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WO2017117695A1 - Method for increasing spectral signal-to-noise ratio of terahertz-based optical detection system - Google Patents

Method for increasing spectral signal-to-noise ratio of terahertz-based optical detection system Download PDF

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Publication number
WO2017117695A1
WO2017117695A1 PCT/CN2016/000614 CN2016000614W WO2017117695A1 WO 2017117695 A1 WO2017117695 A1 WO 2017117695A1 CN 2016000614 W CN2016000614 W CN 2016000614W WO 2017117695 A1 WO2017117695 A1 WO 2017117695A1
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terahertz
sample
signal
light modulator
spatial light
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PCT/CN2016/000614
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French (fr)
Chinese (zh)
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彭滟
苑肖嵘
朱亦鸣
张竹倩
戚彬彬
陈万青
徐博伟
张腾飞
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上海理工大学
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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]

Definitions

  • the invention relates to a signal processing technology, in particular to a method for improving the spectral signal to noise ratio of a terahertz optical detection system.
  • Terahertz (THz) wave refers to far-infrared electromagnetic radiation with a frequency between 0.1 and 10 THz (wavelength between 30 ⁇ m and 3 mm).
  • the band is located between microwave and infrared light, which is a special transition from electron to photon on the electromagnetic spectrum. region. Due to the special position of the terahertz band, terahertz has many unique properties, such as: good transmission, which can be used as a supplement to X-ray imaging and ultrasonic imaging; safety, terahertz wave photon energy is very low,
  • the photon energy of a terahertz wave with a frequency of 1 THz is about 4 meV, which is about 10-6 times that of the X-ray photon energy.
  • Spectral analysis is strong and contains a wealth of spectral information. A large number of molecules exhibit strong absorption and dispersion properties in this frequency band, and different biomolecules have different characteristic spectra, so the terahertz spectral resolution is Terahertz detection technology not only identifies the shape of the object but also identifies the composition of matter.
  • the time domain waveform of the terahertz pulse can be measured with high accuracy on the femtosecond time scale.
  • the typical pulse width of the terahertz wave is on the order of sub-picosecond. It can not only study the transient spectrum of picosecond and femtosecond time, but also effectively prevent background radiation noise interference by sampling measurement technology.
  • the measured signal-to-noise ratio of the terahertz wave can be greater than 10 10 , which is much higher than the Fourier transform infrared spectroscopy technique.
  • the performance indicators are not ideal; the terahertz modulator designed by T.Kleine-Ostman et al. can only amplitude modulate the terahertz signal and has a small modulation range; the modulation frequency of the terahertz modulator designed by J. Saxler et al. is not enough. Fast, only a few kilohertz. In view of the previous terahertz spectral modulation method or the requirements are too harsh, or the modulation effect is not satisfactory, it is not suitable for the detection of biological samples.
  • the present invention is directed to the problem that the terahertz spectral modulation cannot meet the detection requirements of biological samples, and a method for improving the spectral signal-to-noise ratio of the terahertz optical detection system is proposed, which adds spatial light modulation in the terahertz optical detection system.
  • the device modulates the pump light, so that the generated terahertz spectrum is concentrated in the frequency band where the absorption peak of the sample is concentrated, so that the detected signal line-to-noise ratio is improved, and the characteristic peak of the sample is richer and more obvious, which is convenient and convenient.
  • a method for efficiently and quickly obtaining a high signal-to-noise ratio, high-definition terahertz spectrum is provided.
  • the technical solution of the present invention is: a method for improving the spectrum signal to noise ratio of a terahertz optical detection system, which specifically includes the following steps:
  • the laser emitted by the femtosecond laser is divided into two parts when passing through the beam splitter.
  • the reflected beam passes through the shaping device and then passes through the reflection of the mirror group to reach the terahertz generating device, generating the terahertz.
  • the sample detecting device After passing through the sample detecting device, the light reaches the terahertz detecting device, and the other transmitted light passes through the attenuator and passes through the delay device to reach the terahertz detecting device through the mirror.
  • the shaping device includes the first a grating, a first lens, a first mirror, a spatial light modulator, a second mirror, a second lens, and a second grating, the first grating and the first lens dispersing the ultrashort laser pulse into respective optical frequency components, in two Inserting a programmable spatial light modulator at a position intermediate the optical path of the lens modulates the optical frequency, and then the second lens and the second grating collect and spatially compress the components;
  • the liquid crystal spatial light modulator is set to a state in which no modulation is performed, and when the sample is not placed in the sample detecting device, the terahertz time domain signal is first measured, and the frequency domain spectrum after Fourier transform is first measured.
  • the line is used as a reference signal; the sample is placed in the sample detecting device, and the unmodulated terahertz wave is transmitted through the sample, and the measured time domain signal is Fourier transformed to obtain a complete spectrum of the sample in the frequency domain, and After the reference signal is calculated, the absorption line of the initial sampling is obtained, and the range of the frequency band in which the characteristic peak of the sample is concentrated is obtained by observation;
  • step 3 input the frequency range obtained in step 2) into the computer software for controlling the liquid crystal spatial light modulator, so that the liquid crystal spatial light modulator modulates the pump light, and obtains the newly generated terahertz wave energy concentrated on the characteristic peak band of the sample. Then, the reference signal without the sample and the sample signal after the sample is repeatedly collected to obtain the spectral data with high signal to noise ratio.
  • the spatial light modulator modulates the amplitude and phase of each optical frequency component of the spatial dispersion.
  • the spatial light modulator selects any one of a liquid crystal light valve, a ferroelectric liquid crystal spatial light modulator, and a liquid crystal micro display panel.
