CN-122016704-A - Novel terahertz spectrum measuring instrument and method

Abstract

The invention provides a novel terahertz spectrometer. The terahertz tunable light source mainly comprises a terahertz complex color light source system, a collimation module, a long-wave pass filter, a terahertz tunable filter, a voltage supply module, a chopper, a controller, a sample to be tested, a focusing module, a terahertz detector, a data acquisition device and a measurement and control system. The terahertz multi-color light source system is used for generating a multi-color terahertz light beam, the collimation system is used for generating parallel light, the long-wave pass filter is used for filtering long-wave band components in the light source, the terahertz tunable filter and the voltage supply module are used for converting the multi-color light beam into a monochromatic light beam, the chopper and the controller are used for reducing measurement noise, the focusing module, the terahertz detector and the data collector are used for measuring the intensity of the terahertz light beam, and the measurement and control system is used for controlling the whole system. Compared with the existing common terahertz spectrometer, the novel terahertz spectrometer has the advantages of low cost, high ordinate measurement precision (about 0.5%), high measurement speed (about second order) and the like. The novel terahertz spectrometer can provide a new scheme for the field of terahertz spectrum measurement, can form a potential of a bending angle with the existing terahertz spectrum measurement method, can provide better terahertz spectrum measurement selection for a plurality of application scenes, and is expected to induce novel terahertz time-resolved spectroscopy technology, novel terahertz spectrum pumping detection technology and novel terahertz spectrum imaging technology.

Inventors

• WANG SHENGHAO
• XIAO DEHUA
• YAN HANG
• PAN QIANG
• LUO YINGJUN
• SHI CUNXIU
• ZHANG ZHONGYI
• WU SONG

Assignees

• 湖北工业职业技术学院

Dates

Publication Date

20260512

Application Date

20251117

Claims (3)

1. 1. A terahertz spectrum measuring instrument comprises a terahertz polychromatic light source system (1), a collimation module (2), a long-wave pass filter (3), a terahertz tunable filter (4), a chopper (5), a sample to be measured (6), a focusing module (7), a voltage supply module (8), a controller (9), a measurement and control system (10), a data acquisition device (11) and a terahertz detector (12). The terahertz light source system is characterized in that the collimation module (2) is arranged at the beam emergent direction of the terahertz light source system (1), the long-wave pass filter (3), the terahertz tunable filter (4), the chopper (5), the sample (6) to be detected and the focusing module (7) are sequentially arranged at the emergent beam propagation direction of the collimation module (2), and the terahertz detector (12) is arranged at the beam emergent direction of the focusing module (7). The voltage supply module (8) is used for providing input voltage for the terahertz tunable filter (4). The controller (9) is used for operating the chopper (5). The data acquisition device (11) is used for measuring the output signal of the terahertz detector (12). The measurement and control system (10) is used for controlling the whole system by automatic measurement.
2. 2. A terahertz tunable filter is composed of a filtering module 1, a module 2, a module 3, a module 4, a module 5 and a module 6. The filter module 1 is composed of 2 terahertz polaroids and 1 terahertz liquid crystal, and the modules 2, 3, 4, 5 and 6 are composed of 1 terahertz polaroid and 1 terahertz liquid crystal.
3. 3. A terahertz spectrum measurement method, comprising the steps of: ① Measuring a dark field intensity value of the terahertz detector (12) under the condition that the terahertz multi-color light source system (1) is turned off; ② The terahertz multi-color light source system (1) is started, a sample is not placed in a light path, and a test light beam directly passes through the focusing module (7) and irradiates on the terahertz detector (12); ③ The emergent wavelength of the terahertz tunable filter (4) is set to be lambda 1 through a voltage supply module (8), and then the bright field intensity value of the terahertz detector (12) is measured and recorded as I 1 r ; ④ The outgoing wavelength of the terahertz tunable filter (4) is sequentially set to be lambda 2 ,λ 3 ··· λ n through a voltage supply module (8), the steps ③ are repeated respectively, and the intensity values of the visible field of the terahertz detector under each wavelength are respectively recorded as I 2 r ,I 3 r ··· I n r ; ⑤ Installing a sample (6) to be tested in the light path; ⑥ The outgoing wavelength of the terahertz tunable filter (4) is set to be lambda 1 through a voltage supply module (8), and then the signal intensity value of the terahertz detector (12) is measured and recorded as I 1 s ; ⑦ The outgoing wavelength of the terahertz tunable filter (4) is sequentially set to be lambda 2 ,λ 3 ··· λ n through a voltage supply module (8), the steps ⑥ are repeated respectively, and the signal intensity values of the terahertz detector under each wavelength are respectively recorded as I 2 s ,I 3 s ··· I n s ; ⑧ According to the dark field intensity value of the terahertz detector (12), the bright field intensity value and the signal intensity value at each wavelength, the transmission spectrum of the sample to be measured at the wavelength lambda 1 ,λ 2 ··· λ n is calculated according to the following formula: ··· ⑨ And drawing the transmission spectrum of the sample (6) to be tested according to the transmission spectrum values at the positions of the wavelengths, and completing the measurement of the terahertz transmission spectrum.

