阅读说明：本技术 一种基于电子自旋发射的太赫兹光谱仪及光谱分析系统 (Terahertz spectrograph based on electron spin emission and spectral analysis system ) 是由 吴斌 杨延召 刘红元 纪宝平 李国超 王恒飞 应承平 李京松 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种基于电子自旋发射的太赫兹光谱仪及光谱分析系统,包括：光纤飞秒激光器,空间光输出口的飞秒光入射至发射端；所述光纤输出口的相干探测光经光学延迟线入射至接收端；样品架,位于所述发射端与接收端之间；发射端,基于异质结构的电子自旋效应在飞秒激光激发和内部磁场共同作用下产生太赫兹脉冲；接收端,在样品太赫兹脉冲电场作用下形成电流,基于电流大小测量太赫兹脉冲波形特定点位的强度并输出至数据采集与处理模块从而进行光谱分析。本发明可有效提高太赫兹时域光谱仪的带宽和动态范围这两项关键的性能指标,并在提高整机可靠性的同时有效降低研制难度和成本。(The invention discloses a terahertz spectrograph based on electron spin emission and a spectral analysis system, which comprises: the fiber femtosecond laser device is used for leading femtosecond light of the space light output port to be incident to the transmitting end; coherent detection light of the optical fiber output port is incident to a receiving end through an optical delay line; the sample holder is positioned between the transmitting end and the receiving end; the transmitting terminal is used for generating terahertz pulses under the combined action of femtosecond laser excitation and an internal magnetic field based on the electron spin effect of the heterostructure; and the receiving end forms current under the action of the terahertz pulse electric field of the sample, measures the intensity of a specific point of the terahertz pulse waveform based on the magnitude of the current and outputs the intensity to the data acquisition and processing module so as to perform spectral analysis. The terahertz time-domain spectrograph can effectively improve two key performance indexes of the bandwidth and the dynamic range of the terahertz time-domain spectrograph, and effectively reduces the development difficulty and the cost while improving the reliability of the whole spectrograph.)

1. A terahertz spectrometer based on electron spin emission is characterized by comprising:

the optical fiber femtosecond laser comprises a space light output port and an optical fiber output port, wherein femtosecond light of the space light output port is incident to an emitting end; coherent detection light of the optical fiber output port is incident to a receiving end through an optical delay line; wherein the delay amount of the optical delay line is adjustable;

the sample holder is positioned between the transmitting end and the receiving end and used for fixing a sample to be detected;

the emitter comprises a substrate and one or more film periods plated on the substrate, wherein the film period consists of a non-magnetic metal film/magnetic metal film heterostructure and a dielectric covering layer covering the heterostructure, and a magnetic field generator is arranged inside or outside the emitter; the transmitting end is used for generating terahertz pulses, and the terahertz pulses penetrate through a sample fixed on the sample rack to form a sample terahertz pulse electric field;

the receiving end comprises a photoconductive chip, coherent detection light excites a photon-generated carrier on the photoconductive chip, current is formed under the action of a sample terahertz pulse electric field, and the intensity of a specific point position of a terahertz pulse waveform is measured based on the current and is output to the data acquisition and processing module.

2. The terahertz spectrometer based on electron spin emission as claimed in claim 1, wherein the femtosecond light from the spatial light output port is reflected by a mirror and then incident on the emission end.

3. The terahertz spectrometer based on electron spin emission as claimed in claim 1, wherein the coherent probe light at the output port of the optical fiber is incident on the receiving end and then transmitted to the photoconductive chip through the tail fiber.

4. The terahertz spectrometer based on electron spin emission as claimed in claim 1, wherein the data collection and processing module receives intensities of a plurality of points of the terahertz pulse waveform obtained based on a plurality of delay amounts, and recovers the terahertz spectrum of the sample to be measured.

5. The terahertz spectrometer based on electron spin emission as claimed in claim 4, wherein the restoring the terahertz spectrum of the sample to be measured comprises:

restoring to obtain terahertz time-domain spectrum information of the measured object according to the intensities of a plurality of point positions of the terahertz pulse waveform; and transforming the time domain spectrum of the measured object into a terahertz spectrum in a frequency domain by adopting wavelets.

