CN112611736B - Terahertz wave band spectrum diffuse reflectance calibration device - Google Patents
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Abstract
The invention belongs to the technical field of optical metering, mainly relates to a terahertz calibration device, and particularly relates to a terahertz waveband spectrum diffuse reflectance calibration device. The continuous terahertz radiation type spectrum diffuse reflectance calibration device is formed by a continuous terahertz radiation emission system, a terahertz diffuse reflectance integrating sphere transfer standard and a high-yield terahertz detection system; a terahertz pulse emission system, a time delay system, a terahertz diffuse reflection integrating sphere transmission standard and a terahertz pulse detection system are adopted to form a pulse terahertz radiation type spectrum diffuse reflection ratio calibration device; therefore, the calibration of the terahertz diffuse reflectance parameter testing equipment for the material in the (0.1-3) THz waveband range is realized, the problem of accurate testing of terahertz diffuse reflectance of various non-polar materials widely applied at present is solved, and the terahertz diffuse reflectance parameter testing equipment has a wide application prospect.
Description
Technical Field
The invention belongs to the technical field of optical measurement, mainly relates to a terahertz calibration device, and particularly relates to a terahertz waveband spectrum diffuse reflectance calibration device.
Background
The international material detection technology mainly comprises a terahertz time-domain spectroscopy detection technology, millimeter wave scanning, a laser induction breakdown spectroscopy detection technology and the like. By adopting the terahertz time-domain spectroscopy detection principle, the method can image the concealed article and identify the residual trace substance components on the surface of the article, and has the advantages of a radiographic detection technology and a trace detection technology. The terahertz spectrum technology is widely applied to the field of material identification.
In recent years, with the wide application of non-polar materials such as stealth materials, special coatings, engineering plastics, carbon fibers, biochemical warfare agents, toxic agents, explosives and the like in the fields of special combat hidden target detection, tactical confidential communication, deep space exploration and communication, nondestructive testing of materials, anti-terrorism mine detection and the like, the accurate measurement of the spectral diffuse reflectance of the terahertz waveband spectrum of the material is required.
In the utility model discloses an in "optics integrating sphere and sample terahertz reflection spectrum collection system now", related to an optics integrating sphere and sample terahertz reflection spectrum collection system now, solved the terahertz spectrum reflection collection efficiency and the test result precision of the sample that awaits measuring because of the response difference of sample form, terahertz beam shape and terahertz detection antenna different positions now to the terahertz reflection spectrum collection efficiency who leads to is low, the great problem of test result error.
However, compared with the existing needs, the scheme has the following problems: 1) The method for irradiating the terahertz radiation antenna by using the pump light of the laser light source generates terahertz light beams, and the terahertz light beams obtained by the method are pulse terahertz light beams which are not suitable for the situation of measuring the diffuse reflectance of the continuous terahertz radiation spectrum; 2) Only one optical integrating sphere and a sample terahertz reflection spectrum acquisition device are designed, a calibration method is not provided, and the accuracy of a measurement result cannot be guaranteed.
Disclosure of Invention
Technical problem to be solved
The technical problem to be solved by the invention is as follows: how to provide a terahertz spectrum diffuse reflectance calibration device.
(II) technical scheme
In order to solve the above technical problem, the present invention provides a terahertz waveband spectrum diffuse reflectance calibration apparatus, including: the device comprises a continuous terahertz radiation type spectrum diffuse reflectance calibration device and a pulse terahertz radiation type spectrum diffuse reflectance calibration device;
the continuous terahertz radiation type spectrum diffuse reflectance calibration device is used for (0.1-3) calibrating the terahertz spectrum diffuse reflectance parameter at a certain specific frequency within the THz range; the pulse terahertz radiation type spectrum diffuse reflectance calibration device is used for calibrating terahertz spectrum diffuse reflectance parameters in a THz full spectrum range (0.1-3).
Wherein the continuous terahertz radiation type spectral diffuse reflectance calibration device includes: the system comprises a continuous terahertz radiation emission system, a first terahertz diffuse reflection integrating sphere transfer standard component 2 and a Gaolai terahertz detection system 3;
the continuous terahertz radiation emission system comprises emission sources with different frequencies including an avalanche terahertz source 1-1, a Schottky terahertz source 1-2, a frequency doubling terahertz source 1-3, a terahertz gas laser 1-4 and a terahertz quantum cascade laser 1-5, and the corresponding emission sources are selected according to the required terahertz radiation frequency;
the continuous terahertz radiation emission system is placed at a first entrance port 2-1 of a first terahertz diffuse reflection integrating sphere transmission standard component 2, and the center of the emitted terahertz radiation and the geometric center of the first entrance port 2-1 are located on the same optical axis;
the first terahertz diffuse reflection integrating sphere transmission standard component 2 comprises three different sizes, the diameters of the three different sizes are respectively 30mm, 50mm and 80mm, and the achievable spectral diffuse reflection ratio range is 0.5-0.8; the first terahertz diffuse reflection integrating sphere transmits a gold-plated film of a standard component 2, and comprises a first entrance port 2-1, a first sample window 2-2, a first terahertz radiation absorption trap 2-3, a first detection port 2-4 and a first standard metal plane reflector 2-5; the terahertz radiation enters a first terahertz diffuse reflection integrating sphere transmission standard component 2 through a first entrance port 2-1, a first sample window 2-2 is opposite to the first entrance port 2-1, and a first standard metal plane reflector 2-5 and a first material sample block 2-6 with known reflectance are placed in sequence during calibration; a first terahertz radiation absorption trap 2-3 is arranged in the integrating sphere corresponding to the mirror reflection direction of the standard metal plane reflector; the first standard metal plane mirror 2-5 diffuse reflectance is known and calibrated;
the high-yield terahertz detection system 3 receives terahertz spectrum diffuse reflection information of a first terahertz diffuse reflection integrating sphere transmission standard component 2 and comprises a chopper 3-1 and a high-yield detector 3-2; the chopper 3-1 is placed at a first detection port 2-4, and the geometric center of the first detection port 2-4 and the geometric center of a probe of the Gaolai detector 3-2 are positioned on the same optical axis; the chopper piece of the chopper 3-1 is set to realize complete covering detection and terahertz radiation modulation, and a fixed shaft of the chopper can not shield terahertz radiation; the tall-rice detector 3-2 is placed close to the chopping plate to ensure that the terahertz radiation is incident as completely as possible.
