CN210487596U - High-sensitivity terahertz spectrum detection device for liquid concentration - Google Patents

Abstract

The utility model discloses a high sensitivity terahertz spectrum detection device of liquid concentration, the device include a terahertz metamaterial array structure now, constitute for medium basement, polyethylene apron and the polyethylene closed baffle of silicon by a plurality of lithium tantalite medium cylinder, a material, will await measuring liquid dress between polyethylene apron and silicon substrate, in the cavity of depositing the liquid that awaits measuring that sets up around the medium cylinder. When the terahertz waves are incident from the polyethylene cover plate side, terahertz wave response is obtained on the silicon substrate side, and then terahertz spectrum analysis is carried out. The device has the characteristics of short detection time, capability of working at room temperature and the like, and meanwhile, the analysis device highly integrates a plurality of unit devices together, can efficiently carry out terahertz spectrum analysis on the concentration change of liquid to be detected, and has wide application potential in the aspect of measuring the concentration of the liquid.

Description

High-sensitivity terahertz spectrum detection device for liquid concentration

Technical Field

The utility model belongs to the technical application field of terahertz wave, in particular to high sensitivity terahertz spectrum detection device of liquid concentration.

Background

Terahertz wave (terahertz wave) means a frequency of 0.1 to 10.0THz (1THz is 10)¹²Hz), which is located next to the microwave band and next to the infrared band, has the advantages of both, the spatial resolution is better than that of microwaves, and the penetrability is also stronger than that of infrared rays. The terahertz wave has the characteristic of low photon energy (1THz is about 4.1meV), and does not generate ionization effect to destroy organisms and biological tissues. The terahertz spectrum of a substance has rich information, and due to the fact that chemical molecules such as hydrogen bonds between molecules or in molecules, Van der Waals force, dipole rotation and the like have vibration and rotation energy levels corresponding to a terahertz frequency band, and especially the energy levels of a plurality of organic molecules are located in the band, the molecules have unique transmission spectra in the terahertz frequency band, so that the THz spectrum (including emission, reflection and transmission spectra) of the substance contains rich physical properties and chemical information, and has important application values in the aspects of physics, chemistry, biomedicine, astronomy, material science, environmental science and the like.

The ferroelectric phase lithium tantalate crystal is a universal material in the field of functional materials. They have the advantages of good mechanical and physical properties and low cost, and are widely used in the optical technology industry today as nonlinear optical crystals, electro-optical crystals, piezoelectric crystals, acousto-optical crystals, birefringent crystals, and the like. Previous work has shown that the structure of crystalline materials is closely related to their optical properties.

The spectral analysis is a method for establishing the mutual relation between the molecular structure of a substance and electromagnetic radiation by taking the interaction of the substance and light as a condition on the basis of an optical theory so as to analyze and identify the geometric isomerism, the stereoisomerism, the conformational isomerism and the molecular structure of the substance. Spectroscopic analysis has become one of the major methods for the modern analysis and identification of molecular structures of substances. With the development of science and technology, innovation of technology and computer application, the spectrum analysis is rapidly developed. The wave spectrum analysis method has the characteristics of outstanding advantages, wide application and the like, and is an indispensable tool in various scientific research and production fields. With the development of science and technology and the continuous improvement of analysis requirements, researchers are continuously innovated in the wave spectrum analysis method. The wave spectrum analysis method is a common analysis tool and an important analysis method for material analysis and identification due to the fact that the wave spectrum analysis method is rapid, sensitive and accurate, has low requirements on environmental conditions and plays an important role in detecting the refractive index of a material.

In recent years, with the development of terahertz radiation generation and detection technology, THz technology has achieved many remarkable results. Metamaterials are increasingly being used in the terahertz field as functional devices, such as wave absorbers, filters, modulators, sensors and polarizers. In particular, the THz metamaterial has great potential in the aspect of non-ionization biochemical sensing application, not only because many substances have fingerprint spectrums in THz wave bands. Compared with the conventional terahertz time-domain spectroscopy method, the terahertz metamaterial-based sensing measurement method has the advantages of simplicity and convenience and higher sensitivity. Therefore, the terahertz sensor based on the metamaterial has been a hot spot for the research of the THz technology.

Disclosure of Invention

The utility model discloses an overcome the not enough of current liquid concentration detection method, utilize terahertz wave to carry out the analysis and detection of liquid concentration to the transmission characteristic of liquid, provided a liquid concentration's high sensitivity terahertz spectrum sensing detection device now, satisfy security, high sensitivity, detection time quantum, convenient operation, can be at room temperature requirement such as work.

