CN117147485A - Photon mixing terahertz spectrometer - Google Patents
Photon mixing terahertz spectrometer Download PDFInfo
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- CN117147485A CN117147485A CN202311189236.XA CN202311189236A CN117147485A CN 117147485 A CN117147485 A CN 117147485A CN 202311189236 A CN202311189236 A CN 202311189236A CN 117147485 A CN117147485 A CN 117147485A
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- 238000001514 detection method Methods 0.000 claims abstract description 43
- 230000003287 optical effect Effects 0.000 claims abstract description 35
- 230000005855 radiation Effects 0.000 claims abstract description 23
- 239000013307 optical fiber Substances 0.000 claims description 31
- 230000010287 polarization Effects 0.000 claims description 14
- 239000000835 fiber Substances 0.000 claims description 13
- 238000001228 spectrum Methods 0.000 claims description 9
- 230000003321 amplification Effects 0.000 claims description 8
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 8
- 238000005070 sampling Methods 0.000 claims description 4
- 238000004804 winding Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 27
- 238000010521 absorption reaction Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 9
- 239000004065 semiconductor Substances 0.000 description 5
- 230000003595 spectral effect Effects 0.000 description 4
- 230000005684 electric field Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000035559 beat frequency Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000012792 core layer Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000035772 mutation Effects 0.000 description 1
- 238000000819 phase cycle Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
- G01N21/3586—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation by Terahertz time domain spectroscopy [THz-TDS]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/59—Transmissivity
Abstract
A photon mixing terahertz spectrometer comprises two lasers, two beam splitters, terahertz photoconductive radiation antennas, terahertz beam splitters, an optical delay line, two terahertz photoconductive detection antennas, two phase-locked amplifying modules, an emission power supply module and a control module. The spectrometer adopts double-path detection and simultaneous measurement, and can reduce the requirement on the stability of the laser and improve the measurement efficiency by utilizing the intensity and phase contrast of the double paths, and can stably and accurately obtain the phase delay amount of the measurement sample to the terahertz wave, thereby calculating the refractive index and the absorption coefficient of the sample.
Description
Technical Field
The invention relates to the field of terahertz spectrum measurement based on photon mixing, in particular to a terahertz photon mixing spectrometer capable of measuring the phase delay of a sample.
Background
In the terahertz wave field, general spectrometers mainly include a terahertz time-domain spectrometer, a back-wave tube terahertz spectrometer, a semiconductor terahertz spectrometer, and a photon mixing terahertz spectrometer. The terahertz time-domain spectrometer has wide spectral range, but lower spectral resolution and high equipment cost. The backward wave tube terahertz spectrometer has high resolution, but the output has large fluctuation along with the change of frequency, and the problem of high equipment cost is also faced. Semiconductor terahertz spectrometers are small in size and low in cost, but the spectral ranges of a single radiation source and detector are narrow, and multiple combinations are required to complete the spectral test. The photon mixing terahertz spectrometer has the advantages of wide spectrum range, high resolution, small volume and low cost, and is therefore valued.
The photon mixing terahertz spectrometer is equipment which mixes two beams of laser with the difference value of the frequencies being terahertz, irradiates the photoconductive transmitting antenna and the photoconductive detecting antenna respectively to generate and detect terahertz waves and completes spectrum test. The signal output by the photoconductive detection antenna is related to the phase difference between the terahertz wave at the detection antenna and the laser mixing low-frequency signal, so that the maximum value of the detection signal needs to be obtained as the intensity of the terahertz wave electric field on the premise of actively modulating the phase difference.
However, in a large number of spectroscopic tests, it is necessary to obtain the phase retardation of the sample. If the refractive index spectrum and the absorption coefficient spectrum of the sample need to be obtained in the material test, the phase modulation type metamaterial needs to obtain the phase mutation condition at the resonance frequency. At present, all the measurements can only be tested by a terahertz time-domain spectrometer.
In the measurement of the photon mixing terahertz spectrometer, although the terahertz wave electric field change curve can be drawn by adjusting an optical delay line, the initial phase of the terahertz wave electric field change curve can be obtained through calculation. However, due to the reasons that the phase, the optical delay line position, the optical path change and the like can be reset by frequency switching, the existing photon mixing terahertz spectrometer can only perform the transmittance test and cannot be qualified for the phase delay test.