  • the spatial light modulator modulates the amplitude and phase of each optical frequency component of the pump light by utilizing the optical polarization and birefringence of the liquid crystal molecules, so that the newly generated terahertz wave energy is concentrated in the frequency band of the characteristic peak of the scanned sample. To obtain spectral data with high signal to noise ratio.
  • the invention has the beneficial effects that the invention improves the spectral signal-to-noise ratio of the terahertz optical detection system, and modulates the pump light by the spatial light modulator and related software algorithms, so that the generated terahertz wave energy is concentrated on the characteristics of the sample.
  • the peak frequency band is used to improve the sharpness and signal-to-noise ratio of the characteristic line of the tested sample, to ensure the accuracy of the data, and to facilitate the later data analysis; compared with the previously proposed method for improving the signal-to-noise ratio, computer optimization
  • the algorithm adjusts the spatial light modulator, which avoids other interference factors caused by artificial adjustment of the system and affects the experimental results.
  • FIG. 1 is a schematic structural view of a reflective device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention
  • FIG. 2 is a schematic structural view of a transmissive device for implementing a method for improving a spectral signal to noise ratio of a terahertz optical detection system according to the present invention.
  • the laser described in the following example system is exemplified by a fiber laser having an emission wavelength of 800 nm, a pulse width of 100 fs, and a power of 150 mW. Other bands are consistent with the implementation of this band.
  • FIG. 1 is a schematic structural diagram of a reflective device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention.
  • the laser is generated by the femtosecond laser 1 and is divided into two parts when passing through the beam splitter 2.
  • the reflected beam passes through the shaping device 3, and then passes through the reflections of the mirrors 4 and 5 to reach the terahertz generating device 6, generating the terahertz
  • the light reaches the terahertz detecting device 13, wherein in order to ensure that the optical paths of the two beams are equal, the other transmitted light passes through the attenuator 16 and passes through the delay device 15 and then passes through the mirror 14 to the terahertz detecting device. 13.
  • the shaping device 3 for pumping light for generating terahertz waves consists of seven parts: a grating 17, a lens 18, a mirror 19, a spatial light modulator 20, a mirror 21, a lens 22, and a grating 23.
  • the diffraction grating 17 and the lens 18 are used to disperse ultrashort laser pulses into respective optical frequency components, and a programmable spatial light modulator 20 is inserted in the middle of the optical paths of the two lenses 18 and 22 for the purpose of modulating the spatial dispersion.
  • the amplitude and phase of the optical frequency components Subsequent lens 22 and grating 23
  • the components are collected and spatially compressed to obtain a shaped laser in the time domain.
  • the modulated pump light generates a terahertz wave on the terahertz generating device 6 and reaches the sample detecting device 7.
  • the reflective sample detecting device 7 is composed of a parabolic mirror 8, a parabolic mirror 9, a sample detecting station 10, a parabolic mirror 11, and a parabolic mirror. 12, the terahertz wave is reflected by the parabolic mirror 9 and the parabolic mirror 10, passes through the biological sample, passes through the parabolic mirror 11 and the parabolic mirror 12, and reaches the detecting device 13.
  • the liquid crystal spatial light modulator 20 is first set to a state in which modulation is not performed, so that it does not perform any modulation on the pump light.
  • the terahertz time domain signal is measured first, and the frequency domain line after Fourier transform is used as the reference signal; then the sample is placed on the sample inspection station, and the unmodulated terahertz wave is transmitted through the sample, and the measurement is performed.
  • the time domain signal is subjected to Fourier transform to obtain a complete spectrum of the sample in the frequency domain, and the absorption line of the initial sampling is obtained after the reference signal is compared with the reference signal.
  • the frequency value is input into the computer software for controlling the liquid crystal spatial light modulator, and the computer software modulates the pump light by the liquid crystal spatial light modulator through a correlation algorithm, so that a new generation is generated.
  • the terahertz wave energy is concentrated in the characteristic peak frequency band of the sample, and the reference signal without the sample and the sample signal after the sample is repeatedly collected are collected, and a new sample absorption line is obtained after the comparison calculation, and the absorption line ratio of the sample is not obtained.
  • the modulated initial sample absorption line has a higher signal to noise ratio.
  • FIG. 2 is a schematic structural diagram of a transmissive device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention.
  • the laser is generated by the femtosecond laser 1 and is divided into two parts when passing through the beam splitter 2.
  • the reflected beam passes through the shaping device 3, and then passes through the reflections of the mirrors 4 and 5 to reach the terahertz generating device 6, generating the terahertz
  • the light passes through the sample detecting device 71 and reaches the detecting device 13, wherein in order to ensure that the optical paths of the two beams are equal, the other transmitted light passes through the attenuator 16 and passes through the delay device 15 and then passes through the mirror 14 to the terahertz detecting device 13.
  • the shaping device 3 for pumping light for generating terahertz waves consists of seven parts: a grating 17, a lens 18, a mirror 19, a spatial light modulator 20, a mirror 21, a lens 22, and a grating 23.
  • the diffraction grating 17 and the lens 18 are used to disperse ultrashort laser pulses into respective optical frequency components, and a programmable spatial light modulator 20 is inserted in the middle of the optical paths of the two lenses 18 and 22 for the purpose of modulating the spatial dispersion.
  • the subsequent lens 22 and grating 23 are used to collect and spatially compress the individual components to obtain a shaped laser in the time domain.
  • the modulated pump light generates a terahertz wave on the terahertz generating device 6, and reaches the sample detecting device 7.
  • the reflective sample detecting device 71 is formed by a convex lens A24, a convex lens B25, a sample detecting table, a convex lens C27, and a convex lens.
  • the mirror D28 is composed, and the terahertz wave is concentrated by the convex lens A and the convex lens B, passes through the biological sample, passes through the convex lens C and the convex lens D, and reaches the detecting device 13.
