Terahertz detector linearity calibration device and method

Abstract

The invention discloses a terahertz detector linearity calibration device and method. The terahertz detector linearity calibration device comprises a terahertz radiation source, a monitoring detector, a baffle, a terahertz film attenuator, a diaphragm, a standard terahertz detector, a digital multimeter, a computer and measurement and control software. The terahertz radiation source is used for radiating parallel or divergent terahertz wave beams; the monitoring detector is used for monitoring the fluctuation condition of the terahertz radiation source; the baffle plate is used for being inserted into a terahertz light path when the noise of the detector is detected so as to play a role in cutting off the terahertz light path; the terahertz thin film attenuator is used for carrying out quantitative attenuation on terahertz power without changing the transmission state of a wave beam; the digital multimeter is used for measuring an electric signal output by the detected terahertz detector, and the electric signal is collected by the computer and sent to the data processing software, and then the linearity is calculated according to the linearity. According to the invention, the interference of the attenuator on beam transmission characteristics can be effectively reduced, so that the calibration precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz detectors, and in particular relates to a terahertz detector linearity calibration device and method. Background Art

[0002] The linearity calibration of terahertz detectors is directly related to the accuracy of terahertz spectrum intensity measurement, and plays an important role in the design, development and application of terahertz devices and systems. For example, in biological imaging detection, it is necessary to detect the absorption distribution characteristics of the measured tissue to terahertz waves, and the parameter to be based on is the terahertz radiation intensity detected by the detector. However, the response of terahertz detectors is generally nonlinear, so there will be large errors when used to measure the terahertz intensity of the strong and weak distribution of different tissue parts, which will ultimately affect the absorption characteristics of biological tissues and medical imaging effects. Similar situations have attracted more and more attention from terahertz device and system development and application units, and there is an urgent need to carry out calibration research on the linearity of terahertz detectors.

[0003] In the test of the linearity of terahertz detectors, the existing technical solution is the attenuation method based on silicon wafers. The test device consists of a terahertz source, a silicon attenuator and a detector to be tested, such as Figure 1 shown.

[0004] When testing the linearity of the terahertz detector under test, first place the silicon attenuator in the terahertz optical path. The silicon attenuator consists of a base and multiple silicon discs, and the discs are parallel to each other. Then adjust the position of the silicon attenuator so that the terahertz beam is perpendicular to the surface of the silicon attenuator. Next, adjust the attenuation of the silicon attenuator by adjusting the number of attenuation plates in the silicon attenuator, and measure the terahertz wave transmission intensity under different attenuations. Calculate the linearity of the terahertz detector under test based on the test results.

[0005] The existing solutions have the following main deficiencies:

[0006] ① Low calibration accuracy. When the terahertz wave propagates in the silicon attenuator, there is a Fabry-Perot interference effect between the silicon chips, which will affect the transmission of the terahertz wave. However, the existing scheme does not take into account the influence of this effect, thus affecting the calibration accuracy;

[0007] ② The operating band is narrow. The operating band of silicon wafers ranges from 0.1THz to 4THz, so this solution cannot meet the testing requirements of terahertz detectors with wider bands.

[0008] ③ Narrow scope of application. The existing solution is well applicable when the terahertz optical path is a parallel beam, but when the terahertz source is a focused beam, the thickness of the silicon wafer will change the beam propagation characteristics, causing some terahertz waves to deviate from the established path and fail to enter the terahertz detector under test, thereby introducing large errors. Summary of the invention

[0009] In view of the above problems existing in the prior art, the present invention proposes a terahertz detector linearity calibration device and method, which are reasonably designed, solve the shortcomings of the prior art, and have good effects.

[0010] In order to achieve the above purpose 1, the present invention adopts the following technical solution:

[0011] A terahertz detector linearity calibration device, comprising a terahertz radiation source, a monitoring detector, a baffle, a terahertz film attenuator, an aperture, a standard terahertz detector, a digital multimeter, and a computer;

[0012] The terahertz radiation source is used to radiate a parallel or divergent terahertz beam;

[0013] The monitoring detector is used to monitor the fluctuation of the terahertz radiation source;

[0014] The baffle is used to be inserted into the terahertz optical path when detecting the noise of the detector, so as to cut off the terahertz optical path;

[0015] The terahertz thin film attenuator is used to quantitatively attenuate the terahertz power without changing the transmission state of the beam;

[0016] The digital multimeter is used to measure the electrical signal output from the terahertz detector under test, and calculate the linearity after collecting the signal through a computer.

