Terahertz time domain spectroscopy testing apparatus

Abstract

The application discloses a terahertz time-domain spectroscopy testing device, which comprises a laser for outputting femtosecond laser; a light splitting element arranged on an output light path of the laser and used for splitting the femtosecond laser into probe laser, first pump laser and second pump laser; a spin terahertz source arranged in a magnetic field and used for receiving the first pump laser and the second pump laser to irradiate from front and back surfaces respectively and generating first terahertz pulse and second terahertz pulse; wherein the first terahertz pulse and the second terahertz pulse are used for combined light incidence to a sample to be measured; and a terahertz pulse detector used for detecting an optical wave signal after the probe laser, the first terahertz pulse and the second terahertz pulse combined light after passing through the sample to be measured, so as to obtain characteristic information of the sample to be measured. In the application, the spin terahertz source is irradiated by pump laser from two surfaces, the terahertz pulse intensity is improved, and then the accuracy and practicability of the terahertz time-domain spectroscopy testing are improved.

Description

Technical Field

[0001] This invention relates to the field of terahertz spectroscopy detection technology, and in particular to a terahertz time-domain spectroscopy testing device. Background Technology

[0002] THz-TDS (Terahertz Time Domain Spectroscopy) is a novel spectroscopic measurement technique developed in the 1980s. It utilizes a wide-band terahertz pulse obtained based on femtosecond laser technology, transmits the terahertz pulse through a sample or reflects it from the sample, and measures the change in the intensity of the terahertz electric field generated by the pulse over time, thereby obtaining information about the sample.

[0003] Terahertz waves have frequencies ranging from 0.1 to 10 THz (1 THz = 10 THz). 12 Terahertz waves are electromagnetic waves in the range of 100 Hz (3 mm to 30 μm), corresponding to wavelengths between millimeter waves (or submillimeter waves) and infrared waves. Terahertz photons correspond to an energy range of 0.414–41.4 meV, matching the low-frequency vibrational and rotational energy range of molecules and materials. This determines the special position of terahertz waves in the electromagnetic spectrum and their complementarity with millimeter-wave and infrared detection technologies in terms of propagation, scattering, reflection, absorption, and penetration. Therefore, terahertz signal detection technology can be widely applied to detect the properties and physical phenomena of materials between the far-infrared and microwave ranges.

[0004] like Figure 1 As shown, Figure 1 This is a schematic diagram of the basic optical path structure for terahertz time-domain spectroscopy. First, the laser beam generated by the femtosecond laser 01 is split into two beams by a beam splitter 02. One beam is incident on a terahertz source 03 to generate a terahertz wave. This terahertz wave is repeatedly reflected by multiple spherical mirrors 04 and transmitted to the object under test 05. After being transmitted through the object under test 05, it, along with the other laser beam generated by the beam splitter 02, is incident on a terahertz sensor 06. The signal generated by the terahertz wave and the laser beam received by the terahertz sensor 06 is analyzed by a signal analysis device 07 to obtain the final detection result.

[0005] In the research of terahertz wave time-domain spectroscopy, improving the accuracy and practicality of the detection results of the analytes has always been one of the key research directions in the industry. At present, there are various research directions on how to improve the detection results of terahertz waves, such as improving the detection capability of terahertz wave sensors and exploring the accuracy of the analysis of signals measured by terahertz wave sensors. However, there is still a lot of room for improvement in the detection effect of terahertz wave time-domain spectroscopy on the analytes. Summary of the Invention

[0006] The application aims to provide a terahertz time-domain spectroscopy testing device which can improve the terahertz signal intensity in the optical path to some extent, and further improve the accuracy and practicability of the detection result.

[0007] To solve the above technical problems, the application provides a terahertz time-domain spectroscopy testing device, which comprises:

[0008] a laser for outputting femtosecond laser;

[0009] a light splitting element arranged on the output optical path of the laser and used for splitting the femtosecond laser into detection laser, first pump laser and second pump laser;

[0010] a spin terahertz source arranged in a magnetic field and used for receiving the first pump laser and the second pump laser from the front and back surfaces respectively, and generating first terahertz pulse and second terahertz pulse; wherein the first terahertz pulse and the second terahertz pulse are used for combined light to be incident on a sample to be detected;

[0011] a terahertz pulse detector used for detecting the optical wave signal after the detection laser and the combined light of the first terahertz pulse and the second terahertz pulse after passing through the sample to be detected, so as to obtain the characteristic information of the sample to be detected.