  • the related software for the liquid crystal spatial light modulator has been installed in the computer.
  • the liquid crystal space light modulator is first set to a state in which modulation is not performed, so that it does not perform any modulation on the pump light.
  • the terahertz time domain signal is measured first, and the frequency domain line after Fourier transform is used as the reference signal; then the sample is placed on the sample inspection station, and the unmodulated terahertz wave is transmitted through the sample, and the measurement is performed.
  • the time domain signal is subjected to Fourier transform to obtain a complete spectrum of the sample in the frequency domain, and the absorption line of the initial sampling is obtained after the reference signal is compared with the reference signal.
  • the frequency value is input into the computer software for controlling the liquid crystal spatial light modulator, and the computer software modulates the pump light by the liquid crystal spatial light modulator through a correlation algorithm, so that a new generation is generated.
  • the terahertz wave energy is concentrated in the characteristic peak frequency band of the sample, and the reference signal without the sample and the sample signal after the sample is repeatedly collected are collected, and a new sample absorption line is obtained after the comparison calculation, and the absorption line ratio of the sample is not obtained.
  • the modulated initial sample absorption line has a higher signal to noise ratio.
  • the spatial light modulator may be a liquid crystal light valve, a ferroelectric liquid crystal spatial light modulator, or a liquid crystal micro display panel.
  • the spatial light modulator can input a control signal in the form of electrical addressing (OA-SLM) or optical addressing (EA-SLM).
  • OA-SLM electrical addressing
  • EA-SLM optical addressing
  • the invention performs targeted regulation on the detectable frequency band in the terahertz detection system, and is convenient for accurate detection of different biological samples. Since the biological sample contains a wide variety of substances and the signal is complicated, if the initial terahertz signal is weak in the spectrum range where the characteristic peak is located, the obtained spectral line is easily regarded as noise, and the accuracy cannot be guaranteed, and it is inevitable that many important information is lost. Therefore, a high signal to noise ratio at the characteristic line is required. For this reason, the present invention modulates the pump light by a spatial light modulator and related software algorithms during the detection process, so that the generated terahertz wave energy is concentrated on the characteristic peak band of the sample to improve the characteristic line of the sample under test.
  • the spatial light modulator is adjusted by a computer optimization algorithm, which avoids other interference factors caused by artificial adjustment of the system and affects the experimental result.

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Abstract

Provided is a method for increasing a spectral signal to noise ratio of a terahertz-based optical detection system. In the method, a spatial light modulator (20) is added to a terahertz-based optical detection system to modulate pump light such that a generated terahertz spectrum is concentrated in a frequency band in which absorption peaks of the biological sample are more concentrated, thereby increasing clearness of a characteristic spectral line and a signal-to-noise ratio in a test sample, ensuring data accuracy, and facilitating convenience for a subsequent data analysis. Compared with the prior art methods for increasing signal-to-noise ratios, the invention modulates a spatial light modulator by means of a computer optimization algorithm, thereby preventing an experiment result from being affected by interference accompanying a manual adjustment of a system.

Description

一种提高太赫兹光学检测系统频谱信噪比的方法Method for improving spectral signal to noise ratio of terahertz optical detection system 技术领域Technical field
本发明涉及一种信号处理技术，特别涉及一种提高太赫兹光学检测系统频谱信噪比的方法。The invention relates to a signal processing technology, in particular to a method for improving the spectral signal to noise ratio of a terahertz optical detection system.
背景技术Background technique
太赫兹(THz)波是指频率在0.1至10THz(波长在30μm至3mm)区间的远红外电磁辐射，其波段位于微波和红外光之间，是电磁波谱上由电子学向光子学过渡的特殊区域。正是由于太赫兹波段的特殊位置，太赫兹具有很多独特的性质，例如：良好的透射性，可作为X射线成像和超声波成像等技术的补充；安全性，太赫兹波的光子能量很低，频率为1THz的太赫兹波的光子能量约为4meV，大约为X射线光子能量的10-6倍，因此不会对生物组织产生有害的电离，适合于对生物组织进行活体检查。光谱分析本领强，包含丰富的光谱信息，大量的分子其转动和振动跃迁在这一频段表现出强烈的吸收和色散性质，且不同的生物分子有不同的特征光谱，因此太赫兹光谱分辨特性在太赫兹探测技术上不仅可以辨别物体形貌而且可以鉴别物质成分。Terahertz (THz) wave refers to far-infrared electromagnetic radiation with a frequency between 0.1 and 10 THz (wavelength between 30 μm and 3 mm). The band is located between microwave and infrared light, which is a special transition from electron to photon on the electromagnetic spectrum. region. Due to the special position of the terahertz band, terahertz has many unique properties, such as: good transmission, which can be used as a supplement to X-ray imaging and ultrasonic imaging; safety, terahertz wave photon energy is very low, The photon energy of a terahertz wave with a frequency of 1 THz is about 4 meV, which is about 10-6 times that of the X-ray photon energy. Therefore, it does not cause harmful ionization to biological tissues and is suitable for biopsy of biological tissues. Spectral analysis is strong and contains a wealth of spectral information. A large number of molecules exhibit strong absorption and dispersion properties in this frequency band, and different biomolecules have different characteristic spectra, so the terahertz spectral resolution is Terahertz detection technology not only identifies the shape of the object but also identifies the composition of matter.
