Abstract-Application of Terahertz Spectroscopy and Imaging in the Diagnosis of Prostate Cancer

Ping Zhang, Shuncong Zhong, Junxi Zhang, Jian Ding, Zhenxiang Liu, Yi Huang, Ning Zhou, Walter Nsengiyumva, and Tianfu Zhang

https://www.osapublishing.org/copp/abstract.cfm?uri=copp-4-1-31

The feasibility of the application of terahertz electromagnetic waves in the diagnosis of prostate cancer was examined. Four samples of incomplete cancerous prostatic paraffin-embedded tissues were examined using terahertz spectral imaging (TPI) system and the results obtained by comparing the absorption coefficient and refractive index of prostate tumor, normal prostate tissue and smooth muscle from one of the paraffin tissue masses examined were reported. Three hundred and sixty cases of absorption coefficients from one of the paraffin tissues examined were used as raw data to classify these three tissues using the Principal Component Analysis (PCA) and Least Squares Support Vector Machine (LS-SVM). An excellent classification with an accuracy of 92.22% in the prediction set was achieved. Using the distribution information of THz reflection signal intensity from sample surface and absorption coefficient of the sample, an attempt was made to use the TPI system to identify the boundaries of the different tissues involved (prostate tumors, normal and smooth muscles). The location of three identified regions in the terahertz images (frequency domain slice absorption coefficient imaging, 1.2 THz) were compared with those obtained from the histopathologic examination. The tissue tumor region had a distinctively visible color and could well be distinguished from other tissue regions in terahertz images. Results indicate that a THz spectroscopy imaging system can be efficiently used in conjunction with the proposed advanced computer-based mathematical analysis method to identify tumor regions in the paraffin tissue mass of prostate cancer.

Abstract-Optical bistability induced by nonlinear surface plasmon polaritons in graphene in terahertz regime

Matthew Sanderson¹, Yee Sin Ang¹, Sen Gong^2,3, Tao Zhao^2,3, Min Hu^2,3, Renbin Zhong^2,3, Xiaoxing Chen^2,3, Ping Zhang^2,3, Chao Zhang^1,3,a) and Shenggang Liu^2,3
http://scitation.aip.org/content/aip/journal/apl/107/20/10.1063/1.4936232?TRACK=RSS
a) czhang@uow.edu.au
Appl. Phys. Lett. 107, 203113 (2015); http://dx.doi.org/10.1063/1.4936232

We demonstrate optical bistability in a prism-air-graphene-dielectric structure. Under a moderate electric field in the terahertz frequency regime, the third order nonlinear optical conductivity is comparable to the linear conductivity. The nonlinear conductivity enhances the energy of surface plasmonpolaritons. Both the energy and frequency of the surface plasmonpolaritons depend on the strength of the nonlinear current in the graphene layer. When considering excitation in the Kretschmann configuration, the reflectance as a function of frequency exhibits bistability. The origin of the bistability is the field dependence of the plasmon mode. We have determined the parameter regime for the occurrence of bistability in this structure.

Abstract-Coherent and Tunable Terahertz Radiation from Graphene Surface Plasmon Polarititions Excited by Cyclotron Electron Beam

Tao Zhao

, Sen Gong

, Min Hu

, Renbin Zhong

, Diwei Liu

, Xiaoxing Chen

, Ping Zhang

, Xinran Wang

,Chao Zhang

, Peiheng Wu

 & Shenggang Liu

http://www.nature.com/articles/srep16059

Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 105 W/cm2. The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime.

Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

Shenggang Liu^1,2,a), Chao Zhang^1,2,3, Min Hu^1,2, Xiaoxing Chen^1,2, Ping Zhang^1,2, Sen Gong^1,2, Tao Zhao^1,2 and Renbin Zhong^1,2
 HIDE AFFILIATIONS
1 Terahertz Research Centre, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
2 Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan 610054, China
3 School of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522, Australia
a) liusg@uestc.edu.cn
Appl. Phys. Lett. 104, 201104 (2014); http://dx.doi.org/10.1063/1.4879017
http://scitation.aip.org/content/aip/journal/apl/104/20/10.1063/1.4879017

Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The radiation intensity generated with this method is 400 times stronger than that from SPPs at a conventional dielectric or semiconducting surface and is comparable to that from the most advanced photonics source such as a quantum cascade laser. The physical mechanism for this strong radiation is presented. The phase diagrams defining the parameters range for the occurrence of radiation is also shown.

Abstract-Free electron terahertz wave radiation source with two-section periodical waveguide structures

http://jap.aip.org/resource/1/japiau/v111/i6/p063107_s1?isAuthorized=no

Weihao Liu, Sen Gong, Yaxin Zhang, Jun Zhou, Ping Zhang, and Shenggang Liu

Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu 610054, China 

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(Received 20 December 2011; accepted 24 February 2012; published online 26 March 2012)

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We analyze a free electron terahertz wave radiation source with two-section periodical waveguide structure (PWS), where the first section (section-I) is used to pre-modulate the electron beam and the second section (section-II) is for terahertz wave generation. By means of theoretical analysis and numerical simulations, we demonstrate that the starting current density of the beam-wave interaction in section-II can be significantly reduced provided that the operation frequency is the harmonic of electron beam’s pre-modulation frequency. This kind of source can generate relatively high power terahertz wave radiation but only need moderate beam current density. And it may have great potential application in developing the compact and high power terahertz wave radiation source.

© 2012 American Institute of Physics