Terahertz detection apparatus and detection method therefor

Abstract

A terahertz detection apparatus and a detection method therefor. The terahertz detection apparatus comprises a laser emitting module (1), a semiconductor structure (2), a terahertz optical module (3) and a signal processing module (4), wherein the laser emitting module (1) is used for emitting a first optical signal; the semiconductor structure (2) is used for receiving the first optical signal, forming Rydberg excitons after being excited by the first optical signal, and converting the first optical signal into a second optical signal; the semiconductor structure (2) converts the first optical signal into a third optical signal under the action of a terahertz signal; the terahertz optical module (3) is used for controlling the propagation direction of the terahertz signal and focusing the terahertz signal, such that at least some light spots (101) of the first optical signal coincide with terahertz spots (301) of the terahertz signal on the semiconductor structure (2); and the signal processing module (4) is used for acquiring a first electrical signal converted from the second optical signal and a second electrical signal converted from the third optical signal, so as to determine the intensity of the terahertz signal. The apparatus and method can realize miniaturization of a device and achieve a high integration level.

Description

Terahertz detection devices and their detection methods Technical Field

[0001] This disclosure relates to the field of terahertz detection technology, specifically to a terahertz detection device and its detection method. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies ranging from 0.1 to 10 THz in the electromagnetic spectrum, adjacent to the mid-infrared and microwave frequencies. Compared to other electromagnetic waves, terahertz waves possess unique properties, such as low photon energy (millielectronvolt level), excellent penetrability to many non-metallic and non-polar materials (plastics, fats, ceramics, etc.), and a wide spectral range (operating bandwidth an order of magnitude larger than millimeter waves). Therefore, terahertz waves have shown revolutionary application prospects in many fields, including industrial non-destructive testing, security inspection, and broadband wireless communication.

[0003] The widespread application of terahertz technology relies on high-performance detectors. Related research indicates that terahertz waves can be converted into light waves using alkali metal atomic vapor (i.e., Rydberg atomic gas) for detection. However, since alkali metal atomic vapor needs to be sealed in a vacuum chamber, the space occupied by the vacuum chamber limits the miniaturization of the atomic devices. Furthermore, the fabrication and sealing of the vacuum chamber must meet the high stability requirements and complexity of the optical system, posing significant challenges to optical integration and limiting the scalability and integration of the optical system. Summary of the Invention

[0004] This disclosure addresses the shortcomings of related technologies by proposing a terahertz detection device to solve the problems of difficulty in improving the integration of terahertz detection devices or miniaturization of devices in related technologies.

[0005] This disclosure provides a terahertz detection device, including a laser emitting module, a semiconductor structure, a terahertz optical module, and a signal processing module. The laser emitting module emits a first optical signal; the semiconductor structure receives the first optical signal, is excited by the first optical signal to form Rydberg excitons, and converts the first optical signal into a second optical signal; the semiconductor structure also receives a terahertz signal; under the influence of the terahertz signal, the semiconductor structure converts the first optical signal into a third optical signal, the third optical signal being different from the second optical signal; the terahertz optical module controls the propagation direction of the terahertz signal and focuses the terahertz signal so that at least a portion of the light spot of the first optical signal coincides with the terahertz spot of the terahertz signal in the semiconductor structure; the signal processing module acquires a first electrical signal converted from the second optical signal and a second electrical signal converted from the third optical signal, and determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal.

[0006] In one embodiment, the terahertz detection device further includes a first electrode and a second electrode disposed on the surface of a semiconductor structure. The first electrode and the second electrode are both electrically connected to the semiconductor structure to form a first photoelectric conversion structure. The first photoelectric conversion structure is electrically connected to the signal processing module. The second optical signal is converted into the first electrical signal through the first photoelectric conversion structure, and the third optical signal is converted into the second electrical signal through the first photoelectric conversion structure.

[0007] In one embodiment, the semiconductor structure is made of a light-transmitting material, and the terahertz detection device includes a second photoelectric conversion structure. The second photoelectric conversion structure is disposed on the side of the semiconductor structure away from the laser emitting module. The second photoelectric conversion structure is electrically connected to the signal processing module. The second optical signal is converted into the first electrical signal by the second photoelectric conversion structure, and the third optical signal is converted into the second electrical signal by the second photoelectric conversion structure.

[0008] In one embodiment, the second photoelectric conversion structure includes a photodiode, a photomultiplier tube, a phototransistor, a CCD image sensor, or a CMOS image sensor.

[0009] In one embodiment, the signal processing module determines a frequency domain signal reflecting the intensity distribution of the terahertz signal based on the first electrical signal and the second electrical signal.

[0010] In one embodiment, the terahertz detection device further includes a wavelength controller connected to the laser emitting module, which controls the wavelength of the first optical signal emitted by the laser emitting module to match a target wavelength, wherein the target wavelength is the wavelength required for the semiconductor structure to be excited to form Rydberg excitons.

[0011] In one embodiment, the terahertz optical module includes at least one parabolic mirror and / or at least one terahertz lens, wherein the at least one parabolic mirror and / or the at least one terahertz lens are disposed on one side of the semiconductor structure for focusing the terahertz signal and allowing the terahertz signal to enter the semiconductor structure.

