A coherent near-field detection system based on free electron excitation and photodetection

A technology of electron excitation and photoelectric detection, which is applied in the cross-field of vacuum electronics and terahertz photodetection technology, can solve problems such as difficulty in upgrading, resolution dependence, contradiction between near-field coupling efficiency and imaging resolution, etc., to achieve deeper near-field The understanding of characteristics, the effect of less interference factors

Active Publication Date: 2022-03-15
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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Problems solved by technology

However, this type of near-field system has certain defects in detecting the near-field on the surface of materials or structures. For example, both excitation and detection come from the probe, so the spatial phase of the surface near-field cannot be directly seen; and the resolution of the system depends on the probe. , not only is it difficult to further improve, but also there is a contradiction between near-field coupling efficiency and imaging resolution

Method used

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  • A coherent near-field detection system based on free electron excitation and photodetection
  • A coherent near-field detection system based on free electron excitation and photodetection

Examples

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Embodiment 1

[0025] This example figure 1 As shown in , the femtosecond laser source produces a femtosecond laser with a certain repetition rate (such as 10MHz), and the femtosecond laser is divided into two beams by a beam splitter, which are used to excite the photocathode to generate photoelectron emission and excite the low temperature of the photoconductive antenna respectively. Gallium arsenide substrates generate freely moving charge carriers. Among them, the femtosecond laser connected to the photoconductive antenna needs to pass through an optical delay optical path (not shown in the figure), and then converge from the lower surface of the photoconductive antenna to the slit of the two metal electrodes. The corresponding 2D material to be tested. The pulsed electron beam generated by the photocathode skims the surface of the photoconductive antenna. When the electron projected field passes between the two metal electrodes of the photoconductive antenna, corresponding surface wave...

Embodiment 2

[0027] This example figure 2 As shown, the principle is similar to the first embodiment, except that the material to be tested is a metal grating structure, so two adjacent metal gratings are used as metal electrodes. The surface wave of the metal grating structure is generated by the interaction between the pulsed electron beam and the metal grating. Two adjacent metal gratings are used as the electrodes of the photoconductive antenna. The substrate is also made of low-temperature gallium arsenide. The propagation of the surface wave leads to a gap between the metal gratings used as electrodes. A changing potential difference is produced. This method can detect surface waves with different frequencies caused by changing the grating parameters.

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Abstract

The invention discloses a coherent near-field detection system based on free electron excitation and photoelectric detection, which belongs to the cross field of vacuum electronics and terahertz photoelectric detection technology. The invention uses a femtosecond laser source to generate a femtosecond laser, which is divided into two beams by a beam splitter, one of which excites the photocathode to generate a pulsed electron beam, and the pulsed electron beam excites the surface wave of the material to be tested, and is placed on the lower surface of the material to be tested. A photoconductive antenna composed of a substrate and a metal electrode (if the material to be tested is a metal grating, the two adjacent gratings are used as metal electrodes) directly senses the surface wave of the material to be tested; another femtosecond laser is injected again through the delayed optical path On the photoconductive antenna, photoelectric sampling is realized, and the detection of the surface wave of the material to be tested is completed. The method of the invention does not have the influence of the needle tip on the near-field signal, and meanwhile, the intensity of the electron projection field on the surface of the object is far less than that of the surface wave, which can realize the direct detection of relatively pure near-field signals in the time domain.

Description

technical field [0001] The invention belongs to the intersecting field of vacuum electronics and terahertz photoelectric detection technology, and relates to a photocathode photoelectron emission and a time-domain detection method of a photoconductive antenna. Background technique [0002] Photocathode electron emission, together with thermal electron emission, field electron emission, and secondary electron emission, constitutes four basic forms of electron emission; in the process of photocathode electron emission, the electrons inside the cathode material absorb the laser photon energy , produce an energy level transition and leave the surface of the material, and finally complete electron emission, and the emission period is consistent with the pulse laser repetition period. [0003] Photoconductive antennas are terahertz generation or detection devices based on semiconductors (commonly used materials are gallium arsenide and sapphire silicon wafers) and bimetallic anten...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N21/62G01R29/08
CPCG01N21/62G01R29/0885G01N2021/625
Inventor 胡旻许星星张倬铖张晓秋艳张天宇王月莹常少杰肖丰钟任斌吴振华刘盛纲
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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