[0012] In an optional embodiment of the application, the optical path of the first pump laser and the second pump laser before being incident on the spin terahertz source is equal;

[0013] the optical path of the first terahertz pulse and the second terahertz pulse from the spin terahertz source to the sample to be detected is equal.

[0014] In an optional embodiment of the application, an optical delay line for adjusting the optical path is arranged on at least one of the optical paths of the first pump laser and the second pump laser.

[0015] In an optional embodiment of the application, the difference between the sum of the optical path of the first pump laser and the first terahertz pulse and the optical path of the detection laser is within the interval of ±2000ps.

[0016] In an optional embodiment of the application, the terahertz pulse detector comprises an electro-optic crystal, a polarizer, a quarter-wave plate, a Wollaston prism and a photoelectric balance detector arranged in sequence along the optical path.

[0017] In an optional embodiment of the application, the electro-optic crystal is ZnTe crystal or GaP crystal; the thickness of the electro-optic crystal is less than 100um.

[0018] In an optional embodiment of the present application, the spin terahertz source comprises an insulating substrate and a nanometer film layer arranged on the insulating substrate.

[0019] The nanometer film layer comprises a double-layer nanometer film layer formed by a magnetic nanometer film layer and a non-magnetic nanometer film layer.

[0020] Alternatively, the nanometer film layer comprises two non-magnetic nanometer film layers and a magnetic nanometer film layer arranged between the two non-magnetic nanometer film layers.

[0021] In an optional embodiment of the present application, the insulating substrate is a MgO layer with a thickness of 0.1mm-1mm.

[0022] In an optional embodiment of the present application, the magnetic nanometer film layer is a Fe layer with a thickness of 0.1nm-10nm.

[0023] In an optional embodiment of the present application, the non-magnetic nanometer film layer is a W layer and / or a Pt layer with a thickness of 0.1nm-10nm.

[0024] The present application provides a terahertz time-domain spectroscopy testing device, comprising: a laser for outputting femtosecond laser; a light splitting element arranged on the output light path of the laser, for splitting the femtosecond laser into probe laser, first pump laser and second pump laser; a spin terahertz source arranged in a magnetic field, for receiving the first pump laser and the second pump laser from the front and rear surfaces respectively, and generating first terahertz pulse and second terahertz pulse; wherein the first terahertz pulse and the second terahertz pulse are used for combined light to be incident on the sample to be tested; a terahertz pulse detector for detecting the light wave signal after the probe laser, the first terahertz pulse and the second terahertz pulse combined light after passing through the sample to be tested, to obtain the characteristic information of the sample to be tested.

[0025] The terahertz time-domain spectroscopy device in the present application, when performing terahertz time-domain spectroscopy testing, divides the femtosecond laser generated by the laser into three beams of laser, and then one of the three beams of laser after splitting as a probe laser, and the other two as pump lasers can excite and irradiate the spin terahertz source from the front and rear surfaces of the spin terahertz source, to a certain extent, improve the efficiency of the spin terahertz source radiating terahertz waves, and then improve the accuracy and practicability of subsequent testing of the sample to be tested using terahertz waves, which is conducive to the wide application of terahertz time-domain spectroscopy testing technology.

[0026] On this basis, in another optional embodiment of the present application, a polarizer is further arranged between the electro-optic crystal and the quarter-wave plate in the terahertz pulse detector, which can greatly improve the terahertz photoelectric signal strength; in addition, the combination of the spin terahertz source, the narrow pulse width pump femtosecond laser and the electro-optic crystal can obtain a terahertz spectral width greater than 10 THz, and the polarization can be regulated by an external magnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 It is a basic optical path structure diagram of terahertz time domain spectroscopy technology.

