- 标题
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- 实验方案
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Fabrication of large-scale freestanding THz wire grid polarizers by femtosecond laser micromachining
摘要： High-performance THz polarizers, as a quasi-optical device to manipulate THz waves, are highly demanded for THz spectroscopy and imaging applications. In this work, we have employed the femtosecond laser micro-machining technique to fabricate freestanding THz wire grid polarizers with two kinds of reinforced line structures which weaken the e?ects of gravity sagging and entanglement of long free wires, thus enabling large-scale processing. The e?ect of the reinforced lines on the polarizers were simulated by the Finite-Di?erence Time-Domain (FDTD) method, and the performances of the polarizer were characterized by THz time-domain spectroscopy and compared with that of a commercial wire gird polarizer. The calculated transmittance is in good agreement with the FDTD results. The degree of polarization and the extinction ratio of the polarizer with discontinuous reinforced lines are better than those of a commercial wire grid polarizer.
关键词： Time-domain THz spectroscopy,THz,Femtosecond laser micro-machining,Wire grid polarizer
更新于2025-09-23 15:21:01
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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) - Tuneable Optical Frequency Comb Generator for THz Spectroscopy
摘要： We present an optical frequency comb generator with a record span of 3.8 THz suitable for high resolution THz spectroscopy, based on a single phase modulator system. The line spacing, exactly referenced to a microwave synthesizer, can be continuously tuned from 17.5 GHz to 20 GHz overcoming the limitation otherwise imposed by the free spectral range of the fibre loop, making the system capable of generating a continuously tuneable electrical signal from 122.5 GHz to >2.7 THz. The system noise has been measured up to a record frequency of 300 GHz, and shown to be limited by the multiplied phase noise of the reference synthesizer.
关键词： THz spectroscopy,tuneable,heterodyne signal,phase modulator,optical frequency comb generator
更新于2025-09-23 15:21:01
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Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells
摘要： n-type Ge/SiGe asymmetric coupled quantum wells represent the building block of a variety of nanoscale quantum devices, including recently proposed designs for a silicon-based THz quantum cascade laser. In this paper, we combine structural and spectroscopic experiments on 20-module superstructures, each featuring two Ge wells coupled through a Ge-rich SiGe tunnel barrier, as a function of the geometry parameters of the design and the P dopant concentration. Through a comparison of THz spectroscopic data with numerical calculations of intersubband optical absorption resonances, we demonstrated that it is possible to tune, by design, the energy and the spatial overlap of quantum confined subbands in the conduction band of the heterostructures. The high structural/interface quality of the samples and the control achieved on subband hybridization are promising starting points towards a working electrically pumped light-emitting device.
关键词： quantum wells,THz spectroscopy,group IV epitaxy,intersubband transitions,silicon–germanium heterostructures
更新于2025-09-23 15:19:57
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The TeraFERMI Electro-Optic Sampling Set-Up for Fluence-Dependent Spectroscopic Measurements
摘要： TeraFERMI is the THz beamline at the FERMI free-electron-laser facility in Trieste (Italy). It uses superradiant Coherent Transition Radiation emission to produce THz pulses of 10 to 100 μJ intensity over a spectral range which can extend up to 12 THz. TeraFERMI can be used to perform non-linear, ?uence-dependent THz spectroscopy and THz-pump/IR-probe measurements. We describe in this paper the optical set-up based on electro-optic-sampling, which is presently in use in our facility and discuss the properties of a representative THz electric ?eld pro?le measured from our source. The measured electric ?eld pro?le can be understood as the superimposed emission from two electron bunches of different length, as predicted by electron beam dynamics simulations.
关键词： THz spectroscopy,free-electron-lasers,nonlinear optics
更新于2025-09-23 15:19:57
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Conformational assignment of gas phase peptides and their H-Bonded complexes using far-IR/THz: IR- UV ion dip experiment, DFT-MD spectroscopy, and Graph Theory for modes assignment.
摘要： The combined approach of gas phase IR-UV ion dip spectroscopy experiments and DFT-based molecular dynamics simulations for theoretical spectroscopy reveals the 3D structures of (Ac-Phe-OMe)1,2 peptides using the far-IR/THz signatures. Both experimental and simulated IR spectra are well-resolved in the 100-800 cm?1 domain, allowing an unambiguous assignment of the conformers, that could not be achieved in other more congested spectral domains. We also present and make proofs-of-principles for our newly developed theoretical method for the assignment of (anharmonic) vibrational modes from MD simulations based on Graph Theory coupled to APT weighted-internal coordinates velocities DOS spectra. The principles of the method are reviewed, applications to the simple gas phase water and NMA (N-Methyl-Acetamide) molecules are presented, and the application to the more complex (Ac-Phe-OMe)1,2 peptidic systems shows that the complexity in assigning vibrational modes from MD simulations is released with the graphs. Our newly developed graph-based methodology is furthermore shown to allow an easy comparison between the vibrational modes of isolated monomer(s) and their complexes, as illustrated by the (Ac-Phe-OMe)1,2 peptides.
