Time-resolved broadband terahertz device and control method

Abstract

The application provides a time-resolved broadband terahertz device and a control method. The device comprises a femtosecond laser, a beam splitter, a terahertz generation cavity, an experimental cavity, a terahertz detection cavity and a lock-in amplifier. The femtosecond laser is used to generate femtosecond laser; the beam splitter is used to divide the femtosecond laser into generation light, pump light and gate light; the terahertz generation cavity is used to receive the generation light, and make the generation light reach the gas injection area, generate gas plasma to emit broadband terahertz light, and form pure terahertz light after filtering the broadband terahertz light by high resistance silicon; the pure terahertz light is transmitted through the sample to generate transmitted terahertz light, which carries the non-equilibrium state transmission spectrum information of the sample excited by the pump light; the transmitted terahertz light is used to modulate the second harmonic of the gate light; and the lock-in amplifier is used to receive the second harmonic of the gate light modulated by the transmitted terahertz light to detect the change of the transient terahertz, so as to realize the detection of the time-resolved terahertz spectrum of the sample.

Description

Technical Field

[0001] This application relates to the field of terahertz spectroscopy technology, and more specifically, to a time-resolved broadband terahertz device and its control method. Background Technology

[0002] Terahertz waves, due to their high penetrability, low photon energy, and water absorption sensitivity, are widely used in fields such as materials electronics, phonon and magnetic structure research, and non-destructive testing, including security inspection, chemical analysis, and biological tissue analysis. High-intensity terahertz spectra can be obtained using gas plasma methods.

[0003] However, conventional gas plasma generation methods and broadband terahertz spectroscopy devices are only suitable for sample testing in room temperature gas environments, such as nitrogen environments, and cannot meet the needs of terahertz measurement under a wide range of low-temperature conditions for various materials.

[0004] Researchers have proposed using a time-resolved device to generate and detect terahertz waves using crystals to provide low-temperature conditions for sample testing. However, although this time-resolved device can easily place the crystal in a vacuum chamber to achieve the high vacuum environment required for low-temperature testing, it can only generate and detect narrowband terahertz waves.

[0005] Researchers then proposed placing a small vacuum cryogenic cavity (with optical windows such as diamond or sapphire) inside a large nitrogen cavity to achieve broadband terahertz frequencies under both vacuum and cryogenic conditions. However, because terahertz waves experience significant absorption when passing through the optical window, especially due to phonon absorption by the optical window itself, terahertz frequencies become unusable in certain frequency bands.

[0006] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To address the aforementioned issues, this application proposes a time-resolved broadband terahertz device and its control method.

[0008] According to a first aspect of this application, a time-resolved broadband terahertz device is proposed, comprising a femtosecond laser, a beam splitter, a terahertz generation cavity, an experimental cavity, a terahertz detection cavity, and a lock-in amplifier, wherein:

[0009] The femtosecond laser is used to generate femtosecond lasers;

[0010] The beam splitter is used to split the femtosecond laser into a generating beam, a pump beam, and a gated beam.

[0011] The terahertz generating cavity is used to receive the generated light and bring the generated light to the gas injection area to generate gas plasma to emit broadband terahertz light. The broadband terahertz light is then filtered by high-resistivity silicon to form pure terahertz light.

[0012] The experimental cavity is connected to the terahertz generation cavity and is used to receive the pump light and the pure terahertz light; the pure terahertz light is transmitted through the sample to generate transmitted terahertz light; the transmitted terahertz light carries the non-equilibrium transmission spectrum information of the sample excited by the pump light;

[0013] The terahertz detection cavity is connected to the experimental cavity and is used to receive the gated light and the transmitted terahertz light; the gated light reaches the gas injection region to generate gas plasma; the transmitted terahertz light is used to modulate the second harmonic of the gated light.

[0014] The lock-in amplifier is used to receive the second harmonic of the gated light modulated by the transmitted terahertz light, so as to detect the transient terahertz change and realize the detection of the time-resolved terahertz spectrum of the sample.

[0015] According to some embodiments, the terahertz generating cavity, the experimental cavity, and the terahertz detection cavity are respectively equipped with vacuum pump sets through evacuation holes, and are connected to each other through small holes to achieve differential evacuation between the cavities, so as to ensure that the experimental cavity can be maintained in a high vacuum state when the terahertz generating cavity and the terahertz detection cavity are in a low vacuum state.