[0012] In one embodiment, the terahertz optical module includes a parabolic mirror disposed between the laser emitting module and the semiconductor structure. The parabolic mirror has a conical aperture, with the openings at opposite ends of the conical aperture facing the laser emitting module and the semiconductor structure, respectively. The conical aperture is used to allow the first optical signal to pass through and enter the semiconductor structure.

[0013] In one embodiment, the semiconductor structure is made of cuprous oxide, gallium arsenide, indium phosphide, silver oxide, tin dioxide, two-dimensional materials, or perovskite materials.

[0014] This disclosure also provides a detection method for a terahertz detection device, applied to the controller of the terahertz detection device of the foregoing embodiments, the method comprising:

[0015] The laser emitting module is controlled to emit the first optical signal toward the semiconductor structure, so that the semiconductor structure is excited to form the Rydberg exciton after receiving the first optical signal and converts the first optical signal into the second optical signal.

[0016] The signal processing module is controlled to acquire the first electrical signal after the second optical signal is converted.

[0017] The signal processing module is controlled to acquire the second electrical signal after the conversion of the third optical signal, so that the signal processing module determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal; the third optical signal is obtained by the semiconductor structure converting the first optical signal under the action of the terahertz signal, at least a portion of the light spot of the first optical signal coincides with the terahertz spot of the terahertz signal in the semiconductor structure, and the third optical signal is different from the second optical signal.

[0018] The beneficial effects of this disclosure include:

[0019] In this embodiment, a terahertz detection device is fabricated using a solid-state structure with a semiconductor structure. The semiconductor structure is compatible with semiconductor processes, enabling miniaturization and integration of the device, reducing structural complexity, and offering strong scalability and practicality. Furthermore, since the Rydberg excitons in the semiconductor structure rely on a solid-state system, it has a natural advantage in facilitating solid-state integration.

[0020] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this disclosure. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this disclosure, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0022] Figure 1 shows a schematic diagram of a terahertz detection device in related technologies.

[0023] Figure 2 shows a schematic diagram of the structure of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0024] Figure 3 shows a schematic diagram of the energy levels of the Rydberg exciton shift in a semiconductor structure provided by an exemplary embodiment of the present disclosure.

[0025] Figure 4 shows a schematic diagram of the structure of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0026] Figure 5 shows a schematic diagram of the shape of the first photoelectric conversion structure of a terahertz detection device provided in an exemplary embodiment of the present disclosure.

[0027] Figure 6 shows a schematic diagram of the structure of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0028] Figure 7 shows a schematic diagram of the structure of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0029] Figure 8 is a schematic diagram of the structure of a terahertz detection device provided in an exemplary embodiment of the present disclosure.

[0030] Figure 9 shows experimental data of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0031] Figure 10 shows experimental data of a terahertz detection device provided in an exemplary embodiment of this disclosure.

[0032] Figure 11 shows experimental data of a terahertz detection device provided in an exemplary embodiment of this disclosure. Detailed Implementation

[0033] Research has found that terahertz waves can be converted into light waves using alkali metal atomic vapor based on electromagnetically induced transparency (EIT) and the AC Stark effect, thus enabling terahertz wave detection. The specific structure is shown in Figure 1. The terahertz detection device based on alkali metal atomic vapor (Rydberg atomic gas) mainly consists of a laser emission module 1', an atomic gas chamber 2', a terahertz signal generator 3', and a signal processing module 4'. The laser emission module 1' generates laser light that interacts with the alkali metal atomic vapor within the atomic gas chamber 2'. The laser emission module 1' includes a probe laser 11' and a coupling laser 12'. The probe laser 11' provides the probe light, and the coupling laser 12' provides the coupling light. The atomic gas chamber 2' contains alkali metal atomic vapor, which converts the terahertz waves emitted by the terahertz signal generator 3' into a transmitted light intensity signal of the probe light. The signal processing module 4' includes a photodetector 41', an oscilloscope 42', and a spectrum analysis unit (not shown in the figure). The photodetector 41' receives the transmitted light intensity signal of the probe light and converts it into an electrical signal. The oscilloscope 42' converts the electrical signal converted by the photodetector into a time-domain voltage signal for observation. The spectrum analysis unit performs a fast Fourier transform on the time-domain voltage signal to a frequency-domain signal for spectrum analysis. However, because alkali metal atomic vapors need to be sealed in a vacuum chamber, the size of the vacuum chamber limits the miniaturization of atomic devices. Furthermore, the fabrication and sealing of the vacuum chamber must meet the high stability requirements and complexity of the optical system, posing a significant challenge to optical integration and limiting the scalability and integration of the optical system.

[0034] The terahertz detection device and detection method disclosed herein are intended to solve the above-mentioned technical problems in related technologies.

[0035] The terahertz detection device and its detection method according to the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments can complement or combine with each other.

[0036] This disclosure provides a terahertz detection device, as shown in FIG2, including a laser emitting module 1 (also referred to as a laser emitter), a semiconductor structure 2, a terahertz optical module 3, and a signal processing module 4. The laser emitting module 1 is used to emit a first optical signal. The semiconductor structure 2 is used to receive the first optical signal, be excited by the first optical signal to form Rydberg excitons, and convert the first optical signal into a second optical signal; the semiconductor structure 2 is also used to receive the terahertz signal to be measured; under the action of the terahertz signal, the semiconductor structure 2 converts the first optical signal into a third optical signal, the third optical signal being different from the second optical signal; the terahertz optical module 3 is used to control the propagation direction of the terahertz signal and focus the terahertz signal so that at least a portion of the light spot 101 of the first optical signal coincides with the terahertz spot 301 of the terahertz signal on the semiconductor structure 2; the signal processing module 4 is used to acquire a first electrical signal after the conversion of the second optical signal and a second electrical signal after the conversion of the third optical signal, and determine the intensity of the terahertz signal based on the first and second electrical signals.