Wherein the pulsed terahertz radiation type spectral diffuse reflectance calibration device comprises: the pulse terahertz radiation type spectrum diffuse reflectance calibration device comprises a terahertz pulse emission system, a second terahertz diffuse reflection integrating sphere transfer standard component 02, a time delay system 03 and a terahertz pulse detection system 04
The terahertz pulse transmitting system comprises a femtosecond laser 01-1, a beam splitter 01-2 and a terahertz transmitting antenna 01-3; the method comprises the following steps that a femtosecond laser pulse emitted by a femtosecond laser device 01-1 is divided into two beams by a beam splitter 01-2, one beam is a pumping beam and is incident to a terahertz emission antenna to excite terahertz pulse radiation; the other beam is a probe beam and enters the time delay system 03 to adjust the optical path;
the second terahertz diffuse reflection integrating sphere transmission standard component 02 is the same as the first terahertz diffuse reflection integrating sphere transmission standard component 2; pulse terahertz radiation emitted by the terahertz transmitting antenna 01-3 enters the second terahertz diffuse reflection integrating sphere transmission standard component 02 through the second entrance port 02-1, and the geometric center of the terahertz transmitting antenna 01-3 and the geometric center of the second entrance port 02-1 are located on the same optical axis;
the time delay system 03 adopts a mode that a one-dimensional electric translation stage 03-1 is combined with a plane mirror 04-1 or an optical fiber 03-2 to adjust the optical path of a detection beam to be equal to that of a pump beam;
the terahertz pulse detection system 04 comprises a plane reflector 04-1, a parabolic mirror 04-2, a terahertz detection antenna 04-3 and a photoelectric weak signal processing system 04-4; the femtosecond laser beam is converted to the parabolic mirror 04-2 by the plane reflector 04-1, the parabolic mirror 04-2 is provided with a small hole, and the femtosecond laser beam and the terahertz beam simultaneously pass through the small hole and are focused to the terahertz detection antenna 04-3 by the parabolic mirror 04-2; the photoelectric weak signal processing system 04-4 processes the signal detected by the detection antenna to obtain a terahertz spectrum diffuse reflectance value; the geometric center of the plane reflector 04-1 and the geometric center of the plane reflector on the one-dimensional electric translation stage 03-1 are positioned on the same optical axis, and the geometric center of the parabolic mirror 04-2 in the x direction, the geometric center of the plane reflector 04-1 and the geometric center of the terahertz detection antenna 04-3 are positioned on the same optical axis; the focus of the parabolic mirror 04-2 is located at the first detection port 2-4, and the geometric center of the parabolic mirror in the y direction and the geometric center of the first detection port 2-4 are located on the same optical axis.
In the continuous terahertz radiation type spectrum diffuse reflectance calibration device, an optical path from a continuous terahertz radiation emission system to a high-yield terahertz detection system 3 is placed in a first shielding case 4.
The first shielding cover 4 is made of acrylic materials and provided with a nitrogen input port and an air outlet, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
In the pulse terahertz radiation type spectrum diffuse reflectance calibration device, an optical path from a terahertz transmitting antenna 01-3 to a Hertz detecting antenna 04-3 is placed in a second shielding case 05.