[0017] Furthermore, the terahertz radiation source includes but is not limited to a CO2 pumped gas terahertz laser, a quantum cascade laser, a Schottky terahertz source, and a photoconductive antenna.

[0018] Furthermore, when the size of the beam incident on the receiving surface of the detector is larger than the receiving aperture of the terahertz detector, a terahertz converging device is provided between the terahertz radiation source and the baffle.

[0019] Furthermore, the baffle is made of metal and has a thickness of 3 mm.

[0020] Furthermore, the terahertz thin film attenuator includes an attenuation plate and a 4-position fixed rotation angle turntable; the attenuation plate is designed as a circular plate structure, which is equally divided into 4 areas, each area is a fan-shaped structure with an angle of 90°; the base material of each fan-shaped area is a 25μm thick PET film, and a metal film layer with thickness parameters of 16.5nm, 10.1nm, 5.5nm, and 2.3nm is sputtered on the 4 fan-shaped areas through a plasma sputtering process, and the transmittance corresponding to the terahertz band is 6.25%, 12.5%, 25%, and 50%, respectively; the fan-shaped area cut into the optical path is controlled by the 4-position fixed rotation angle turntable to achieve the purpose of adjusting the terahertz attenuation.

[0021] Furthermore, the sputtering target material is an Inconel 600 alloy target with a purity of 99.99%, a target diameter of 101.6 mm, a thickness of 6.4 mm, and a sputtering gas with a purity of 99.999% argon. The backing vacuum is better than 6.65×10 - 5 Pa, the sputtering gas pressure is 0.5 Pa, the substrate rotation speed is 30 rpm, the film deposition temperature is room temperature, and the fixed sputtering power is 100 W.

[0022] In order to achieve the above purpose 2, the present invention adopts the following technical solution:

[0023] A terahertz detector linearity calibration method, using the terahertz detector linearity calibration device as described above, comprises the following steps:

[0024] Step 1: Trace the terahertz radiation source, monitoring detector and attenuation sheet to the superior metrological standard;

[0025] Step 2: Arrange the terahertz radiation source, the terahertz film attenuator and the terahertz detector to be measured in sequence along the propagation direction of the terahertz light, and use a terahertz beam splitter to split 20% of the terahertz wave to the monitoring detector, and preheat the terahertz radiation source and the monitoring detector;

[0026] Step 3: Adjust the terahertz radiation source to a stable power working state, and adjust the aperture of the aperture so that the terahertz power reaching the receiving surface of the terahertz detector to be measured is within the range of the detector;

[0027] Step 4: Adjust the position of the terahertz detector to ensure that the center of the detector's receiving surface is consistent with the center of the aperture hole;

[0028] Step 5: Place a baffle between the terahertz radiation source and the terahertz film attenuator to block the light path. After the output of the terahertz detector under test is stable, collect and record the noise electrical signal U of the terahertz detector under test. Nd ;

[0029] Step 6: Remove the baffle, and after the output of the terahertz detector under test is stable, collect and record the output electrical signal value U of the terahertz detector under test. M,i ;

[0030] Step 7: Rotate the 4-position fixed rotation angle turntable to change the attenuation A of the terahertz film i , and calculate the nonlinearity under this attenuation, repeating steps 5 to 7;

[0031] Step 8: Determine the nonlinearity of the terahertz detector.

[0032] Furthermore, in step 7, the nonlinearity of the terahertz detector under test at the i-th attenuation is calculated, and the expression is:

[0033]

[0034] Where:

[0035] U F,i = kA i +b(i=1,2,3,4);(2)

[0036] Let U S,i =U M,i -U Nd ,but

[0037]

[0038] Among them, D i is the nonlinearity of the terahertz detector under the attenuation of the inserted attenuator; U M,i is the measured value of the output electrical signal of the terahertz detector under the attenuation of the inserted attenuator; U Nd is the measured value of the noise electrical signal of the terahertz detector under test; U F,i is the least square linear fitting value of the difference between the output electrical signal of the terahertz detector and the noise electrical signal under the attenuation of the inserted attenuator; S is the difference in the electrical output of the terahertz detector under test when no attenuator is added during the calibration process and when the attenuator with the maximum attenuation is added; N is the number of different attenuations used in the calibration process; A i is the attenuation of the attenuator; is the average value of the attenuation used in the calibration process;

[0039] In step 8, the nonlinearity of the terahertz detector is determined according to formula (5):

[0040] D=max(D i )(5).