太赫兹脉冲的时域波形可以在飞秒时间尺度上以很高的精度测量出来。太赫兹波的典型脉宽在亚皮秒量级，不但可以进行皮秒、飞秒时间分辨的瞬态光谱研究，而且可以通过取样测量技术有效地防止背景辐射噪声干扰。太赫兹波的测量信噪比可大于1010，远高于傅立叶变换红外光谱测量技术。虽然太赫兹波在生物检测方面有较好的应用前景，但是目前对太赫兹波缺乏有效的调制手段。比如：R.Kersting等人设计的太赫兹调制器需要极低的温度才能运作；Jiusheng Li和M.Koch等人设计的电控、温控和磁控太赫兹光子调制器，调制深度或者插入损耗等性能指标都不甚理想；T.Kleine-Ostman等人设计的太赫兹调制器只能对太赫兹信号进行振幅调制，并且调制范围小；J.Saxler等人设计的太赫兹调制器调制频率不够快，只能达到几千赫兹。鉴于之前的太赫兹光谱调制方式或是要求条件过于严苛，或是调制效果不尽如人意，均不适用于生物样品的检测。 The time domain waveform of the terahertz pulse can be measured with high accuracy on the femtosecond time scale. The typical pulse width of the terahertz wave is on the order of sub-picosecond. It can not only study the transient spectrum of picosecond and femtosecond time, but also effectively prevent background radiation noise interference by sampling measurement technology. The measured signal-to-noise ratio of the terahertz wave can be greater than 10 10 , which is much higher than the Fourier transform infrared spectroscopy technique. Although terahertz waves have a good application prospect in biological detection, there is currently no effective modulation method for terahertz waves. For example, the terahertz modulator designed by R. Kersting et al. requires very low temperatures to operate; the electronically controlled, temperature-controlled and magnetron-controlled terahertz photonic modulators designed by Jiusheng Li and M. Koch et al., modulation depth or insertion loss. The performance indicators are not ideal; the terahertz modulator designed by T.Kleine-Ostman et al. can only amplitude modulate the terahertz signal and has a small modulation range; the modulation frequency of the terahertz modulator designed by J. Saxler et al. is not enough. Fast, only a few kilohertz. In view of the previous terahertz spectral modulation method or the requirements are too harsh, or the modulation effect is not satisfactory, it is not suitable for the detection of biological samples.
发明内容Summary of the invention
本发明是针对现在太赫兹光谱调制不能满足生物样品的检测要求的问题，提出了一种提高太赫兹光学检测系统频谱信噪比的方法，该方法通过在太赫兹光学检测系统中添加空间光调制器对泵浦光进行调制，使产生的太赫兹光谱集中于样品吸收峰较为集中的频段，使检测得到的谱线信噪比提高，样品特征峰更丰富、更明显，是一种可以便捷、高效、迅速地获得高信噪比、高精细度太赫兹频谱的方法。The present invention is directed to the problem that the terahertz spectral modulation cannot meet the detection requirements of biological samples, and a method for improving the spectral signal-to-noise ratio of the terahertz optical detection system is proposed, which adds spatial light modulation in the terahertz optical detection system. The device modulates the pump light, so that the generated terahertz spectrum is concentrated in the frequency band where the absorption peak of the sample is concentrated, so that the detected signal line-to-noise ratio is improved, and the characteristic peak of the sample is richer and more obvious, which is convenient and convenient. A method for efficiently and quickly obtaining a high signal-to-noise ratio, high-definition terahertz spectrum.
本发明的技术方案为：一种提高太赫兹光学检测系统频谱信噪比的方法，具体包括如下步骤：The technical solution of the present invention is: a method for improving the spectrum signal to noise ratio of a terahertz optical detection system, which specifically includes the following steps:
1)搭建光路：由飞秒激光器出射的激光，通过分束器时被分为两个部分，反射光束经过整形装置，再依次通过反光镜组的反射，到达太赫兹发生装置，产生的太赫兹光通过样品检测装置后到达太赫兹探测装置，另一束透射光线通过衰减器后经过延时装置后通过反射镜到达太赫兹探测装置，两路光束的光程相等；其中整形装置依次包括第一光栅、第一透镜、第一反射镜、空间光调制器、第二反射镜、第二透镜以及第二光栅，第一光栅和第一透镜将超短激光脉冲色散成各个光频成份，在两个透镜的光路中间位置上插入可编程的空间光调制器对光频进行调制，随后的第二透镜和第二光栅将各个成份再进行收集和空间压缩；1) Setting up the optical path: The laser emitted by the femtosecond laser is divided into two parts when passing through the beam splitter. The reflected beam passes through the shaping device and then passes through the reflection of the mirror group to reach the terahertz generating device, generating the terahertz. After passing through the sample detecting device, the light reaches the terahertz detecting device, and the other transmitted light passes through the attenuator and passes through the delay device to reach the terahertz detecting device through the mirror. The optical paths of the two beams are equal; wherein the shaping device includes the first a grating, a first lens, a first mirror, a spatial light modulator, a second mirror, a second lens, and a second grating, the first grating and the first lens dispersing the ultrashort laser pulse into respective optical frequency components, in two Inserting a programmable spatial light modulator at a position intermediate the optical path of the lens modulates the optical frequency, and then the second lens and the second grating collect and spatially compress the components;
2)通过光路采集初始信号：首先将液晶空间光调器设置为不进行调制的状态，样品检测装置中不放样品时，先测一次太赫兹时域信号，傅里叶变换后的频域谱线作为参考信号；再在样品检测装置中放入样品，未调制的太赫兹波透射通过样品，对测得的时域信号进行傅里叶变换，获得样品在频域上的完整谱线，与参考信号比对计算后获得初次采样的吸收谱线，通过观察获得样品特征峰较为集中的频段范围；2) Collecting the initial signal through the optical path: firstly, the liquid crystal spatial light modulator is set to a state in which no modulation is performed, and when the sample is not placed in the sample detecting device, the terahertz time domain signal is first measured, and the frequency domain spectrum after Fourier transform is first measured. The line is used as a reference signal; the sample is placed in the sample detecting device, and the unmodulated terahertz wave is transmitted through the sample, and the measured time domain signal is Fourier transformed to obtain a complete spectrum of the sample in the frequency domain, and After the reference signal is calculated, the absorption line of the initial sampling is obtained, and the range of the frequency band in which the characteristic peak of the sample is concentrated is obtained by observation;
3)将步骤2)所得频段范围输入到控制液晶空间光调制器的计算机软件中，使得液晶空间光调制器对泵浦光进行调制，得到新产生的太赫兹波能量集中于样品的特征峰频段，再重复采集无样品时的参考信号和放置样品后的样品信号，以获得高信噪比的频谱数据。3) input the frequency range obtained in step 2) into the computer software for controlling the liquid crystal spatial light modulator, so that the liquid crystal spatial light modulator modulates the pump light, and obtains the newly generated terahertz wave energy concentrated on the characteristic peak band of the sample. Then, the reference signal without the sample and the sample signal after the sample is repeatedly collected to obtain the spectral data with high signal to noise ratio.