The second shielding case 05 is made of acrylic materials and provided with a nitrogen input port and an air outlet, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
Aiming at the continuous terahertz radiation type spectrum diffuse reflectance calibration process, the calibration steps are as follows:
step 1: a block of known reflectance is given as ρ 0λ The first standard metal plane reflector 2-5 is closely attached to the first sample window 2-2;
and 2, step: starting a continuous terahertz radiation type spectrum diffuse reflectance calibration device, and measuring a terahertz reflection flux signal I of the first standard metal plane reflector 2-5 0 ；
And step 3: replacing a first material sample block 2-6 to be calibrated at the same position, wherein the error is in the order of mum, the regular reflection part reflected by the sample completely enters a first terahertz radiation absorption trap 2-3 to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz waveband reflection flux signal is measured to be I, and the spectral diffuse reflection ratio rho of the material sample block in the terahertz waveband is calculated according to the formula (1) λ
Aiming at the calibration process of the pulse terahertz radiation type spectrum diffuse reflectance, the calibration steps are as follows:
step 1: one piece of known reflectance is rho' 0λ The second standard metal plane reflector 02-5 is closely attached to the second sample window 02-2;
step 2: starting a pulse terahertz radiation type spectrum diffuse reflectance calibration device, and measuring a terahertz reflection flux signal I 'of a second standard metal plane reflector 02-5' 0 ；
And step 3: replacing a second material sample block 02-6 to be corrected at the same position, wherein the error is in the order of mum, the regular reflection part reflected by the sample completely enters a second terahertz radiation absorption well 02-3 to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz wave band reflection flux signal is measured to be I ', and the spectral diffuse reflection ratio rho ' of the material sample block at the terahertz wave band is calculated according to the formula (2) ' λ
During calibration, a material sample block to be calibrated is closely attached to an integrating sphere to be transmitted to a standard sample window, all the part reflected by a sample enters a terahertz radiation absorption trap to be completely absorbed, and the integrating sphere only collects a diffuse reflection part;
and when the standard metal plane reflector and the sample block of the terahertz material to be corrected are required to be placed at the same position of the terahertz diffuse reflection integrating sphere transmission standard, the error is in the order of mum.
(III) advantageous effects
In order to solve the problems of the prior art, the invention provides a terahertz spectrum diffuse reflectance calibration device which comprises: the main characteristics are that:
(1) The device comprises a continuous terahertz radiation type spectrum diffuse reflectance calibration device and a pulse terahertz radiation type spectrum diffuse reflectance calibration device, and is used for calibrating terahertz diffuse reflectance parameter test equipment for materials in a (0.1-3) THz waveband range;
(2) The device provides 3 sets of terahertz diffuse reflection integrating spheres for transmission standard, and the accurate magnitude of the calibrating device is ensured by matching with a standard metal plane reflector with calibrated reflectance.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention provides a continuous terahertz radiation type spectrum diffuse reflectance calibration device and a pulse terahertz radiation type spectrum diffuse reflectance calibration device, which can realize the calibration of terahertz spectrum diffuse reflectance parameters of THz materials in the spectral range of (0.1-3);
(2) The invention provides three terahertz diffuse reflection integrating sphere transmission standards with different sizes, and the accurate magnitude of the terahertz waveband spectrum diffuse reflection ratio range of 0.5-0.8 is realized by combining a metal reflector with known diffuse reflection ratio and calibrated.
Drawings
Fig. 1 is a schematic view of a continuous terahertz radiation type spectral diffuse reflectance calibration apparatus according to the present invention.
Fig. 2 is a schematic diagram of a configuration of a pulsed terahertz radiation type spectral diffuse reflectance calibration apparatus according to the present invention.
Fig. 3 is a schematic diagram of a terahertz diffuse reflection integrating sphere transfer standard.
Detailed Description
In order to make the objects, contents, and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.
In order to solve the above technical problem, the present invention provides a terahertz waveband spectrum diffuse reflectance calibration apparatus, including: the device comprises a continuous terahertz radiation type spectrum diffuse reflectance calibration device and a pulse terahertz radiation type spectrum diffuse reflectance calibration device;
the continuous terahertz radiation type spectrum diffuse reflectance calibration device is used for calibrating terahertz spectrum diffuse reflectance parameters under a certain specific frequency within a THz range (0.1-3); the pulse terahertz radiation type spectrum diffuse reflectance calibration device is used for (0.1-3) calibrating terahertz spectrum diffuse reflectance parameters in the THz full spectrum range.
Wherein the continuous terahertz radiation type spectral diffuse reflectance calibration device includes: the system comprises a continuous terahertz radiation emission system, a first terahertz diffuse reflection integrating sphere transmission standard component 2 and a high-yield terahertz detection system 3;
the continuous terahertz radiation emission system comprises different frequency emission sources including an avalanche terahertz source 1-1, a Schottky terahertz source 1-2, a frequency doubling terahertz source 1-3, a terahertz gas laser 1-4 and a terahertz quantum cascade laser 1-5, and the corresponding emission sources are selected according to the required terahertz radiation frequency;
the continuous terahertz radiation emission system is placed at a first incident port 2-1 of a first terahertz diffuse reflection integrating sphere transmission standard component 2, and the center of the emitted terahertz radiation and the geometric center of the first incident port 2-1 are positioned on the same optical axis;
the first terahertz diffuse reflection integrating sphere transmission standard component 2 comprises three different sizes, the diameters of the three different sizes are respectively 30mm, 50mm and 80mm, and the achievable spectral diffuse reflection ratio range is 0.5-0.8; the first terahertz diffuse reflection integrating sphere transmits a gold-plated film of a standard component 2, and comprises a first entrance port 2-1, a first sample window 2-2, a first terahertz radiation absorption trap 2-3, a first detection port 2-4 and a first standard metal plane reflector 2-5; the terahertz radiation enters a first terahertz diffuse reflection integrating sphere transmission standard component 2 through a first entrance port 2-1, a first sample window 2-2 is opposite to the first entrance port 2-1, and a first standard metal plane reflector 2-5 and a first material sample block 2-6 with known reflectance are placed in sequence during calibration; a first terahertz radiation absorption trap 2-3 is arranged in the integrating sphere corresponding to the mirror reflection direction of the standard metal plane reflector; the first standard metal plane mirror 2-5 diffuse reflectance is known and calibrated;
the high-yield terahertz detection system 3 receives terahertz spectrum diffuse reflection information of a first terahertz diffuse reflection integrating sphere transmission standard component 2 and comprises a chopper 3-1 and a high-yield detector 3-2; the chopper 3-1 is placed at the first detection port 2-4, and the geometric center of the first detection port 2-4 and the geometric center of the probe of the Gaolai detector 3-2 are positioned on the same optical axis; the chopper piece of the chopper 3-1 is set to realize complete covering detection and terahertz radiation modulation, and a fixed shaft of the chopper can not shield terahertz radiation; the tall-rice detector 3-2 is placed close to the chopping plate to ensure that the terahertz radiation is incident as completely as possible.