The utility model discloses technical scheme as follows:

the high-sensitivity terahertz spectrum detection device for the liquid concentration comprises a femtosecond laser, a chopper, a beam splitter, a photoconductive antenna, a first paraboloid mirror, a first polytetrafluoroethylene lens, a first silicon lens, a terahertz metamaterial array structure, a second silicon lens, a second polytetrafluoroethylene lens, a second paraboloid mirror, a delay line, a first reflector, a second reflector, a thin-film beam splitter, a ZnTe crystal, a quarter-wave plate, a Wollaston prism, a photoelectric balance detector, a phase-locked amplifier and a computer; the terahertz metamaterial array structure comprises a silicon substrate, a dielectric cylinder, a polyethylene cover plate and a polyethylene closed baffle; the medium cylinders are arranged between the polyethylene cover plate and the silicon substrate, two end faces of the medium cylinders are respectively abutted against the polyethylene cover plate and the silicon substrate, and the plurality of medium cylinders are in a periodic array structure; a cavity for storing liquid to be detected is arranged between the polyethylene cover plate and the silicon substrate and around the medium cylinder, and is sealed by a polyethylene sealing baffle plate between the polyethylene cover plate and the silicon substrate; the electromagnetic waves are coupled in the periodic array structure to obtain a specific terahertz transmission spectral line, and the terahertz transmission spectral line is obviously shifted due to slight change of substances on the surface of the structure, so that the sensing effect of the liquid to be detected in a terahertz region can be enhanced, and the detection sensitivity of the terahertz transmission spectrum of the liquid with different concentrations is effectively improved.

Furthermore, a chopper and a beam splitter are sequentially arranged on a laser light path generated by the femtosecond laser, and the beam splitter divides the laser generated by the femtosecond laser into stronger pumping light and weaker detection light; a photoconductive antenna is arranged on a pump light path, pump light excites terahertz pulses through the photoconductive antenna, the terahertz pulses sequentially pass through the first paraboloidal mirror collimation and the first polytetrafluoroethylene lens for focusing and then reach an incident spherical surface of the first silicon lens, the terahertz pulses penetrate through the polyethylene cover plate through the first silicon lens in a coupling mode, enter a cavity for storing liquid to be detected, then enter an incident plane of the second silicon lens through the silicon substrate and are coupled and emergent from an emergent spherical surface of the second silicon lens, and the emergent terahertz pulses sequentially pass through the second polytetrafluoroethylene lens collimation and the second paraboloidal mirror for focusing and then reach an incident surface of a ZnTe crystal through the thin film beam splitter; a delay line, a first reflector, a second reflector and a film beam splitter are sequentially arranged on the optical path of the detection light; after being reflected by the thin-film beam splitter, the detection light is converged with the terahertz pulse on the incidence surface of the ZnTe crystal, and then sequentially penetrates through the ZnTe crystal, the quarter-wave plate and the Wollaston prism to be detected by the photoelectric balance detector; the photoelectric balance detector is connected with the computer through the lock-in amplifier.

Liquid concentration's high sensitivity terahertz spectrum detection device's working process as follows:

1) adding liquid to be detected into the terahertz metamaterial array structure until a cavity for storing the liquid to be detected is completely filled;

2) laser generated by the femtosecond laser passes through the chopper and the beam splitter, and the beam splitter divides the laser generated by the femtosecond laser into pump light and probe light; pumping light excites terahertz pulses through a photoconductive antenna, the terahertz pulses sequentially pass through a first paraboloidal mirror for collimation and a first polytetrafluoroethylene lens for focusing and then reach an incident spherical surface of a first silicon lens, the terahertz pulses penetrate through a polyethylene cover plate through the coupling of the first silicon lens and enter a cavity for storing liquid to be detected, then enter an incident plane of a second silicon lens through a silicon substrate and are coupled and emitted from an emergent spherical surface of the second silicon lens, and the emitted terahertz pulses sequentially pass through the second polytetrafluoroethylene lens for collimation and the focusing of a second paraboloidal mirror and then reach an incident plane of a ZnTe crystal through a film beam splitter; the detection light sequentially passes through the delay line, the first reflector, the second reflector and the film beam splitter, is converged with the terahertz pulse on the incidence surface of the ZnTe crystal, and then sequentially penetrates through the ZnTe crystal, the quarter-wave plate and the Wollaston prism to be detected by the photoelectric balance detector; the measured electric signal is sent to a computer after being amplified by a phase-locked amplifier, and the transmittance data information measured by the terahertz time-domain spectroscopy system is subjected to fitting processing by the computer to obtain a terahertz transmission spectrum of the liquid to be measured;