[0037] In this embodiment, by utilizing the characteristics of semiconductor structure 2, when semiconductor structure 2 receives the first optical signal, the energy of the photons generated by the first optical signal can be matched with the energy level of semiconductor structure 2. For example, as shown in Figure 3, the energy of the first optical signal is less than the band gap of semiconductor structure 2, or semiconductor structure 2 directly absorbs photons, exciting electrons in semiconductor structure 2 to the corresponding energy band, forming electron-hole pairs, i.e., Rydberg excitons. When no terahertz signal is applied, semiconductor structure 2 absorbs the first optical signal and converts it into a second optical signal. When a terahertz signal is applied, the Rydberg excitons in semiconductor structure 2 undergo frequency shift, causing a change in the absorption and conversion of the first optical signal by semiconductor structure 2, thereby causing semiconductor structure 2 to convert the first optical signal into a third optical signal. Then, the second optical signal is converted into a first electrical signal and the third optical signal is converted into a second electrical signal, and the intensity of the terahertz signal can be determined based on the first and second electrical signals. Therefore, compared to the traditional method of using a large atomic gas cell for terahertz detection, this embodiment uses a solid-state structure, semiconductor structure 2, to fabricate a terahertz detection device. Semiconductor structure 2 is compatible with semiconductor processes, enabling miniaturization and integration of the device, reducing the complexity of the device structure, and offering strong scalability and high practicality. Furthermore, since the Rydberg excitons in semiconductor structure 2 are based on a solid-state system, it has a natural advantage in facilitating solid-state integration.

[0038] It should be noted that the frequency shift of the Rydberg exciton in semiconductor structure 2 is proportional to the intensity of the applied terahertz signal, and the difference between the first electrical signal and the second electrical signal is proportional to the frequency shift of the Rydberg exciton. Therefore, a mathematical relationship between the first electrical signal, the second electrical signal and the terahertz signal can be established based on the above proportional relationship, and the intensity of the terahertz signal can be determined according to the first electrical signal and the second electrical signal.

[0039] In some embodiments, the semiconductor structure 2 can be formed using a single semiconductor wafer with a thickness ranging from 10 to 500 μm. In some embodiments, the thickness of the single semiconductor wafer can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, or 500 μm. In one example, the thickness of the single semiconductor wafer is 300 μm, and the thickness direction of the single semiconductor wafer is parallel to the direction from the laser emitting module 1 to the semiconductor structure 2.

[0040] In some embodiments, the semiconductor structure 2 is made of cuprous oxide (Cu2O), gallium arsenide (GaAs), indium phosphide (InP), silver oxide (Ag2O), tin dioxide (SnO2), two-dimensional materials (e.g., graphene, hexagonal boron nitride, or other two-dimensional materials), or perovskite materials (ABX3, where A and B are two cations, and X is an anion bonded to them). In one example, the semiconductor structure 2 is made of cuprous oxide. Exemplarily, when the semiconductor structure 2 is made of cuprous oxide, the energy level spectrum comparison before and after the Rydberg exciton frequency shift in the semiconductor structure 2 is shown in Figure 3.

[0041] In some embodiments, as shown in FIG2, the terahertz spot 301 of the terahertz signal is located within the spot 101 of the first optical signal. In other embodiments, the spot 101 of the first optical signal and the terahertz spot 301 of the terahertz signal completely overlap in the semiconductor structure 2 (not shown in the figure).

[0042] In some embodiments, as shown in FIG4, the terahertz detection device further includes a first electrode 5 and a second electrode 6 disposed on the surface of the semiconductor structure 2. The first electrode 5 and the second electrode 6 are both electrically connected to the semiconductor structure 2 to form a first photoelectric conversion structure 10. The first photoelectric conversion structure 10 is electrically connected to the signal processing module 4. The second optical signal is converted into a first electrical signal through the first photoelectric conversion structure 10, and the third optical signal is converted into a second electrical signal through the first photoelectric conversion structure 10.

[0043] In this embodiment, the first electrode 5, the second electrode 6, and the semiconductor structure 2 constitute a first photoelectric conversion structure 10. When the first optical signal is incident on the semiconductor structure 2, the energy of the photons generated by the first optical signal can be matched with the energy level of the semiconductor structure 2, or the semiconductor structure 2 can directly absorb the photons, causing the electrons in the semiconductor structure 2 to be excited to the corresponding energy band, forming electron-hole pairs. Under the action of an applied reverse bias voltage, the electrons and holes move in opposite directions, thereby forming a photocurrent. Specifically, when no terahertz signal is applied, the semiconductor structure 2 converts the second optical signal into a first photocurrent signal, i.e., a first electrical signal; when a terahertz signal is applied, the semiconductor structure 2 converts the third optical signal into a second photocurrent signal, i.e., a second electrical signal.

[0044] In some embodiments, the first electrode 5 is the anode and the second electrode 6 is the cathode. In other embodiments, the first electrode 5 is the anode and the second electrode 6 is the cathode.