Wherein the pulsed terahertz radiation type spectral diffuse reflectance calibration device comprises: the pulse terahertz radiation type spectrum diffuse reflectance calibration device comprises a terahertz pulse transmitting system, a second terahertz diffuse reflectance integrating sphere transmission standard component 02, a time delay system 03 and a terahertz pulse detection system 04
The terahertz pulse transmitting system comprises a femtosecond laser 01-1, a beam splitter 01-2 and a terahertz transmitting antenna 01-3; the femtosecond laser pulse emitted by the femtosecond laser device 01-1 is divided into two beams by the beam splitter 01-2, one beam is a pumping beam and is incident to the terahertz transmitting antenna to excite terahertz pulse radiation; the other beam is a probe beam, and is incident to the time delay system 03 for adjusting the optical path;
the second terahertz diffuse reflection integrating sphere transmission standard component 02 is the same as the first terahertz diffuse reflection integrating sphere transmission standard component 2; pulse terahertz radiation emitted by the terahertz transmitting antenna 01-3 enters the second terahertz diffuse reflection integrating sphere transmission standard component 02 through the second entrance port 02-1, and the geometric center of the terahertz transmitting antenna 01-3 and the geometric center of the second entrance port 02-1 are located on the same optical axis;
the time delay system 03 adopts a mode that a one-dimensional electric translation stage 03-1 is combined with a plane mirror 04-1 or an optical fiber 03-2 to adjust the optical path of a detection beam to be equal to that of a pump beam;
the terahertz pulse detection system 04 comprises a plane reflector 04-1, a parabolic mirror 04-2, a terahertz detection antenna 04-3 and a photoelectric weak signal processing system 04-4; the femtosecond laser beams are converted to the parabolic mirror 04-2 by the plane reflector 04-1, the parabolic mirror 04-2 is provided with a small hole, and the femtosecond laser beams and the terahertz beams pass through the small hole simultaneously and are focused to the terahertz detection antenna 04-3 by the parabolic mirror 04-2; the photoelectric weak signal processing system 04-4 processes the signal detected by the detection antenna to obtain a terahertz spectrum diffuse reflection ratio value; the geometric center of the plane reflector 04-1 and the geometric center of the plane reflector on the one-dimensional electric translation stage 03-1 are positioned on the same optical axis, and the geometric center of the parabolic mirror 04-2 in the x direction, the geometric center of the plane reflector 04-1 and the geometric center of the terahertz detection antenna 04-3 are positioned on the same optical axis; the focus of the parabolic mirror 04-2 is located at the first detection port 2-4, and the geometric center of the parabolic mirror in the y direction and the geometric center of the first detection port 2-4 are located on the same optical axis.
In the continuous terahertz radiation type spectrum diffuse reflectance calibration device, an optical path from a continuous terahertz radiation emission system to a high-yield terahertz detection system 3 is placed in a first shielding case 4.
The first shielding cover 4 is made of acrylic materials and provided with a nitrogen input port and an air outlet, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
In the pulse terahertz radiation type spectrum diffuse reflectance calibration device, an optical path from a terahertz transmitting antenna 01-3 to a Hertz detecting antenna 04-3 is placed in a second shielding case 05.