[0016] According to some embodiments, the time-resolved broadband terahertz device further includes a gas tube, and the terahertz generation cavity and the terahertz detection cavity each include a gas guide hole. The gas tube is introduced into the interior of the terahertz generation cavity and the terahertz detection cavity through the gas guide hole, so that high-pressure nitrogen gas is injected into the terahertz generation cavity and the terahertz detection cavity through the gas tube to form a gas injection region.

[0017] According to some embodiments, the terahertz generating cavity includes a high-resistivity silicon wafer and a first off-axis parabolic mirror, wherein:

[0018] The high-resistivity silicon is used to filter the femtosecond laser in the broadband terahertz light to generate the pure terahertz light.

[0019] The first off-axis parabolic mirror is used to focus the pure terahertz light so that the pure terahertz light enters the experimental cavity.

[0020] According to some embodiments, the experimental cavity includes a second off-axis parabolic mirror and a third off-axis parabolic mirror, wherein:

[0021] The second off-axis parabolic mirror is used to focus the pure terahertz light so that the pure terahertz light illuminates the sample;

[0022] The third off-axis parabolic mirror is used to focus the transmitted terahertz light so that the transmitted terahertz light enters the terahertz detection cavity.

[0023] According to some embodiments, the time-resolved broadband terahertz device further includes a cryostat connected to the sample in the experimental chamber, so as to enable the time-resolved broadband terahertz device to test the sample at different temperatures.

[0024] According to some embodiments, the terahertz detection cavity includes a fourth off-axis parabolic mirror and a reflector, wherein:

[0025] The fourth off-axis parabolic mirror is used to focus the transmitted terahertz light so that the transmitted terahertz light reaches the gas plasma region.

[0026] The reflector is used to extract the second harmonic of the gated light modulated by the transmitted terahertz light from the terahertz detection cavity.

[0027] According to some embodiments, the time-resolved broadband terahertz device further includes a second harmonic filter and a photoavalanche diode, wherein:

[0028] The second harmonic filter is used to filter the second harmonic of the extracted gated light;

[0029] The photoelectric avalanche tube is used to receive the second harmonic of the filtered gated light and transmit it to the lock-in amplifier.

[0030] According to some embodiments, the time-resolved broadband terahertz device further includes a chopper for modulating the frequencies of the generated light and the pump light, and transmitting the frequencies of the generated light and the pump light to the lock-in amplifier.

[0031] According to a second aspect of this application, a control method for a time-resolved broadband terahertz device is provided, characterized in that it is used for the time-resolved broadband terahertz device as described in any one of the first aspects, the control method comprising:

[0032] Differential evacuation is controlled between the terahertz generation cavity, the experimental cavity, and the terahertz detection cavity to maintain the experimental cavity in a high vacuum state;

[0033] Controlled gas is introduced into the terahertz generation cavity and the terahertz detection cavity to form a gas injection area;

[0034] Control the femtosecond laser to generate femtosecond laser;

[0035] The beam splitter is controlled to receive the femtosecond laser to generate the generating light, pump light, and gated light;

[0036] The lock-in amplifier receives the frequency of the generated light, the pump light, and the second harmonic of the modulated gated light to detect transient terahertz changes and realize the detection of the time-resolved terahertz spectrum of the sample.

[0037] Through the above exemplary embodiments, this application provides a time-resolved broadband terahertz device and control method. The time-resolved broadband terahertz device includes a low-vacuum terahertz generation cavity and a detection cavity, as well as a high-vacuum experimental cavity. The cavities are connected by a small aperture, eliminating the need for optical windows and ensuring that the terahertz waves can pass through the aperture without loss. A differential pumping method is used to generate and detect broadband terahertz waves in a localized region within the rough vacuum cavity using high-pressure gas plasma. A cryostat is installed in the high-vacuum experimental cavity, allowing sample measurements to be performed under low-temperature conditions. This achieves a time-resolved terahertz device combining high vacuum, low temperature, and high-pressure gas, suitable for variable-temperature time-resolved broadband terahertz spectroscopy research required for materials science.

