Terahertz source radiation intensity far-field measurement device and method and method for debugging light path

Abstract

The invention provides a terahertz source radiation intensity far-field measurement device and method and a method for debugging an optical path. The device belongs to the field of optical measurement and metering and comprises a terahertz emission system, a terahertz attenuation system, a terahertz detection system, an extension adapter plate and a computer. And the far-field distribution test of the radiation intensity of the terahertz source with the output power greater than 1mW in the (0.1-10) THz wave band range can be realized. The measurement method comprises the following steps: recording the terahertz radiation power measured by the terahertz power meter as Pm, the diameter of the adjusting diaphragm as D, the transmittance of the terahertz attenuator as tau1, the transmittance of the terahertz narrow-band filter as tau2, the reflectivity of each wedge-shaped reflector as R, the number of the wedge-shaped reflectors being n, and the Terahertz radiation power measured by the Terahertz power meter as Pm, the diameter of the adjusting diaphragm as D, the transmittance of the Terahertz attenuator as tau1 and the transmittance of the Terahertz narrow-band filter as tau2, and the reflectivity of each wedge-shaped reflector as R; the distance between the measured terahertz radiator and the variable diaphragm is recorded as L, and the radiation intensity value of the measured terahertz radiator is calculated by using a formula. And accurate magnitude of a far-field measurement terahertz source radiation result can be ensured.

Description

Technical Field

[0001] The present application relates to the field of optical measurement and metrology, and in particular to a device and method for far-field measurement of terahertz source radiation intensity and a method for debugging an optical path. Background Art

[0002] The terahertz band is located between infrared and microwaves, and terahertz technology is an interdisciplinary cutting-edge technology that is the focus of international research. With the rapid development of terahertz technology, a variety of terahertz sources have been developed at home and abroad, including terahertz free electron lasers, terahertz quantum cascade lasers, terahertz gas lasers, Schottky terahertz sources, backward wave tubes, traveling wave tubes, photoconductive antennas, etc. Terahertz sources are an important development direction of terahertz technology, and the performance of terahertz sources is directly related to the overall indicators of terahertz imaging, communication and other systems. Radiation intensity is an important indicator to characterize the spatial distribution of the output radiation of a terahertz source, and is related to parameters such as the imaging distance and imaging resolution of the terahertz imaging system, as well as parameters such as the communication distance of the terahertz communication system.

[0003] The publication number is: CN205483257U, and the name is a utility model patent for a terahertz radiation intensity distribution detection device based on compressed sensing. A detection device including a beam expansion lens group, a mask plate, a one-dimensional electric displacement platform, a terahertz power meter or energy meter, a focusing lens and a computer is designed. On the basis of a specific mask plate, only a one-dimensional mobile platform and a terahertz radiation power meter are used to achieve fast and high-sensitivity detection of terahertz radiation intensity distribution. Mask plates with different resolutions and different lens combinations can be used to achieve imaging of radiation intensity distribution with different resolutions. This method can be applied to the measurement of radiation intensity distribution in different bands. In conjunction with the infrared thermal radiation detector Bolometer, pW-level power detection can be achieved. However, the defect is that the Bolometer detector must be cooled by liquid helium during use, and the upper limit of power measurement is only a few microwatts, which cannot achieve the measurement of the far-field radiation intensity of a terahertz source with an output power greater than 1mW. In addition, the existing terahertz source radiation intensity measurement system is only applicable to near-field terahertz radiation measurement, and the measurement result is inaccurate in far-field measurement. Summary of the invention

[0004] The purpose of the present application is to provide a device and method for far-field measurement of terahertz source radiation intensity and a method for debugging an optical path, which can ensure the accuracy of the value of the far-field measurement result of terahertz source radiation.