所述空间光调制器调制空间色散的各光频成份的振幅和位相。The spatial light modulator modulates the amplitude and phase of each optical frequency component of the spatial dispersion.
所述空间光调制器选液晶光阀、铁电液晶空间光调制器和液晶微显示面板中的任意一种。 The spatial light modulator selects any one of a liquid crystal light valve, a ferroelectric liquid crystal spatial light modulator, and a liquid crystal micro display panel.
所述空间光调制器利用液晶分子的旋光偏振性和双折射性对泵浦光各光频成份的振幅和相位进行调制，使新产生的太赫兹波能量集中于被扫描样品特征峰所在频段，以获得高信噪比的频谱数据。The spatial light modulator modulates the amplitude and phase of each optical frequency component of the pump light by utilizing the optical polarization and birefringence of the liquid crystal molecules, so that the newly generated terahertz wave energy is concentrated in the frequency band of the characteristic peak of the scanned sample. To obtain spectral data with high signal to noise ratio.
本发明的有益效果在于：本发明提高太赫兹光学检测系统频谱信噪比的方法，通过空间光调制器及相关软件算法对泵浦光进行调制，使产生的太赫兹波能量集中于样品的特征峰频段，以提高所测试样品特征谱线的清晰度和信噪比，保证数据的准确率，为后期的数据分析提供便利；相较于之前提出的提高信号信噪比的方法，通过计算机优化算法调节空间光调制器，避免了人为调整系统时带来其他的干扰因素而影响实验结果。The invention has the beneficial effects that the invention improves the spectral signal-to-noise ratio of the terahertz optical detection system, and modulates the pump light by the spatial light modulator and related software algorithms, so that the generated terahertz wave energy is concentrated on the characteristics of the sample. The peak frequency band is used to improve the sharpness and signal-to-noise ratio of the characteristic line of the tested sample, to ensure the accuracy of the data, and to facilitate the later data analysis; compared with the previously proposed method for improving the signal-to-noise ratio, computer optimization The algorithm adjusts the spatial light modulator, which avoids other interference factors caused by artificial adjustment of the system and affects the experimental results.
附图说明DRAWINGS
图1为本发明实现提高太赫兹光学检测系统频谱信噪比的方法的反射式装置结构示意图；1 is a schematic structural view of a reflective device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention;
图2为本发明实现提高太赫兹光学检测系统频谱信噪比的方法的透射式装置结构示意图。2 is a schematic structural view of a transmissive device for implementing a method for improving a spectral signal to noise ratio of a terahertz optical detection system according to the present invention.
具体实施方式detailed description
以下示例系统中所述激光器以发射波长为800nm的光纤激光器为例，脉宽100fs，功率150mW。其他波段与该波段的实施方法一致。The laser described in the following example system is exemplified by a fiber laser having an emission wavelength of 800 nm, a pulse width of 100 fs, and a power of 150 mW. Other bands are consistent with the implementation of this band.
如图1为本发明实现提高太赫兹光学检测系统频谱信噪比的方法的反射式装置结构示意图。FIG. 1 is a schematic structural diagram of a reflective device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention.
激光由飞秒激光器1产生，通过分束器2时被分为两个部分，反射光束经过整形装置3，再依次通过反光镜4和5的反射，到达太赫兹发生装置6，产生的太赫兹光通过样品检测装置7后到达太赫兹探测装置13，其中为了保证两路光束的光程相等，另一束透射光线通过衰减器16后经过延时装置15后通过反射镜14到达太赫兹探测装置13。用于对产生太赫兹波的泵浦光的整形装置3由七个部分组成：光栅17、透镜18、反射镜19、空间光调制器20、反射镜21、透镜22以及光栅23。其中，衍射光栅17以及透镜18用以将超短激光脉冲色散成各个光频成份，在两透镜18、22的光路中间位置上插入可编程的空间光调制器20，目的是调制空间色散的各光频成份的振幅和位相。随后的透镜22以及光栅23用 以将各个成份再进行收集和空间压缩，以得到时域上的整形过后的激光。调制后的泵浦光在太赫兹发生装置6上产生太赫兹波，到达样品检测装置7，反射式样品检测装置7由抛物面镜8、抛物面镜9、样品检测台10、抛物面镜11、抛物面镜12组成，太赫兹波经过抛物面镜9和抛物面镜10反射，透过生物样品后经过抛物面镜11和抛物面镜12，到达探测装置13。The laser is generated by the femtosecond laser 1 and is divided into two parts when passing through the beam splitter 2. The reflected beam passes through the shaping device 3, and then passes through the reflections of the mirrors 4 and 5 to reach the terahertz generating device 6, generating the terahertz After passing through the sample detecting device 7, the light reaches the terahertz detecting device 13, wherein in order to ensure that the optical paths of the two beams are equal, the other transmitted light passes through the attenuator 16 and passes through the delay device 15 and then passes through the mirror 14 to the terahertz detecting device. 13. The shaping device 3 for pumping light for generating terahertz waves consists of seven parts: a grating 17, a lens 18, a mirror 19, a spatial light modulator 20, a mirror 21, a lens 22, and a grating 23. The diffraction grating 17 and the lens 18 are used to disperse ultrashort laser pulses into respective optical frequency components, and a programmable spatial light modulator 20 is inserted in the middle of the optical paths of the two lenses 18 and 22 for the purpose of modulating the spatial dispersion. The amplitude and phase of the optical frequency components. Subsequent lens 22 and grating 23 The components are collected and spatially compressed to obtain a shaped laser in the time domain. The modulated pump light generates a terahertz wave on the terahertz generating device 6 and reaches the sample detecting device 7. The reflective sample detecting device 7 is composed of a parabolic mirror 8, a parabolic mirror 9, a sample detecting station 10, a parabolic mirror 11, and a parabolic mirror. 12, the terahertz wave is reflected by the parabolic mirror 9 and the parabolic mirror 10, passes through the biological sample, passes through the parabolic mirror 11 and the parabolic mirror 12, and reaches the detecting device 13.