The second shielding case 05 is made of acrylic materials and provided with a nitrogen input port and an air outlet, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
Aiming at the calibration process of the continuous terahertz radiation type spectrum diffuse reflectance, the calibration steps are as follows:
step 1: a block of known reflectance is given as ρ 0λ The first standard metal plane reflector 2-5 is closely attached to the first sample window 2-2;
step 2: starting the continuous terahertz radiation type spectrum diffuse reflectance calibration device, and measuring the terahertz reflected flux signal of the first standard metal plane reflector 2-5 as I 0 ；
And 3, step 3: replacing a first material sample block to be calibrated 2-6 at the same position, wherein the error is in the order of mum, the regular reflection part reflected by the sample completely enters a first terahertz radiation absorption trap 2-3 to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz wave band reflection flux signal is measured to be I, and the material sample block to be calibrated is calculated according to the formula (1)Spectral diffuse reflectance of Hertz band λ
Aiming at the calibration process of the pulse terahertz radiation type spectrum diffuse reflectance, the calibration steps are as follows:
step 1: one block of known reflectance is rho' 0λ The second standard metal plane reflector 02-5 is closely attached to the second sample window 02-2;
and 2, step: starting a pulse terahertz radiation type spectrum diffuse reflectance calibration device, and measuring a terahertz reflected flux signal I 'of a second standard metal plane reflector 02-5' 0 ；
And step 3: replacing a second material sample block 02-6 to be corrected at the same position, wherein the error is in the order of mum, the regular reflection part reflected by the sample completely enters a second terahertz radiation absorption well 02-3 to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz wave band reflection flux signal is measured to be I ', and the spectral diffuse reflection ratio rho ' of the material sample block at the terahertz wave band is calculated according to the formula (2) ' λ
During calibration, a material sample block to be calibrated is closely attached to an integrating sphere to transmit a standard sample window, all the regularly reflected part reflected by a sample enters a terahertz radiation absorption trap to be completely absorbed, and only the diffuse reflection part is collected by the integrating sphere;
and when the standard metal plane reflector and the sample block of the terahertz material to be corrected are required to be placed at the same position of the transmission standard of the terahertz diffuse reflection integrating sphere, the error is in the magnitude of mum.
Example 1
As shown in fig. 1, the continuous terahertz radiation type spectral diffuse reflectance calibration apparatus of the present embodiment includes: the terahertz radiation detection system comprises a continuous terahertz radiation emission system, a first terahertz diffuse reflection integrating sphere transmission standard component 2, a high-yield terahertz detection system 3 and a shielding case 4;
the continuous terahertz radiation emitting system includes: 1-1 parts of an avalanche terahertz source, 1-2 parts of a Schottky terahertz source, 1-3 parts of a frequency doubling terahertz source, 1-4 parts of a terahertz gas laser and 1-5 parts of a terahertz quantum cascade laser;
the output frequency of the avalanche terahertz source 1-1 is 0.1THz, the output frequency of the Schottky terahertz source 1-2 is 0.315THz, the output frequency of the frequency doubling terahertz source 1-3 is 0.66THz, 0.67THz and 0.68THz, the output frequency of the terahertz gas laser is 1.40THz, 1.89THz and 2.35THz, and the output frequency of the terahertz quantum cascade laser 1-5 is 2.944THz; and selecting different terahertz emission sources according to different terahertz radiation frequencies.
The continuous terahertz radiation emission system is placed at a first incident port 2-1 of a first terahertz diffuse reflection integrating sphere transmission standard component 2, and the center of the emitted terahertz radiation and the geometric center of the first incident port 2-1 are positioned on the same optical axis;
the first terahertz diffuse reflection integrating sphere transfer standard component 2 comprises three different sizes, the diameters of the three different sizes are respectively 30mm, 50mm and 80mm, and the achievable spectral diffuse reflection ratio range is 0.5-0.8; the first terahertz diffuse reflection integrating sphere transmits a gold-plated film of a standard component 2 and comprises a first incident port 2-1, a first sample window 2-2, a first terahertz radiation absorption trap 2-3, a first detection port 2-4 and a first standard metal plane reflector 2-5; the terahertz radiation enters a first terahertz diffuse reflection integrating sphere transmission standard component 2 through a first entrance port 2-1, a first sample window 2-2 is opposite to the first entrance port 2-1, and a first standard metal plane reflector 2-5 and a first material sample block 2-6 with known reflectance are placed in sequence during calibration; a first terahertz radiation absorption trap 2-3 is arranged in the integrating sphere corresponding to the mirror reflection direction of the standard metal plane reflector; the substrate material of the first standard metal plane reflector 2-5 is BK7 quartz glass, the surface of the first standard metal plane reflector is plated with a gold film, and the calibration value of the reflectance ratio is 99%;
the high-yield terahertz detection system 3 receives terahertz spectrum diffuse reflection information of the first terahertz diffuse reflection integrating sphere transfer standard component 2 and comprises a chopper 3-1 and a high-yield detector 3-2; chopping blockThe range of the chopping modulation frequency of the wave filter 3-1 is 40 Hz-3.7 kHz, and the modulation frequency stability precision is as follows: 0.05Hz; the Gaolai detector 3-2 is a GC-1P type product of Tydex company, the detection aperture is 5mm, and the spectral range (0.02-20) THz; maximum detection power: 1 x 10 -5 W；
The chopper 3-1 is placed at the first detection port 2-4, and the geometric center of the first detection port 2-4 and the geometric center of the probe of the Gaolai detector 3-2 are positioned on the same optical axis; the chopper piece of the chopper 3-1 is set to realize terahertz radiation modulation, and a fixed shaft of the chopper can not shield terahertz radiation; the Kaully detector 3-2 is placed close to the chopping plate to ensure that the terahertz radiation is incident as completely as possible.