[0005] This application is implemented as follows:

[0006] In a first aspect, the present application provides a far-field measurement device for terahertz source radiation intensity, comprising: a terahertz emission system, a terahertz attenuation system, a terahertz detection system, an extension adapter plate, and a computer;

[0007] The above-mentioned terahertz emission system includes a terahertz radiator to be measured;

[0008] The above-mentioned terahertz attenuation system includes a variable iris installed on an extended adapter plate, an optical reflection group and a terahertz attenuator; the center of the variable iris and the geometric center of the terahertz wave radiator outlet are located on the same optical axis, which is used to control the amount of radiation incident from the terahertz wave radiator to be measured; the optical reflection group includes an off-axis parabolic mirror and n wedge-shaped reflection mirrors, the focus of the off-axis parabolic mirror coincides with the exit of the terahertz radiator to be measured, and is used to refract the terahertz radiation emitted by the terahertz radiator to be measured into parallel light incident on the wedge-shaped reflection mirror, and the n wedge-shaped reflection mirrors attenuate the terahertz radiation and then incident on the terahertz attenuator; the terahertz attenuator is used to achieve different attenuation multiples;

[0009] The terahertz detection system comprises a terahertz narrowband filter, a rotating wheel, a chopper and a terahertz power meter installed on an extended adapter plate. The terahertz narrowband filter is installed on the rotating wheel and is used to control the rotating wheel to rotate the corresponding terahertz narrowband filter into the optical path according to the output frequency of the terahertz radiator to be measured when measuring the radiation intensity, so as to filter out the infrared radiation of the terahertz wave radiator to be measured in sections; the chopper is used to convert continuous terahertz radiation into pulsed terahertz radiation; the terahertz power meter is used to receive the pulsed terahertz radiation incident on its detection surface, and output the signal to the computer to calculate the radiation intensity value of the terahertz radiator to be measured.

[0010] Based on the first aspect, the terahertz emission system further includes a turntable; the emission port of the terahertz radiator under test is located at the center of the turntable, the emission position of the terahertz wave radiator does not change with the rotation of the turntable, and the focus of the off-axis parabolic mirror is located at the center of the turntable.

[0011] Based on the first aspect, the extended adapter plate is connected to the turntable and can rotate synchronously with the turntable.

[0012] Based on the first aspect, the aperture of the variable iris can be adjusted to be larger than the exit aperture of the terahertz wave radiator to be measured.

[0013] Based on the first aspect, a reflective film with a certain reflectivity is coated on the surface of the wedge-shaped reflector, which is used to attenuate the terahertz radiation and then input it into the terahertz attenuator.

[0014] Based on the first aspect, the terahertz attenuator includes several groups of metal thin film attenuation sheets with different transmittances, and the several groups of metal thin film attenuation sheets with different transmittances can be used alone or in combination to achieve different attenuation multiples.

[0015] In a second aspect, the present application provides a far-field measurement method for terahertz source radiation intensity, using the above-mentioned measurement device, the measurement method comprises the following steps:

[0016] The terahertz radiation power measured by the terahertz power meter is recorded as Pm. During the measurement, the diameter of the aperture is adjusted according to the radiation outlet of the terahertz radiator under test as D, the transmittance of the terahertz attenuator is recorded as τ1, the transmittance of the terahertz narrowband filter is recorded as τ2, the reflectivity of each wedge-shaped reflector is R, the number of wedge-shaped reflectors is n, and the distance between the terahertz radiator under test and the variable aperture is recorded as L. The radiation intensity value I of the terahertz radiator under test 1-1 is calculated using formula (1):

[0017]

[0018] Based on the second aspect, the method for determining the number of wedge-shaped reflectors comprises the following steps:

[0019] The output power of the terahertz radiator under test is P O ; The detection power limit of the terahertz power meter is P max , the attenuation factor of the terahertz attenuator is α, the reflectivity of each wedge-shaped reflector is R, and the number of wedge-shaped reflectors required is n. Calculate P o α R n ≤P max ; n value satisfies when If n is not an integer, the value is rounded up.