[0029] Figure 2 It is a schematic diagram of the optical path structure of the terahertz time domain spectroscopy test equipment provided by the embodiment of the present application. DETAILED DESCRIPTION

[0030] Reference Figure 1 At present, the terahertz pulse in the conventional terahertz time domain spectroscopy test is generated by irradiating the terahertz source 03 with a laser beam. Obviously, the laser beam incident to the terahertz source 03 cannot be 100% absorbed, and obviously, the absorption efficiency of the terahertz source 03 to the laser beam is positively correlated with the intensity of the terahertz pulse radiated by the excited terahertz source 03.

[0031] Therefore, the present application proposes a technical solution capable of improving the absorption efficiency of the terahertz source to the laser beam, and further improving the radiation efficiency of the terahertz source to the terahertz pulse, thereby improving the detection result accuracy and practicability of the terahertz time domain spectroscopy detection technology to a certain extent.

[0032] In order to enable those skilled in the art to better understand the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0033] As shown in Figure 2 , the present application provides a terahertz time domain spectroscopy test equipment, which can include: Figure 2 It is a schematic diagram of the optical path structure of the terahertz time domain spectroscopy test equipment provided by the embodiment of the present application.

[0034] Laser 1 for outputting femtosecond laser; laser 1 can be a femtosecond laser or a laser 1 capable of outputting femtosecond laser, and no specific restrictions are made in this embodiment.

[0035] A beam splitting element is set in the output optical path of laser 1 to split the femtosecond laser into a probe laser A-1, a first pump laser A-2, and a second pump laser A-3.

[0036] A spin terahertz source 5 is placed in a magnetic field to receive first pump laser A-2 and second pump laser A-3 irradiating from the front and rear surfaces respectively, and to generate first terahertz pulses and second terahertz pulses; wherein the first terahertz pulse and the second terahertz pulse are used to combine the light and incident it onto the sample to be tested 7.

[0037] Terahertz pulse detector 8 is used to detect the light wave signal after the detection laser A-1 combines with the first terahertz pulse and the second terahertz pulse after passing through the sample 7, so as to obtain the characteristic information of the sample 7.

[0038] It should be noted that this embodiment should also include an optical path element that combines the first terahertz pulse and the second terahertz pulse so that the two combined terahertz pulses are incident on the sample 7 to be tested; and an optical path element that combines the two terahertz pulses after passing through the sample 7 to be tested and the probe laser. These are all commonly used optical combining elements in optical paths, and will not be described in detail in this embodiment.

[0039] Reference Figure 2 , Figure 2 The beam splitting element for splitting the femtosecond laser output from laser 1 consists of two beam splitters. The first beam splitter 2-1 first splits the femtosecond laser output from the laser into two laser beams. One of the laser beams is the probe laser A-1, while the other beam is used as the pump laser and is split again by the second beam splitter 2-2 to form the first pump laser A-2 and the second pump laser A-3.

[0040] Understandably, in practical applications it is not limited to Figure 2 The beam splitting method shown can also be achieved by directly setting an optical coupler beam splitter as a beam splitting element at the output end of laser 1, which can split the femtosecond laser output by the laser into three equal laser beams at one time. This can also realize the technical solution in this application.

[0041] In addition, in optional embodiments of this application, it is also possible to directly use three lasers to output three laser beams respectively, or to use two lasers 1, and split the femtosecond laser output by one of the lasers 1 into two laser beams through a beam splitter, etc.; in short, as long as three laser beams can be obtained in the end.

[0042] Further, the terahertz source generating the terahertz pulse in the embodiment is a spin terahertz source 5, which can generate a terahertz pulse with an ultra-wide spectrum greater than 10 THz under excitation of a femtosecond laser pulse less than 50 fs. The spin terahertz source 5 can include an insulating substrate and a nanometer film layer arranged on the insulating substrate.

[0043] The insulating substrate can include one or more structural layers of an Al2O3 layer, an MgO layer, an SiO2 layer, a PET layer, a PEN layer, a LaAlO3 layer, a SrTiO3 layer, a TiO2 layer, a ZrO2 layer, a ZnO layer, a La2O3 layer, a GeO2 layer, a VO2 layer, and a Y2O3 layer, and the thickness of the insulating substrate can be 0.1 mm to 1.0 mm.

[0044] The nanometer film layer can include a double-layer nanometer film layer formed by one magnetic nanometer film layer and one non-magnetic nanometer film layer adhering to each other.

