Terahertz detector calibration device and method for single terahertz energy measurement

Abstract

The invention discloses a terahertz detector calibration device and method for single terahertz energy measurement, and belongs to the technical field of terahertz radiation detection and measurement. Comprising a terahertz source, a first chopper, a first terahertz lens, a second chopper, a terahertz attenuator, a second terahertz lens, an optical shutter and a Golaycell terahertz detector which are connected in sequence. Terahertz radiation is emitted by the terahertz source, after passing through the first chopper, terahertz is focused into parallel light beams through the first terahertz lens, the parallel light beams enter the second chopper, after passing through the terahertz attenuator, the light beams are focused through the second terahertz lens, and the light beams are focused through the second terahertz lens. And then, the light enters the Golaycell terahertz detector through the optical shutter. Through calibration and measurement technologies, the application range of the Golaycell terahertz detector in a single-shot experiment is expanded, so that the Golaycell terahertz detector not only can measure relative intensity, but also can provide absolute energy data.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz radiation detection and measurement, and particularly to a terahertz detector calibration device and method for single-shot terahertz energy measurement. Background Art

[0002] Terahertz radiation has broad application prospects in accelerator physics and ultrafast material control. Currently, a large number of studies are devoted to the development of high-power terahertz sources. With the rapid development of terahertz technology, the Golay cell terahertz detector has become the most commonly used terahertz detector in laboratories. The Golay cell has become an efficient detector for terahertz radiation due to its high sensitivity at room temperature and flat optical response in a wide wavelength range. In most application scenarios, the Golay cell terahertz detector is commonly used to detect periodic terahertz signals with a repetition rate of dozens of hertz, and usually collects relative voltage values. However, currently, many high-power terahertz radiations generated by ultra-strong laser pulses are in single-shot mode, and it is necessary to measure the absolute energy of single-shot terahertz pulses, which poses a great challenge to the measurement of traditional Golay cell terahertz detectors. Summary of the Invention

[0003] Aiming at the defects of the prior art, the present invention provides a terahertz detector calibration device and method for single-shot terahertz energy measurement, which calibrates the relationship between the voltage value measured by the Golay cell and the absolute energy of terahertz radiation in single-shot mode, so as to realize the use of the Golay cell terahertz detector to measure terahertz energy in single-shot experiments.

[0004] To achieve the above purpose, the present invention provides a terahertz detector calibration device for single-shot terahertz energy measurement, including: a terahertz source, a first chopper, a first terahertz lens, a second chopper, a terahertz attenuator, a second terahertz lens, an optical shutter, and a Golay cell terahertz detector connected in sequence;

[0005] The terahertz source emits terahertz radiation, which, after passing through the first chopper, is focused into a parallel beam by the first terahertz lens. The parallel beam enters the second chopper, and then, after passing through the terahertz attenuator, is focused by the second terahertz lens, and then enters the Golay cell terahertz detector through the optical shutter.

[0006] Further, the terahertz source is a standard continuous terahertz source.

[0007] Further, the Golay cell terahertz detector is connected to an oscilloscope for recording voltage waveforms.

[0008] Further, the terahertz attenuator is a terahertz attenuator with adjustable transmittance.

[0009] The present invention also provides a calibration method for a terahertz detector used for single-shot terahertz energy measurement. Based on the above-mentioned calibration device for a terahertz detector used for single-shot terahertz energy measurement, the method includes the following steps:

[0010] (1) Remove the first chopper in the calibration device, use the terahertz source to emit a continuous terahertz signal, and measure the output voltage of the Golay cell terahertz detector at N modulation frequencies by adjusting the speed of the second chopper;

[0011] (2) According to the response coefficient of the Golay cell terahertz detector, the measured output voltage at N modulation frequencies, and the transmittance of the terahertz attenuator, obtain the terahertz power reaching the Golay cell terahertz detector at N modulation frequencies;

[0012] (3) According to the terahertz power reaching the Golay cell terahertz detector at N modulation frequencies, obtain the input power of the Golay cell terahertz detector;

[0013] (4) Add the first chopper, chop the continuous terahertz signal emitted by the terahertz source into a pulsed signal with a low duty cycle, adjust the second chopper and the optical shutter to obtain single-shot terahertz pulses at M modulation frequencies, and record the output voltage of the Golay cell terahertz detector at M modulation frequencies;

[0014] (5) According to the input power of the Golay cell terahertz detector and in combination with the pulse widths at M modulation frequencies, obtain the single-shot terahertz energy at M modulation frequencies;

[0015] (6) Based on the single-shot terahertz energy at M modulation frequencies obtained in step (5) and the corresponding output voltage of the Golay cell terahertz detector obtained in step (4), obtain the responsivity of single-shot measurement;

[0016] (7) According to the responsivity of single-shot measurement and the output voltage of the Golay cell terahertz detector, the single-shot terahertz energy can be estimated.