[0020] In a third aspect, the present application provides a method for debugging an optical path, which is applied to the above-mentioned measuring device, and the method for debugging an optical path comprises the following steps:

[0021] S1: Target No. 1 is placed at the center of the turntable. The visible laser beam emitted by the collimated laser is incident on target No. 1. The position of the collimated laser is adjusted so that the center of its beam spot coincides with the cross center of target No. 1. The center of the collimated laser beam spot and the cross center of target No. 1 together constitute the main optical path of the debugging optical path;

[0022] S2: Place target No. 2 perpendicular to the main light path so that the cross center of target No. 2 coincides with the center of the laser beam spot;

[0023] S3: Place the semi-transparent and semi-reflective mirror on the main optical path and adjust the position of the semi-transparent and semi-reflective mirror so that the center of the spot of the transmitted laser beam coincides with the center of the cross of target No. 2;

[0024] S4: Place target No. 3 in the reflected light path so that the cross center of target No. 3 coincides with the center of the light spot of the reflected light path;

[0025] S5: Move the semi-transparent and semi-reflective mirror 7 out of the main light path, put the off-axis parabolic mirror into the main light path, and adjust the position of the parabolic mirror so that the center of its outgoing light beam coincides with the center of the cross of target No. 3;

[0026] S6: Remove the collimating laser, target No. 1, target No. 2 and target No. 3, and the optical path debugging is completed.

[0027] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0028] The present application provides a terahertz source radiation intensity far-field measurement device, including a terahertz emission system, a terahertz attenuation system, a terahertz detection system, an extension adapter plate and a computer, which can realize the far-field distribution test of the terahertz source radiation intensity with an output power greater than 1mW in the (0.1-10)THz band. The terahertz attenuation system includes a variable aperture, an optical reflection group and a terahertz attenuator, the optical reflection group includes an off-axis parabolic mirror and a wedge-shaped reflector, the wedge-shaped reflector group replaces the plane reflector group, and solves the problem of inaccurate measurement of terahertz radiation intensity caused by multiple reflections on the front and rear surfaces of the plane reflector; the reflectivity of the wedge-shaped reflector and the attenuation multiple of the terahertz attenuator are set to obtain the overall attenuation coefficient of the terahertz attenuation system, thereby ensuring the accuracy of the measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a schematic structural diagram of an embodiment of a far-field measurement device for terahertz source radiation intensity of the present application;

[0031] Figure 2 A schematic diagram of a debugging optical path in an embodiment of a method for debugging an optical path of the present application;

[0032] Figure 3 This is a flow chart of an embodiment of a method for debugging an optical path of the present application.

[0033] icon:

[0034] 1. Terahertz emission system; 11. Terahertz radiator to be measured; 12. Turntable; 2. Terahertz attenuation system; 21. Variable aperture; 22. Optical reflection group; 221. Off-axis parabolic mirror; 222. Wedge-shaped reflector; 23. Terahertz attenuator; 3. Terahertz detection system; 31. Terahertz narrow-band filter; 32. Rotating wheel; 33. Chopper; 34. Terahertz power meter; 4. Extension adapter plate; 5. Computer; 6. Collimated laser; 7. Semi-transparent and semi-reflective mirror; 81. Target No. 1; 82. Target No. 2; 83. Target No. 3. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0036] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0037] Example

[0038] After long-term research and practice, the applicant found that the Bolometer detector used in a terahertz radiation intensity measurement method in the prior art must be cooled by liquid helium during use, and the upper limit of power measurement is only a few microwatts, which cannot achieve the measurement of the far-field radiation intensity of a terahertz source with an output power greater than 1mW. In addition, the existing terahertz source radiation intensity measurement method is only applicable to near-field terahertz radiation measurement, and the measurement results are inaccurate in far-field measurement.

[0039] In view of this, an embodiment of the present application provides a far-field measurement device for terahertz source radiation intensity, which is used to measure the far-field spatial distribution of terahertz source radiation intensity, and can improve the accuracy of far-field measurement of terahertz source radiation.

