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Investigation of Keratinizing Squamous Cell Carcinoma of the Tongue Using Terahertz Reflection Imaging
摘要： We investigated the feasibility of using terahertz (THz) reflection imaging to detect keratinizing squamous cell carcinoma (SCC) of the tongue. Four fresh keratinizing SCC tissues were studied, which had been surgically resected. All of the keratinizing SCCs were well distinguished from normal healthy tissues. We showed that the tumor regions exhibited low THz reflection despite having higher water content than normal regions. The refractive indices and absorption coefficients were low in the tumor tissues despite the relatively high water content. Our results showed that there were dominant factors such as keratin pearls, other than the water content affecting the THz reflection signal.
关键词： Optical diagnostics for medicine,Tissue diagnostics,Terahertz imaging,Medical and biological imaging,Terahertz spectroscopy
更新于2025-09-23 15:23:52
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Non-destructive inspection of food and technical oils by terahertz spectroscopy
摘要： Quality control and non-destructive monitoring are of notable interest of food and pharmaceutical industries. It relies on the ability of non-invasive inspection which can be employed for manufacturing process control. We hereby apply terahertz (THz) time-domain spectroscopy as non-destructive technique to monitor pure and degraded oils as well as hydrocarbon chemicals. Significant differences in the spectra of refractive index (RI) and absorption coefficient arising from the presence of ester linkages in the edible and technical oils were obtained. Explicit increase from 1.38 to 1.5 of the RI in all THz spectrum range was observed in hydrocarbons and mono-functional esters with the increase of molar mass. This fact is in contrast of RI dependence on molar mass in multi-functional esters, such as Adipate or vegetable oils, where it is around 1.54. Degradation products, Oleic Acid (OA) and water in particular, lead only to some changes in absorption coefficient and RI spectra of vegetable oils. We demonstrate that complex colloidal and supramolecular processes, such as dynamics of inverse micelles and oil hydrolysis, take part during oil degradation and are responsible for non-uniform dependence of optical properties on extent of degradation.
关键词： absorption coefficient,terahertz spectroscopy,oils,degradation,non-destructive inspection,refractive index
更新于2025-09-23 15:23:52
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[OSA CLEO: Science and Innovations - San Jose, California (2014..-..)] CLEO: 2014 - Terahertz near-field phase contrast imaging
摘要： We demonstrate a method, permitting the observation of dielectric loading of hydrocarbons into a porous coordination polymer nanocrystal (PCP), by spatially resolving the phase difference between the near-field responses of two terahertz resonators.
关键词： Near-field microscopy,terahertz,Spectroscopy,Metamaterials
更新于2025-09-23 15:22:29
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Dual-prism based terahertz time-domain attenuated total reflection spectroscopy and its application to characterise the hydration state of L-threonine in solution
摘要： To investigate the hydration state of amino acids, terahertz time-domain attenuated total internal reflection (THz TD-ATR) spectroscopy is often adopted to measure the complex permittivity. However, the classical THz TD-ATR spectroscopy system has only a single ATR prism and requires prism cleaning for different measuring modes, increasing the time consumed and easily introducing errors due to the changing environment. To accelerate the measurements and avoid the influence of environmental fluctuations, in this paper, we designed and built a dual-prism based THz TD-ATR spectroscopy: two ATR prisms with and without samples setting on the optical rail can be sequentially switched to optical systems for easily and rapidly collecting both sample and reference ATR spectra. According to the measurements of deionised water, the dual-prism based THz TD-ATR spectroscopy system can measure the sample complex permittivity rapidly and with high accuracy. The complex permittivity of L-threonine in aqueous solution is measured and analysed via the proposed system, and the hydration numbers of L-threonine solutions in different concentrations are quantitatively characterised. It is believed that the dual-prism based THz TD-ATR technique is a powerful tool for quickly and accurately investigating the hydration of amino acids.
关键词： Terahertz spectroscopy,Complex permittivity,Time-domain attenuated total internal reflection,Amino acid hydration
更新于2025-09-23 15:22:29
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High-frequency breakdown of the integer quantum Hall effect in GaAs/AlGaAs heterojunctions
摘要： The integer quantum Hall effect is a well-studied phenomenon at frequencies below about 100 Hz. The plateaus in high-frequency Hall conductivity were experimentally proven to retain up to 33 GHz, but the behavior at higher frequencies has remained largely unexplored. Using continuous-wave terahertz spectroscopy, the complex Hall conductivity of GaAs/AlGaAs heterojunctions was studied in the range of 69–1100 GHz. Above 100 GHz, the quantum plateaus are strongly smeared out and replaced by weak quantum oscillations in the real part of the conductivity. The amplitude of the oscillations decreases with increasing frequency. Near 1 THz, the Hall conductivity does not reveal any features related to the filling of Landau levels. Similar oscillations are observed in the imaginary part as well; this effect has no analogy at zero frequency. This experimental picture is in disagreement with existing theoretical considerations of the high-frequency quantum Hall effect.
关键词： integer quantum Hall effect,GaAs/AlGaAs heterojunctions,terahertz spectroscopy,high-frequency Hall conductivity,quantum oscillations
更新于2025-09-23 15:22:29
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Evaluating intrinsic mobility from transient terahertz conductivity spectra of microcrystal samples of organic molecular semiconductors
摘要： In microcrystal samples of the prototypical organic molecular semiconductors rubrene and C10-DNTT (2,9-didecyl-dinaphtho[2,3-b:20,30-f]thieno[3,2-b]thiophene), we measured spectra of complex optical conductivity caused by photocarriers with optical-pump terahertz-probe spectroscopy. We analyzed the ~r xe T spectra using the Drude-Smith model and evaluated the DC mobility lDC, which includes extrinsic effects, and the intrinsic mobility lint. The resulting lDC and lint values are comparable to the mobility values obtained using transport measurements of polycrystalline and single-crystalline ?eld-effect transistors, respectively. This correspondence demonstrates that the intrinsic mobility values of organic molecular semiconductors can be evaluated from the measurements of microcrystal samples using transient terahertz spectroscopy.