[0045] In some embodiments, the first electrode 5 may be made of aluminum (Al), gold (Au), silver (Ag), nickel (Ni), chromium (Cr), platinum (Pt), indium (In), tin (Sn), palladium (Pd), or copper (Cu). In one example, the first electrode 5 is made of gold (Au).

[0046] In some embodiments, the second electrode 6 may be made of aluminum (Al), gold (Au), silver (Ag), nickel (Ni), chromium (Cr), platinum (Pt), indium (In), tin (Sn), palladium (Pd), or copper (Cu). In one example, the second electrode 6 is made of gold (Au).

[0047] In some embodiments, the first electrode 5 may be disposed on the side of the semiconductor structure 2 facing the laser emitting module 1 or on the side of the semiconductor structure 2 facing away from the laser emitting module 1.

[0048] In some embodiments, the second electrode 6 may be disposed on the side of the semiconductor structure 2 facing the laser emitting module 1 or on the side of the semiconductor structure 2 facing away from the laser emitting module 1.

[0049] In some embodiments, as shown in FIG4, the first electrode 5 and the second electrode 6 are both disposed on the side surface of the semiconductor structure 2 facing the laser emitting module 1.

[0050] In some embodiments, both the first electrode 5 and the second electrode 6 are electrically connected to the photocurrent readout circuit to enable the photocurrent signal formed by the semiconductor structure 2 under optical signal excitation to be read through the photocurrent readout circuit.

[0051] In some embodiments, a substrate 7 is provided on the side of the semiconductor structure 2 away from the laser emitting module 1. When the thickness direction of the semiconductor structure 2 is vertical, that is, when the semiconductor structure 2 is laid flat, the substrate 7 can be used to support the semiconductor structure 2.

[0052] In some embodiments, as shown in FIG4, the first electrode 5 and the second electrode 6 are both laid on the surface of the semiconductor structure 2 in a comb-like patterned structure. In some embodiments, as shown in FIG5(a), the first electrode 5 and the second electrode 6 can jointly form a first pattern, for example, a spiral pattern, suitable for rotating polarized light, which can enhance the intensity of the electrical signal. In some embodiments, as shown in FIG5(b), the first electrode 5 and the second electrode 6 can jointly form a second pattern, for example, in the second pattern, the first electrode 5 is a T-shape composed of a first horizontal portion and a first vertical portion, and the second electrode 6 is an inverted T-shape composed of a second horizontal portion and a second vertical portion. The first vertical portion and the second vertical portion are corresponding in position, the cross-section of the first vertical portion is a trapezoid that is wider at the top and narrower at the bottom, and the cross-section of the second vertical portion is a trapezoid that is narrower at the top and wider at the bottom, which can enhance the intensity of the electrical signal. In some embodiments, as shown in FIG5(c), the first electrode 5 and the second electrode 6 can jointly form a third pattern, for example, a butterfly-shaped patterned structure, which can enhance the intensity of the electrical signal. In some embodiments, as shown in FIG5(d), the first electrode 5 and the second electrode 6 can jointly form a fourth pattern. For example, in the fourth pattern, the first electrode 5 is a T-shape composed of a third horizontal portion and a third vertical portion, and the second electrode 6 is an inverted T-shape composed of a fourth horizontal portion and a fourth vertical portion. The third and fourth vertical portions are corresponding in position, and the cross-section of the third and fourth vertical portions is rectangular. This can improve the bandwidth of the electrical signal. As shown in FIG5(e), the first electrode 5 and the second electrode 6 can jointly form a fifth pattern. In the fifth pattern, the first electrode 5 is an inverted T-shape composed of a fifth horizontal portion and a fifth vertical portion, and the second electrode 6 is a T-shape composed of a sixth horizontal portion and a sixth vertical portion. The sixth horizontal portion is closest to the fifth horizontal portion in the second electrode 6, and the fifth and sixth horizontal portions are corresponding in position. The cross-section of the fifth vertical portion is a trapezoid that is wider at the top and narrower at the bottom, and the cross-section of the sixth vertical portion is a trapezoid that is narrower at the top and wider at the bottom. This can be applied to lower laser intensities. In the above embodiments, the interaction between terahertz waves and semiconductor structure 2 can be enhanced by designing patterned structures of different shapes, thereby increasing the intensity of electrical signals.

[0053] In some embodiments, as shown in FIG6, the semiconductor structure 2 is made of a light-transmitting material, and the terahertz detection device further includes a second photoelectric conversion structure 20. The second photoelectric conversion structure 20 is disposed on the side of the semiconductor structure 2 away from the laser emission module 1. The second photoelectric conversion structure 20 is electrically connected to the signal processing module 4. The second optical signal is converted into a first electrical signal by the second photoelectric conversion structure 20, and the third optical signal is converted into a second electrical signal by the second photoelectric conversion structure 20.

[0054] In this embodiment, when no terahertz signal is applied, the first optical signal is converted into a second optical signal through the semiconductor structure 2. The second optical signal is then converted into a first electrical signal after entering the second photoelectric conversion structure 20. When a terahertz signal is applied, the first optical signal is converted into a third optical signal through the semiconductor structure 2. The third optical signal is then converted into a second electrical signal after entering the second photoelectric conversion structure 20. Therefore, the optical signal can be converted into an electrical signal through the second photoelectric conversion structure 20, and the intensity of the terahertz signal can then be obtained.