[0040] Please refer to Figure 1 , the device includes a terahertz emission system 1, a terahertz attenuation system 2, a terahertz detection system 3, an extension adapter plate 4 and a computer 5;

[0041] The terahertz emission system 1 includes a terahertz radiator 11 to be measured; specifically, the terahertz radiator 11 to be measured is used to generate electromagnetic radiation in the terahertz band.

[0042] The terahertz attenuation system 2 includes a variable iris 21, an optical reflection group 22 and a terahertz attenuator 23 installed on an extension adapter plate 4; the center of the variable iris 21 and the geometric center of the terahertz wave radiator outlet are located on the same optical axis, and are used to control the amount of radiation incident from the terahertz wave radiator to be measured; the optical reflection group 22 includes an off-axis parabolic mirror 221 and n wedge-shaped reflection mirrors 222, the focus of the off-axis parabolic mirror 221 coincides with the exit of the terahertz radiator to be measured 11, and is used to refract the terahertz radiation emitted by the terahertz radiator to be measured 11 into parallel light incident on the wedge-shaped reflection mirror 222, and the n wedge-shaped reflection mirrors 222 attenuate the terahertz radiation and then incident on the terahertz attenuator 23; the terahertz attenuator 23 is used to achieve different attenuation multiples;

[0043] Specifically, the variable aperture 21 can accurately control the amount of terahertz wave radiation passing through it, and reduce or increase the radiation amount by adjusting the size of the opening. The optical reflection group 22 consists of an off-axis parabolic mirror 221 and a plurality of wedge-shaped reflectors 222. Preferably, the off-axis parabolic mirror 221 is made of super-hard aluminum, with a gold reflective film coated on the surface, 90° off-axis, a reflectivity greater than 99.5%, a clear aperture of 50.8mm, and a focal length of 101.6mm. After passing through the variable aperture 21, the terahertz wave radiation is refracted into parallel light by the off-axis parabolic mirror 221. Parallel light helps to ensure that the terahertz wave maintains a stable intensity and direction during the subsequent propagation process. When parallel light is incident on the wedge-shaped reflector 222, part of the terahertz wave will be reflected back, while the other part will continue to propagate. Furthermore, the surface of the wedge-shaped reflector 222 is coated with a reflective film with a certain reflectivity, and this film can reflect a specific proportion of light. Such processing enables the wedge-shaped reflector 222 to more effectively perform its functions in the optical system, such as changing the direction of light and adjusting the optical path. By adjusting the number and angle of the wedge-shaped reflector 222, the attenuation degree of the terahertz wave can be further controlled. Finally, the terahertz attenuator 23 performs the final intensity adjustment as needed. Further, the terahertz attenuator 23 includes several groups of metal film attenuation sheets with different transmittances, and several groups of metal film attenuation sheets with different transmittances can be used in single or multiple combinations to achieve different attenuation multiples. When only slight attenuation is required, a single metal film attenuation sheet with higher transmittance can be selected. In this way, most of the terahertz waves can pass through, and only a small part is attenuated. When greater attenuation is required, multiple metal film attenuation sheets can be combined and used together. Each sheet will further attenuate the terahertz wave, so the attenuation effect after the combination will be more significant. By selecting different combinations of attenuation sheets, different attenuation multiples can be achieved. Through such a setting, the attenuation degree of the terahertz wave can be flexibly controlled to meet different test requirements. This embodiment uses a wedge-shaped reflector group to replace the existing plane reflector group, which solves the problem of inaccurate measurement of terahertz radiation intensity caused by multiple reflections on the front and rear surfaces of the plane reflector; the reflectivity of the wedge-shaped reflector 222 and the attenuation multiple of the terahertz attenuator 23 are set to obtain the overall attenuation coefficient of the terahertz attenuation system 2, thereby ensuring the accuracy of the measurement result.