3) taking the frequency corresponding to the point with the lowest transmittance in the terahertz transmission spectrum of the liquid to be detected as a resonance frequency point, wherein the positions of the resonance frequency points of the liquid to be detected and the concentration of the liquid to be detected are in one-to-one correspondence; and obtaining the concentration of the liquid to be measured according to a calibration curve between the resonant frequency point of the liquid to be measured and the concentration of the liquid to be measured.

The utility model has the advantages of as follows:

1) the terahertz is low in photon energy and cannot generate an ionization effect, so that the terahertz is safe to use and cannot cause damage to a human body;

2) the terahertz metamaterial array structure is made of all-dielectric materials, ohmic loss does not exist, and the result is more accurate;

3) the propagation speed of the electromagnetic wave is the speed of light, the detection waiting time of the system is mostly the processing time of the computer to the signal, and the method has the advantage of short detection time;

4) the liquid concentration high-sensitivity terahertz spectrum sensing detection device can generate electromagnetic waves at room temperature to detect a sample, and has the advantages of simple equipment and normal-temperature detection;

the utility model discloses can the wide application in the accurate determination of liquid concentration, can carry out concentration sensing to liquid high-efficiently, provide a convenient, swift, accurate detection device for the measurement of unknown concentration liquid.

Drawings

FIG. 1 is a structural diagram of the high-sensitivity terahertz spectrum detection device for liquid concentration of the present invention;

FIG. 2 is a structural diagram of a terahertz metamaterial array structure according to the present invention;

fig. 3 is a schematic diagram of a three-layer structure in the front view direction of the terahertz metamaterial array structure of the present invention;

fig. 4 is a terahertz transmission spectrum for detecting the concentration of the alcohol solution from 0% to 100% according to the present invention;

fig. 5 is a calibration curve between the resonance frequency point of alcohol and the alcohol concentration of the present invention;

in the figure: the terahertz laser comprises a femtosecond laser 1, a chopper 2, a beam splitter 3, a photoconductive antenna 4, a first paraboloid mirror 5, a first polytetrafluoroethylene lens 6, a first silicon lens 7, a terahertz metamaterial array structure 8, a second silicon lens 9, a second polytetrafluoroethylene lens 10, a second paraboloid mirror 11, a delay line 12, a first reflector 13, a second reflector 14, a thin film beam splitter 15, a ZnTe crystal 16, a quarter-wave plate 17, a Wollaston prism 18, a photoelectric balance detector 19, a phase-locked amplifier 20, a computer 21, a polyethylene cover plate 22, a silicon substrate 23, a single period 24 in the whole periodic array structure, a dielectric cylinder 25, a cavity 26 for storing liquid to be detected and a polyethylene closed baffle 27.

Detailed Description

The invention will be further described with reference to the following figures and examples:

as shown in fig. 1, a high-sensitivity terahertz spectrum sensing detection device for liquid concentration includes a femtosecond laser 1, a chopper 2, a beam splitter 3, a photoconductive antenna 4, a first parabolic mirror 5, a first polytetrafluoroethylene lens 6, a first silicon lens 7, a terahertz metamaterial array structure 8, a second silicon lens 9, a second polytetrafluoroethylene lens 10, a second parabolic mirror 11, a delay line 12, a first reflective mirror 13, a second reflective mirror 14, a thin film beam splitter 15, a ZnTe crystal 16, a quarter wave plate 17, a wollaston prism 18, a photoelectric balance detector 19, a lock-in amplifier 20, and a computer 21.

As shown in fig. 2, the terahertz metamaterial array structure 8 includes a silicon substrate 23, a dielectric cylinder 25, a polyethylene cover plate 22 and a polyethylene closed baffle 27; the medium cylinders 25 are arranged between the polyethylene cover plate 22 and the silicon substrate 23, two end faces of the medium cylinders 25 are respectively abutted to the polyethylene cover plate 22 and the silicon substrate 23, the plurality of medium cylinders are in a periodic array structure, and each single period comprises four medium cylinders with the same size; a cavity 26 for storing the liquid to be measured is arranged between the polyethylene cover plate 22 and the silicon substrate 23 and around the medium cylinder 25, and is sealed by a polyethylene closed baffle 27 between the polyethylene cover plate 22 and the silicon substrate 23.

