Polarization information for terahertz imaging

Zhang, Ranxi; Cui, Yun; Zhang, Yan

doi:10.1364/ao.47.006422

Cited by 34 publications

(19 citation statements)

References 8 publications

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“…Since light is a transverse wave, polarization is a very important physical property that can provide more useful information about the targets [5,6]. Applying imaging approaches based on the degree of polarization of scattered light can distinguish the edges of objects more clearly and hence identify the target object with higher precision since more information can be obtained from the polarization state of the scattered light [7,8]. Zhang et al found that THz polarization imaging is sensitive to the edge of the sample [8].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulation of Stokes vectors of polarized light scattering from two-dimensional random rough surfaces

Shu

Wang

Lai

et al. 2011

Journal of Modern Optics

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A Monte Carlo model was established to simulate polarized scattering fields of two-dimensional rough surfaces based on the Kirchhoff approximation. Based on this model, numerical studies of the hemispherical distribution of Stokes vectors of scattered light from dielectric and metal rough surfaces were carried out. These surfaces have Gaussian distributions with correlation length of 3.1 mm and standard deviation varying between 0.1 and 0.6 mm. The results reveal that the V component of metal surfaces has peaks antisymmetric with the incident plane, whereas the V component of dielectric surfaces is almost zero. We consider that this property of the V component would provide a new method which could be used to distinguish the target material.

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Section: Introductionmentioning

confidence: 99%

Monte Carlo simulation of Stokes vectors of polarized light scattering from two-dimensional random rough surfaces

Shu

Wang

Lai

et al. 2011

Journal of Modern Optics

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“…1b as a In order to present a practical application of the this measurement method, a cross dipole antenna coupled silicon FET detector is used for polarization imaging. Terahertz polarimetry [7] is selected as it applied widely to analyze birefringent materials [8], metamaterials, notnormal incidence reflection, and multiple scattering samples [9]. The used detector is manufactured in standard 180nm feature sized CMOS technology with 440nm drawn width and 330nm length.…”

mentioning

confidence: 99%

Current steering detection scheme of three terminal antenna-coupled terahertz field effect transistor detectors

Földesy

2013

Opt. Lett.

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Antenna coupled field effect transistor (FET) as plasma wave THz detector is used with current steering to record separately the gate-source, gate-drain photoresponse, and their phase sensitive combination. The method based on the observation that the plasmon-terminal coupling is cut-off in saturation resulting in only one side sensitivity. A polarimetric example is presented with intensity and polarization angle reconstruction using a single three terminal antenna coupled Si-MOSFET. The technique is applicable to various detection schemes and technologies (HEMT, GaAs-, GaN-, Si-MOSFETs) and other application possibilities are discussed. . Though other exotic approaches may provide better properties, in focal plane solutions, the commercial silicon technology is the common platform. Using optical elements and multiple detectors (e.g. two detector arms) complex properties can be measured beside absorption and reflection parameters, such as phase delay or polarization angle. The distinguishing feature of the introduced method is that a single antenna coupled FET detector is used to measured different radiation properties selected by means of simple electronic control. First, the FET plasma wave detection is revised briefly. In the conducting channel of a FET a 2D electron sheet is formed as a function of the gate potential. The high frequency (RF) radiation is coupled to the gate and e.g. to the source terminal. The RF signal of the gate modulates the electron density while the source coupled signal is fed into this varying conductivity channel. The resulting behavior is equal to a powerlaw detector (like a bolometer) that measures the time averaged intensity. With decreasing gate potential, the electron sheet becomes thinner and more sensitive to the RF perturbation, thus the response becomes higher. As the transistor reaches subthreshold region, the photoresponse saturates and driving further the transistor into accumulation region, the response quickly drops as the inversion electron sheet disappears. In a symmetrically connected FET structure, there is no difference between the gate-source and gate-drain coupled signal rectification. At the same RF signal the photoresponses are equal but of opposite sign. The practical difference comes from the electronic and RF connectivity of the FET. The biasing is usually distinguished as open drain and current biased modes. In the former, beside the instrumentation load there is no active element connected to the source or drain terminals. In the current biased mode, non zero source drain current is forced to the transistor. It was demonstrated in various works, that the non zero sourcedrain current results in significantly higher responsivity, with the connotation of the increasing sensor noise due to 1/f flicker and shot noise [4]. Let be u ac GS , u ac GD the gate-source and gate-drain RF signals, than the ∆U S and ∆U D photoresponse can be modeled by DC current characteristics as [5]:η S(D) efficiency is derived from the coupling efficiency of the incoming radiation a...