实验操作前，计算机中已安装有与液晶空间光调制器配套的相关软件。实验操作时，首先将液晶空间光调器20设置为不进行调制的状态，使其对泵浦光不进行任何调制。无样品时，先测一次太赫兹时域信号，傅里叶变换后的频域谱线作为参考信号；再在样品检测台上放上样品，未调制的太赫兹波透射通过样品，对测得的时域信号进行傅里叶变换，获得样品在频域上的完整谱线，与参考信号比对计算后获得初次采样的吸收谱线。通过观察获得样品特征峰较为集中的频段范围，将该频段数值输入到控制液晶空间光调制器的计算机软件中，计算机软件通过相关算法使得液晶空间光调制器对泵浦光进行调制，使得新产生的太赫兹波能量集中于样品的特征峰频段，再重复采集无样品时的参考信号和放置样品后的样品信号，比对计算后得到新的样品吸收谱线，该样品吸收谱线比未经调制的初始样品吸收谱线具有更高的信噪比。Before the experiment, the related software for the liquid crystal spatial light modulator has been installed in the computer. In the experimental operation, the liquid crystal spatial light modulator 20 is first set to a state in which modulation is not performed, so that it does not perform any modulation on the pump light. When there is no sample, the terahertz time domain signal is measured first, and the frequency domain line after Fourier transform is used as the reference signal; then the sample is placed on the sample inspection station, and the unmodulated terahertz wave is transmitted through the sample, and the measurement is performed. The time domain signal is subjected to Fourier transform to obtain a complete spectrum of the sample in the frequency domain, and the absorption line of the initial sampling is obtained after the reference signal is compared with the reference signal. By observing the frequency range in which the characteristic peaks of the sample are concentrated, the frequency value is input into the computer software for controlling the liquid crystal spatial light modulator, and the computer software modulates the pump light by the liquid crystal spatial light modulator through a correlation algorithm, so that a new generation is generated. The terahertz wave energy is concentrated in the characteristic peak frequency band of the sample, and the reference signal without the sample and the sample signal after the sample is repeatedly collected are collected, and a new sample absorption line is obtained after the comparison calculation, and the absorption line ratio of the sample is not obtained. The modulated initial sample absorption line has a higher signal to noise ratio.
如图2为本发明实现提高太赫兹光学检测系统频谱信噪比的方法的透射式装置结构示意图。FIG. 2 is a schematic structural diagram of a transmissive device for implementing a method for improving a spectrum signal to noise ratio of a terahertz optical detection system according to the present invention.
激光由飞秒激光器1产生，通过分束器2时被分为两个部分，反射光束经过整形装置3，再依次通过反光镜4和5的反射，到达太赫兹发生装置6，产生的太赫兹光通过样品检测装置71后到达探测装置13，其中为了保证两路光束的光程相等，另一束透射光线通过衰减器16后经过延时装置15后通过反射镜14到达太赫兹探测装置13。用于对产生太赫兹波的泵浦光的整形装置3由七个部分组成：光栅17、透镜18、反射镜19、空间光调制器20、反射镜21、透镜22以及光栅23。其中，衍射光栅17以及透镜18用以将超短激光脉冲色散成各个光频成份，在两透镜18、22的光路中间位置上插入可编程的空间光调制器20，目的是调制空间色散的各光频成份的振幅和位相。随后的透镜22以及光栅23用以将各个成份再进行收集和空间压缩，以得到时域上的整形过后的激光。调制后的泵浦光在太赫兹发生装置6上产生太赫兹波，到达样品检测装置7，反射式样品检测装置71由凸透镜A24、凸透镜B25、26样品检测台、凸透镜C27、凸透 镜D28组成，太赫兹波经过凸透镜A和凸透镜B汇聚，透过生物样品后，经过凸透镜C和凸透镜D，到达探测装置13。The laser is generated by the femtosecond laser 1 and is divided into two parts when passing through the beam splitter 2. The reflected beam passes through the shaping device 3, and then passes through the reflections of the mirrors 4 and 5 to reach the terahertz generating device 6, generating the terahertz The light passes through the sample detecting device 71 and reaches the detecting device 13, wherein in order to ensure that the optical paths of the two beams are equal, the other transmitted light passes through the attenuator 16 and passes through the delay device 15 and then passes through the mirror 14 to the terahertz detecting device 13. The shaping device 3 for pumping light for generating terahertz waves consists of seven parts: a grating 17, a lens 18, a mirror 19, a spatial light modulator 20, a mirror 21, a lens 22, and a grating 23. The diffraction grating 17 and the lens 18 are used to disperse ultrashort laser pulses into respective optical frequency components, and a programmable spatial light modulator 20 is inserted in the middle of the optical paths of the two lenses 18 and 22 for the purpose of modulating the spatial dispersion. The amplitude and phase of the optical frequency components. The subsequent lens 22 and grating 23 are used to collect and spatially compress the individual components to obtain a shaped laser in the time domain. The modulated pump light generates a terahertz wave on the terahertz generating device 6, and reaches the sample detecting device 7. The reflective sample detecting device 71 is formed by a convex lens A24, a convex lens B25, a sample detecting table, a convex lens C27, and a convex lens. The mirror D28 is composed, and the terahertz wave is concentrated by the convex lens A and the convex lens B, passes through the biological sample, passes through the convex lens C and the convex lens D, and reaches the detecting device 13.