[0038] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0039] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application and are not intended to limit the scope of this application.

[0040] Figure 1 An exemplary embodiment of a time-resolved broadband terahertz device is shown;

[0041] Figure 2 A flowchart illustrating an exemplary embodiment of a time-resolved broadband terahertz device control method is shown. Detailed Implementation

[0042] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0043] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0044] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0045] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0046] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0047] Example 1

[0048] According to a first aspect of this application, a time-resolved broadband terahertz device is provided. This device includes a rough vacuum terahertz generation cavity and a detection cavity, as well as a high vacuum experimental cavity. The cavities are connected by a small aperture, eliminating the need for optical windows and ensuring lossless passage of terahertz waves. A differential pumping method is used to generate and detect broadband terahertz waves in a localized region within the low vacuum cavity using high-pressure gas plasma. A cryostat is installed in the high vacuum experimental cavity, allowing sample measurements to be performed under cryogenic conditions. This achieves a time-resolved terahertz device combining high vacuum, cryogenic temperature, and high-pressure gas for use in materials research requiring variable-temperature time-resolved broadband terahertz spectroscopy.

[0049] Terahertz waves are electromagnetic waves that fall between microwaves and infrared light, with energy levels between the photonics and electronics filtering regions.

[0050] Figure 1An exemplary embodiment of a time-resolved broadband terahertz device is shown. See also Figure 1 The time-resolved broadband terahertz device includes a femtosecond laser 20, a beam splitter 12, a terahertz generation cavity 1, an experimental cavity 2, a terahertz detection cavity 3, and a lock-in amplifier 21.

[0051] According to the example embodiment, the terahertz generation cavity 1, the experimental cavity 2 and the terahertz detection cavity 3 are respectively equipped with vacuum pump groups through the evacuation port 6 to realize differential evacuation between the cavities, so as to ensure that the experimental cavity 2 reaches a high vacuum state.

[0052] According to some embodiments, differential pumping is a technique that uses a small hole or capillary tube to connect multiple vacuum chambers with significantly different vacuum levels and maintain the original vacuum level of each chamber.

[0053] According to some embodiments, when the vacuum degree is between 1×10 -1 ~1×10 -5 A pressure of 1 Pa is called a high vacuum.

[0054] According to an example embodiment, the time-resolved broadband terahertz device further includes a gas pipe 8. The terahertz generation chamber 1 and the terahertz detection chamber 3 each include gas guide holes 701 and 703. The gas pipe 8 is introduced into the terahertz generation chamber 1 and the terahertz detection chamber 3 through the gas guide holes 701 and 703, respectively, so that high-pressure nitrogen gas is injected into the terahertz generation chamber 1 and the terahertz detection chamber 3 through the gas pipe 8, forming a gas injection region.

[0055] This application uses high-pressure nitrogen as an example, but other gases may also be used, but this application is not limited to this.

[0056] According to the example embodiment, this application takes the optical path from left to right as an example, but this application is not limited thereto: the femtosecond laser 20 generates a femtosecond laser. After passing through the beam splitter 12, the femtosecond laser is split into three beams: the generating beam, the pump beam, and the probe beam.

[0057] According to the example embodiment, the time-resolved broadband terahertz device also includes a cryostat 22, which is connected to the sample in the experimental chamber 2 to enable the time-resolved broadband terahertz device to test the sample at different temperatures and achieve controllable low-temperature-room-temperature conditions.

[0058] According to an example embodiment, the time-resolved broadband terahertz device further includes a second harmonic filter 18 and a photoavalanche diode 19. The second harmonic filter 18 filters the second harmonic of the extracted gated light. The photoavalanche diode 19 receives the filtered second harmonic and transmits it to a lock-in amplifier 21.

[0059] According to an example embodiment, the time-resolved broadband terahertz device further includes choppers 1301 and 1302, lenses 1001, 1002, 1003 and 1004, delay lines 1401 and 1402, and reflectors 1501, 1504, 1505 and 1506.

[0060] According to some embodiments, chopper 1301 is used to modulate the frequency of the generated light, chopper 1302 is used to modulate the frequency of the pump light, and transmits the frequencies of the generated light and the pump light to lock-in amplifier 21, respectively.