[0055] In some embodiments, the second photoelectric conversion structure 20 includes a photodiode, a photomultiplier tube, a phototransistor, a CCD image sensor, or a CMOS image sensor. In some examples, the second photoelectric conversion structure 20 is a CCD image sensor. The CCD image sensor may be formed in the CCD camera 9 and connected to the signal processing circuitry 8 in the CCD camera 9.

[0056] In some embodiments, the signal processing module 4 determines a frequency domain signal reflecting the intensity distribution of the terahertz signal based on the first electrical signal and the second electrical signal.

[0057] In some embodiments, the signal processing module 4 may include an oscilloscope and a frequency domain analysis unit. The oscilloscope is used to convert the first electrical signal and the second electrical signal into a time-domain voltage signal. The frequency domain analysis unit is used to perform a Fast Fourier Transform (FFT) on the time-domain voltage signal to a frequency domain signal, which can be used for spectrum analysis. In some embodiments, the frequency domain analysis unit may include a memory and a processor to perform the FFT on the time-domain voltage signal to a frequency domain signal.

[0058] In some embodiments, when the terahertz detection device includes a first photoelectric conversion structure 10, the photocurrent readout circuit connected to the first electrode 5 and the second electrode 6 is electrically connected to the signal processing module 4 to convert the photocurrent signal into a frequency domain signal.

[0059] In some embodiments, when the terahertz detection device includes a second photoelectric conversion structure 20, the signal processing circuit 8 connected to the second photoelectric conversion structure 20 is electrically connected to the signal processing module 4, and is used to convert the photocurrent signal into a frequency domain signal.

[0060] In some embodiments, the terahertz detection device further includes a wavelength controller connected to the laser emission module 1, which controls the wavelength of the first optical signal emitted by the laser emission module 1 to match the target wavelength, which is the wavelength required for the semiconductor structure 2 to be excited to form Rydberg excitons.

[0061] In this embodiment, the wavelength of the first optical signal is stabilized within the target range to ensure that the first optical signal can successfully excite the semiconductor structure 2 to form Rydberg excitons.

[0062] In some embodiments, the wavelength controller includes a wavelength meter and a feedback control system. The wavelength meter measures the wavelength of the current first optical signal, and the feedback control system adjusts the laser emission module 1 when the wavelength of the current first optical signal is not equal to the target wavelength of the first optical signal. In some embodiments, the wavelength meter can be replaced by an ultra-stable cavity.

[0063] In some embodiments, the laser emitting module 1 can be a probe laser or a narrow linewidth laser diode. When the laser emitting module 1 is a narrow linewidth laser diode, it can be integrated with the semiconductor structure 2, the first electrode 5, and the second electrode 6.

[0064] In some embodiments, the terahertz optical module 3 includes at least one parabolic mirror and / or at least one terahertz lens, disposed on one side of the semiconductor structure 2, for focusing the terahertz signal and allowing the terahertz signal to enter the semiconductor structure 2. In some embodiments, the terahertz optical module 3 includes at least one parabolic mirror. In some embodiments, the terahertz optical module 3 includes at least one terahertz lens. In some embodiments, the terahertz optical module 3 includes at least one parabolic mirror and at least one terahertz lens.

[0065] In some embodiments, as shown in FIG7, the terahertz optical module 3 has only one parabolic mirror, namely the first parabolic mirror 31.

[0066] In some embodiments, as shown in FIG8, the terahertz optical module 3 includes two parabolic mirrors, namely a first parabolic mirror 31 and a second parabolic mirror 32.

[0067] In some embodiments, as shown in FIG7 or FIG8, the terahertz optical module 3 includes a first parabolic mirror 31 disposed between the laser emitting module 1 and the semiconductor structure 2. The first parabolic mirror 31 has a conical aperture 31a, with the openings at opposite ends of the conical aperture 31a facing the laser emitting module 1 and the semiconductor structure 2, respectively. The conical aperture 31a is used to allow a first optical signal to pass through and enter the semiconductor structure 2. In this embodiment, by setting the conical aperture 31a, the first optical signal emitted by the laser emitting module 1 can pass smoothly through the first parabolic mirror 31 without being blocked. At the same time, the incident direction of the terahertz signal can be controlled by the first parabolic mirror 31, so that the terahertz spot 301 formed by the terahertz signal on the semiconductor structure 2 is located within the range of the light spot 101 formed by the first optical signal on the semiconductor structure 2. In some embodiments, the transmission path of the first optical signal and the transmission path of the terahertz signal can be partially collinear and incident on the semiconductor structure 2 along the same path by utilizing the first parabolic mirror 31 with the conical aperture 31a.

[0068] Based on the same inventive concept, this disclosure also provides a detection method for a terahertz detection device, applied to the controller of the terahertz detection device in the foregoing embodiments, comprising the following steps:

[0069] The laser emitting module 1 is controlled to emit a first optical signal to the semiconductor structure 2, so that the semiconductor structure 2 is excited to form a Rydberg exciton after receiving the first optical signal and converts the first optical signal into a second optical signal.

[0070] The control signal processing module 4 acquires the first electrical signal after the second optical signal is converted;

[0071] The control signal processing module 4 acquires the second electrical signal after the conversion of the third optical signal, so that the signal processing module 4 determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal; the third optical signal is obtained by the semiconductor structure 2 converting the first optical signal under the action of the terahertz signal, at least a part of the light spot 101 of the first optical signal coincides with the terahertz spot 301 of the terahertz signal in the semiconductor structure 2, and the third optical signal is different from the second optical signal.