[0045] Alternatively, the nanometer film layer can include two non-magnetic nanometer film layers and a magnetic nanometer film layer arranged between the two non-magnetic nanometer film layers.

[0046] The magnetic nanometer film layer can be one or more structural layers of an Fe layer, a Co layer, a Ni layer, a FeNi layer, a CoFe layer, a CoFeB layer, a Fe3Si layer, a YIG layer, a Fe3O4 layer, a GdFeCo layer, a GdCo5 layer, a DyCo5 layer, a TbFe2 layer, and a BaFe12O19 layer, and the thickness of the magnetic nanometer film layer can be 0.1 nm to 10 nm.

[0047] The non-magnetic nanometer film layer can include one or more structural layers of a Pt layer, a W layer, a Pd layer, a Ta layer, a Bi layer, a Cr layer, an Ir layer, an IrMn layer, a PtMn layer, a PdMn layer, a FeMn layer, an AuPt layer, an AuW layer, a PtBi layer, a CuBi layer, a CuIr layer, a CuPb layer, a Bi2Se3 layer, a Bi2Te3 layer, a Bi2Se2Te layer, a Bi2Te2Se layer, a Sn-doped Bi2Te2Se layer, a BiSbTeSe layer, a (BixSb1-x)2Te3 layer, an α-Sn layer, a TaAs layer, a TaP layer, a NbAs layer, a NbP layer, a WTe2 layer, a MoTe2 layer, a ZrSiS layer, a graphene layer, and a MoS2 layer, and the thickness of the non-magnetic nanometer film layer can be 0.1 nm to 10 nm.

[0048] On this basis, the first pump laser A-2 and the second pump laser A-3 are respectively irradiated from the front and rear surfaces of the spin terahertz source 5, so that the absorption efficiency of the spin terahertz source 5 to the femtosecond laser is greatly improved, and then the efficiency of the spin terahertz source 5 to the terahertz pulse excited and radiated by the femtosecond laser is greatly improved.

[0049] It can be understood that the spin terahertz source 5 is a thin film structure, and the pump laser is irradiated from the front and rear surfaces thereof, that is, the pump laser is respectively incident from the two surfaces of the insulating substrate surface and the magnetic nanometer film layer of the spin terahertz source 5, so as to ensure the high efficiency absorption of the spin terahertz source 5 to the pump laser.

[0050] The front and rear surfaces of the spin terahertz source 5 respectively receive the irradiation of the first pump laser A-2 and the second pump laser A-3, so that the pulse signal intensity of the first terahertz pulse and the second terahertz pulse radiated outward by the front and rear surfaces is greatly improved.

[0051] It should be noted that, in order to distinguish the pump laser and the terahertz pulse, Figure 2 the transmission light path of the pump laser and the probe laser A-1 is represented by a solid line with an arrow, and the light path of the terahertz pulse is represented by a dashed line with an arrow.

[0052] In addition, the spin terahertz source 5 needs to be excited by the pump laser to generate the terahertz pulse under the action of a certain magnetic field, and therefore the spin terahertz source 5 should be arranged in a magnetic field; optionally, the spin terahertz source 5 can be arranged in a magnetic field generating device 6, and the magnetic field generating device 6 can be an electromagnet, a rotatable permanent magnet block, etc., and the magnetic field direction of the generated magnetic field is 360 degrees adjustable.

[0053] On this basis, an optical path element for adjusting the optical path can be further arranged on at least one of the first pump laser A-2 and the second pump laser A-3, so that the optical paths of the first pump laser A-2 and the second pump laser A-3 are equal, that is, the optical paths of the first pump laser A-2 and the second pump laser A-3 from the light splitting element to the spin terahertz source 5 are equal.

[0054] Referring to Figure 2 , Figure 2 the light path delay line B formed by a plurality of reflective elements or other optical path elements can be arranged on the light path of the first pump laser A-2 and the light path of the second pump laser A-3. Figure 2 For example, Figure 2The optical path elements with serial numbers 3-1, 3-2, 3-3 to 3-10 and the like can be regarded as reflective elements, and the embodiment will not be described in detail. The reflective element 3-1 and the reflective element 3-2 are components of the optical delay line B, and the optical delay line C, the optical delay line E and the like are similar, and the embodiment will not be described in detail.