[0061] According to an example embodiment, the terahertz generation cavity includes a high-resistivity silicon 16 and a first off-axis parabolic mirror 1701.

[0062] According to some embodiments, high-resistivity silicon, also known as intrinsic silicon, refers to silicon materials with a resistivity greater than 1 kiloohm·cm.

[0063] According to some embodiments, an off-axis parabolic mirror is a reflector with a parabolic surface that can focus incident parallel light after reflection, with the incident light and the outgoing light forming a certain angle.

[0064] According to the example embodiment, the experimental cavity 2 includes a reflector 1502, a second off-axis parabolic mirror 1702 and a third off-axis parabolic mirror 1703.

[0065] According to an example embodiment, the terahertz detection cavity 3 includes a fourth off-axis parabolic mirror 1704 and a reflector 1503.

[0066] After being focused by chopper 1301 and lens 1001, the generated light enters terahertz generation cavity 1 through optical window 501, reaches gas jet region, generates gas plasma 9, and thus emits broadband terahertz light.

[0067] According to some embodiments, gas plasma is an ionized gaseous substance composed of positive and negative ions formed when a gas is heated to a sufficiently high temperature by a laser (such as at the focal point of a strong laser).

[0068] The high-resistivity silicon 16 filters out the remaining femtosecond laser light in the broadband terahertz light, generating pure terahertz light. The first off-axis parabolic mirror 1701 focuses the pure terahertz light, allowing it to enter the experimental cavity 2 through the pinhole communicating vessel 401.

[0069] This application uses a pinhole communicating vessel for connecting cavities as an example, but it is not limited to this. The terahertz generation cavity, experimental cavity, and terahertz detection cavity are connected by a pinhole to ensure that terahertz waves pass through without loss.

[0070] The pump light passes through chopper 1302, delay line 1401, mirror 1501, and lens 1002, and then enters experimental cavity 2 through optical window 502. After being reflected by mirror 1502, the pump light is focused onto the sample, exciting the sample to a non-equilibrium state.

[0071] The second off-axis parabolic mirror 1702 focuses pure terahertz light, which then illuminates the sample, generating transmitted terahertz light. This transmitted terahertz light carries the non-equilibrium transmission spectrum information of the sample after being excited by the pump light. The third off-axis parabolic mirror 1703 focuses the transmitted terahertz light, allowing it to enter the terahertz detection cavity 3 through the pinhole connector 402.

[0072] After passing through mirror 1504, delay line 1402, mirror 1505, lens 1003 and mirror 1506, the gated light enters the terahertz detection cavity 3 through optical window 503, and is focused on the gas jet region through the small hole of the fourth off-axis parabolic mirror 1704 to generate gas plasma 11.

[0073] The fourth off-axis parabolic mirror 1704 focuses the transmitted terahertz light, allowing it to reach the gas plasma region to modulate the intensity of the second harmonic generated by the gated light. The modulated second harmonic of the gated light is then extracted from the terahertz detection cavity 3 after passing through the reflector 1503 and the optical window 504.

[0074] The second harmonic of the modulated gated light passes through lens 1004, second harmonic filter 18 and photoavalanche tube 19, and is then input to lock-in amplifier 21.

[0075] A photoavalanche diode is connected to a lock-in amplifier (LPA), which extracts the second harmonic signal and outputs the detected electrical signal to a computer. A chopper is connected to the LPA, providing a reference signal to aid in the extraction of the second harmonic signal. A delay line is connected to the computer to help extract the terahertz signal at different time points, thus obtaining the complete terahertz spectrum. The LPA, connected to the computer, performs a linked scanning to determine the intensity of the second harmonic after the terahertz light modulates the gated light, achieving time-resolved terahertz spectrum detection.

[0076] According to the example embodiment, chopper 1301 is used to provide a reference frequency for terahertz generation, and delay line 1401 is used to measure the terahertz spectrum. Chopper 1302 receives pump light and provides a reference frequency for pump on / off, and delay line 1402 is used to measure the time-resolved terahertz spectrum at different time points after pump light excitation.

[0077] Example 2

[0078] Figure 2A flowchart illustrating an exemplary embodiment of a time-resolved broadband terahertz device control method is shown. Figure 2 As shown, the control method of this embodiment includes steps S201-S205:

[0079] In step S201, differential evacuation is controlled between the terahertz generation cavity, the experimental cavity, and the terahertz detection cavity.