[0072] In this embodiment, the intensity of the terahertz signal can be determined by acquiring a first electrical signal and a second electrical signal, and by analyzing and calculating the mathematical relationship between the first electrical signal, the second electrical signal, and the terahertz signal. This embodiment allows for real-time acquisition of the terahertz signal intensity; the method is simple and highly operable.

[0073] In some embodiments, the terahertz detection device further includes a high-frequency modulator and a lock-in amplifier for modulating and demodulating the terahertz signal to be measured, thereby improving the signal-to-noise ratio and measurement accuracy. Specifically, the signal-to-noise ratio can be improved by using a high-frequency modulator to modulate the terahertz signal to be measured and then sending the modulated terahertz signal into the lock-in amplifier for phase locking. In one example, the high-frequency modulation frequency is 20 kHz.

[0074] In some embodiments, the terahertz detection device can be specifically applied to a terahertz imaging system to achieve real-time acquisition of terahertz imaging by analyzing the intensity of the terahertz signal to be measured in the spatial distribution.

[0075] For ease of understanding, this disclosure provides two specific embodiments of the terahertz detection device and its detection method described in the foregoing embodiments as follows:

[0076] Example 1

[0077] The terahertz detection device is used in the field of terahertz imaging. As shown in Figure 8, the terahertz detection device includes a laser emission module 1, a semiconductor structure 2, a terahertz optical module 3, and a signal processing module 4. The laser emission module 1 includes a probe laser, which generates a first optical signal with a wavelength of 610 nm. The semiconductor structure 2 is designed as a 300 μm thick semiconductor wafer made of cuprous oxide. The terahertz optical module 3 includes a first parabolic mirror 31 and a second parabolic mirror 32. The first parabolic mirror 31 has a conical aperture 31a, with its openings at opposite ends facing the laser emission module 1 and the semiconductor structure 2, respectively. The conical aperture 31a allows the first optical signal to pass through and enter the semiconductor structure 2. Therefore, the terahertz signal can be projected onto the semiconductor structure 2 using the parabolic mirror. In this embodiment, the terahertz signal and the first optical signal generated by the laser emission module 1 are collinear when incident on the semiconductor structure 2. The focal length of both the first parabolic mirror 31 and the second parabolic mirror 32 is 101.6 mm, and the projection ratio is 1:1. The terahertz spot 301 formed by the terahertz signal on the semiconductor structure 2 completely overlaps with the light spot 101 formed by the first optical signal on the semiconductor structure 2.

[0078] The terahertz detection device also includes a wavelength meter and a feedback control system (not shown in the figure). The wavelength meter measures the current wavelength of the first optical signal, with a frequency accuracy of 600 MHz. The feedback control system is specifically a PID (proportional-integral-derivative) feedback control system, which stabilizes the wavelength of the first optical signal at a target wavelength. The target wavelength of the first optical signal is the wavelength required to excite Rydberg excitons in the semiconductor structure 2. By controlling the wavelength of the first optical signal, Rydberg excitons can be formed in the semiconductor structure 2.

[0079] As shown in Figure 4, the terahertz detection device also includes a first electrode 5 and a second electrode 6 disposed on the surface of the semiconductor structure 2. The first electrode 5, the second electrode 6 and the semiconductor structure 2 together form a first photoelectric conversion structure 10. The first electrode 5 and the second electrode 6 are both made of gold. The first electrode 5 and the second electrode 6 are externally connected to a voltage measuring device.

[0080] When no terahertz signal is applied, the first optical signal is converted into a second optical signal in the semiconductor structure 2, and then converted into a first photocurrent signal, i.e., a first electrical signal, through the first photoelectric conversion structure 10. When a terahertz signal is applied, the first optical signal is converted into a third optical signal in the semiconductor structure 2, and then converted into a second photocurrent signal, i.e., a second electrical signal, through the first photoelectric conversion structure 10. As shown in Figure 9, this embodiment provides experimental data on the changes in photocurrent signals detected under the action of a terahertz signal. It can be seen that the photocurrent signals during the THZ off period and the THZ on period are the first electrical signal and the second electrical signal, respectively. The absorption peak distribution of Rydberg excitons can be obtained from the first and second electrical signals. Since the frequency shift of Rydberg exciton energy is proportional to the terahertz field strength, the spatial distribution of the terahertz signal can be deduced. Figure 10 shows the spectrum of the terahertz signal provided in this embodiment. It can be seen that the sensitivity of the terahertz detection device provided in this embodiment is 1.7nW@4.7THz under the action of 1.7nW terahertz power, the equivalent noise bandwidth is 88Hz, the current signal-to-noise ratio is 2.3, that is, the signal-to-noise ratio (SNR) is 7.2dB. It can be seen that the sensitivity of the terahertz detection device provided in this embodiment is relatively high.

[0081] When applying a terahertz detection device to terahertz imaging, multiple pixels can be formed by arranging multiple first photoelectric conversion structures 10 in an array on the surface of a semiconductor structure 2. The light signal incident on the region corresponding to each first photoelectric conversion structure 10 on the semiconductor structure 2 is converted into a photocurrent signal after being processed by the semiconductor structure 2. The photocurrent signal corresponding to each first photoelectric conversion structure 10 is recorded using an array readout circuit. The intensity distribution of the terahertz signal can be deduced from the distribution of the photocurrent signal in each region. The signal processing module 4 analyzes and processes the signal to determine the object under test corresponding to the terahertz signal being measured, thus achieving terahertz imaging.