[0044] The terahertz detection system 3 includes a terahertz narrowband filter 31, a rotating wheel 32, a chopper 33 and a terahertz power meter 34 installed on the extension adapter plate 4. The terahertz narrowband filter 31 is installed on the rotating wheel 32 and is used to control the rotating wheel 32 to rotate the corresponding terahertz narrowband filter 31 into the optical path according to the output frequency of the terahertz radiator 11 to be measured when measuring the radiation intensity, so as to filter out the infrared radiation of the terahertz wave radiator to be measured in sections; the chopper 33 is used to convert continuous terahertz radiation into pulsed terahertz radiation; the terahertz power meter 34 is used to receive the pulsed terahertz radiation incident on its detection surface, and output a signal to the computer 5 to calculate the radiation intensity value of the terahertz radiator 11 to be measured.

[0045] Specifically, the terahertz narrowband filter 31 is a filter that can selectively transmit terahertz waves in a specific frequency range. It is mounted on a rotating wheel 32 so that different filters can be selected as needed. The rotating wheel 32 is a device for rotating the terahertz narrowband filter 31. By rotating, filters of different frequency ranges can be rotated into the optical path so as to filter out the terahertz waves in sections. The chopper 33 is a device for converting continuous terahertz radiation into pulsed terahertz radiation. The chopper 33 includes a fast-switching blade that can be quickly opened and closed when the terahertz wave passes through, thereby converting continuous radiation into a series of pulses. The terahertz power meter 34 is a device for measuring the intensity of terahertz waves. It has a detection surface that can receive incident pulsed terahertz radiation and convert it into an electrical signal. Then, this electrical signal can be processed by the computer 5 to calculate the radiation intensity value of the measured terahertz radiator 11. Preferably, the terahertz power meter 343-4 uses the TK100 detector produced by Thomas Keating of the United Kingdom, which can realize automatic calibration of terahertz absolute power, frequency 30GHz~3THz, window diameter 40mm, continuous power measurement upper limit 500mW, pulse energy 100mJ at 5Hz repetition frequency, NEP value 5μW / Hz1 / 2. Through the coordinated work of the terahertz narrowband filter 31, the rotating wheel 32, the chopper 33 and the terahertz power meter 34 installed on the extension adapter plate 4, the device can accurately measure the radiation intensity value of the measured terahertz radiator 11. Realize the far-field distribution test of the radiation intensity of the terahertz source with an output power greater than 1mW in the (0.1~10)THz band.

[0046] Based on the first aspect, the terahertz emission system 1 also includes a turntable 12; the emission port of the terahertz radiator 11 under test is located at the center of the turntable 12, the emission position of the terahertz wave radiator does not change with the rotation of the turntable 12, and the focus of the off-axis parabolic mirror 221 is located at the center of the turntable 12.

[0047] Specifically, the turntable 12 is a high-precision turntable 12, and the turntable 12 has high accuracy and stability during rotation. A bearing portion for bearing the terahertz radiator 11 to be measured is provided on the turntable 12. The emission port of the terahertz radiator 11 to be measured (i.e., the element generating the terahertz wave) is located at the center of the turntable 12. No matter how the turntable 12 rotates, the emission port of the terahertz radiator 11 to be measured is maintained at a fixed position relative to the center of the turntable 12, and the position where the terahertz wave is emitted will not change, thereby ensuring the stability and consistency of the terahertz wave during the emission process. The off-axis parabola is placed at the center of the turntable 12, and its focus coincides with the emission port of the terahertz radiator 11 to be measured. The terahertz wave emitted from the terahertz radiator 11 to be measured will be directly focused on the focus of the off-axis parabolic mirror 221, and then reflected or collimated into the desired beam shape. The purpose of this setting is to ensure the stability and consistency of the light beam during the emission of the terahertz wave.

[0048] Furthermore, the extended adapter plate 4 is connected to the turntable 12 and can rotate synchronously with the turntable 12 .