In the continuous terahertz radiation type spectrum diffuse reflectance calibration device, a light path from a continuous terahertz radiation emission system to a high-yield terahertz detection system 3 is placed in a first shielding case 4; the first shielding cover 4 is made of acrylic materials and is provided with a nitrogen input port and an air outlet, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
As shown in fig. 2, the pulse terahertz radiation type spectral diffuse reflectance calibration device includes a terahertz pulse emission system, a second terahertz diffuse reflection integrating sphere transfer standard component 02, a time delay system 03, a terahertz pulse detection system 04, and a second shield case 05, and outputs a terahertz frequency range (0.1-3.0) THz.
The terahertz pulse transmitting system comprises a femtosecond laser 01-1, a beam splitter 01-2 and a terahertz transmitting antenna 01-3; the femtosecond laser pulse emitted by the femtosecond laser device 01-1 is divided into two beams by the beam splitter 01-2, one beam is a pumping beam and is incident to the terahertz transmitting antenna to excite terahertz pulse radiation; the other beam is a probe beam, and is incident to the time delay system 03 for adjusting the optical path; the femtosecond laser 01-1 adopts FFPRONIR-FFVAR model product of TOPTICA company, outputs 780nm and 1560nm with switchable dual wavelength output power of 140mW (780 nm) and 350mW (1560 nm), and pulse width of 100fs (780 nm) and 100fs (1560 nm); the response wavelength of the beam splitter 01-2 is 1560nm; the terahertz transmitting antenna 01-3 adopts a TERA15-TX-FC product of Menlosystems company, the photoconductive material is InGaAs/InAIAs, the central wavelength is 1560nm, the output terahertz frequency range is (0.1-3.0) THz, and the terahertz power is more than 100 mu W.
The second terahertz diffuse reflection integrating sphere transmission standard component 02 is the same as the first terahertz diffuse reflection integrating sphere transmission standard component 2 used in fig. 1; pulse terahertz radiation emitted by the terahertz transmitting antenna 01-3 enters the second terahertz diffuse reflection integrating sphere transmission standard component 02 through the second entrance port 02-1, and the geometric center of the terahertz transmitting antenna 01-3 and the geometric center of the second entrance port 02-1 are located on the same optical axis.
The time delay system 03 adopts a one-dimensional electric translation stage 03-1 or an optical fiber 03-2 to adjust the optical path of the detection light beam to be equal to that of the pump light beam; the one-dimensional electric translation table 03-1 adopts a product of GTS150-SMC100CC model of Newport company, the minimum step is 100nm, the stroke is 150mm, and the precision is +/-0.50 mu m; the optical fiber 03-2 adopts a single mode optical fiber;
the terahertz pulse detection system 04 comprises a plane reflector 04-1, a parabolic mirror 04-2, a terahertz detection antenna 04-3 and a photoelectric weak signal processing system 04-4; the plane reflector 04-1 is a GCCH-1015 femtosecond laser reflector made of K9 glass, and the surface type is lambda/8; the parabolic mirror adopts a MPD229-M01 type surface gold-plated film parabolic mirror of Thorlabs company, and has a reflection focal length of 50.8mm and a caliber of 50.8mm.
The femtosecond laser beam is converted to the parabolic mirror 04-2 by the plane reflector 04-1, the parabolic mirror 04-2 is provided with a small hole, and the femtosecond laser beam and the terahertz beam simultaneously pass through the small hole and are focused to the terahertz detection antenna 04-3 by the parabolic mirror 04-2; and the photoelectric weak signal processing system 04-4 processes the signal detected by the detection antenna to obtain a terahertz spectrum diffuse reflection ratio value. The geometric center of the plane mirror 04-1 and the geometric center of the plane mirror on the one-dimensional electric translation table are located on the same optical axis, and the geometric center of the parabolic mirror 04-2 in the x direction, the geometric center of the plane mirror 04-1 and the geometric center of the terahertz detection antenna 04-3 are located on the same optical axis; the focus of the parabolic mirror 04-2 is located at the first detection port 2-4, and the geometric center of the parabolic mirror in the y direction and the geometric center of the first detection port 2-4 are located on the same optical axis.