Disclosure of Invention
In order to solve the problems, the invention discloses a photon mixing terahertz spectrometer which can be used for simultaneously carrying out transmittance test and phase delay test. The invention comprises the following specific contents:
the utility model provides a photon mixing terahertz spectrum appearance, includes first laser instrument, second laser instrument, first beam splitter, second beam splitter, terahertz photoconduction radiation antenna, first terahertz photoconduction detection antenna, second terahertz photoconduction detection antenna, terahertz beam splitter, optical delay line, emission power module, first lock-in amplification module, second lock-in amplification module and control module, wherein:
the first laser and the second laser are both continuously output and the output laser has the same polarization state, and at least one of the first laser and the second laser is a laser with adjustable output frequency.
The first beam splitter is a two-in two-out beam splitter, the first beam splitter right divides the laser output by the first laser and the second laser into two beams for output after combining, and each beam of output light contains the laser output by the first laser and the laser output by the second laser.
One output beam of the first beam splitter is used as pump light of the terahertz photoconductive radiation antenna, and the other output beam group of the first beam splitter is used as an input beam of the second beam splitter.
The second beam splitter is a one-in two-out beam splitter, and the second beam splitter divides an input beam into two beams and then respectively serves as pump light of the first terahertz photoconduction detection antenna and the second terahertz photoconduction detection antenna.
The terahertz wave beam radiated by the terahertz photoconductive radiation antenna is divided into two beams by the terahertz beam splitter and is respectively used as input signals of the first terahertz photoconductive detection antenna and the second terahertz photoconductive detection antenna.
The optical delay line may be located between the first beam splitter and the terahertz photoconductive radiation antenna or between the first beam splitter and the second beam splitter.
The transmitting power supply module provides alternating power for the terahertz photoconductive radiation antenna and transmits the same-frequency signal to the first phase-locked amplifying module and the second phase-locked amplifying module.
The first phase-locked amplifying module is connected with the output end of the first terahertz photoconduction detection antenna and is responsible for amplifying the output signal of the first terahertz photoconduction detection antenna.
The second lock-in amplifying module is connected with the output end of the second terahertz photoconduction detection antenna and is responsible for amplifying the output signal of the second terahertz photoconduction detection antenna.
After the control module controls and changes the output frequency of the first laser or the second laser, the optical delay line is started and the output values of the first phase-locked amplifying module and the second phase-locked amplifying module are recorded.
Further, the output beam splitting ratio of the first beam splitter is 1:2, the output end with the 1/3 ratio is used as the pump light of the terahertz photoconductive radiation antenna, and the output end with the 2/3 ratio is used as the input end of the second beam splitter.
Further, neither the first beam splitter nor the second beam splitter changes the polarization state of the operated laser light.
Further, the sample to be measured can be located on any one of two terahertz waves output by the terahertz beam splitter, and the terahertz beam with larger intensity is used as the optimal choice.
Further, after each signal acquisition, two terahertz photoconductive detection antennas respectively correspond to a section of discrete sinusoidal signals, and the amplitude and the initial phase of each signal need to be obtained through calculation.
Further, the difference value of the two initial phases obtained by sampling at the same time when the sample is not placed is used as a reference phase, the difference value of the two initial phases obtained by sampling at the same time when the sample is placed is used as a signal phase, and the phase delay amount of the frequency point of the measured sample is obtained by subtracting the reference phase from the signal phase.
Further, when a wound optical fiber optical delay line is used as the optical delay line, the optical delay line further comprises a compensating optical fiber; the compensating optical fiber and the optical fiber used in the winding type optical fiber optical delay line have the same or similar lengths; when the optical delay line is positioned between the first beam splitter and the terahertz photoconductive radiation antenna, the compensating optical fiber is positioned between the first beam splitter and the second beam splitter; when the optical delay line is located between the first beam splitter and the second beam splitter, the compensation fiber is located between the first beam splitter and the terahertz photoconductive radiation antenna.
The beneficial effects of the invention are as follows:
(1) The phase delay amount of the sample to the terahertz wave can be stably and accurately obtained. Because of adopting the double-path detection to measure simultaneously, the influence of interference factors of laser frequency switching, optical delay line positioning and various light path disturbance on phase measurement on output values of two detectors is the same, and the only factor affecting the phase is the optical path difference of two detection branches. The insertion of the sample itself alters this optical path difference so that it can be accurately measured.
(2) The requirement for the stability of the laser is reduced. In the measuring process of the photon mixing spectrometer with the traditional structure, the reference signal and the sample signal are measured separately, and the stability requirement on the laser is high, so that the cost is increased. In the invention, the two-way detection is used for simultaneous measurement, the influence of the power floating of the laser on the two-way detection is the same, and the two-way detection can be removed through calculation.