[0041] Furthermore, in step 1, the terahertz radiation source, the monitoring detector and the attenuation film are all traced back to the superior metrological standard; the parameters of the terahertz source traceability include the terahertz output power and the terahertz frequency, the terahertz output power and the transmittance of the attenuation film are traced back to the national power standard by an overall traceability method, and the terahertz frequency index is traced back to the rubidium atomic frequency standard item by item;

[0042] The overall traceability method of terahertz output power and attenuator transmittance is as follows: Use the terahertz standard power meter of the China Institute of Metrology to directly calibrate the power value output from the aperture of the terahertz film attenuator, so as to achieve traceability to the national power standard. The terahertz standard power meter is developed based on the thermopile principle, with a power measurement range of 0.1mW to 300mW, an uncertainty of 3.2%, and a coverage factor of k = 2;

[0043] The terahertz frequency parameters are traced back to the rubidium atomic frequency standard through a terahertz frequency comb. The terahertz frequency comb down-converts a near-infrared fundamental frequency comb signal with a central wavelength of 1560nm to a terahertz band based on a photoconductive device, and the spectral range is 0.1THz to 3THz. During tracing, a single-frequency terahertz signal radiated from a Schottky terahertz source horn antenna is incident on the photoconductive device. The single-frequency terahertz signal and the comb teeth of the terahertz frequency comb are mixed in the photoconductive device to output an electrical signal with a frequency in the radio frequency band. The electrical signal is input into a spectrum analyzer after current amplification and voltage amplification to measure the frequency of the electrical signal. The output frequency of the Schottky terahertz source after tracing is obtained according to the measurement results and parameters such as the repetition rate of the terahertz frequency comb.

[0044] The traceability of the monitoring detector is achieved through the radiation-type terahertz power standard device and terahertz standard power meter of the China Institute of Metrology. The response rate of the monitoring detector is ultimately traced back to the national power standard by the substitution method.

[0045] Beneficial technical effects brought by the present invention:

[0046] (1) High calibration accuracy: The proposed method and device are not affected by the Fabry-Perot effect. At the same time, the method takes into account the traceability of the device and the influence of environmental background radiation on the calibration results. Therefore, the calibration accuracy is higher than that of existing schemes.

[0047] (2) Applicable to various terahertz optical paths: The thickness of the proposed thin film attenuation sheet is on the order of tens of microns, which will not change the propagation state of the optical path. Therefore, it is applicable to both parallel terahertz beams and non-parallel terahertz beams.

[0048] (3) Wide working band: The proposed method and device have no wavelength selectivity for terahertz waves and can cover the entire terahertz band. From the perspective of working band, they are more applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of linearity calibration of silicon-based terahertz detectors;

[0050] Figure 2 It is a schematic diagram of the linearity calibration device of the terahertz detector in the present invention; DETAILED DESCRIPTION

[0051] The specific implementation of the present invention is further described below in conjunction with specific embodiments:

[0052] A terahertz detector linearity calibration device, such as Figure 2 As shown, it includes a terahertz radiation source, a monitoring detector, a baffle, a terahertz film attenuator, an aperture, a standard terahertz detector, a digital multimeter, and a computer;

[0053] The terahertz radiation source is used to radiate parallel or divergent terahertz beams, including but not limited to CO2 pumped gas terahertz lasers, quantum cascade lasers, Schottky terahertz sources, and photoconductive antennas. In this embodiment, a 110 GHz to 170 GHz Schottky terahertz source is used;

[0054] The monitoring detector is used to monitor the fluctuation of the terahertz radiation source and to correct the output results of the subsequent detector under test, thereby greatly reducing the error caused by the instability of the light source and ultimately improving the calibration accuracy;

[0055] The baffle is used to be inserted into the terahertz optical path when detecting the noise of the detector, and plays a role in cutting off the terahertz optical path. The baffle is made of metal and has a thickness of 3 mm.

