EffectSmith-Purcell radiation: Diffraction

Implementation Method 2

a mirror configured to recover most of the electromagnetic radiation in order to redirect it parallel to the diffraction grating to an outlet downstream of the diffraction grating

Methodology Applied
Scientific EffectReflection: Reflection

Data Source

PatentEP4559059B1Device and method for generating coherent terahertz radiation
Publication Date: 2026.03.18 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
  • EP4559059B1 patent drawingFigure 1A~1B
  • EP4559059B1 patent drawingFigure 2~3
  • EP4559059B1 patent drawingFigure 4A~4B

AI summary

The invention relates to a method and a device (1) for producing coherent Smith-Purcell electromagnetic radiation, which device comprises: an electrically conductive diffraction grating (5) laterally defined by two electrically conductive outer side walls (51, 52); a source (7) for generating an electron beam (11) above the diffraction grating (5), the electron beam being configured to interact with the diffraction grating so as to produce coherent Smith-Purcell electromagnetic radiation (3) directed upstream of the diffraction grating (5) in a predetermined direction; and a mirror (9) configured to collect all of the electromagnetic radiation and redirect it parallel to the diffraction grating (5) to an exit (15) downstream of the diffraction grating (5).