[0049] Specifically, the extension adapter plate 4 is mechanically connected to the turntable 12 and has a synchronous motion relationship. When the turntable 12 rotates, the extension adapter plate 4 also rotates. This synchronous motion ensures that the components on the extension adapter plate 4 can be rotated and positioned in a predetermined manner.

[0050] The embodiment of the present invention further provides a method for measuring the far-field radiation intensity of a terahertz source, which uses the above-mentioned far-field measurement device for measuring the far-field spatial distribution of the radiation intensity of a terahertz source. The measurement method comprises the following steps:

[0051] The terahertz radiation power measured by the terahertz power meter 34 is recorded as Pm. During the measurement, the diameter of the aperture is adjusted according to the radiation outlet of the terahertz radiator 11 under test as D, the transmittance of the terahertz attenuator 23 is recorded as τ1, the transmittance of the terahertz narrowband filter 31 is recorded as τ2, the reflectivity of each wedge-shaped reflector 222 is R, the number of wedge-shaped reflectors 222 is n, the distance between the terahertz radiator 11 under test and the variable aperture 21 is recorded as L, and the radiation intensity value I of the terahertz radiator 11 under test is calculated using formula (1):

[0052]

[0053] Specifically, in this embodiment, the radiation intensity value I of the terahertz radiator 11 under test is obtained by formula (1).

[0054] Furthermore, a method for determining the number of the n wedge-shaped reflectors 222 (a method for determining n) includes the following steps:

[0055] The output power of the terahertz radiator 11 under test is P O ; The detection power upper limit of the terahertz power meter 34 is P max , the attenuation multiple of the terahertz attenuator 23 is α, the reflectivity of each wedge-shaped reflector 222 is R, and the number of wedge-shaped reflectors 222 required is n. Calculate P o α R n ≤P max ; n value satisfies when If n is not an integer, the value is rounded up.

[0056] Specifically, this embodiment determines the number of wedge-shaped reflectors 222 through this step.

[0057] Please refer to Figure 2-3 The embodiment of the present invention further provides a method for debugging an optical path, which is applied to the above-mentioned measuring device. The method for debugging an optical path comprises the following steps:

[0058] S1: Target No. 1 81 is placed at the center of the turntable 12, and the visible laser beam emitted by the collimated laser 6 is incident on target No. 1 81. The position of the collimated laser 6 is adjusted so that the center of its beam spot coincides with the cross center of target No. 1 81. The center of the beam spot of the collimated laser 6 and the cross center of target No. 1 81 together constitute the main optical path of the debugging optical path;

[0059] Specifically, there is a cross mark in the middle of target No. 1 81, target No. 2 82 and target No. 3 83, which is used as a reference point for beam alignment. The laser beam emitted by the collimator laser 6 is visible. By adjusting the position of the collimator laser 6, the spot center of the laser beam (i.e., the brightest and most concentrated part of the beam) is completely coincident with the cross center of target No. 1 81. When the spot center of the laser beam coincides with the cross center of the target, these two points together constitute a reference, i.e., the main optical path of the debugging optical path. The main optical path is a key reference in the optical path debugging process, which is used to ensure that subsequent laser beam or optical path adjustments are based on this precise reference.

[0060] S2: Place target No. 2 82 perpendicular to the main light path so that the cross center of target No. 2 82 coincides with the center of the laser beam spot;

[0061] Specifically, target No. 2 82 is adjusted so that its plane forms an angle of 90 degrees with the main light path, and the spot center of the laser beam (i.e., the brightest and most concentrated part of the beam) completely coincides with the cross center of target No. 2 82 .