(3) And the measurement efficiency is improved. As the measurement results are obtained by comparing the two paths of detection signals, the measurement times of the reference signals can be greatly reduced in actual measurement, thereby improving the measurement efficiency.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment photon mixing terahertz spectrometer.
Fig. 2 is an example of reference signal measurements and a fitted curve.
Fig. 3 is an example of sample signal measurements and a fitted curve.
Detailed Description
The following describes specific embodiments of the present invention with reference to the drawings.
The first laser (11) is a continuous output line polarized semiconductor laser, and has an output wavelength of 1550.03nm and an output power of about 60mW. The second laser (12) is a continuous output line polarized semiconductor laser with adjustable output laser frequency, the output wavelength is adjustable in the range of 1520-1630nm, and the output power is about 60mW. The laser beams output by the first laser (11) and the second laser (12) have the same polarization state. The output ends of the first laser (11) and the second laser (12) are provided with optical fiber coupling modules, and output laser can be coupled into a single-mode polarization maintaining optical fiber. The invention is not limited to be realized by using the optical fiber system, but compared with a free space optical path, the optical path construction and the component selection of the optical fiber system are more flexible, so that the optical fiber is selected to be used for realizing the related functional optical path in the embodiment. The optical fiber jumper, the optical fiber beam splitter, the optical fiber retarder and the like used in the embodiment are all single-mode polarization maintaining optical fibers to ensure that the polarization state of the laser is not changed.
The first beam splitter (21) is a two-in two-out single-mode polarization maintaining fiber beam splitter. The beam splitter splits two input laser beams into two beams according to the ratio of 1:2. It should be noted that there is no need to split beams exactly in a 1:2 ratio. In order to reduce the component cost, the first beam splitter (21) can also be formed by cascading a two-in-one-out optical fiber combiner and a one-in-two-out optical fiber beam splitter with a beam splitting ratio of 1:2.
The output end of the first beam splitter (21) with the proportion of 1/3 is connected to the terahertz photoconductive radiation antenna (41) after passing through the compensating optical fiber (32). The compensation fiber (32) is a single-mode polarization maintaining fiber with a length of about 60 meters, and is mainly used for compensating the phase delay caused by the fiber optical delay line (31). The terahertz photoconductive radiation antenna (41) is a commercial integrated module, uses a single-mode polarization maintaining fiber jumper to input pump beat frequency laser, uses a coaxial cable to input bias voltage, and outputs parallel terahertz beams.
The output end of the first beam splitter (21) with the proportion of 2/3 is connected to the second beam splitter (22) after passing through the optical fiber optical delay line (31). The optical fiber optical delay line (31) is formed by tightly winding a core layer formed by piezoelectric ceramics by a section of single-mode polarization maintaining optical fiber. The length of the fiber is about 60 meters and can be varied by 400 microns under the control of the piezoelectric ceramic. Since the length of the optical fiber is too long and exceeds the coherence length of the semiconductor laser, the coherence measurement effect is affected, and a compensating optical fiber (32) needs to be added in another optical path to eliminate the influence on the coherence of the laser.
The second beam splitter (22) is a one-in two-out single-mode polarization maintaining fiber beam splitter with a beam splitting ratio of 1:1. The two output ends of the antenna are respectively connected to a first terahertz photoconduction detection antenna (51) and a second terahertz photoconduction detection antenna (52). The two terahertz photoconductive detection antennas are the same commercial integrated module, receive parallel terahertz wave beams, input pump beat frequency laser by using a single-mode polarization maintaining fiber jumper, and output detection signals by using a coaxial cable.
The terahertz beam output by the terahertz photoconductive radiation antenna (41) is divided into two beams by the terahertz beam splitter (7) after the direction of the terahertz beam is adjusted by the metal reflector (61). The terahertz beam splitter (7) is a high-resistance silicon wafer with double-sided polishing. Because the refractive index of the silicon wafer in the terahertz wave band is higher, the light splitting ratio is not strictly 1:1, but the light splitting ratio has no influence on the light splitting test. The terahertz wave reflected by the terahertz beam splitter (7) is directly irradiated to the input end of the first terahertz photoconductive detection antenna (51). The terahertz wave beam transmitted through the terahertz beam splitter (7) passes through the sample stage (8) and then is reflected to the input end of the second terahertz photoconductive detection antenna (52) by the metal reflector (62).