实验操作前，计算机中已安装有与液晶空间光调制器配套的相关软件。实验操作时，首先将液晶空间光调器设置为不进行调制的状态，使其对泵浦光不进行任何调制。无样品时，先测一次太赫兹时域信号，傅里叶变换后的频域谱线作为参考信号；再在样品检测台上放上样品，未调制的太赫兹波透射通过样品，对测得的时域信号进行傅里叶变换，获得样品在频域上的完整谱线，与参考信号比对计算后获得初次采样的吸收谱线。通过观察获得样品特征峰较为集中的频段范围，将该频段数值输入到控制液晶空间光调制器的计算机软件中，计算机软件通过相关算法使得液晶空间光调制器对泵浦光进行调制，使得新产生的太赫兹波能量集中于样品的特征峰频段，再重复采集无样品时的参考信号和放置样品后的样品信号，比对计算后得到新的样品吸收谱线，该样品吸收谱线比未经调制的初始样品吸收谱线具有更高的信噪比。Before the experiment, the related software for the liquid crystal spatial light modulator has been installed in the computer. In the experimental operation, the liquid crystal space light modulator is first set to a state in which modulation is not performed, so that it does not perform any modulation on the pump light. When there is no sample, the terahertz time domain signal is measured first, and the frequency domain line after Fourier transform is used as the reference signal; then the sample is placed on the sample inspection station, and the unmodulated terahertz wave is transmitted through the sample, and the measurement is performed. The time domain signal is subjected to Fourier transform to obtain a complete spectrum of the sample in the frequency domain, and the absorption line of the initial sampling is obtained after the reference signal is compared with the reference signal. By observing the frequency range in which the characteristic peaks of the sample are concentrated, the frequency value is input into the computer software for controlling the liquid crystal spatial light modulator, and the computer software modulates the pump light by the liquid crystal spatial light modulator through a correlation algorithm, so that a new generation is generated. The terahertz wave energy is concentrated in the characteristic peak frequency band of the sample, and the reference signal without the sample and the sample signal after the sample is repeatedly collected are collected, and a new sample absorption line is obtained after the comparison calculation, and the absorption line ratio of the sample is not obtained. The modulated initial sample absorption line has a higher signal to noise ratio.
所述空间光调制器可以是液晶光阀、铁电液晶空间光调制器、液晶微显示面板。The spatial light modulator may be a liquid crystal light valve, a ferroelectric liquid crystal spatial light modulator, or a liquid crystal micro display panel.
所述空间光调制器其输入控制信号的方式可以是电寻址(OA-SLM)，也可以是光寻址(EA-SLM)。The spatial light modulator can input a control signal in the form of electrical addressing (OA-SLM) or optical addressing (EA-SLM).
调节液晶空间光调制器，利用液晶分子的旋光偏振性和双折射性实现对泵浦光各光频成份的振幅和相位的调制，使新产生的太赫兹波能量集中于被扫描样品特征峰所在频段，以获得更高信噪比的频谱数据。Adjusting the liquid crystal spatial light modulator, using the optical polarization and birefringence of the liquid crystal molecules to realize the modulation of the amplitude and phase of each optical frequency component of the pump light, so that the newly generated terahertz wave energy is concentrated on the characteristic peak of the scanned sample. Frequency band to obtain spectral data with higher signal-to-noise ratio.
本发明对太赫兹检测系统中可检测的频段进行针对性调控，方便对于不同生物样品的准确检测。由于生物样品包含物质种类繁多，信号繁杂，若特征峰所在的频谱范围内初始太赫兹信号很弱，则所得谱线易被当做噪声，准确度无法得到保证，难免遗失许多重要信息。因而要求特征谱线处具有高的信噪比。正因如此，本发明在检测过程中通过空间光调制器及相关软件算法对泵浦光进行调制，使产生的太赫兹波能量集中于样品的特征峰频段，以提高所测试样品特征谱线的清晰度和信噪比，保证数据的准确率，为后期的数据分析提供便利。相较于之前提出的提高信号信噪比的方法，是通过计算机优化算法调节空间光调制器，避免了人为调整系统时带来其他的干扰因素而影响实验结果。 The invention performs targeted regulation on the detectable frequency band in the terahertz detection system, and is convenient for accurate detection of different biological samples. Since the biological sample contains a wide variety of substances and the signal is complicated, if the initial terahertz signal is weak in the spectrum range where the characteristic peak is located, the obtained spectral line is easily regarded as noise, and the accuracy cannot be guaranteed, and it is inevitable that many important information is lost. Therefore, a high signal to noise ratio at the characteristic line is required. For this reason, the present invention modulates the pump light by a spatial light modulator and related software algorithms during the detection process, so that the generated terahertz wave energy is concentrated on the characteristic peak band of the sample to improve the characteristic line of the sample under test. Sharpness and signal-to-noise ratio ensure data accuracy and facilitate later data analysis. Compared with the previously proposed method for improving the signal-to-noise ratio of the signal, the spatial light modulator is adjusted by a computer optimization algorithm, which avoids other interference factors caused by artificial adjustment of the system and affects the experimental result.