[0017] Further, step (2) is specifically:

[0018] P = (V / C) / T

[0019] Where: P is the terahertz power reaching the Golaycell terahertz detector; V is the peak-to-peak output voltage of the measured Golaycell terahertz detector; C is the response coefficient in the Golaycell terahertz detector manual; T is the transmittance of the terahertz attenuator.

[0020] Further, step (3) is specifically: Select the terahertz power reaching the Golaycell terahertz detector at the lowest modulation frequency or the minimum terahertz power reaching the Golaycell terahertz detector among N modulation frequencies as the input power of the Golaycell terahertz detector.

[0021] Further, step (5) is specifically: Multiply the input power of the Golaycell terahertz detector by the pulse width of a single-shot terahertz signal to obtain the single-shot terahertz energy.

[0022] Further, step (6) is specifically: Perform a linear fit on the single-shot terahertz energies at M modulation frequencies and the corresponding output voltages of the Golaycell terahertz detector. The slope of the fitting curve is the responsivity of the single-shot measurement.

[0023] Advantages of the present invention:

[0024] Through calibration and measurement techniques, the present invention expands the application range of the Golaycell terahertz detector in single-shot experiments, enabling it to not only measure relative intensities but also provide absolute energy data.

[0025] The present invention is applicable to terahertz energy measurements under various experimental conditions, especially in the research of terahertz pulses generated by high-intensity laser pulses, and has important practical value. It improves the reliability and accuracy of experimental results and helps to promote the further application of terahertz technology in fields such as material regulation and accelerator physics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of a terahertz detector calibration device for single-shot terahertz energy measurement according to an embodiment of the present invention.

[0027] Figure 2 is a schematic waveform diagram of the Golaycell output voltage signal measured by adjusting the chopper 3 at different modulation frequencies according to an embodiment of the present invention.

[0028] Figure 3 is a corresponding curve of the single-shot terahertz pulse energy and the peak-to-peak value of the Golaycell output voltage according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below in conjunction with embodiments and the accompanying drawings.

[0030] As Figure 1 shown, the present invention provides a terahertz detector calibration device for single-shot terahertz energy measurement, including a terahertz source 1, a first chopper 2, a first terahertz lens 7, a second chopper 3, a terahertz attenuator 4, a second terahertz lens 8, an optical shutter 5, and a Golay cell terahertz detector 6 connected in sequence.

[0031] The terahertz source 1 emits terahertz radiation at a used frequency. After passing through the first chopper 2, the terahertz is focused into a parallel beam by the first terahertz lens 7. The parallel beam enters the second chopper 3, and then after passing through the terahertz attenuator 4, the beam is focused by the second terahertz lens 8, and then enters the Golay cell terahertz detector 6 through the optical shutter 5.

[0032] Among them, the terahertz source 1 is a standard continuous wave (CW) terahertz source. In the embodiment of the present invention, a standard continuous wave (CW) terahertz source with 0.34 terahertz and an output power of 17.67 mW is adopted. The first chopper 2 is used to reduce the repetition frequency. The second chopper 3 is used to switch the continuous terahertz signal into a pulsed signal. The terahertz attenuator 4 is a terahertz attenuator with adjustable transmittance, which is used to prevent the detector from saturating. By controlling the optical shutter 5, the low-repetition-rate pulsed signal can be further switched into a single-shot signal, and then enters the Golay cell terahertz detector 6. Finally, the Golay cell terahertz detector 6 is connected to an oscilloscope to record the voltage waveform.