In terms of circuitry, fig. 1 reveals all circuit wiring using dashed line identification. The bias voltage required by the terahertz photoconductive radiation antenna (41) is provided by a transmitting power supply module (42). The offset voltage output by the transmitting power supply module (42) is not direct current, but a square wave signal of about 5KHz, and the peak-to-peak value is 2.5V. This is to generate a terahertz wave of 5KHz in order to facilitate the operation of lock-in amplification in the following signal processing. The transmitting power supply module (42) also outputs TTL waves with the same frequency as the bias voltage as reference signals for phase-locked amplification in signal processing.
The current signal output by the first terahertz photoconduction detection antenna (51) is received by a first phase-locking amplification module (53), and the current signal output by the second terahertz photoconduction detection antenna (52) is received by a second phase-locking amplification module (54). Both phase-locked amplifying modules use TTL signals output by the transmitting power supply module (42) as phase-locked amplified reference signals. Besides amplifying, the two phase-locked amplifying modules can convert the amplified signals into digital signals and output the digital signals to a computer (9) through a serial port.
The computer (9) controls the starting and closing of the first laser (11) through the serial port, controls the starting, closing and output wavelength adjustment of the second laser (12) through the serial port, and controls the internal voltage of the optical fiber optical delay line (31) through the serial port so as to realize the control of different delay amounts. Thus, the computer (9) needs to be provided with 5 serial ports. The other 4 serial ports are realized by a USB-to-4 serial port adapter except the serial port of the computer (9).
In the measurement of each frequency point, a computer (9) is required to control the optical fiber optical delay line (31) to uniformly and continuously change the delay amount, and simultaneously, the output values of the two terahertz photoconductive detection antennas (51 and 52) are respectively detected and recorded. When the sample was not placed, the recording results are shown as black squares (51 output values) and open squares (52 output values) in fig. 2. The measurements were triangulated using a mathematical tool, the fitting results being shown in fig. 2 as solid lines (51 fitting results) and dashed lines (52 fitting results). From the fitting, the amplitude I for the output of (51) 1R =5.60, initial phase Φ 1R =28.6°; for the output of (52), amplitude I 2R =7.31, initial phase Φ 2R =108.7°。
After placing the sample on the sample stage (8), the laser output wavelength is changed and then readjusted back to the original value, and then the measurement is repeated. The measurement and fitting results are shown in fig. 3. From the fitting, the amplitude I for the output of (51) 1S =5.63, initial phase Φ 1S = 257.8 °; for the output of (52), amplitude I 2S =3.96, initial phase Φ 2S = 392.6 °. As can be seen from fig. 3, although the first terahertz photoconductive detection antenna (51) is measuring the same signal, the initial phase difference obtained by measurement is 229.2 ° due to the change of the laser mode, and the intensity obtained by measurement is also 0.03 ° due to the instability of the laser output. But due to the two-way simultaneous measurement, the true result of the sample can be obtained by the following calculation:
t=(I 2S /I 1S )/( I 2R /I 1R )= (I 2S /I 2R )×( I 1R /I 1S )≈0.54
T=t 2 ≈0.29
Φ=(Φ 2S -Φ 1S )-(Φ 2R -Φ 2R )≈54.7°
from this, it was found that the transmittance T of the sample at this frequency was 0.29 and the phase retardation Φ was 54.7 °. Of course, due to the periodicity of the trigonometric function calculation itself, the true phase delay amount Φ should be (360×n+54.7) °, where n is an integer not less than 0. For a single frequency point measurement, the specific value of n is indeterminate. But n may be implemented by successive accumulation for the case of measurements made sequentially from low to high frequency. Most data processing tools now have a phase unwrapping function to automatically calculate n for a phase sequence.
In the spectrum measurement process, the computer (9) controls the output wavelength of the second laser (12) to gradually change from 1550.11nm to 1570.30nm, and records and processes data one by one, so that the spectrum recording in the frequency range from 0.01THz to 2.50THz can be completed. Although the second laser (12) can output laser light of a longer wavelength, the highest frequency to which the terahertz photoconductive radiation antenna (41) can respond has been exceeded, and therefore is not used in actual measurement.
The optical paths in the embodiment are based on optical fibers, and the beam splitters and the beam combiners are optical fiber beam splitters and optical fiber beam combiners. The invention is not limited to the form of the light path. The free space optical path is already a common crystal or sheet beam splitter and combiner and the optical path of the present invention can also be implemented.