The electromagnetic waves are coupled in the periodic array structure to obtain a specific terahertz transmission spectral line, and the terahertz transmission spectral line is obviously shifted due to slight change of substances on the surface of the structure, so that the sensing effect of the liquid to be detected in a terahertz region can be enhanced, and the detection sensitivity of the terahertz transmission spectrum of the liquid with different concentrations is effectively improved.

A chopper and a beam splitter are sequentially arranged on a laser light path generated by the femtosecond laser, and the beam splitter divides the laser generated by the femtosecond laser into stronger pumping light and weaker detection light; a photoconductive antenna is arranged on a pump light path, pump light excites terahertz pulses through the photoconductive antenna, the terahertz pulses sequentially pass through the first paraboloidal mirror collimation and the first polytetrafluoroethylene lens for focusing and then reach an incident spherical surface of the first silicon lens, the terahertz pulses penetrate through the polyethylene cover plate through the first silicon lens in a coupling mode, enter a cavity for storing liquid to be detected, then enter an incident plane of the second silicon lens through the silicon substrate and are coupled and emergent from an emergent spherical surface of the second silicon lens, and the emergent terahertz pulses sequentially pass through the second polytetrafluoroethylene lens collimation and the second paraboloidal mirror for focusing and then reach an incident surface of a ZnTe crystal through the thin film beam splitter; a delay line, a first reflector, a second reflector and a film beam splitter are sequentially arranged on the optical path of the detection light; after being reflected by the thin-film beam splitter, the detection light is converged with the terahertz pulse on the incidence surface of the ZnTe crystal, and then sequentially penetrates through the ZnTe crystal, the quarter-wave plate and the Wollaston prism to be detected by the photoelectric balance detector; the photoelectric balance detector is connected with the computer through the lock-in amplifier.

In a preferred embodiment of the present invention, 4 × 4 arrays of identical dielectric cylinders are selected, and the distance between adjacent dielectric cylinders is equal, specifically, the radius of the selected dielectric cylinder is 5 micrometers, the height is 1 micrometer, and the distance between adjacent dielectric cylinders is 5 micrometers.

In a preferred embodiment of the present invention, the dielectric material of the dielectric cylinder 25 is lithium tantalate with high dielectric constant.

In a preferred embodiment of the present invention, the substrate material is dielectric silicon.

The alcohol concentration is detected by using the high-sensitivity terahertz spectrum sensing detection device for the liquid concentration in the embodiment, and the steps are as follows:

1) adding an alcohol solution to be detected into the terahertz metamaterial array structure until a cavity for storing liquid to be detected is completely filled;

2) laser generated by the femtosecond laser passes through the chopper and the beam splitter, and the beam splitter divides the laser generated by the femtosecond laser into pump light and probe light; pumping light excites terahertz pulses through a photoconductive antenna, the terahertz pulses sequentially pass through a first paraboloidal mirror for collimation and a first polytetrafluoroethylene lens for focusing and then reach an incident spherical surface of a first silicon lens, the terahertz pulses penetrate through a polyethylene cover plate through the coupling of the first silicon lens and enter a cavity for storing liquid to be detected, then enter an incident plane of a second silicon lens through a silicon substrate and are coupled and emitted from an emergent spherical surface of the second silicon lens, and the emitted terahertz pulses sequentially pass through the second polytetrafluoroethylene lens for collimation and the focusing of a second paraboloidal mirror and then reach an incident plane of a ZnTe crystal through a film beam splitter; the detection light sequentially passes through the delay line, the first reflector, the second reflector and the film beam splitter, is converged with the terahertz pulse on the incidence surface of the ZnTe crystal, and then sequentially penetrates through the ZnTe crystal, the quarter-wave plate and the Wollaston prism to be detected by the photoelectric balance detector; the measured electric signal is sent to a computer after being amplified by a lock-in amplifier, and the computer performs fitting processing on the transmittance data information measured by the terahertz time-domain spectroscopy system to finally obtain the terahertz transmission spectrum of the alcohol solution to be detected;