[0033] The embodiment of the present invention also provides a terahertz detector calibration method for single-shot terahertz energy measurement. Using the above-mentioned terahertz detector calibration device for single-shot terahertz energy measurement, it includes the following steps:

[0034] S101. Remove the first chopper in the calibration device, use the terahertz source to emit a continuous terahertz signal, and measure the output voltage of the Golay cell terahertz detector at different modulation frequencies by adjusting the speed of the second chopper.

[0035] First, remove the first chopper, and then use the standard continuous terahertz source 1 with a frequency of 0.34 terahertz and an output power of 17.67 mW to send a continuous terahertz signal. By adjusting the speed of the second chopper, measure the output voltage of the Golay cell terahertz detector at five modulation frequencies (10, 20, 30, 40, 50 Hz). As Figure 2 shown. In the embodiment of the present invention, N = 5.

[0036] S102. Obtain the terahertz power reaching the Golaycell terahertz detector at N modulation frequencies based on the response coefficient of the Golaycell terahertz detector, the measured output voltage at N modulation frequencies, and the transmittance of the terahertz attenuator.

[0037] Calculate the power value P_GC according to the response coefficient and voltage value given in the Golaycell terahertz detector manual:

[0038] P_GC = V / C

[0039] Where: V is the peak-to-peak value of the output voltage measured by the Golaycell terahertz detector at N modulation frequencies; C is the response coefficient provided in the Golaycell terahertz detector manual.

[0040] Then determine the terahertz power P reaching the Golaycell terahertz detector by dividing P_GC by the transmittance T of the terahertz attenuator 4:

[0041] P = P_GC / T

[0042] Calculate the terahertz power reaching the Golaycell terahertz detector at five modulation frequencies respectively according to the above formula.

[0043] S103. Obtain the input power of the Golaycell terahertz detector based on the terahertz power reaching the Golaycell terahertz detector at N modulation frequencies.

[0044] Set the terahertz power reaching the Golaycell terahertz detector at the lowest modulation frequency or the minimum terahertz power among the N modulation frequencies as the input power of the Golaycell terahertz detector.

[0045] S104. Add the first chopper to chop the continuous terahertz signal emitted by the terahertz source into a pulsed signal with a low duty cycle, adjust the second chopper and the optical shutter to obtain single-shot terahertz pulses at M modulation frequencies, and record the output voltage of the Golaycell terahertz detector at M modulation frequencies.

[0046] In the embodiment of the present invention, M = 4. Adjust the second chopper 3 and the optical shutter 5 to obtain single-shot terahertz pulse signals at F = 2000, 1000, 400, 200 Hz, and record their output voltages.

[0047] S105. Obtain the single-shot terahertz energy at M modulation frequencies based on the input power of the Golaycell terahertz detector and in combination with the pulse widths at M modulation frequencies.

[0048] The input power of the Golay cell terahertz detector is multiplied by the pulse width of the single-shot terahertz signal to obtain the single-shot terahertz energy.

[0049] S106. Based on the single-shot terahertz energy at M modulation frequencies obtained in step S105 and the corresponding output voltage of the Golay cell terahertz detector obtained in step S104, the responsivity of the single-shot measurement is obtained.

[0050] As Figure 3 shown, the single-shot terahertz energy at M modulation frequencies and the corresponding output voltage of the Golay cell terahertz detector are linearly fitted, and the slope of the fitted curve is the responsivity of the single-shot measurement (responsivity = voltage / energy), which is the calibrated responsivity coefficient of the terahertz detector for single-shot terahertz energy measurement.

[0051] S107. Based on the responsivity of the single-shot measurement and the output voltage of the Golay cell terahertz detector, the single-shot terahertz energy can be estimated.

[0052] According to: energy = voltage / responsivity, the measurement of the single-shot terahertz energy by the Golay cell terahertz detector can be realized.

[0053] In summary, through the initial calibration process, the present invention accurately measures the response of the Golay cell terahertz detector at different modulation frequencies, and combines the use of an optical shutter and a chopper to achieve precise energy measurement of single-shot terahertz pulses. This method not only solves the limitations of traditional detectors in single-shot experiments, but also provides a reliable measurement means for future research on generating terahertz pulses with high-intensity laser pulses. It has a wide range of applications, especially suitable for fields such as material control and accelerator physics, and has important scientific research and practical value. The present invention significantly improves the reliability and accuracy of experimental data, and provides a solid foundation for the development and application of terahertz technology.