Description

Novel terahertz spectrum measuring instrument and method Technical Field The invention relates to the field of terahertz spectrum measurement, in particular to a novel terahertz spectrometer. Background Terahertz spectrum contains abundant physical and chemical information of substances, such as vibration energy level, rotation energy level, hydrogen bond, van der Waals force and the like, has a plurality of characteristic peaks in terahertz wave bands, and the terahertz spectrum technology has very wide application [1-5] in the fields of national defense, military, biomedicine, nondestructive detection and the like, such as different explosives and different glucose have completely different terahertz absorption spectra [6, 7]. Terahertz spectrometry technology is a very important research content in the field of terahertz spectroscopy (mainly comprising spectroscopic principles, spectroscopic measurement and spectroscopic analysis). The existing common terahertz spectrum measurement methods mainly comprise classical time domain spectroscopy [8-10], asynchronous sampling time domain spectroscopy [11-15], fourier transform spectrometer measurement [16-19], back wave oscillator-based light source wavelength scanning method [20-22], mixed frequency-based light source wavelength scanning method [23, 24] and array detector-based single exposure measurement method [25, 26]. The measurement principle of classical time-domain spectroscopy is as follows, with pulsed light from a femtosecond laser being split into two beams by a beam splitter. One beam of light is incident on the terahertz generator to generate terahertz pulses, the terahertz pulses are collected by the terahertz detector after passing through a system containing a sample to be detected, and the other beam of light is also collected by the terahertz detector after passing through a time delay system. The transient electric field intensity of the terahertz pulse when the femtosecond laser pulse arrives can be measured by a photoconductive sampling or free space electro-optic sampling mode. The time delay system is controlled to adjust the time delay between two bundles of pulse light, the transient electric field intensity of the terahertz pulse is measured sequentially under different time delays, the time domain waveform of the terahertz pulse can be obtained, and the spectrum of the terahertz pulse can be obtained after the time domain waveform is subjected to Fourier transformation. And comparing terahertz spectrums before and after placing the sample, and obtaining an absorption spectrum of the sample to be detected. The classical time domain spectroscopy has the main advantages of (1) adopting a coherent measurement mode to obtain the amplitude and the phase of a measured electric field so as to extract parameters such as absorption coefficient, refractive index, dielectric constant and the like of a sample, (2) measuring a wide spectrum range (about 0.1-10 THz), and (3) having transient property, wherein the typical pulse width of terahertz pulse is in the picosecond order. The method has the main defects that (1) the measurement time is long (about Zhong Liangji) depending on repeated mechanical scanning, (2) the spectrum resolution is not high, about tens of GHz, (3) the price is high (about 100 ten thousand), and (4) the spectrum calculation process needs Fourier transformation, and the spectrum ordinate measurement precision is not high (about 3%). Compared with classical time domain spectroscopy, the asynchronous sampling time domain spectroscopy is mainly characterized by adopting 2 femtosecond lasers. The periods of the output pulse light have small differences, so the time difference between the terahertz pulse and the corresponding laser pulse reaching the detector can be sequentially increased, and the time domain waveform of the terahertz pulse can be obtained without depending on a time delay system (avoiding repeated mechanical scanning). Besides the advantages of classical time-domain spectroscopy, asynchronous sampling time-domain spectroscopy also has the characteristics of high measurement speed (about second order) and high spectral resolution (about tens of MHz). The main disadvantages of asynchronous sampling time domain spectroscopy are (1) 2 femtosecond lasers are needed, the whole system is more expensive (about 150 ten thousand), and (2) the spectrum calculation process still needs Fourier transformation, and the spectrum ordinate measurement precision is not high (about 3%). The principle of measuring the terahertz spectrum by the Fourier transform spectrometer method is that the terahertz light beam forms two light beams after passing through a beam splitter, and the two light beams are combined and interfered at the position of a detector after being reflected by a movable mirror and a static mirror respectively. The terahertz spectrum information can be obtained by mechanically scanning the movable mirror, sequentia