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“…The rapidly growing demand for high performance terahertz imaging and spectroscopy systems necessitates the development of high quality terahertz polarizing beam splitters with high extinction ratios, large angular apertures, low attenuation, and broad frequency bandwidths [4][5][6]. Most optical polarizing beam splitter schemes based on natural birefringence effects or polarization selectivity of multilayer dielectric coatings do not operate efficiently at a broad range of terahertz frequencies [7-9], due to the lack of materials with the desired properties at terahertz frequencies and/or the practical difficulties in scaling device dimensions to efficiently operate at terahertz frequencies.…”

mentioning

confidence: 99%

Broadband Terahertz Polarizing Beam Splitter on a Polymer Substrate

Berry

Jarrahi

2011

J Infrared Milli Terahz Waves

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Polarizing beam splitters are key elements for numerous imaging [1], data storage [2] and routing systems [3] which utilize different polarization states to achieve higher sensitivity and broader operation bandwidth. The rapidly growing demand for high performance terahertz imaging and spectroscopy systems necessitates the development of high quality terahertz polarizing beam splitters with high extinction ratios, large angular apertures, low attenuation, and broad frequency bandwidths [4][5][6]. Most optical polarizing beam splitter schemes based on natural birefringence effects or polarization selectivity of multilayer dielectric coatings do not operate efficiently at a broad range of terahertz frequencies [7-9], due to the lack of materials with the desired properties at terahertz frequencies and/or the practical difficulties in scaling device dimensions to efficiently operate at terahertz frequencies.Among various polarizing beam splitter schemes, wire-grating polarizing beam splitters have been the most promising candidate for operation at terahertz frequencies offering very high extinction ratios, large angular apertures and geometry-controllable operation bandwidth. The operation of a wire-grating polarizing beam splitter is based on the existence of TEM modes supported by the subwavelength slab waveguides formed by metallic gratings [10]. Excitation of surface diffraction modes on the periodic metallic grating allows efficient coupling of the TM-polarized portion of an incident electromagnetic wave (magnetic field lines in parallel with metallic gratings) into the subwavelength TEM waveguide modes of metallic gratings [10][11][12]. The TE-polarized portion of the incident electromagnetic wave is not coupled to the subwavelength TEM waveguide modes of metallic gratings and, therefore, is reflected back from the grating surface. The grating periodicity is directly proportional to the cutoff wavelength of the excited diffraction modes, setting the frequency bandwidth of the wire-grating polarizing beam splitter. The demonstrated free-standing wire-grating polarizers offer low loss, polarizing beam splitter operation [13]. However, their operation bandwidth is limited due to the technical challenges in fabricating micrometer-scale metallic gratings without a substrate. The micrometer-scale wire-grid polarizing beam splitters fabricated on a Mylar film through standard photolithography

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Polarization information for terahertz imaging

Cited by 34 publications

References 8 publications

Monte Carlo simulation of Stokes vectors of polarized light scattering from two-dimensional random rough surfaces

Monte Carlo simulation of Stokes vectors of polarized light scattering from two-dimensional random rough surfaces

Current steering detection scheme of three terminal antenna-coupled terahertz field effect transistor detectors

Broadband Terahertz Polarizing Beam Splitter on a Polymer Substrate

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