[0054] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the principle and spirit of the present invention shall be included in the protection scope of the present invention.

Claims

1. A terahertz detector calibration device for single-shot terahertz energy measurement, characterized in that: include: A terahertz source, a first chopper, a first terahertz lens, a second chopper, a terahertz attenuator, a second terahertz lens, an optical shutter, and a Golaycell terahertz detector connected in sequence; The terahertz source is used to emit terahertz radiation, which passes through the first chopper and is then focused into a parallel light beam by the first terahertz lens. The parallel light beam enters the second chopper, passes through the terahertz attenuator and is then focused by the second terahertz lens, and then enters the Golaycell terahertz detector through the optical shutter.

2. The terahertz detector calibration device for single-shot terahertz energy measurement according to claim 1, characterized in that: The terahertz source is a standard continuous terahertz source.

3. The terahertz detector calibration device for single-shot terahertz energy measurement according to claim 1, characterized in that: The Golaycell terahertz detector is connected to an oscilloscope to record a voltage waveform.

4. The terahertz detector calibration device for single-shot terahertz energy measurement according to claim 1, characterized in that: The terahertz attenuator is a terahertz attenuator with adjustable transmittance.

5. A terahertz detector calibration method for single-shot terahertz energy measurement, based on the terahertz detector calibration device for single-shot terahertz energy measurement according to any one of claims 1 to 4, characterized in that: The steps include: (1) removing the first chopper from the calibration device, using a terahertz source to emit a continuous terahertz signal, and measuring the output voltage of the Golaycell terahertz detector at N modulation frequencies by adjusting the speed of the second chopper; (2) according to the response coefficient of the Golaycell terahertz detector, the measured output voltage at N modulation frequencies, and the transmittance of the terahertz attenuator, the terahertz power reaching the Golaycell terahertz detector at the N modulation frequencies is obtained; (3) obtaining the input power of the Golaycell terahertz detector according to the terahertz powers reaching the Golaycell terahertz detector at N modulation frequencies; (4) adding a first chopper to chop the continuous terahertz signal emitted by the terahertz source into a pulse signal with a low duty cycle, adjusting the second chopper and the optical shutter to obtain single-shot terahertz pulses at M modulation frequencies, and recording the output voltage of the Golaycell terahertz detector at the M modulation frequencies; (5) According to the input power of the Golaycell terahertz detector and the pulse width at the M modulation frequencies, the single-shot terahertz energy at the M modulation frequencies is obtained; (6) obtaining a single-shot measurement responsivity based on the single-shot terahertz energy at the M modulation frequencies obtained in step (5) and the output voltage of the corresponding Golaycell terahertz detector obtained in step (4); (7) Based on the responsivity of the single-shot measurement and the output voltage of the Golaycell terahertz detector, the single-shot terahertz energy can be estimated.

6. The terahertz detector calibration method for single-shot terahertz energy measurement according to claim 5, characterized in that: The step (2) is specifically: P=(V / C) / T Where: P is the terahertz power reaching the Golaycell terahertz detector; V is the measured peak-to-peak value of the output voltage of the Golaycell terahertz detector; C is the response coefficient in the Golaycell terahertz detector manual; T is the transmittance of the terahertz attenuator.

7. The terahertz detector calibration method for single-shot terahertz energy measurement according to claim 5, characterized in that: The step (3) is specifically: selecting the terahertz power reaching the Golaycell terahertz detector at the lowest modulation frequency or the minimum terahertz power reaching the Golaycell terahertz detector among N modulation frequencies as the input power of the Golaycell terahertz detector.

8. The terahertz detector calibration method for single-shot terahertz energy measurement according to claim 5, characterized in that: The step (5) is specifically as follows: the input power of the Golaycell terahertz detector is multiplied by the pulse width of the single-shot terahertz signal to obtain the single-shot terahertz energy.

9. The terahertz detector calibration method for single-shot terahertz energy measurement according to claim 5, characterized in that: The step (6) specifically comprises: performing a linear fit on the single-shot terahertz energy at M modulation frequencies and the output voltage of the corresponding Golaycell terahertz detector, wherein the slope of the fitting curve is the responsivity of the single-shot measurement.

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