In the pulse terahertz radiation type spectrum diffuse reflectance calibration device, a light path from a terahertz transmitting antenna 01-3 to a Hertz detecting antenna 04-3 is placed in a second shielding case 05; the second shielding case 05 is made of acrylic materials and is provided with a nitrogen input port and an air outlet, and nitrogen is filled in during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
Aiming at the calibration process of the continuous terahertz radiation type spectrum diffuse reflectance, the calibration steps are as follows:
step 1: a block of known reflectance is given as ρ 0λ The first standard metal plane reflector 2-5 is closely attached to the first sample window 2-2;
step 2: starting the continuous terahertz radiation type spectrum diffuse reflectance calibration device, and measuring the terahertz reflected flux signal of the first standard metal plane reflector 2-5 as I 0 ；
And step 3: replacing a first material sample block 2-6 to be calibrated at the same position, wherein the error is in the order of mum, the regular reflection part reflected by the sample completely enters a first terahertz radiation absorption trap 2-3 to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz waveband reflection flux signal is measured to be I, and the spectral diffuse reflection ratio rho of the material sample block in the terahertz waveband is calculated according to the formula (1) λ
Aiming at the calibration process of the pulse terahertz radiation type spectrum diffuse reflectance, the calibration steps are as follows:
step 1: one piece of known reflectance is rho' 0λ The second standard metal plane reflector 02-5 is closely attached to the second sample window 02-2;
step 2: starting a pulse terahertz radiation type spectrum diffuse reflectance calibration device, and measuring a terahertz reflected flux signal I 'of a second standard metal plane reflector 02-5' 0 ；
And 3, step 3: replacing a second material sample block 02-6 to be calibrated at the same position, wherein the error is in the order of mum, and the part reflected by the sample regularly enters a second terahertz radiation absorption trap 02-3 is completely absorbed, an integrating sphere collects a diffuse reflection part, a terahertz wave band reflection flux signal is measured to be I ', and the spectral diffuse reflection ratio rho ' of the material sample block in the terahertz wave band is obtained through calculation according to the formula (2) ' λ
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A terahertz waveband spectrum diffuse reflectance calibration device is characterized by comprising: the device comprises a continuous terahertz radiation type spectrum diffuse reflectance calibration device and a pulse terahertz radiation type spectrum diffuse reflectance calibration device;
the continuous terahertz radiation type spectrum diffuse reflectance calibration device is used for calibrating terahertz spectrum diffuse reflectance parameters under a certain specific frequency within the range of 0.1 THz-3 THz; the pulse terahertz radiation type spectrum diffuse reflectance calibration device is used for calibrating terahertz spectrum diffuse reflectance parameters in a full spectrum range of 0.1 THz-3 THz;
wherein the continuous terahertz radiation type spectral diffuse reflectance calibration device includes: the terahertz radiation detection system comprises a continuous terahertz radiation emission system, a first terahertz diffuse reflection integrating sphere transmission standard component (2) and a high-yield terahertz detection system (3);
the continuous terahertz radiation emission system comprises emission sources with different frequencies, including an avalanche terahertz source (1-1), a Schottky terahertz source (1-2), a frequency doubling terahertz source (1-3), a terahertz gas laser (1-4) and a terahertz quantum cascade laser (1-5), and the corresponding emission sources are selected according to the required terahertz radiation frequency;
the continuous terahertz radiation emission system is placed at a first entrance port (2-1) of a first terahertz diffuse reflection integrating sphere transmission standard component (2), and the center of the emitted terahertz radiation and the geometric center of the first entrance port (2-1) are located on the same optical axis;
the first terahertz diffuse reflection integrating sphere transmission standard component (2) comprises three different sizes, the diameters of the three different sizes are respectively 30mm, 50mm and 80mm, and the achievable spectral diffuse reflection ratio range is 0.5-0.8; the first terahertz diffuse reflection integrating sphere transmits a gold-plated film of a standard component (2), and comprises a first entrance port (2-1), a first sample window (2-2), a first terahertz radiation absorption trap (2-3), a first detection port (2-4) and a first standard metal plane reflector (2-5); the terahertz radiation enters a first terahertz diffuse reflection integrating sphere transmission standard component (2) through a first incident port (2-1), a first sample window (2-2) is opposite to the first incident port (2-1), and a first standard metal plane reflector (2-5) with a known reflectance and a first sample block (2-6) to be calibrated are placed in sequence during calibration; a first terahertz radiation absorption trap (2-3) is arranged in the integrating sphere corresponding to the mirror reflection direction of the standard metal plane reflector; the diffuse reflectance of the first standard metal plane mirror (2-5) is known and calibrated;
the high-yield terahertz detection system (3) receives terahertz spectrum diffuse reflection information of a first terahertz diffuse reflection integrating sphere transmission standard component (2), and comprises a chopper (3-1) and a high-yield detector (3-2); the chopper (3-1) is placed at the first detection port (2-4), and the geometric center of the first detection port (2-4) and the geometric center of the probe of the Gaolai detector (3-2) are positioned on the same optical axis; the chopper piece of the chopper (3-1) is set to be capable of realizing complete coverage detection and terahertz radiation modulation, and a fixed shaft of the chopper can not shield terahertz radiation; the Gaolai detector (3-2) is placed close to the chopper slice to ensure that the terahertz radiation is incident as completely as possible;
wherein the pulsed terahertz radiation type spectral diffuse reflectance calibration device comprises: the pulse terahertz radiation type spectrum diffuse reflectance calibration device comprises a terahertz pulse transmitting system, a second terahertz diffuse reflectance integrating sphere transmission standard component (02), a time delay system (03) and a terahertz pulse detection system (04)