[0080] According to the example embodiment, the vacuum pump group controls the differential pumping between the terahertz generation chamber, the experimental chamber and the terahertz detection chamber through a small hole connector to maintain the experimental chamber at a high vacuum state.

[0081] In step S202, control gas is introduced into the terahertz generation cavity and the terahertz detection cavity.

[0082] According to an example embodiment, a controlled gas is introduced into the terahertz generation cavity and the terahertz detection cavity to form a gas injection region. Optionally, the gas can be nitrogen.

[0083] In step S203, the femtosecond laser is controlled to generate a femtosecond laser.

[0084] In step S204, the beam splitter is controlled to receive the femtosecond laser.

[0085] According to the example embodiment, the femtosecond laser generated by the femtosecond laser is split into three beams after passing through a beam splitter: the generating beam, the pump beam, and the probe beam.

[0086] The pump light is focused onto the sample after passing through a chopper, delay line, mirror, and lens, and excites the sample to a non-equilibrium state.

[0087] After being focused by a reflector, delay line, and lens, the gated light enters the terahertz detection cavity; it is then focused onto the gas jet region through a small hole in the off-axis parabolic mirror, generating gas plasma.

[0088] The generated light, after being focused by a chopper and lens, reaches the gas jet region of the terahertz generation cavity, generating gas plasma and emitting broadband terahertz light. This broadband terahertz light is then filtered by a high-resistivity silicon filter to remove residual femtosecond laser light, forming pure terahertz light. This pure terahertz light is focused by an off-axis parabolic mirror and enters the experimental cavity through a pinhole connector. The pure terahertz light then illuminates the sample via the off-axis parabolic mirror, detecting the non-equilibrium transmission spectrum information of the sample after pump light excitation, and is transmitted through the sample. The transmitted terahertz light is then focused by an off-axis parabolic mirror, enters the terahertz detection cavity through the pinhole connector, and is focused by an off-axis parabolic mirror onto the gas plasma region generated by the gated light.

[0089] The intensity of the second harmonic generated by the gated light is modulated by the transmitted terahertz light, and then led out of the terahertz detection cavity through the reflector, and focused onto the photoavalanche tube by the lens and the second harmonic filter.

[0090] In step S205, the lock-in amplifier receives the frequency of the generated light, the pump light, and the second harmonic of the modulated gated light.

[0091] According to the example embodiment, a chopper modulates the frequencies of the generated light and pump light, and a photoavalanche diode receives the second harmonic of the modulated gated light. The chopper and photoavalanche diode are then connected to a lock-in amplifier to detect the second harmonic of the gated light modulated by the transmitted terahertz light: the chopper, connected to the lock-in amplifier, provides a reference signal to the lock-in amplifier to help extract the second harmonic signal. The photoavalanche diode is connected to the lock-in amplifier, which extracts the second harmonic signal and outputs the detected electrical signal to a computer. A delay line receives the gated light and pump light. Both the lock-in amplifier and the delay line are connected to the computer to detect transient terahertz changes, achieving time-resolved terahertz spectrum detection of the sample: the delay line, connected to the computer, helps extract signals at different time points of the terahertz spectrum to obtain a complete terahertz spectrum. The lock-in amplifier, connected to the computer, performs a linked scan to determine the intensity of the second harmonic of the gated light modulated by the terahertz light, achieving time-resolved terahertz spectrum detection.

[0092] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.

