Terahertz radiator based on coherent SPR amplified by stimulation

Patent metadata

Field	Value
Publication number	US-12149041-B2
Application number	US-202117304582-A
Country	US
Kind code	B2
Filing date	Jun 23, 2021
Priority date	Jun 24, 2020
Publication date	Nov 19, 2024
Grant date	Nov 19, 2024

Abstract

A terahertz radiator is based on coherent Smith-Purcell radiation amplified by stimulation. The terahertz radiator includes an electron emission source configured to emit electron beams and a pumping source configured to emit pumping signals. The pumping signal interacts with a primary grating structure to obtain preliminarily bunched electrons. The preliminarily bunched electrons interact with the primary grating structure to generate coherent Smith-Purcell radiation. The coherent Smith-Purcell radiation and the pumping signals vertically resonate in a primary resonant cavity structure, so that the electron bunching density is increased, and in turn, the coherent Smith-Purcell radiation is enhanced. A positive feedback process is formed by free electrons and the coherent Smith-Purcell radiation, and the coherent Smith-Purcell radiation amplified by stimulation and periodic bunched electron bunches are obtained. The terahertz radiator can be used to realize a stimulated amplification phenomenon under the conditions of small current and large beam spots.

First claim

What is claimed is:

1. A terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation, comprising: an electron emission source, a pumping source, a primary resonant cavity structure, and a primary grating structure; wherein the primary grating structure is located inside the primary resonant cavity structure;
the electron emission source is located at an axial inlet position of the primary resonant cavity structure, and is configured to emit electron beams which are incident into the primary resonant cavity structure along an axial direction of the primary resonant cavity structure and then fly along a surface of the primary grating structure;
the pumping source is located at an inlet position on a side wall of the primary resonant cavity structure, and is configured to emit pumping signals which are incident into the primary resonant cavity structure and then interacts with the primary grating structure on the surface of the primary grating structure to generate a periodic electromagnetic field; the periodic electromagnetic field causes electrons flying along the surface of the primary grating structure to preliminarily bunch to obtain preliminarily bunched electrons; wherein the frequency of the pumping source is in a vertical resonance mode of the primary resonant cavity structure;
the preliminarily bunched electrons interact with the primary grating structure to generate coherent Smith-Purcell radiation;
the coherent Smith-Purcell radiation and the pumping signals vertically resonate in the primary resonant cavity structure, and together modulate the electron energy in the primary resonant cavity structure, causing an increase in the electron bunching density, thereby enhancing the coherent Smith-Purcell radiation;
in the primary resonant cavity structure, a positive feedback process is formed by an energy interaction between free electrons and the coherent Smith-Purcell radiation to obtain coherent Smith-Purcell radiation amplified by stimulation and periodic bunched electron bunches.

2. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 1 , further comprising:
a secondary resonant cavity structure and a secondary grating structure;
wherein an electron beam input end of the secondary resonant cavity structure is connected to an electron beam output end of the primary resonant cavity structure;
the secondary grating structure is located inside the secondary resonant cavity structure, and a period of the secondary grating structure is smaller than a period of the primary grating structure;
after entering the secondary resonant cavity structure, the periodic bunched electron bunches output from the primary resonant cavity structure interact with the secondary grating structure on the surface of the secondary grating structure to generate a high-order frequency multiplication coherent Smith-Purcell radiation with a preset frequency multiplication order;
wherein, the frequency multiplication order is a frequency multiplication order of the high-order frequency multiplication coherent Smith-Purcell radiation relative to the pumping source.

3. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 2 , wherein an electron bunching comprises three states: preliminary bunching, optimal bunching and over-bunching; correspondingly, the secondary resonant cavity structure and the secondary grating structure are disposed at positions where the electrons are in the optimal bunching state.

4. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 2 , wherein the period of the secondary grating structure and the frequency multiplication order satisfy a first relationship model which is expressed as:

L
2

m

⁢

(

c
v

-

cos
⁢
θ

)

=

c

nf
p

;

wherein, L 2 represents the period of the secondary grating structure, m represents the order of the Smith-Purcell radiation, c represents the speed of light in vacuum, v represents the velocity of electrons, θ represents the radiation angle, n represents the frequency multiplication order, n is a positive integer greater than or equal to 1, and f p represents the pumping frequency of the pumping source.

5. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 2 , wherein the pumping source outputs a first terahertz signal, the secondary resonant cavity structure outputs a second terahertz signal, and the frequency of the second terahertz signal is higher than the frequency of the first terahertz signal.

6. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 2 , wherein the pumping source outputs a microwave signal, and the secondary resonant cavity structure outputs a terahertz signal.

7. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 1 , wherein electron velocity v, period Li of the primary grating structure, and the pumping frequency f p of the pumping source satisfy a second relationship model which is expressed as: f p =v/L 1 .

8. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 1 , wherein the electron beam has an energy of 10 to 30 keV, a current of 10 to 50 mA, and a beam spot diameter of 100 to 120 μm.

9. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 1 , further comprising a magnetic ring structure;
the magnetic ring structure is wrapped outside the resonant cavity structure for focusing the electron beam.

10. The terahertz radiator based on coherent Smith-Purcell radiation amplified by stimulation of claim 2 , further comprising an electron collector;
wherein the electron collector is configured to collect the electron beam which is emitted by the electron emission source and passes through the primary and secondary grating structures and the primary and secondary resonant cavity structures.

Assignees

• Univ Tsinghua

Inventors

• Liu Fang
• Lin Yuechai
• Li Jinyu
• Huang Yidong
• Cui Kaiyu
• Feng Xue
• Zhang Wei

Classifications

• H01S5/1234

  Actively induced grating, e.g. acoustically or electrically induced · CPC title

• G01N21/3581

  using far infrared light; using Terahertz radiation · CPC title

• H01S2302/02

  THz - lasers, i.e. lasers with emission in the wavelength range of typically 0.1 mm to 1 mm · CPC title

• H01S3/0959 Primary

  by an electron beam · CPC title

• H01S1/005 Primary

  using a relativistic beam of charged particles, e.g. electron cyclotron maser, gyrotron · CPC title