[0082] Specifically, terahertz signals can be obtained by analyzing and processing photocurrent signals based on the following principles.

[0083] In semiconductor structure 2, the frequency shift of the Rydberg exciton energy is proportional to the terahertz field strength: Frequency shift ∝|E THZ | 2

[0084] After the Rydberg exciton absorption peak undergoes a frequency shift, the photocurrent signal induced by the probe light also changes accordingly, which can be written as: ΔI=I(ω+δω)-I(ω)

[0085] In the above formula, ΔI is the change signal of photocurrent before and after the application of terahertz field, that is, the difference between the second electrical signal and the first electrical signal; I(ω) is the photocurrent when the probe light frequency is ω, that is, the first electrical signal; I(ω+δω) is the photocurrent after the δω frequency shift, that is, the second electrical signal.

[0086] The relationship between the change in photocurrent ΔI and the frequency shift δω can be written as:

[0087] From the above formula, we can derive the first derivative. The photocurrent is most sensitive to frequency shift at its maximum, and the change in photocurrent ΔI is proportional to the frequency shift δω. Therefore, by measuring the change in the photocurrent signal, the magnitude of the frequency shift can be deduced, and thus the magnitude of the terahertz field intensity can be further deduced.

[0088] Specific detection methods may include the following steps:

[0089] Step S1: Control the laser emitting module 1 to emit a first optical signal to the semiconductor structure, so that the semiconductor structure 2 is excited to form a Rydberg exciton after receiving the first optical signal and converts the first optical signal into a second optical signal; at the same time, the wavelength can be controlled within the target wavelength range by the wavelength controller.

[0090] Step S2: The control signal processing module 4 acquires the first electrical signal after the second optical signal is converted by the first photoelectric conversion structure 10.

[0091] Step S3: The control signal processing module 4 acquires the second electrical signal after the third optical signal is converted by the first photoelectric conversion structure 10, so that the signal processing module 4 determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal; the third optical signal is obtained by the semiconductor structure 2 converting the first optical signal under the action of the terahertz signal, the light spot 101 of the first optical signal and the terahertz spot 301 of the terahertz signal coincide in the semiconductor structure 2, and the third optical signal is different from the second optical signal.

[0092] Example 2

[0093] The difference between this embodiment and embodiment one is that the structure for converting light signals into electrical signals is different in this embodiment. As shown in Figure 6, this embodiment uses a second photoelectric conversion structure 20 for photoelectric conversion. The second photoelectric conversion structure 20 is a CCD image sensor and is formed in the CCD camera 9.

[0094] When no terahertz signal is applied, the first optical signal is transmitted through the semiconductor structure 2 to form the second optical signal, which is then converted into the first electrical signal in the second photoelectric conversion structure 20. When a terahertz signal is applied, the first optical signal is transmitted through the semiconductor structure 2 to form the third optical signal, which is then converted into the second electrical signal in the second photoelectric conversion structure 20. As shown in Figure 11, this embodiment provides experimental data on the changes in electrical signals detected under the action of a terahertz signal. It can be seen that the electrical signals during the THZ off period and the THZ on period are the first and second electrical signals, respectively. The absorption peak distribution of Rydberg excitons can be obtained from the first and second electrical signals. Since the frequency shift of Rydberg exciton energy is proportional to the terahertz field strength, the spatial distribution of the terahertz signal can be deduced.

[0095] When applying a terahertz detection device to terahertz imaging, a second and third optical signal can be recorded using a CCD camera 9 (visible light imaging). These signals are then converted into a first and a second electrical signal, respectively. The intensity distribution of the terahertz signal can be deduced from the first and second electrical signals. The signal processing module 4 analyzes and processes the signal to determine the object corresponding to the terahertz signal being measured, thus achieving terahertz imaging.

[0096] Specifically, terahertz signals can be obtained by analyzing and processing photocurrent signals based on the following principles.

[0097] In semiconductor structure 2, the frequency shift of the Rydberg exciton energy is proportional to the terahertz field strength: Frequency shift ∝|E THZ | 2

[0098] After the Rydberg exciton absorption peak undergoes a frequency shift, the transmission intensity of the probe light also changes accordingly, which can be written as: ΔT=T(ω+δω)-T(ω)

[0099] In the above formula, ΔT is the change signal of the transmission intensity of the probe light before and after the application of the terahertz field, that is, the difference between the intensity of the third optical signal and the intensity of the second optical signal; T(ω) is the transmission intensity of the probe light at frequency ω, that is, the intensity of the second optical signal; T(ω+δω) is the transmission intensity of the probe light after the δω frequency shift, that is, the intensity of the third optical signal.

[0100] The change in transmission intensity ΔT of the probe light and the frequency shift δω can be written as:

[0101] From the above formula, we can derive the first derivative. The maximum value is most sensitive to frequency shift, and the change in the transmission intensity ΔT of the probe light is proportional to the frequency shift δω. Therefore, the magnitude of the frequency shift can be deduced by measuring the change in the transmission intensity of the probe light. The change in the transmission intensity of the probe light can be obtained by analyzing the voltage signal output by the CCD camera 9, thereby further deducing the magnitude of the terahertz field intensity.