[0056] The terahertz film attenuator is used to quantitatively attenuate the terahertz power without changing the transmission state of the beam. It is developed based on the attenuation effect of metal film on terahertz waves, and includes an attenuation plate and a 4-position fixed rotation angle turntable; the attenuation plate is designed as a circular plate structure, which is equally divided into 4 areas, each of which is a fan-shaped structure with an angle of 90°; the base material of each fan-shaped area is a 25μm thick PET film, and metal film layers with thickness parameters of 16.5nm, 10.1nm, 5.5nm, and 2.3nm are sputtered on the 4 fan-shaped areas through a plasma sputtering process, and the transmittances corresponding to the terahertz band are 6.25%, 12.5%, 25%, and 50% respectively; the fan-shaped area cut into the optical path is controlled by a 4-position fixed rotation angle turntable to achieve the purpose of adjusting the terahertz attenuation; the sputtering target material adopts Inconel with a purity of 99.99% 600 alloy target, target diameter is 101.6mm, thickness is 6.4mm, sputtering gas uses argon with purity of 99.999%, and the back vacuum is better than 6.65×10 -5 Pa, the sputtering gas pressure is 0.5 Pa, the substrate rotation speed is 30 rpm, the film deposition temperature is room temperature, and the fixed sputtering power is 100 W.

[0057] The digital multimeter is used to measure the electrical signal output from the terahertz detector under test, and calculate the linearity after collecting it through a computer.

[0058] When the size of the beam incident to the detector receiving surface is larger than the receiving aperture of the terahertz detector, a terahertz converging device is provided between the terahertz radiation source and the baffle. When the size of the beam incident to the detector receiving surface is smaller than the receiving aperture of the terahertz detector, it is not necessary to use it.

[0059] A terahertz detector linearity calibration method, using the terahertz detector linearity calibration device as described above, comprises the following steps:

[0060] Step 1: Trace the terahertz radiation source, monitoring detector and attenuation sheet to the superior metrological standard;

[0061] Traceability is the prerequisite for ensuring the accuracy and reliability of calibration results. Figure 2 In the calibration device shown, the terahertz radiation source, monitoring detector and attenuation film are all traced back to the superior metrological standard; the traceability parameters of the terahertz source include the terahertz output power and the terahertz frequency. The terahertz output power and the transmittance of the attenuation film are traced back to the national power standard by the overall traceability method, and the terahertz frequency index is traced back to the rubidium atomic frequency standard item by item;

[0062] The overall traceability method of terahertz output power and attenuator transmittance is as follows: Use the terahertz standard power meter of the China Institute of Metrology to directly calibrate the power value output from the aperture of the terahertz film attenuator, so as to achieve traceability to the national power standard. The terahertz standard power meter is developed based on the thermopile principle, with a power measurement range of 0.1mW to 300mW, an uncertainty of 3.2%, and a coverage factor of k = 2;

[0063] The terahertz frequency parameters are traced back to the rubidium atomic frequency standard through a terahertz frequency comb. The terahertz frequency comb down-converts a near-infrared fundamental frequency comb signal with a central wavelength of 1560nm to a terahertz band based on a photoconductive device, and the spectral range is 0.1THz to 3THz. During tracing, a single-frequency terahertz signal radiated from a Schottky terahertz source horn antenna is incident on the photoconductive device. The single-frequency terahertz signal and the comb teeth of the terahertz frequency comb are mixed in the photoconductive device to output an electrical signal with a frequency in the radio frequency band. The electrical signal is input into a spectrum analyzer after current amplification and voltage amplification to measure the frequency of the electrical signal. The output frequency of the Schottky terahertz source after tracing is obtained according to the measurement results and parameters such as the repetition rate of the terahertz frequency comb.

[0064] The traceability of the monitoring detector is achieved through the radiation-type terahertz power standard device and terahertz standard power meter of the China Institute of Metrology. The response rate of the monitoring detector is ultimately traced back to the national power standard by the substitution method.

[0065] Step 2: Arrange the terahertz radiation source, the terahertz film attenuator and the terahertz detector to be measured in sequence along the propagation direction of the terahertz light, and use a terahertz beam splitter to split 20% of the terahertz wave to the monitoring detector, and preheat the terahertz radiation source and the monitoring detector;

[0066] Step 3: Adjust the terahertz radiation source to a stable power working state, and adjust the aperture of the aperture so that the terahertz power reaching the receiving surface of the terahertz detector to be measured is within the range of the detector;

[0067] Step 4: Adjust the position of the terahertz detector to ensure that the center of the detector's receiving surface is consistent with the center of the aperture hole;