[0062] S3: placing the semi-transparent and semi-reflective mirror 7 on the main optical path, and adjusting the position of the semi-transparent and semi-reflective mirror 7 so that the center of the spot of the transmitted laser beam coincides with the center of the cross of target No. 2 82;

[0063] Specifically, the semi-transparent and semi-reflective mirror 7 allows a portion of the light to pass through, while reflecting another portion of the light. When the laser beam passes through the semi-transparent and semi-reflective mirror 7, a portion of the beam will be transmitted, while the other portion will be reflected. By adjusting the position of the semi-transparent and semi-reflective mirror 7, it can be observed that the position of the beam passing through the lens on the target No. 2 82 changes. The goal of the adjustment is to accurately align the center of the light spot with the center of the cross of the target No. 2 82.

[0064] S4: placing target No. 3 83 in the reflected light path so that the cross center of target No. 3 83 coincides with the center of the light spot of the reflected light path;

[0065] Specifically, the reflected light path refers to the path formed by the laser beam after being reflected by the semi-transparent and semi-reflective mirror 7, and the target No. 3 83 is placed in the reflected light path. The center of the light spot of the reflected light beam is adjusted so that the center of the cross of the target No. 3 83 completely coincides.

[0066] S5: Move the semi-transparent and semi-reflective mirror 7 out of the main light path, put the off-axis parabolic mirror 221 into the main light path, and adjust the position of the parabolic mirror so that the center of its outgoing light beam coincides with the center of the cross of target No. 3 83;

[0067] Specifically, after removing the semi-transparent and semi-reflective mirror 7, the off-axis parabolic mirror 221 is placed in the main light path. The off-axis parabolic mirror 221 is a special optical lens, which has a parabola shape and is designed to focus the incident light parallel to a portion of the mirror surface onto a point, or to collimate the light emitted by a point light source into parallel light. The off-axis parabolic mirror 221 is used to replace the semi-transparent and semi-reflective mirror 7 to change the propagation path and characteristics of the laser beam. By adjusting the position of the parabolic mirror, it can be observed that the position of the outgoing light beam on target No. 3 83 changes. Adjust so that the center of this outgoing light beam is precisely aligned with the cross center of target No. 3 83.

[0068] S6: Move out the collimating laser 6, target No. 1 81, target No. 2 82 and target No. 3 83, and the optical path debugging is completed.

[0069] Specifically, when the collimating laser 6 and all targets are removed, the debugging process of the optical path is officially completed. The optical path has been verified and adjusted according to the design requirements and can be used for practical applications.

[0070] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A far-field measurement device for terahertz source radiation intensity, characterized in that: include: Terahertz emission system, terahertz attenuation system, terahertz detection system, extension adapter plate and computer; The terahertz emission system includes a terahertz radiator to be measured; The terahertz attenuation system comprises a variable iris, an optical reflection group and a terahertz attenuator installed on an extended adapter plate; the center of the variable iris and the geometric center of the terahertz wave radiator outlet are located on the same optical axis, and are used to control the amount of radiation incident from the terahertz wave radiator to be measured; the optical reflection group comprises an off-axis parabolic mirror and n wedge-shaped reflection mirrors, the focus of the off-axis parabolic mirror coincides with the exit of the terahertz radiator to be measured, and is used to refract the terahertz radiation emitted by the terahertz radiator to be measured into parallel light incident on the wedge-shaped reflection mirror, and the n wedge-shaped reflection mirrors attenuate the terahertz radiation and then incident on the terahertz attenuator; the terahertz attenuator is used to achieve different attenuation multiples; The terahertz detection system includes a terahertz narrowband filter, a rotating wheel, a chopper and a terahertz power meter installed on an extended adapter plate. The terahertz narrowband filter is installed on the rotating wheel and is used to control the rotating wheel to rotate the corresponding terahertz narrowband filter into the optical path according to the output frequency of the terahertz radiator to be measured when measuring the radiation intensity, so as to filter out the infrared radiation of the terahertz wave radiator to be measured in sections; the chopper is used to convert continuous terahertz radiation into pulsed terahertz radiation; the terahertz power meter is used to receive the pulsed terahertz radiation incident on its detection surface, and output a signal to a computer to calculate the radiation intensity value of the terahertz radiator to be measured.