关键词： mobility,C10-DNTT,organic molecular semiconductors,terahertz spectroscopy,rubrene
更新于2025-09-23 15:19:57
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Terahertz Spectroscopy of Thermal Radiation from AlGaN/GaN Heterostructure on Sapphire at Low Temperatures
摘要： Terahertz spectroscopy of thermal radiation from electrically pumped AlGaN/GaN structures on sapphire substrate was investigated in this work. Comparison of experimental THz spectroscopy results to theoretical spectra calculations shows that thermal radiation of the sample lattice is the main mechanism causing the emission above T = 155 K, and it is mainly influenced by sapphire substrate. Here, the emission was attributed to the radiative electron transitions in shallow impurities and nitrogen vacancies as well as to radiative decay of longitudinal optical phonons (387 cm?1) in sapphire substrate. We have successfully demonstrated that THz emission spectroscopy can be used to define the temperature at which thermal emission from AlGaN/GaN HEMT structures dominates the emission spectrum.
关键词： terahertz spectroscopy,AlGaN/GaN heterostructure,electroluminescence,thermal radiation
更新于2025-09-23 15:19:57
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Terahertz Polarization Imaging and Its Applications
摘要： This review focuses on several recent research activities regarding precise and fast polarization-sensitive terahertz time-domain spectroscopy systems for imaging purposes, and explains three interesting application examples. Owing to modulation techniques that have recently been developed for the evaluation of the instantaneous terahertz electric-field (E-field) vector, fast and precise terahertz polarization imaging becomes feasible. This terahertz technology enables high-resolution surface topography, precise understanding of the spatial E-field vector distribution of the focused terahertz pulse, and examination of strain-induced birefringence in polymeric materials. These examples constitute a new application area of terahertz photonics with emphasis on both fundamental optics and industrial applications.
关键词： topography,birefringence,polarization,parabolic mirror,terahertz spectroscopy
更新于2025-09-19 17:15:36
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - 300 GHz Photonic Self-Mixing Imaging-System with vertical illuminated Triple-Transit-Region Photodiode Terahertz Emitters
摘要： In this paper, we report a phase-sensitive photonic THz two-tone self-mixing imaging system, comprising a self-developed vertical illuminated triple transit region photodiode (TTR-PD) and a commercial square law Schottky barrier diode as THz emitter and THz detector, respectively. Using the two-tone self-mixing approach, the phase information of a device-under-test can be extracted by down-mixing two THz signals inside the SBD, whereas the phase information remains in the output signal. The THz tones are generated by two free-running lasers and the TTR-PD, while one optical signal is externally modulated for double sideband carrier suppression. By means of the self-mixing, the phase noises of the free running lasers are canceled out. Using a second PD for the trigger, lock-in detection allows fast imaging speed, only limited by the integration constant. Beside the imaging system, we present the characteristics of the used vertically illuminated terahertz triple transit region photodiodes with thin depletion zone and small active areas. Numerical analysis by energy-balance model based TCAD simulations show transit-time limitations over 200 GHz, due to the electron field management within the active photodiode layers and the resulting high electron velocities. Therefore, the fabricated TTR-PDs show a flat ±2 dB frequency response within the frequency range from 225 GHz to 305 GHz. By employing the proposed photonic two-tone imaging system with the fabricated TTR-PDs, amplitude and phase difference vector images are taken at 299.5 GHz and 300.5 GHz. Metal and acrylic glass items inside a paper envelope are clearly visible, which demonstrates the potential of the system.
关键词： energy balance,self-mixing,TCAD,Terahertz spectroscopy,terahertz imaging,terahertz photodiodes
更新于2025-09-19 17:13:59
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N-glycosylation state of TRPM8 protein revealed by terahertz spectroscopy and molecular modelling
摘要： TRPM8 member of the TRP superfamily of membrane proteins participates to various cellular processes ranging from Ca2+ uptake and cold sensation to cellular proliferation and migration. TRPM8 is a large tetrameric protein with more than 70% of its residues located in the cytoplasm. TRPM8 is N-glycosylated, with a single site per subunit. This work focuses on the N-glycosylation of TRPM8 channel that was previously studied by our group in relation to proliferation and migration of tumoral cells. Here, experimental data performed with deglycosylating agents assess that the sole glycosylation site contains complex glycans with a molecular weight of 2.5 kDa. The glycosylation state of TRPM8 in cells untreated and treated with a deglycosylating agent was addressed with Terahertz (THz) spectroscopy. Results show a clear difference between cells comprising glycosylated and deglycosylated TRPM8, the first presenting an increased THz absorption. Human TRPM8 was modelled using as templates the available TRPM8 and other TRPM channels structures. Glycosylations were modelled by considering two glycan structures with molecular weight close to the experiment: shorter and branched at the first sugar unit (glc1) and longer and unbranched (glc2). Simulation of THz spectra based on the molecular dynamics of unglycosylated and the two glycosylated TRPM8 models in lipid membrane and solvation box showed that glycan structure strongly influences the THz spectrum of the channel and of other components from the simulation system. Only spectra of TRPM8 with glc1 glycans were in agreement with the experiment, leading to the validation of glc1 glycan structure.
关键词： N-glycosylation,Terahertz spectroscopy,TRPM8,Molecular modelling,Membrane proteins
更新于2025-09-19 17:13:59