[0093] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0094] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A time-resolved broadband terahertz device, characterized by, The time-resolved broadband terahertz device comprises a femtosecond laser, a beam splitter, a terahertz generation cavity, an experimental cavity, a terahertz detection cavity and a lock-in amplifier, wherein: The femtosecond laser is used to generate femtosecond laser; The beam splitter is used to divide the femtosecond laser into generation light, pump light and gate light; The terahertz generation cavity is used to receive the generation light and make the generation light reach a gas injection area to generate gas plasma to emit broadband terahertz light, and after filtering the broadband terahertz light by high-resistance silicon, pure terahertz light is formed; The experimental cavity is connected with the terahertz generation cavity and is used to receive the pump light and the pure terahertz light; after the pure terahertz light is transmitted through a sample, transmitted terahertz light is generated; the transmitted terahertz light carries non-equilibrium state transmission spectrum information of the sample excited by the pump light; The terahertz detection cavity is connected with the experimental cavity and is used to receive the gate light and the transmitted terahertz light; the gate light reaches the gas injection area to generate gas plasma; the transmitted terahertz light is used to modulate the second harmonic of the gate light; The lock-in amplifier is used to receive the second harmonic of the gate light modulated by the transmitted terahertz light to detect the change of transient terahertz, so as to realize the detection of the time-resolved terahertz spectrum of the sample; The terahertz generation cavity, the experimental cavity and the terahertz detection cavity are respectively provided with a vacuum pump group through an air exhaust hole, and are connected with each other through a small hole to realize differential air exhaust between cavities, so as to ensure that the experimental cavity can be maintained in a high vacuum state when the terahertz generation cavity and the terahertz detection cavity are in a low vacuum state.

2. The time-resolved broadband terahertz device of claim 1, wherein, The time-resolved broadband terahertz device further comprises a gas pipe, and the terahertz generation cavity and the terahertz detection cavity each comprise a gas guide hole; the gas pipe is introduced into the terahertz generation cavity and the terahertz detection cavity through the gas guide hole, so that high-pressure nitrogen gas is injected into the terahertz generation cavity and the terahertz detection cavity through the gas pipe to form a gas injection area.

3. The time-resolved broadband terahertz device of claim 1, wherein, The terahertz generation cavity comprises high-resistance silicon and a first off-axis parabolic mirror, wherein: The high-resistance silicon is used to filter femtosecond laser in the broadband terahertz light to generate the pure terahertz light; The first off-axis parabolic mirror is used to focus the pure terahertz light so that the pure terahertz light enters the experimental cavity.

4. The time-resolved broadband terahertz device of claim 1, wherein, The experimental cavity comprises a second off-axis parabolic mirror and a third off-axis parabolic mirror, wherein: The second off-axis parabolic mirror is used to focus the pure terahertz light so that the pure terahertz light irradiates on the sample; The third off-axis parabolic mirror is used to focus the transmitted terahertz light so that the transmitted terahertz light enters the terahertz detection cavity.

5. The time-resolved broadband terahertz device of claim 1, wherein, The time-resolved broadband terahertz device further comprises a cryostat connected with the sample in the experimental cavity to realize different temperature tests on the sample by the time-resolved broadband terahertz device.

6. The time-resolved broadband terahertz device of claim 1, wherein, The terahertz detection cavity comprises a fourth off-axis parabolic mirror and a mirror, wherein: The fourth off-axis parabolic mirror is used for focusing the transmitted terahertz light to reach a gas plasma region. The mirror is used for leading out the second harmonic of the gating light modulated by the transmitted terahertz light from the terahertz detection cavity.

7. The time-resolved broadband terahertz device of claim 1, wherein, The time-resolved broadband terahertz device further comprises a second harmonic filter and a photo avalanche tube, wherein: The second harmonic filter is used for filtering the second harmonic of the gating light led out; The photo avalanche tube is used for receiving the filtered second harmonic of the gating light and transmitting to the lock-in amplifier.

8. The time-resolved broadband terahertz device of claim 1, wherein, The time-resolved broadband terahertz device further comprises a chopper for modulating the frequency of the generated light and the pump light and transmitting the frequency of the generated light and the pump light to the lock-in amplifier.

9. A control method of a time-resolved broadband terahertz device, characterized by, The control method for the time-resolved broadband terahertz device as claimed in any one of claims 1-8, comprising: controlling differential pumping between the terahertz generation cavity, the experimental cavity and the terahertz detection cavity to maintain the experimental cavity in a high vacuum state; controlling gas to be introduced into the terahertz generation cavity and the terahertz detection cavity to form a gas injection region; controlling the femtosecond laser to generate femtosecond laser; controlling the beam splitter to receive the femtosecond laser to generate generated light, pump light and gating light; the lock-in amplifier receives the frequency of the generated light, the pump light and the modulated second harmonic of the gating light to detect the change of transient terahertz, realizing the detection of the time-resolved terahertz spectrum of the sample.

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