2. A terahertz source radiation intensity far-field measurement device according to claim 1, characterized in that: The terahertz emission system also includes a turntable; the emission port of the terahertz radiator to be measured is located at the center of the turntable, the emission position of the terahertz wave radiator does not change with the rotation of the turntable, and the focus of the off-axis parabolic mirror is located at the center of the turntable.

3. A terahertz source radiation intensity far-field measurement device according to claim 2, characterized in that: The extended adapter plate is connected to the turntable and can rotate synchronously with the turntable.

4. The device for far-field measurement of terahertz source radiation intensity according to claim 1, characterized in that: The aperture of the variable diaphragm can be adjusted to be larger than the exit aperture of the terahertz wave radiator to be measured.

5. The device for far-field measurement of terahertz source radiation intensity according to claim 1, characterized in that: The surface of the wedge-shaped reflector is coated with a reflective film with a certain reflectivity, which is used to attenuate the terahertz radiation before it is incident on the terahertz attenuator.

6. The device for far-field measurement of terahertz source radiation intensity according to claim 4, characterized in that: The terahertz attenuator comprises a plurality of groups of metal thin film attenuation sheets with different transmittances, and the plurality of metal thin film attenuation sheets with different transmittances can be used alone or in combination to achieve different attenuation multiples.

7. A far-field measurement method for terahertz source radiation intensity, characterized in that: Applied to the measuring device according to any one of claims 1 to 6, the measuring method comprises the following steps: The terahertz radiation power measured by the terahertz power meter is recorded as Pm. During the measurement, the diameter of the aperture is adjusted according to the radiation outlet of the terahertz radiator under test as D, the transmittance of the terahertz attenuator is recorded as τ1, the transmittance of the terahertz narrowband filter is recorded as τ2, the reflectivity of each wedge-shaped reflector is R, the number of wedge-shaped reflectors is n, and the distance between the terahertz radiator under test and the variable aperture is recorded as L. The radiation intensity value I of the terahertz radiator under test 1-1 is calculated using formula (1):

8. The method for far-field measurement of terahertz source radiation intensity according to claim 7, characterized in that: The method for determining the number of wedge-shaped reflectors comprises the following steps: The output power of the terahertz radiator under test is P O ; The detection power limit of the terahertz power meter is P max , the attenuation factor of the terahertz attenuator is α, the reflectivity of each wedge-shaped reflector is R, and the number of wedge-shaped reflectors required is n. Calculate P o α R n ≤P max ; n value satisfies when If n is not an integer, the value is rounded up.

9. A method for debugging an optical path, characterized in that: Applied to the measuring device according to any one of claims 1 to 6, the method for debugging the optical path comprises the following steps: S1: Target No. 1 is placed at the center of the turntable. The visible laser beam emitted by the collimated laser is incident on target No.

1. The position of the collimated laser is adjusted so that the center of its beam spot coincides with the cross center of target No.

1. The center of the collimated laser beam spot and the cross center of target No. 1 together constitute the main optical path of the debugging optical path; S2: Place target No. 2 perpendicular to the main light path so that the cross center of target No. 2 coincides with the center of the laser beam spot; S3: Place the semi-transparent and semi-reflective mirror on the main optical path and adjust the position of the semi-transparent and semi-reflective mirror so that the center of the spot of the transmitted laser beam coincides with the center of the cross of target No. 2; S4: Place target No. 3 in the reflected light path so that the cross center of target No. 3 coincides with the center of the light spot of the reflected light path; S5: Move the semi-transparent and semi-reflective mirror 7 out of the main light path, put the off-axis parabolic mirror into the main light path, and adjust the position of the parabolic mirror so that the center of its outgoing light beam coincides with the center of the cross of target No. 3; S6: Remove the collimating laser, target No. 1, target No. 2 and target No. 3, and the optical path debugging is completed.

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