Two detection techniques of broadband terahertz（THz）time-domain spectroscopy-THz air-biased coherent detection（THz-ABCD;from 0.3 to 14 THz）and electro-optical（EO）detection（from 0.3 to 7 THz）-are both performed...Two detection techniques of broadband terahertz（THz）time-domain spectroscopy-THz air-biased coherent detection（THz-ABCD;from 0.3 to 14 THz）and electro-optical（EO）detection（from 0.3 to 7 THz）-are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0%to 40%,and linear fittings show that the slopes are-0.017 and-0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution（17 GHz）than that of EO detection（170 GHz）.The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy（FTIR）.展开更多
We give a brief review of the developments in terahertz time-domain spectroscopy(THz-TDS) systems and microcavity components for probing samples in the University of Shanghai for Science and Technology. The broadband ...We give a brief review of the developments in terahertz time-domain spectroscopy(THz-TDS) systems and microcavity components for probing samples in the University of Shanghai for Science and Technology. The broadband terahertz(THz) radiation sources based on GaAs m-i-n diodes have been investigated by applying high electric fields. Then, the free space THz-TDS and fiber-coupled THz-TDS systems produced in our lab and their applications in drug/cancer detection are introduced in detail. To further improve the signal-to-noise ratio(SNR) and enhance sensitivity, we introduce three general micro-cavity approaches to achieve tiny-volume sample detection, summarizing our previous results about their characteristics, performance, and potential applications.展开更多
Terahertz(THz) time-domain spectroscopy(TDS) has been applied to investigate liquid's optical property in recent years.However,comprehensive discussion of how to compute liquids' complex refractive indices and...Terahertz(THz) time-domain spectroscopy(TDS) has been applied to investigate liquid's optical property in recent years.However,comprehensive discussion of how to compute liquids' complex refractive indices and absorption rates are seldom reported.So,in this work,we try to find a way to compute liquids' optical property accurately and conveniently.展开更多
Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of t...Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins. Upon treatment with guanidine hydrochloride (GuHCl), a 1.8 THz peak appeared for CP47 and free chlorophyll a (Chl a). This peak was deemed to originate from the interaction between Chl a and GuHCl molecules. The Chl a molecules in CP47 interacted with GuHCl more easily than those in CP43.展开更多
We demonstrate theoretically and experimentally how changes of a terahertz （THz） beam induced by the sample affect the accuracy of the determination of THz dielectric properties in THz time-domain transmission spect...We demonstrate theoretically and experimentally how changes of a terahertz （THz） beam induced by the sample affect the accuracy of the determination of THz dielectric properties in THz time-domain transmission spectros- copy （TDTS）. We apply a Gaussian beam and the ABCD matrix formalism to describe the propagation of the THz beam in a focused beam setup. The insertion of the sample induces a focus displacement which is absent in the reference t without a sample. We show how the focus displacement can be corrected. The THz optical properties after focus displacement correction reported in this Letter are in quantitative agreement with those obtained using collimated beam THz-TDTSinpreviouswork.展开更多
High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experim...High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.展开更多
The work presented in this paper was performed at the Oriental Institute at the University of Chicago, on objects from their permanent collection： an ancient Egyptian bird mummy and three ancient Sumerian corroded co...The work presented in this paper was performed at the Oriental Institute at the University of Chicago, on objects from their permanent collection： an ancient Egyptian bird mummy and three ancient Sumerian corroded copper-alloy objects. We used a portable, fibercoupled terahertz （THz） time-domain spectroscopic ima- ging system, which allowed us to measure specimens in both transmission and reflection geometry, and present time- and frequency-based image modes. The results confirm earlier evidence that THz imaging can provide complementary information to that obtainable from X-ray computed tomography （XRCT） scans of mummies, giving better visualisation of low density regions. In addition, we demonstrated that THz imaging can distinguish mineralized layers in metal artifacts.展开更多
基金supported by the NSC(No.100-2917-I-564-045)the National Science FoundationDefense Threat Reduction Agency,and the Department of Homeland Security through the DHS-ALERT Center under Award(No.2008-ST-061-ED0001)
文摘Two detection techniques of broadband terahertz（THz）time-domain spectroscopy-THz air-biased coherent detection（THz-ABCD;from 0.3 to 14 THz）and electro-optical（EO）detection（from 0.3 to 7 THz）-are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0%to 40%,and linear fittings show that the slopes are-0.017 and-0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution（17 GHz）than that of EO detection（170 GHz）.The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy（FTIR）.