Claims (4)

  1. 一种提高太赫兹光学检测系统频谱信噪比的方法，其特征在于，具体包括如下步骤：A method for improving the spectral signal-to-noise ratio of a terahertz optical detection system, characterized in that the method comprises the following steps:
    1)搭建光路：由飞秒激光器出射的激光，通过分束器时被分为两个部分，反射光束经过整形装置，再依次通过反光镜组的反射，到达太赫兹发生装置，产生的太赫兹光通过样品检测装置后到达太赫兹探测装置，另一束透射光线通过衰减器后经过延时装置后通过反射镜到达太赫兹探测装置，两路光束的光程相等；其中整形装置依次包括第一光栅、第一透镜、第一反射镜、空间光调制器、第二反射镜、第二透镜以及第二光栅，第一光栅和第一透镜将超短激光脉冲色散成各个光频成份，在两个透镜的光路中间位置上插入可编程的空间光调制器对光频进行调制，随后的第二透镜和第二光栅将各个成份再进行收集和空间压缩；1) Setting up the optical path: The laser emitted by the femtosecond laser is divided into two parts when passing through the beam splitter. The reflected beam passes through the shaping device and then passes through the reflection of the mirror group to reach the terahertz generating device, generating the terahertz. After passing through the sample detecting device, the light reaches the terahertz detecting device, and the other transmitted light passes through the attenuator and passes through the delay device to reach the terahertz detecting device through the mirror. The optical paths of the two beams are equal; wherein the shaping device includes the first a grating, a first lens, a first mirror, a spatial light modulator, a second mirror, a second lens, and a second grating, the first grating and the first lens dispersing the ultrashort laser pulse into respective optical frequency components, in two Inserting a programmable spatial light modulator at a position intermediate the optical path of the lens modulates the optical frequency, and then the second lens and the second grating collect and spatially compress the components;
    2)通过光路采集初始信号：首先将液晶空间光调器设置为不进行调制的状态，样品检测装置中不放样品时，先测一次太赫兹时域信号，傅里叶变换后的频域谱线作为参考信号；再在样品检测装置中放入样品，未调制的太赫兹波透射通过样品，对测得的时域信号进行傅里叶变换，获得样品在频域上的完整谱线，与参考信号比对计算后获得初次采样的吸收谱线，通过观察获得样品特征峰较为集中的频段范围；2) Collecting the initial signal through the optical path: firstly, the liquid crystal spatial light modulator is set to a state in which no modulation is performed, and when the sample is not placed in the sample detecting device, the terahertz time domain signal is first measured, and the frequency domain spectrum after Fourier transform is first measured. The line is used as a reference signal; the sample is placed in the sample detecting device, and the unmodulated terahertz wave is transmitted through the sample, and the measured time domain signal is Fourier transformed to obtain a complete spectrum of the sample in the frequency domain, and After the reference signal is calculated, the absorption line of the initial sampling is obtained, and the range of the frequency band in which the characteristic peak of the sample is concentrated is obtained by observation;
    3)将步骤2)所得频段范围输入到控制液晶空间光调制器的计算机软件中，使得液晶空间光调制器对泵浦光进行调制，得到新产生的太赫兹波能量集中于样品的特征峰频段，再重复采集无样品时的参考信号和放置样品后的样品信号，以获得高信噪比的频谱数据。3) input the frequency range obtained in step 2) into the computer software for controlling the liquid crystal spatial light modulator, so that the liquid crystal spatial light modulator modulates the pump light, and obtains the newly generated terahertz wave energy concentrated on the characteristic peak band of the sample. Then, the reference signal without the sample and the sample signal after the sample is repeatedly collected to obtain the spectral data with high signal to noise ratio.
  2. 根据权利要求1所述提高太赫兹光学检测系统频谱信噪比的方法，其特征在于，所述空间光调制器调制空间色散的各光频成份的振幅和位相。A method of improving the spectral signal-to-noise ratio of a terahertz optical detection system according to claim 1, wherein said spatial light modulator modulates an amplitude and a phase of each optical frequency component of the spatial dispersion.
  3. 根据权利要求2所述提高太赫兹光学检测系统频谱信噪比的方法，其特征在于，所述空间光调制器选液晶光阀、铁电液晶空间光调制器和液晶微显示面板中的任意一种。The method for improving the spectral signal-to-noise ratio of a terahertz optical detection system according to claim 2, wherein the spatial light modulator selects any one of a liquid crystal light valve, a ferroelectric liquid crystal spatial light modulator, and a liquid crystal microdisplay panel. Kind.
  4. 根据权利要求3所述提高太赫兹光学检测系统频谱信噪比的方法，其特征在于，所述空间光调制器利用液晶分子的旋光偏振性和双折射性对泵浦光各光频成份的振幅和相位进行调制，使新产生的太赫兹波能量集中于被扫描样品特征 峰所在频段，以获得高信噪比的频谱数据。 The method for improving the spectral signal-to-noise ratio of a terahertz optical detection system according to claim 3, wherein the spatial light modulator utilizes the optical polarization and birefringence of the liquid crystal molecules to affect the amplitude of each optical frequency component of the pump light. And phase modulation to concentrate the newly generated terahertz wave energy on the scanned sample characteristics The frequency band in which the peak is located to obtain spectral data with high signal-to-noise ratio.
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