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Measuring effective electro-optic coefficient at 1040?nm by spectral intensity modulation with THz time-domain spectroscopy
摘要： We report a single method for measuring the e?ective electro-optics (EO) coe?cient only by spectral intensity modulation with a terahertz time-domain spectroscopy (THz-TDS) device. Compared with conventional methods, the measuring device based on THz-TDS by probing the spectral intensity modulation is simple, rapid, and highly sensitive. It does not require special preparation process, electrode contact or applying high voltage on the sensor samples. The EO coe?cients of four kinds of materials, namely, ZnTe and GaP crystals, DAST wafer and GaSe ?lm, are measured at 1040 nm. The results showed good agreement with literature data by the conventional methods.
关键词： E?ective electro-optic coe?cient,EO materials,Spectral intensity modulation,THz-TDS
更新于2025-11-28 14:24:03
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Fermi velocity renormalization in graphene probed by terahertz time-domain spectroscopy
摘要： We demonstrate terahertz time-domain spectroscopy (THz-TDS) to be an accurate, rapid and scalable method to probe the interaction-induced Fermi velocity renormalization νF* of charge carriers in graphene. This allows the quantitative extraction of all electrical parameters (DC conductivity σDC, carrier density n, and carrier mobility μ) of large-scale graphene films placed on arbitrary substrates via THz-TDS. Particularly relevant are substrates with low relative permittivity (< 5) such as polymeric films, where notable renormalization effects are observed even at relatively large carrier densities (> 1012 cm-2, Fermi level > 0.1 eV). From an application point of view, the ability to rapidly and non-destructively quantify and map the electrical (σDC, n, μ) and electronic (νF*) properties of large-scale graphene on generic substrates is key to utilize this material in applications such as metrology, flexible electronics as well as to monitor graphene transfers using polymers as handling layers.
关键词： Graphene,THz-TDS,Fermi Velocity Renormalization,Mobility Mapping,Flexible Substrates
更新于2025-09-23 15:19:57
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Including the Effects of Covering Layers in the Determination of Graphene Conductivity from THz-TDS Measurements
摘要： We investigate the effects of covering layers on the determination of graphene conductivity from THz-TDS measurements. Especially the errors arising from the common approach to neglect those layers in the determination process are addressed. To counteract those errors an expanded determination method, based on the classical thin-film approach is introduced.
关键词： thin-film approximation,graphene conductivity,THz-TDS measurements,covering layers
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Terahertz Spectroscopy of Different Phenotypes of Arabidopsis Thaliana
摘要： The recent surge in ‘Precision agriculture’ is fueled by the acute need of food security felt worldwide to feed the global burgeoning population. To this effect, various optical techniques have recently been employed to characterize the biochemical processes in various parts of the plants [1]. Terahertz (THz) region (0.3 – 10 THz) has gathered momentum in this field as it is biologically safe, can penetrate food packaging and most importantly, has fingerprinting ability of various organic and inorganic molecules due to active rotational and vibrational modes [2]. Moreover, unlike other optical spectroscopic techniques, THz time domain spectroscopic (THz-TDS) technique records the information in form of THz electric field; which once converted to frequency domain provides both amplitude and phase information [3]. Additionally, THz waves are highly absorbed by water which in turn can be utilized for quantitative water status monitoring in plants [4]. In this work, we have used THz-TDS with a bandwidth over 5 THz for the detection of biochemicals present in two different T-DNA insertion mutants in two independent genes of Arabidopsis thaliana (Col-0 Columbia ecotype). The plants were grown from mutant seeds in controlled environment. For easier optical access to all parts of the plants, the seedlings were grown parallel to the surface in a petri dish of plant growth medium. Liu et al. has already reported successful discrimination of transgenic Soybean seeds using THz spectroscopy [5]. We have recorded spectroscopic data of several parts of all the mutant plants which were 5, 7, 12 and 13 days old kept under identical conditions. The time domain spectrum obtained from the experiment was converted to frequency domain. Figure 1 shows the frequency domain spectrum of one such set of spectroscopic data collected from the stem part of the two different mutants compared to wild type control Col-0 plants. As it is evident from the spectrum, there are many absorption peaks corresponding to water and other biochemical molecules. For example, the peaks at 1.7 THz and 2.6 THz corresponds to sucrose present in the plants and in the nutri-solution which has been taken as the reference [2]. Our ongoing study involves careful analysis of the variations of the molecular absorption peaks for different mutants which would not only enable a label-free genetic identification, but also would help in our understanding of the underlying shift in biochemical processes contributed by the specific gene.
关键词： Terahertz spectroscopy,Arabidopsis thaliana,THz-TDS,Precision agriculture,biochemical processes
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz Properties of Fe and Ti Oxides Nanoparticles Obtained by Pulsed Laser Ablation
摘要： We present Dielectric properties of Fe and Ti oxides nanoparticles (NPs) measured by THz-TDS. The NPs were obtained via ns pulsed laser ablation (PLA) of the metals in air and water and were annealed at different temperatures. In the paper, we exhibit the dependence of absorption spectra on NPs structure: from magnetite to hematite for Fe, and from anatase to rutile for Ti. The prospects for their use as materials for the THz photonics are discussed.
关键词： THz-TDS,Fe and Ti oxides nanoparticles,THz photonics,dielectric properties,pulsed laser ablation
更新于2025-09-12 10:27:22
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Far Infrared and THz Detectors: Principles of Operation and Figures of Merit
摘要： In this paper we discuss characteristics of detectors and their experimental applications in the Far Infared (FIR) and lower THz spectral range: 50-3000 GHz (6mm-100 μm), with special attention to Plasma Diagnostics, THz-TDS and Free Electron Lasers (FEL). The International System of Units (SI) will be used throughout.
关键词： THz-TDS,Far Infrared,THz Detectors,Plasma Diagnostics,Free Electron Lasers
更新于2025-09-09 09:28:46
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz Near- Field Imaging and Spectroscopy with Nanoscale Resolution
摘要： Scattering-type near-field microscopy can overcome the limits in spatial resolution present in conventional THz imaging and spectroscopy techniques. This talk shows how THz near-field imaging and THz-TDS with a spatial resolution <20 nm can be realized with our neaSNOM microscope and some of the possible applications.
关键词： THz-TDS,nanoscale resolution,neaSNOM microscope,THz near-field imaging
更新于2025-09-04 15:30:14