[0055] Obviously, moving the positions of the reflective elements along the optical axis direction can change the optical path of the first pump laser A-2 and the optical path of the second pump laser A-3 to a certain extent. By adjusting the optical path of the first pump laser A-2 and the optical path of the second pump laser A-3 to be equal, the absorption efficiency of the femtosecond laser by the terahertz source 5 can be further improved. Compared with only irradiating the pump laser on one surface of the terahertz source 5, the embodiment can improve the laser absorption efficiency of the terahertz source 5 from about 40% to more than 90% by exciting the terahertz source 5 from two surfaces, thereby improving the intensity of the generated terahertz pulse.

[0056] On this basis, the terahertz source 5 receives pump lasers from two different surfaces, and the first terahertz pulse and the second terahertz pulse generated by the terahertz source 5 are respectively radiated from the front and rear surfaces of the terahertz source 5, and finally jointly incident on the sample 7 to be measured.

[0057] In order to improve the signal-to-noise ratio, the optical paths of the first terahertz pulse and the second terahertz pulse can be set to be substantially equal, so that the first terahertz pulse and the second terahertz pulse are coherently synthesized to be incident on the sample 7 to be measured, further improving the terahertz intensity and ensuring the ultra-high signal-to-noise ratio of the entire optical path system, and the signal-to-noise ratio can reach 120dB. Figure 2 As shown, the optical path of the first terahertz pulse and the second terahertz pulse can be modulated to be equal by adjusting the optical path delay line E, and the adjustment of the optical path of the first terahertz pulse and the second terahertz pulse to be equal can also be realized by adjusting the relative positions between the optical elements.

[0058] In addition, on the basis that the optical paths of the first terahertz pulse and the second terahertz pulse are equal, the optical path of the probe laser A-1 can also be set to be equal to the sum of the optical paths of the first pump laser A-2 and the first terahertz pulse, and the optical path difference between the two optical paths can be within the interval of ±2000ps, and the optical path difference can also be continuously adjusted within the interval of ±2000ps by adjusting the optical delay line C.

[0059] That is, the optical path difference between the optical path from the beam splitter element to the spin terahertz source 5 of the first pump laser A-2 plus the optical path from the spin terahertz source 5 to the terahertz pulse detector 8 of the first terahertz pulse or the optical path from the beam splitter element to the spin terahertz source 5 of the second pump laser A-3 plus the optical path from the spin terahertz source 5 to the terahertz pulse detector 8 of the second terahertz pulse and the optical path from the beam splitter element to the terahertz pulse detector 8 of the probe laser A-1 is continuously varied within the interval of ±2000 ps by adjusting the optical delay line C.

[0060] When the first terahertz pulse and the second terahertz pulse are coherently synthesized to be incident on the sample under test 7, the synthesis of the first terahertz pulse and the second terahertz pulse can be achieved by using optical path elements such as off-axis parabolic mirrors, and the present embodiment will not be described in detail.

[0061] After the first terahertz pulse and the second terahertz pulse are coherently synthesized, they are transmitted or reflected through the sample under test 7 and finally incident on the terahertz pulse detector 8 together with the probe laser A-1. The terahertz pulse detector 8 senses and receives the first terahertz pulse and the second terahertz pulse and the probe laser A-1 that have passed through the sample under test 7, and the characteristic information of the sample under test 7 can be determined based on the optoelectronic signals detected.

[0062] The terahertz pulse detector 8 can include, in sequence along the optical path, an electro-optic crystal 81, a quarter-wave plate 83, a Wollaston prism 84, and a photoelectric balance detector 85. Of course, the photoelectric balance detector 85 should also be connected to a processor 86 that analyzes the signals output by the photoelectric balance detector 85.

[0063] In addition, in order to further improve the intensity of the terahertz pulse signal, a polarizer 82 can be added between the electro-optic crystal 81 and the quarter-wave plate 83. Compared with conventional terahertz pulse detectors, the present application adds a polarizer 82 between the electro-optic crystal 81 and the quarter-wave plate 83, which greatly improves the intensity of the terahertz optoelectronic signal.