关键词： gas phase peptides,vibrational modes assignment,far-IR/THz spectroscopy,Graph Theory,IR-UV ion dip,DFT-MD simulations,β-sheet structures
更新于2025-09-19 17:15:36
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High-Performance GaAs/AlAs Terahertz Quantum-Cascade Lasers For Spectroscopic Applications
摘要： We have developed terahertz (THz) quantum-cascade lasers (QCLs) based on GaAs/AlAs heterostructures for application-defined emission frequencies between 3.4 and 5.0 THz. Due to their narrow line width and rather large intrinsic tuning range, these THz QCLs can be used as local oscillators in airborne or satellite-based astronomical instruments or as radiation sources for high-resolution absorption spectroscopy, which is expected to allow for a quantitative determination of the density of atoms and ions in plasma processes. The GaAs/AlAs THz QCLs can be operated in mechanical cryocoolers and even in miniature cryocoolers due to the comparatively high wall-plug efficiency of around 0.2% and typical current densities below 500 A/cm2. These lasers emit output powers of more than 1 mW at operating temperatures up to about 70 K, which is sufficient for most of the abovementioned applications.
关键词： terahertz (THz) spectroscopy,Quantum-cascade laser (QCLs)
更新于2025-09-19 17:13:59
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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) - Realtime Coherent cw THz System: Phase Modulation without Phase Modulator
摘要： In optoelectronic continuous wave (cw) THz spectroscopy phase measurement is very beneficial, to improve SNR and/or to obtain depth information. Often, the required phase modulation limits the acquisition speed and increases the complexity of existing cw THz systems. Commonly, optical free space delay lines, fibre stretchers [1] or electro optical modulators [2] are used for phase modulation. In this paper we demonstrate that a simple optical fiber delay in combination with a fast sweeping laser source can be used for ultrafast fast phase modulation. With this technique we demonstrate a fully fibre-coupled cw THz spectrometer with 58 Hz update rate covering a bandwidth of 2.5 THz. To the best of our knowledge this is the fastest coherent cw THz system demonstrated so far. This makes cw THz systems competitive to time-domain approaches in terms of acquisition speed and simplifies the system architecture significantly. Therefore, it paves the way for compact, broadband and cost-effective THz systems.
关键词： continuous wave,phase modulation,fast sweeping laser,fiber delay,THz spectroscopy
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) - Optoelectronic Properties of Tin-Based Hybrid Metal Halide Perovskite Thin Films for Photovoltaics
摘要： Due to their exceptional optoelectronic properties, hybrid metal halide perovskites films have shown extraordinary success as active layers in solar cells. One potential drawback of hybrid perovskites, however, is that the highest performing devices are currently based around toxic, lead-containing materials. Tin is a promising replacement for lead, p-doping in tin-based materials has prevented them from achieving the efficiencies of their lead-based analogues. Using optical-pump/THz-probe spectroscopy and THz time-domain spectroscopy, we compare the intrinsic and extrinsic optoelectronic properties formamidinium tin triiodide thin films and comment on the fundamental limits to charge transport.
关键词： tin-based hybrid metal halide perovskite,optoelectronic properties,photovoltaics,THz spectroscopy
更新于2025-09-12 10:27:22
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An advanced approach to control the electro-optical properties of LT-GaAs-based terahertz photoconductive antenna
摘要： This work reports on an advanced approach to the design of THz photoconductive antenna (PCA). The LT-GaAs thin films used for the PCA fabrication were synthesized by MBE method on GaAs (100) substrate by adjusting the As pressure, As/Ga fluxes ratio, growth/annealing temperatures and annealing time. These parameters crucially affect electro-optical properties of the PCA samples as evidenced by the THz radiation power and time-domain spectroscopy measurements. The annealing temperature of 670 °C was found to be optimal for constructing a PCA possessing high amplitude of the THz radiation over the spectral range up to 1 THz at the resonance of 0.1 THz. The comparison of this PCA with the reference ZnTe crystal reveals a 2-fold increase in THz power. Furthermore, this antenna attains a 1.5-, 3-, and 2-fold increase in THz power, photocurrent efficiency, and actuating dc BV, as compared with the commercial ZOMEGA antenna. These results pave the way towards the creation of highly efficient LT-GaAs-based PCAs.
关键词： THz-antenna,Terahertz (THz) radiation,Photoconductive antenna (PCA),Low temperature-grown gallium arsenide (LT-GaAs),THz-spectroscopy
更新于2025-09-11 14:15:04
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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) - Carrier Dynamics in SnS<inf>2</inf> Single Crystals and Vertical Nanostructures: Role of Edges
摘要： SnS2 is a member of the van der Waals 2D layered materials family. Its moderate bandgap, environmental stability and high carrier mobility makes it attractive for solar energy conversion application. We explore how nanostructuring SnS2 in the form of vertically-aligned nanoflakes to increase the surface area impacts the lifetime and microscopic conductivity of photoinjected carriers compared to the bulk SnS2. Increased surface area and the presence of edges is beneficial to the efficiency of SnS2 photoanode performance but it comes at a cost of increased carrier trapping at surface and edge states.
关键词： THz spectroscopy,van der Waals materials,SnS2,carrier dynamics,nanostructuring
更新于2025-09-11 14:15:04