Claims (7)
1. The utility model provides a photon mixing terahertz spectrum appearance, its characterized in that includes first laser instrument, second laser instrument, first beam splitter, second beam splitter, terahertz photoconduction radiation antenna, first terahertz photoconduction detection antenna, second terahertz photoconduction detection antenna, terahertz beam splitter, optical delay line, emission power supply module, first lock-in amplification module, second lock-in amplification module and control module, wherein:
the first laser and the second laser are continuously output and the output laser has the same polarization state, and at least one of the first laser and the second laser is a laser with adjustable output frequency;
the first beam splitter is a two-in two-out beam splitter, the first beam splitter right divides the laser output by the first laser and the second laser into two beams for output after combining, and each beam of output light contains the laser output by the first laser and the laser output by the second laser;
one output beam of the first beam splitter is used as pump light of the terahertz photoconductive radiation antenna, and the other output beam group of the first beam splitter is used as an input beam of the second beam splitter;
the second beam splitter is a first-in second-out beam splitter, and the second beam splitter divides an input beam into two beams and then respectively serves as pump light of the first terahertz photoconduction detection antenna and the second terahertz photoconduction detection antenna;
the terahertz wave beam radiated by the terahertz photoconductive radiation antenna is divided into two beams by the terahertz beam splitter and is respectively used as input signals of the first terahertz photoconductive detection antenna and the second terahertz photoconductive detection antenna;
the optical delay line may be located between the first beam splitter and the terahertz photoconductive radiation antenna, or may be located between the first beam splitter and the second beam splitter;
the transmitting power supply module provides alternating power for the terahertz photoconductive radiation antenna and transmits the same-frequency signal to the first phase-locked amplifying module and the second phase-locked amplifying module;
the first phase-locked amplifying module is connected with the output end of the first terahertz photoconduction detection antenna and is responsible for amplifying the output signal of the first terahertz photoconduction detection antenna;
the second phase-locked amplifying module is connected with the output end of the second terahertz photoconduction detection antenna and is responsible for amplifying the output signal of the second terahertz photoconduction detection antenna;
and after the control module controls and changes the output frequency of the first laser or the second laser, starting the optical delay line and recording the output values of the first phase-locked amplifying module and the second phase-locked amplifying module.
2. The photonic mixing terahertz spectrometer of claim 1, wherein the output beam splitting ratio of the first beam splitter is 1:2, with an output of 1/3 being used as pump light for the terahertz photoconductive radiation antenna, and an output of 2/3 being used as an input for the second beam splitter.
3. The photonic mixing terahertz spectrometer of claim 1, wherein neither the first beam splitter nor the second beam splitter changes the polarization state of the operating laser light.
4. The photonic mixing terahertz spectrometer of claim 1, wherein the sample to be measured can be located on any one of two terahertz waves output by the terahertz beam splitter, and a terahertz beam with a larger intensity is selected as an optimal choice.
5. The photonic mixing terahertz spectrometer of claim 1, wherein after each signal acquisition, two terahertz photoconductive detection antennas each correspond to a segment of discrete sinusoidal signals, and the amplitude and initial phase of each signal need to be obtained by calculation.
6. A photonic mixing terahertz spectrometer according to claims 1 and 5, characterized in that the difference between two initial phases obtained by simultaneous sampling when no sample is placed is used as a reference phase, the difference between two initial phases obtained by simultaneous sampling when a sample is placed is used as a signal phase, and the phase delay of the frequency point again of the sample to be measured is obtained by subtracting the reference phase from the signal phase.
7. The photonic mixed terahertz spectrometer of claim 1, further comprising a compensation fiber when a wound fiber optic delay line is used as the optical delay line; the compensating optical fiber and the optical fiber used in the winding type optical fiber optical delay line have the same or similar length; the compensating fiber is positioned between the first beam splitter and the second beam splitter when the optical delay line is positioned between the first beam splitter and the terahertz photoconductive radiation antenna; the compensation fiber is positioned between the first beam splitter and the terahertz photoconductive radiation antenna when the optical delay line is positioned between the first beam splitter and the second beam splitter.
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| CN202311189236.XA CN117147485A (en) | 2023-09-15 | 2023-09-15 | Photon mixing terahertz spectrometer |
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| CN202311189236.XA CN117147485A (en) | 2023-09-15 | 2023-09-15 | Photon mixing terahertz spectrometer |
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