[0102] Specific detection methods may include the following steps:

[0103] Step S1: Control the laser emitting module 1 to emit a first optical signal to the semiconductor structure, so that the semiconductor structure 2 is excited to form a Rydberg exciton after receiving the first optical signal and converts the first optical signal into a second optical signal; at the same time, the wavelength can be controlled within the target wavelength range by the wavelength controller.

[0104] Step S2: The control signal processing module 4 acquires the first electrical signal after the second optical signal is converted by the second photoelectric conversion structure 20.

[0105] Step S3: The control signal processing module 4 acquires the second electrical signal after the third optical signal is converted by the second photoelectric conversion structure 20, so that the signal processing module 4 determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal; the third optical signal is obtained by the semiconductor structure 2 converting the first optical signal under the action of the terahertz signal, the light spot 101 of the first optical signal and the terahertz spot 301 of the terahertz signal coincide in the semiconductor structure 2, and the third optical signal is different from the second optical signal.

[0106] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

Claims

1. A terahertz detection device, characterized in that, include: The laser emitting module is used to emit the first optical signal; A semiconductor structure is provided, wherein the semiconductor structure is used to receive the first optical signal, and is excited by the first optical signal to form a Rydberg exciton and convert the first optical signal into a second optical signal; the semiconductor structure is also used to receive a terahertz signal; the semiconductor structure converts the first optical signal into a third optical signal under the action of the terahertz signal, the third optical signal being different from the second optical signal; A terahertz optical module is used to control the propagation direction of the terahertz signal and focus the terahertz signal so that at least a portion of the light spot of the first optical signal coincides with the terahertz spot of the terahertz signal in the semiconductor structure. The signal processing module is used to acquire the first electrical signal after the second optical signal is converted and the second electrical signal after the third optical signal is converted, and to determine the intensity of the terahertz signal based on the first electrical signal and the second electrical signal.

2. The terahertz detection device according to claim 1, characterized in that, The terahertz detection device further includes a first electrode and a second electrode disposed on the surface of a semiconductor structure. The first electrode and the second electrode are both electrically connected to the semiconductor structure to form a first photoelectric conversion structure. The first photoelectric conversion structure is electrically connected to the signal processing module. The second optical signal is converted into the first electrical signal through the first photoelectric conversion structure, and the third optical signal is converted into the second electrical signal through the first photoelectric conversion structure.

3. The terahertz detection device according to claim 1, characterized in that, The semiconductor structure is made of a light-transmitting material. The terahertz detection device includes a second photoelectric conversion structure, which is disposed on the side of the semiconductor structure away from the laser emission module. The second photoelectric conversion structure is electrically connected to the signal processing module. The second optical signal is converted into the first electrical signal by the second photoelectric conversion structure, and the third optical signal is converted into the second electrical signal by the second photoelectric conversion structure.

4. The terahertz detection device according to claim 3, characterized in that, The second photoelectric conversion structure includes a photodiode, a photomultiplier tube, a phototransistor, a CCD image sensor, or a CMOS image sensor.

5. The terahertz detection device according to claim 1, characterized in that, The signal processing module determines a frequency domain signal reflecting the intensity distribution of the terahertz signal based on the first electrical signal and the second electrical signal.

6. The terahertz detection device according to claim 1, characterized in that, The terahertz detection device further includes a wavelength controller connected to the laser emission module, which controls the wavelength of the first optical signal emitted by the laser emission module to match the target wavelength, wherein the target wavelength is the wavelength required for the semiconductor structure to be excited to form Rydberg excitons.

7. The terahertz detection device according to claim 1, characterized in that, The terahertz optical module includes at least one parabolic mirror and / or at least one terahertz lens, wherein the at least one parabolic mirror and / or the at least one terahertz lens are disposed on one side of the semiconductor structure for focusing the terahertz signal and allowing the terahertz signal to enter the semiconductor structure.

8. The terahertz detection device according to claim 1, characterized in that, The terahertz optical module includes a parabolic mirror disposed between the laser emitting module and the semiconductor structure. The parabolic mirror has a conical aperture, with the openings at opposite ends of the conical aperture facing the laser emitting module and the semiconductor structure, respectively. The conical aperture is used to allow the first optical signal to pass through and enter the semiconductor structure.

9. The terahertz detection device according to claim 1, characterized in that, The semiconductor structure is made of materials including cuprous oxide, gallium arsenide, indium phosphide, silver oxide, tin dioxide, two-dimensional materials, or perovskite materials.

10. A detection method for a terahertz detection device, applied to the controller of the terahertz detection device according to any one of claims 1 to 9, characterized in that, The method includes: The laser emitting module is controlled to emit the first optical signal toward the semiconductor structure, so that the semiconductor structure is excited to form the Rydberg exciton after receiving the first optical signal and converts the first optical signal into the second optical signal. The signal processing module is controlled to acquire the first electrical signal after the second optical signal is converted. The signal processing module is controlled to acquire the second electrical signal after the conversion of the third optical signal, so that the signal processing module determines the intensity of the terahertz signal based on the first electrical signal and the second electrical signal; the third optical signal is obtained by the semiconductor structure converting the first optical signal under the action of the terahertz signal, at least a portion of the light spot of the first optical signal coincides with the terahertz spot of the terahertz signal in the semiconductor structure, and the third optical signal is different from the second optical signal.

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