6. The terahertz spectrometer based on electron spin emission as claimed in claim 5, wherein the data acquisition and processing module further obtains the characteristic absorption spectrum information of the sample to be measured based on a reference measurement method.

7. A terahertz spectroscopic analysis system based on electron spin emission, characterized in that the system comprises the terahertz spectrometer of any one of claims 1-6 and a computer; and the computer is respectively connected with the data acquisition and processing and the optical delay line in the terahertz spectrograph.

Technical Field

The invention belongs to the technical field of spectrum testing, and particularly relates to a terahertz spectrograph based on electron spin emission and a spectrum analysis system.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

In the terahertz field, the terahertz time-domain spectroscopy technology is a mainstream spectral analysis technology, and the technology is mainly used for realizing the test and analysis of the terahertz fingerprint spectrum of a substance based on the interaction of broadband terahertz radiation and a detected sample, and simultaneously can also obtain the electromagnetic parameters such as the refractive index, the dielectric constant and the like of the substance, and has shown important application value in various fields such as hazardous article detection, food and drug safety, oil-gas exploration and the like.

In the terahertz time-domain spectroscopy, the generation of terahertz spectrum is one of the key technical problems. The existing miniaturized terahertz time-domain spectrograph generally adopts a photoconductive antenna as a transmitting end. The principle of generating terahertz spectrum using photoconductive antenna is as follows: a bias voltage is applied between two electrodes on the photoconductive chip, and due to the semi-insulating nature of the photoconductor material, a capacitor structure is formed between the two electrodes and an electrostatic potential is stored. If an optical pulse with photon energy higher than the energy gap of the semiconductor is irradiated in the gap of the electrode, transient free carriers are generated on the surface of the semiconductor in the region. The carriers can accelerate in the bias electric field and release the stored electrostatic potential energy in the form of electromagnetic pulses to form terahertz pulse radiation.

The terahertz spectrograph using the photoconductive antenna as the transmitting end has the advantages of flexible structure and easy realization of complete machine integration and miniaturization, so the terahertz spectrograph is widely applied. The femtosecond laser output from the fiber femtosecond laser with tail fiber is divided into two beams by a 1 x 2 coupler after dispersion precompensation, wherein one beam is used as pumping light and enters an emission module through an optical delay line, and a photoconductive chip is excited to generate terahertz waves under the combined action of an external bias power supply; the other path of the light enters a receiving antenna as detection light. The terahertz waves emitted from the transmitting antenna are also incident on the receiving antenna after being acted with the sample, and the intensity of the terahertz pulses at the moment can be calculated through the current output by the detecting antenna. The signal intensity of other time domain positions of the terahertz pulse can be sampled by controlling the delay amount of the optical path through the optical delay line. The complete terahertz time-domain waveform of the measured object can be restored through the data of the sampling points, and then the terahertz spectrum in the frequency domain is obtained through Fourier transform.

The existing miniaturized terahertz time-domain spectrograph has the following problems:

(1) two key performance indexes of the whole machine spectral range and the dynamic range are limited. The upper limit of a spectrum which can be radiated by a photoconductive antenna in the existing terahertz time-domain spectrometer is 6 THz; the optical power which can be borne is up to 40mW, and the larger optical power can cause the nonlinear effect of the optical fiber and the damage of the photoconductive chip. This also limits the dynamic range of the terahertz spectrometer. In addition, fourier transform is generally adopted in the conversion process from the time domain spectrum to the frequency domain spectrum, and noise in the conversion process also influences the dynamic range of the whole machine.

(2) The realization difficulty is high. The femtosecond pump light and the electrodes of the photoconductive chip are required to be precisely adjusted, so that the performance of the whole machine is easily interfered by factors such as vibration, temperature change and the like; the design and development difficulty of the photoconductive chip is also great, and only one German Fraunhofer laboratory in the world can work well under 1560nm center wavelength femtosecond laser pumping.