基金the National Key R&D Program of China (No. 2018YFF01013003)the Program of Shanghai Pujiang Program, China (No. 17PJD028)+4 种基金the National Natural Science Foundation of China (Nos. 61671302, 61601291, and 61722111)the Shuguang Program supported by the Shanghai Education Development Foundation and Shanghai Municipal Education Commission, China (No. 18SG44)the Key Scientific and Technological Project of Science and Technology Commission of Shanghai Municipality, China (No. 15DZ0500102)the Shanghai Leading Talent, China (No. 2016-019)the Young Yangtse Rive Scholar, China (No. Q2016212).
文摘We give a brief review of the developments in terahertz time-domain spectroscopy(THz-TDS) systems and microcavity components for probing samples in the University of Shanghai for Science and Technology. The broadband terahertz(THz) radiation sources based on GaAs m-i-n diodes have been investigated by applying high electric fields. Then, the free space THz-TDS and fiber-coupled THz-TDS systems produced in our lab and their applications in drug/cancer detection are introduced in detail. To further improve the signal-to-noise ratio(SNR) and enhance sensitivity, we introduce three general micro-cavity approaches to achieve tiny-volume sample detection, summarizing our previous results about their characteristics, performance, and potential applications.
基金supported in part by the National Natural Science Foundation of China (Grant No 10874074)the Major State Basic Research Development Program of China (973 Program) (Grant Nos 2006CB601006 and 2007CB310404)PhD Programs Foundation of the Ministry of Education of China (200802840031)
文摘Terahertz(THz) time-domain spectroscopy(TDS) has been applied to investigate liquid's optical property in recent years.However,comprehensive discussion of how to compute liquids' complex refractive indices and absorption rates are seldom reported.So,in this work,we try to find a way to compute liquids' optical property accurately and conveniently.
基金the National Natural Science Foundation of China (Grant No. 39890390)
文摘Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins. Upon treatment with guanidine hydrochloride (GuHCl), a 1.8 THz peak appeared for CP47 and free chlorophyll a (Chl a). This peak was deemed to originate from the interaction between Chl a and GuHCl molecules. The Chl a molecules in CP47 interacted with GuHCl more easily than those in CP43.
基金the support from the Center for Applied Photonics (CAP) at the University of Konstanzthe DFG through the SFB 767 (Germany)the China Scholarship Council (CSC)
文摘We demonstrate theoretically and experimentally how changes of a terahertz （THz） beam induced by the sample affect the accuracy of the determination of THz dielectric properties in THz time-domain transmission spectros- copy （TDTS）. We apply a Gaussian beam and the ABCD matrix formalism to describe the propagation of the THz beam in a focused beam setup. The insertion of the sample induces a focus displacement which is absent in the reference t without a sample. We show how the focus displacement can be corrected. The THz optical properties after focus displacement correction reported in this Letter are in quantitative agreement with those obtained using collimated beam THz-TDTSinpreviouswork.
基金supported by the National Basic Research Program of China (Grant No. 2007CB310408)the Beijing Natural Science Foundation of China (Grant No. KZ201110028035)
文摘High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.
文摘The work presented in this paper was performed at the Oriental Institute at the University of Chicago, on objects from their permanent collection： an ancient Egyptian bird mummy and three ancient Sumerian corroded copper-alloy objects. We used a portable, fibercoupled terahertz （THz） time-domain spectroscopic ima- ging system, which allowed us to measure specimens in both transmission and reflection geometry, and present time- and frequency-based image modes. The results confirm earlier evidence that THz imaging can provide complementary information to that obtainable from X-ray computed tomography （XRCT） scans of mummies, giving better visualisation of low density regions. In addition, we demonstrated that THz imaging can distinguish mineralized layers in metal artifacts.