[0068] Step 5: Place a baffle between the terahertz radiation source and the terahertz film attenuator to block the light path. After the output of the terahertz detector under test is stable, collect and record the noise electrical signal U of the terahertz detector under test. Nd ;

[0069] Step 6: Remove the baffle, and after the output of the terahertz detector under test is stable, collect and record the output electrical signal value U of the terahertz detector under test. M,i ;

[0070] Step 7: Rotate the 4-position fixed rotation angle turntable to change the attenuation A of the terahertz film i , and calculate the nonlinearity under this attenuation, repeating steps 5 to 7;

[0071] Calculate the nonlinearity of the terahertz detector under test at the i-th attenuation, and the expression is:

[0072]

[0073] Where:

[0074] U F,i = kA i +b(i=1,2,3,4);(2)

[0075] Let U S,i =U M,i -U Nd ,but

[0076]

[0077] Among them, D i is the nonlinearity of the terahertz detector under the attenuation of the inserted attenuator; U M,i is the measured value of the output electrical signal of the terahertz detector under the attenuation of the inserted attenuator; U Nd is the measured value of the noise electrical signal of the terahertz detector under test; U F,iis the least square linear fitting value of the difference between the output electrical signal of the terahertz detector and the noise electrical signal under the attenuation of the inserted attenuator; S is the difference in the electrical output of the terahertz detector under test when no attenuator is added during the calibration process and when the attenuator with the maximum attenuation is added; N is the number of different attenuations used in the calibration process; A i is the attenuation of the attenuator; is the average value of the attenuation used in the calibration process;

[0078] Step 8: Determine the nonlinearity of the terahertz detector:

[0079] D=max(D i )(5).

[0080] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A terahertz detector linearity calibration device, characterized in that: Including terahertz radiation source, monitoring detector, baffle, terahertz film attenuator, aperture, standard terahertz detector, digital multimeter, computer; The terahertz radiation source is used to radiate a parallel or divergent terahertz beam; The monitoring detector is used to monitor the fluctuation of the terahertz radiation source; The baffle is used to be inserted into the terahertz optical path when detecting the noise of the detector, so as to cut off the terahertz optical path; The terahertz thin film attenuator is used to quantitatively attenuate the terahertz power without changing the transmission state of the beam; The digital multimeter is used to measure the electrical signal output from the terahertz detector under test, and calculate the linearity after collecting the signal through a computer.

2. A terahertz detector linearity calibration device according to claim 1, characterized in that: The terahertz radiation source includes but is not limited to a CO2 pumped gas terahertz laser, a quantum cascade laser, a Schottky terahertz source, and a photoconductive antenna.

3. The terahertz detector linearity calibration device according to claim 2, characterized in that: When the size of the beam incident on the receiving surface of the detector is larger than the receiving aperture of the terahertz detector, a terahertz converging device is provided between the terahertz radiation source and the baffle.

4. The terahertz detector linearity calibration device according to claim 3, characterized in that: The baffle is made of metal and has a thickness of 3 mm.

5. The terahertz detector linearity calibration device according to claim 4, characterized in that: The terahertz thin film attenuator comprises an attenuation plate and a 4-position fixed rotation angle turntable; the attenuation plate is designed as a circular plate structure, which is equally divided into 4 areas, each area is a fan-shaped structure with an angle of 90°; the base material of each fan-shaped area is a 25μm thick PET film, and metal film layers with thickness parameters of 16.5nm, 10.1nm, 5.5nm and 2.3nm are sputtered on the 4 fan-shaped areas through a plasma sputtering process, and the transmittances corresponding to the terahertz band are 6.25%, 12.5%, 25% and 50% respectively; the fan-shaped area cut into the optical path is controlled by the 4-position fixed rotation angle turntable to achieve the purpose of adjusting the terahertz attenuation.

6. The terahertz detector linearity calibration device according to claim 5, characterized in that: The sputtering target material is Inconel 600 alloy target with a purity of 99.99%, the target diameter is 101.6mm, the thickness is 6.4mm, the sputtering gas is argon with a purity of 99.999%, and the back vacuum is better than 6.65×10 -5 Pa, the sputtering gas pressure is 0.5 Pa, the substrate rotation speed is 30 rpm, the film deposition temperature is room temperature, and the fixed sputtering power is 100 W.