(3) The cost is high. The terahertz spectrograph based on the prior art needs a high-voltage bias power supply and a plurality of optical fibers in the whole machine, and the transmitting end and the receiving end both adopt high-cost photoconductive antennas, so that the cost of the whole machine is high.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the terahertz spectrograph based on electron spin emission and the spectral analysis system, which can effectively improve two key performance indexes of bandwidth and dynamic range of the terahertz time-domain spectrograph, and effectively reduce the development difficulty and cost while improving the reliability of the whole machine.

In order to achieve the above object, one or more embodiments of the present invention provide the following technical solutions:

a terahertz spectrometer based on electron spin emission, comprising:

the optical fiber femtosecond laser comprises a space light output port and an optical fiber output port, wherein femtosecond light of the space light output port is incident to an emitting end; coherent detection light of the optical fiber output port is incident to a receiving end through an optical delay line; wherein the delay amount of the optical delay line is adjustable;

the sample holder is positioned between the transmitting end and the receiving end and used for fixing a sample to be detected;

the emitter comprises a substrate and one or more film periods plated on the substrate, wherein the film period consists of a non-magnetic metal film/magnetic metal film heterostructure and a dielectric covering layer covering the heterostructure, and a magnetic field generator is arranged inside or outside the emitter; the transmitting end is used for generating terahertz pulses, and the terahertz pulses penetrate through a sample fixed on the sample rack to form a sample terahertz pulse electric field;

the receiving end comprises a photoconductive chip, coherent detection light excites a photon-generated carrier on the photoconductive chip, current is formed under the action of a sample terahertz pulse electric field, and the intensity of a specific point position of a terahertz pulse waveform is measured based on the current and is output to the data acquisition and processing module.

Furthermore, the femtosecond light of the spatial light output port is reflected by the reflector and then enters the emission end.

Furthermore, after the coherent detection light at the output port of the optical fiber is incident to the receiving end, the coherent detection light is transmitted to the photoconductive chip through the tail fiber.

Further, the data acquisition and processing module receives intensities of a plurality of point positions of the terahertz pulse waveform acquired based on a plurality of delay amounts, and restores the terahertz spectrum of the detected sample.

Further, restoring the terahertz spectrum of the measured sample comprises:

restoring to obtain terahertz time-domain spectrum information of the measured object according to the intensities of a plurality of point positions of the terahertz pulse waveform; and transforming the time domain spectrum of the measured object into a terahertz spectrum in a frequency domain by adopting wavelets.

Further, the data acquisition and processing module obtains characteristic absorption spectrum information of the measured sample based on a reference measurement method.

One or more embodiments provide a terahertz spectroscopic analysis system based on electron spin emission, the system comprising the terahertz spectrometer and a computer; and the computer is respectively connected with the data acquisition and processing and the optical delay line in the terahertz spectrograph.

The above one or more technical solutions have the following beneficial effects:

(1) the transmitting end of the invention has high damage threshold, the acceptable femtosecond optical power is hundreds of milliwatts, and is far higher than the damage threshold of the existing photoconductive antenna, so that the femtosecond pump light in the whole machine can have larger incident power, thus the whole machine has larger dynamic range, and the measured characteristic information of the sample can be more obvious; meanwhile, the upper limit of the spectrum range of the whole machine can be improved to 10 THz.

(2) Because the whole light receiving surface of the transmitting end can receive femtosecond laser and effectively generate terahertz radiation, the femtosecond pump light and the terahertz transmitter can realize high-efficiency terahertz spectrum generation without precise alignment, the design difficulty of the whole machine is reduced, the stability of the whole machine is improved, and meanwhile, the anti-interference capability to environmental changes such as external vibration, temperature and the like is also improved.

(3) Compared with the prior art, the terahertz pulse generator does not need a high-voltage bias power supply as electric drive of the transmitting end, reduces the volume, the weight and the cost, improves the reliability of the whole generator, and reduces the heat dissipation design requirement.

(4) During time-frequency conversion operation, db9 wavelet transform is used to replace conventional Fourier transform of existing spectrometer, so that noise of frequency domain data is reduced, and dynamic range of whole machine is further improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of a conventional terahertz time-domain spectrometer;

FIG. 2 is a schematic diagram of a terahertz time-domain spectrometer arrangement in one or more embodiments of the invention;

fig. 3 is a schematic view of the structure of the sample holder.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.