[0064] In summary, the terahertz time-domain spectroscopy testing device provided in the present application uses a spin terahertz source as a terahertz source for generating terahertz pulses. On this basis, pump laser irradiation is performed from the front and rear surfaces of the spin terahertz source, which greatly improves the absorption efficiency of the spin terahertz source for laser and to a certain extent improves the signal intensity of the terahertz pulses generated by the spin terahertz source, which is conducive to improving the detection accuracy of the entire terahertz time-domain spectroscopy testing device.

[0065] Further, the optical path is adjusted to coherently superimpose the forward and backward terahertz pulses of the spin terahertz source, further improving the terahertz signal intensity.

[0066] Meanwhile, a polarizer is further optionally added between the electro-optic crystal and the quarter-wave plate, which can greatly improve the intensity of the terahertz photoelectric signal.

[0067] Furthermore, the terahertz spectrum width greater than 10 THz can be obtained by the combination of the spin terahertz source, the pump femtosecond laser with a narrow pulse width, and the electro-optic crystal, and the polarization can be regulated by an external magnetic field. Finally, the detection accuracy of the entire terahertz time-domain spectrum testing device can be improved.

[0068] With reference to Figure 2 In ​The femtosecond laser emitted by the laser 1 in the embodiment is split into a probe laser A-1 and a pump laser beam by a first beam splitter 2-1; the pump laser beam is further split into a first pump laser A-2 and a second pump laser A-3 by a second beam splitter 2-2. The first pump laser A-2 passes through an optical delay line B and is irradiated onto the spin terahertz source 5 from the front through a small hole in the middle of a first off-axis parabolic mirror 4-1 with a hole; the second pump laser A-3 is irradiated onto the spin terahertz source 5 from the back through a small hole in the middle of a second off-axis parabolic mirror 4-2 with a hole; the light spots of the first pump laser A-2 and the second pump laser A-3 on the spin terahertz source 5 coincide. The spin terahertz source 5 is placed in the middle of a magnetic field generating device 6, and the magnetic field generating device 6 applies an in-plane magnetic field to the spin terahertz source 5. The forward-radiated terahertz pulse D-1 and the backward-radiated terahertz pulse D-3 excited by the first pump laser A-2, and the forward-radiated terahertz pulse D-2 and the backward-radiated terahertz pulse D-4 excited by the second pump laser A-3, the forward-radiated terahertz pulses D-1 and D-2 are the first terahertz pulses, and the backward-radiated terahertz pulses D-3 and D-4 are the second terahertz pulses. The spin terahertz source 5 can generate an ultra-wide spectrum greater than 10 THz under the excitation of femtosecond pulses less than 50 fs, and the polarization state can be controlled by changing the direction of the applied magnetic field. By adjusting the optical delay line E to adjust the optical path difference of the first pump laser A-2 and the second pump laser A-3, when the optical path of the first pump laser A-2 and the second pump laser A-3 is equal, the laser absorption utilization rate is the largest, and the radiation efficiency of the terahertz pulses D-1, D-2, D-3 and D-4 is increased. The terahertz pulses D-1, D-2, D-3 and D-4 are collected by a third off-axis parabolic mirror 4-3 and are collimated and focused on the sample 7 to be measured. The two terahertz beams are focused on the terahertz spot on the sample 7 to be measured by the third off-axis parabolic mirror 4-3; adjust the delay line E so that the optical path of the two terahertz beams is the same, so as to synthesize the terahertz coherently and improve the terahertz intensity. The synthesized terahertz is transmitted through the sample 7 to be measured and then enters the fourth off-axis parabolic mirror 4-4 and the fifth off-axis parabolic mirror 4-5 in turn, and is collimated and focused on the electro-optic crystal 81 through the fifth off-axis parabolic mirror 4-5 with a hole and the probe laser A-1; the optical path of the probe laser A-1 can be adjusted to be approximately equal to the sum of the optical paths of the first pump laser A-2 and the terahertz pulse by adjusting the optical path delay line C, and the optical path difference of the two optical paths can be continuously varied within the interval of ±2000 ps by the optical path delay line C.