The terahertz pulse transmitting system comprises a femtosecond laser (01-1), a beam splitter (01-2) and a terahertz transmitting antenna (01-3); femtosecond laser pulses emitted by a femtosecond laser device (01-1) are divided into two beams by a beam splitter (01-2), one beam is a pumping beam and is incident to a terahertz transmitting antenna to excite terahertz pulse radiation; the other beam is a detection beam and enters a time delay system (03) to adjust the optical path;
the second terahertz diffuse reflection integrating sphere transmission standard component (02) is the same as the first terahertz diffuse reflection integrating sphere transmission standard component (2); pulse terahertz radiation emitted by the terahertz transmitting antenna (01-3) enters the second terahertz diffuse reflection integrating sphere transmission standard component (02) through the second entrance port (02-1), and the geometric center of the terahertz transmitting antenna (01-3) and the geometric center of the second entrance port (02-1) are located on the same optical axis;
the time delay system (03) adopts a mode of combining a one-dimensional electric translation stage (03-1) with a plane mirror (04-1) or an optical fiber (03-2) to adjust the optical path of the detection beam to be equal to that of the pump beam;
the terahertz pulse detection system (04) comprises a plane reflector (04-1), a parabolic mirror (04-2), a terahertz detection antenna (04-3) and a photoelectric weak signal processing system (04-4); the femtosecond laser beam is converted to the parabolic mirror (04-2) by the plane reflector (04-1), the parabolic mirror (04-2) is provided with a small hole, and the femtosecond laser beam and the terahertz beam simultaneously pass through the small hole and are focused to the terahertz detection antenna (04-3) by the parabolic mirror (04-2) after passing through the small hole; the photoelectric weak signal processing system (04-4) processes the signal detected by the detection antenna to obtain a terahertz spectrum diffuse reflection ratio value; the geometric center of the plane reflector (04-1) and the geometric center of the plane reflector on the one-dimensional electric translation table (03-1) are positioned on the same optical axis, and the geometric center of the parabolic mirror (04-2) in the x direction, the geometric center of the plane reflector (04-1) and the geometric center of the terahertz detection antenna (04-3) are positioned on the same optical axis; the focus of the paraboloidal mirror (04-2) is positioned at the first detection port (2-4), and the geometric center of the paraboloidal mirror in the y direction and the geometric center of the first detection port (2-4) are positioned on the same optical axis.
2. The terahertz waveband spectral diffuse reflectance calibration device according to claim 1, wherein in the continuous terahertz radiation type spectral diffuse reflectance calibration device, an optical path from the continuous terahertz radiation emission system to the tolith detection system (3) is placed inside the first shield (4).
3. The terahertz waveband spectrum diffuse reflectance calibration device according to claim 2, wherein the first shielding case (4) is made of acrylic materials and is provided with a nitrogen gas input port and an air discharge port, and nitrogen gas is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
4. The terahertz waveband spectral diffuse reflectance calibration device according to claim 3, wherein in the pulsed terahertz radiation type spectral diffuse reflectance calibration device, an optical path from the terahertz transmission antenna (01-3) to the terahertz detection antenna (04-3) is placed in the second shield case (05).
5. The terahertz waveband spectrum diffuse reflectance calibration device as claimed in claim 4, wherein the second shielding case (05) is made of acrylic material and is provided with a nitrogen input port and an air discharge port, and nitrogen is filled during calibration so as to reduce the influence of water vapor absorption on terahertz radiation.
6. The terahertz waveband spectral diffuse reflectance calibration device according to claim 1, wherein for a continuous terahertz radiation type spectral diffuse reflectance calibration process, the calibration step is:
step 1: a block of known reflectance is given as P 0Λ The first standard metal plane reflector (2-5) is closely arranged at the first sample window (2-2);
step 2: starting the continuous terahertz radiation type spectrum diffuse reflectance calibration device, and measuring the terahertz reflected flux signal of the first standard metal plane reflector (2-5) as I 0 ；
And step 3: the first sample block (2-6) of the material to be calibrated is replaced at the same position, the error is in the magnitude of mum, and the part of the sample reflected by the sample and reflected by the regular reflection part completely enters the first terahertz radiationThe absorption trap (2-3) is completely absorbed, the integrating sphere collects the diffuse reflection part, the terahertz wave band reflection flux signal is measured to be I, and the spectral diffuse reflectance P of the material sample block in the terahertz wave band is calculated according to the formula (1) Λ
7. The terahertz waveband spectral diffuse reflectance calibration device according to claim 1, wherein for a pulsed terahertz radiation type spectral diffuse reflectance calibration process, the calibration step is:
step 1: one piece of known reflectance is P' 0Λ The second standard metal plane reflector (02-5) is closely arranged at the second sample window (02-2);
step 2: starting a pulse terahertz radiation type spectrum diffuse reflectance calibration device, and measuring a terahertz reflected flux signal I 'of a second standard metal plane reflector (02-5)' 0 ；
And step 3: replacing a second material sample block (02-6) to be calibrated at the same position, wherein the error is in the order of mum, the part reflected by the sample and regularly reflected enters a second terahertz radiation absorption trap (02-3) to be completely absorbed, an integrating sphere collects the diffuse reflection part, the terahertz waveband reflection flux signal is measured to be I ', and the spectral diffuse reflection ratio P ' of the material sample block in the terahertz waveband is calculated according to the formula (2) ' Λ
8. The terahertz waveband spectrum diffuse reflectance calibration device according to claim 1, wherein during calibration, a material sample block to be calibrated is tightly attached to an integrating sphere to transmit a standard sample window, all the regular reflection part reflected by the sample enters a terahertz radiation absorption trap to be completely absorbed, and the integrating sphere only collects the diffuse reflection part;
and when the standard metal plane reflector and the sample block of the terahertz material to be corrected are required to be placed at the same position of the transmission standard of the terahertz diffuse reflection integrating sphere, the error is in the magnitude of mum.
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