3) the frequency corresponding to the point with the lowest transmittance in the terahertz transmission spectrum of the alcohol solution is used as the resonance frequency point of the alcohol, the position of the resonance frequency point of the alcohol and the concentration of the alcohol solution are in one-to-one correspondence, as shown in fig. 4, the terahertz transmission spectrum of the alcohol solution with the concentration from 0% to 100% in the alcohol concentration calibration is shown, the terahertz transmittances of the alcohol solution with the same concentration are different at different frequencies, and the terahertz transmission spectra of the alcohol solutions with different concentrations are obviously different, the calibration curve between the resonance frequency point and the alcohol concentration of the alcohol solution shown in fig. 5 can be obtained according to the curve shown in fig. 4, and then the concentration of the alcohol solution to be detected is further obtained according to the calibration curve between the resonance frequency point and the alcohol concentration.

The above is only a preferred example of the present invention, and is not intended to limit the present invention. For those skilled in the art, any modification, replacement, etc. made within the spirit and principle of the present invention are considered to be within the protection scope of the present invention.

Claims (4)

1. The high-sensitivity terahertz spectrum detection device for the liquid concentration is characterized by comprising a femtosecond laser (1), a chopper (2), a beam splitter (3), a photoconductive antenna (4), a first parabolic mirror (5), a first polytetrafluoroethylene lens (6), a first silicon lens (7), a terahertz metamaterial array structure (8), a second silicon lens (9), a second polytetrafluoroethylene lens (10), a second parabolic mirror (11), a delay line (12), a first reflector (13), a second reflector (14), a thin-film beam splitter (15), a ZnTe crystal (16), a quarter-wave plate (17), a Wollaston prism (18), a photoelectric balance detector (19), a lock-in amplifier (20) and a computer (21); the terahertz metamaterial array structure (8) comprises a silicon substrate (23), a dielectric cylinder (25), a polyethylene cover plate (22) and a polyethylene closed baffle (27); the medium cylinders are arranged between the polyethylene cover plate and the silicon substrate, two end faces of the medium cylinders are respectively abutted against the polyethylene cover plate and the silicon substrate, and the plurality of medium cylinders are in a periodic array structure; a cavity (26) for storing liquid to be detected is arranged between the polyethylene cover plate and the silicon substrate and around the medium cylinder, and is sealed by a polyethylene closed baffle between the polyethylene cover plate and the silicon substrate;

a chopper (2) and a beam splitter (3) are sequentially arranged on a laser light path generated by the femtosecond laser (1), and the beam splitter (3) divides the laser generated by the femtosecond laser (1) into pump light and probe light; a photoconductive antenna (4) is arranged on a pump light path, the pump light excites terahertz pulses through the photoconductive antenna (4), the terahertz pulses sequentially pass through a first paraboloidal mirror (5) for collimation and a first polytetrafluoroethylene lens (6) for focusing and then reach an incident spherical surface of a first silicon lens (7), the terahertz pulses penetrate through a polyethylene cover plate through the first silicon lens in a coupling manner, enter a cavity for storing liquid to be detected, enter an incident plane of a second silicon lens (9) through a silicon substrate, are coupled and emitted from an emergent spherical surface of the second silicon lens (9), and the emitted terahertz pulses sequentially pass through a second polytetrafluoroethylene lens (10) for collimation and a second paraboloidal mirror (11) for focusing and then reach an incident surface of a ZnTe crystal (16) through a film beam splitter (15); a delay line (12), a first reflector (13), a second reflector (14) and a thin film beam splitter (15) are sequentially arranged on the optical path of the detection light; after being reflected by the thin film beam splitter, the detection light is converged with the terahertz pulse on the incidence surface of the ZnTe crystal, and then sequentially penetrates through the ZnTe crystal, the quarter-wave plate (17) and the Wollaston prism (18) to be detected by a photoelectric balance detector (19); the photoelectric balance detector is connected with a computer (21) through a phase-locked amplifier (20).

2. The apparatus for detecting terahertz spectrum of liquid concentration according to claim 1, wherein the plurality of dielectric cylinders are identical and the distance between adjacent dielectric cylinders is equal.

3. The high-sensitivity terahertz spectrum detection device for liquid concentration according to claim 1, wherein the dielectric material of the dielectric cylinder (25) is lithium tantalate.

4. The high-sensitivity terahertz spectrum detection device for detecting the liquid concentration according to claim 1, wherein the radius of the medium cylinders is 4-6 micrometers, the height of the medium cylinders is 1-2 micrometers, and the distance between adjacent medium cylinders is 5-7 micrometers.

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