[0069] The electro-optic crystal 81 can be a ZnTe or GaP crystal less than 100 um thick. The probe laser A-1 is combined with the focused terahertz after passing through the optical delay line C and overlapping on the electro-optic crystal 81; the terahertz causes a change in the polarization direction of the probe light, and the polarization change is obtained through the polarizer 82, the quarter-wave plate 83, the Wollaston prism 84, the photoelectric balance detector 85, and the processor 86 for reading and processing the photoelectric signal, and by moving the optical delay line C, the entire terahertz pulse waveform can be obtained. In the probe light path, the addition of the polarizer 82 can greatly improve the terahertz photoelectric signal, which can be improved by more than 5 times relative to the conventional terahertz time-domain spectroscopy system. The spin terahertz source 5, the narrow femtosecond pulse width, and the electro-optic crystal 81 ensure that the system is ultra-wideband and polarization-adjustable, with a bandwidth greater than 10 THz and linear polarization adjustable by 360 degrees; the addition of the polarizer 52 in the pump femtosecond laser incident light path, the terahertz coherent synthesis light path, and the probe light path ensures that the system has an ultra-high signal-to-noise ratio, and the signal-to-noise ratio can reach 120 dB.

[0070] It should be noted that, in this document, the terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device inherently includes a series of elements. Without more limitations, the element defined by the statement "includes a" does not exclude the presence of another identical element in the process, method, article or device that includes the element. In addition, the above technical solutions provided by the embodiments of the present application have not been described in detail, so as not to be too verbose.

[0071] The principles and implementation modes of the present application are described by applying specific examples in this document, and the above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A terahertz time-domain spectroscopy testing device, characterized by, The application relates to a terahertz pulse detection device. The device comprises: a laser for outputting femtosecond laser; a light splitting element arranged on an output light path of the laser, for splitting the femtosecond laser into three beams of probe laser, first pump laser and second pump laser; a spin terahertz source arranged in a magnetic field, for receiving the first pump laser and the second pump laser from front and back surfaces respectively, and generating first terahertz pulse and second terahertz pulse, wherein the first terahertz pulse and the second terahertz pulse are used for combined light incidence to a sample to be detected; a terahertz pulse detector for detecting an optical wave signal after the probe laser, the first terahertz pulse and the second terahertz pulse after the combined light pass through the sample to be detected, so as to obtain characteristic information of the sample to be detected. The optical path of the first pump laser and the second pump laser before incidence to the spin terahertz source is equal.

2. The terahertz time-domain spectroscopy testing device of claim 1, wherein, The optical path of the first terahertz pulse and the second terahertz pulse from the spin terahertz source to the sample to be detected is equal.

3. The terahertz time-domain spectroscopy testing device of claim 1, wherein, An optical delay line for adjusting the optical path is arranged in at least one of the optical paths of the first pump laser and the second pump laser.

4. The terahertz time-domain spectroscopy testing device of claim 1, wherein, The difference between the sum of the optical path of the first pump laser and the first terahertz pulse and the optical path of the probe laser is within the range of + / -2000ps.

5. The terahertz time-domain spectroscopy testing device of claim 4, wherein, The terahertz pulse detector comprises, in sequence along the optical path, an electro-optic crystal, a polarizer, a quarter-wave plate, a Wollaston prism and a photoelectric balance detector.

6. The terahertz time-domain spectroscopy testing device of claim 1, wherein, The electro-optic crystal is ZnTe crystal or GaP crystal, and the thickness of the electro-optic crystal is less than 100um. The spin terahertz source comprises an insulating substrate and a nanometer film layer arranged on the insulating substrate. The nanometer film layer comprises a double-layer nanometer film layer formed by a magnetic nanometer film layer and a non-magnetic nanometer film layer.

7. The terahertz time-domain spectroscopy testing device of claim 6, wherein, Alternatively, the nanometer film layer comprises two non-magnetic nanometer film layers and a magnetic nanometer film layer arranged between the two non-magnetic nanometer film layers.

8. The terahertz time-domain spectroscopy testing device of claim 6, wherein, The insulating substrate is MgO layer, and the thickness is 0.1mm-1mm.

9. The terahertz time-domain spectroscopy testing device of claim 6, wherein, The magnetic nanometer film layer is Fe layer, and the thickness is 0.1nm-10nm. The non-magnetic nanometer film layer is W layer and / or Pt layer, and the thickness is 0.1nm-10nm.

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