7. A method for calibrating the linearity of a terahertz detector, characterized in that: A terahertz detector linearity calibration device according to any one of claims 1 to 6 is used, comprising the following steps: Step 1: Trace the terahertz radiation source, monitoring detector and attenuation sheet to the superior metrological standard; Step 2: Arrange the terahertz radiation source, the terahertz film attenuator and the terahertz detector to be measured in sequence along the propagation direction of the terahertz light, and use a terahertz beam splitter to split 20% of the terahertz wave to the monitoring detector, and preheat the terahertz radiation source and the monitoring detector; Step 3: Adjust the terahertz radiation source to a stable power working state, and adjust the aperture of the aperture so that the terahertz power reaching the receiving surface of the terahertz detector to be measured is within the range of the detector; Step 4: Adjust the position of the terahertz detector to be measured to ensure that the center of the detector's receiving surface is consistent with the center of the aperture hole; Step 5: Place a baffle between the terahertz radiation source and the terahertz film attenuator to block the light path. After the output of the terahertz detector under test is stable, collect and record the noise electrical signal U of the terahertz detector under test. Nd ; Step 6: Remove the baffle, and after the output of the terahertz detector under test is stable, collect and record the output electrical signal value U of the terahertz detector under test. M,i ; Step 7: Rotate the 4-position fixed rotation angle turntable to change the attenuation A of the terahertz film i , and calculate the nonlinearity under this attenuation, repeating steps 5 to 7; Step 8: Determine the nonlinearity of the terahertz detector.

8. A terahertz detector linearity calibration method according to claim 7, characterized in that: In step 6 and step 7, the nonlinearity of the terahertz detector under test at the i-th attenuation is calculated, and the expression is: Where: U F,i =kA i +b(i=1,2,3,4); (2) Let U S,i = U M,i - U Nd , then Among them, D i is the nonlinearity of the terahertz detector under the attenuation of the inserted attenuator; U M,i is the measured value of the output electrical signal of the terahertz detector under the attenuation of the inserted attenuator; U Nd is the measured value of the noise electrical signal of the terahertz detector under test; U F,i is the least square linear fitting value of the difference between the output electrical signal of the terahertz detector and the noise electrical signal under the attenuation of the inserted attenuator; S is the difference in the electrical output of the terahertz detector under test when no attenuator is added during the calibration process and when the attenuator with the maximum attenuation is added; N is the number of different attenuations used in the calibration process; A i is the attenuation of the attenuator; is the average value of the attenuation used in the calibration process; In step 8, the nonlinearity of the terahertz detector is determined according to formula (5): D=max(D i )(5)。 9. The method for calibrating the linearity of a terahertz detector according to claim 8, characterized in that: In step 1, the terahertz radiation source, the monitoring detector and the attenuation film are all traced back to the superior metrological standard; the parameters of the terahertz source traceability include the terahertz output power and the terahertz frequency, the terahertz output power and the transmittance of the attenuation film are traced back to the national power standard by an overall traceability method, and the terahertz frequency index is traced back to the rubidium atomic frequency standard item by item; The overall traceability method of terahertz output power and attenuator transmittance is as follows: Use the terahertz standard power meter of the China Institute of Metrology to directly calibrate the power value output from the aperture of the terahertz film attenuator, so as to achieve traceability to the national power standard. The terahertz standard power meter is developed based on the thermopile principle, with a power measurement range of 0.1mW to 300mW, an uncertainty of 3.2%, and a coverage factor of k = 2; The terahertz frequency parameters are traced back to the rubidium atomic frequency standard through a terahertz frequency comb. The terahertz frequency comb down-converts a near-infrared fundamental frequency comb signal with a central wavelength of 1560nm to a terahertz band based on a photoconductive device, and the spectral range is 0.1THz to 3THz. During tracing, a single-frequency terahertz signal radiated from a Schottky terahertz source horn antenna is incident on the photoconductive device. The single-frequency terahertz signal and the comb teeth of the terahertz frequency comb are mixed in the photoconductive device to output an electrical signal with a frequency in the radio frequency band. The electrical signal is input into a spectrum analyzer after current amplification and voltage amplification to measure the frequency of the electrical signal. The output frequency of the Schottky terahertz source after tracing is obtained according to the measurement results and parameters such as the repetition rate of the terahertz frequency comb. The traceability of the monitoring detector is achieved through the radiation-type terahertz power standard device and terahertz standard power meter of the China Institute of Metrology. The response rate of the monitoring detector is ultimately traced back to the national power standard by the substitution method.

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