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- 摘要
- 关键词
- 实验方案
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Cation disorder and epitaxial strain modulated Drude–Smith type terahertz conductivity and Hall-carrier switching in Ca <sub/> 1? <i>x</i> </sub> Ce <sub/><i>x</i> </sub> RuO <sub/>3</sub> thin films
摘要： The CaRuO3 is a non-Fermi liquid pseudo-cubic perovskite with a magnetic ground state on the verge of phase transition and it lies in the vicinity of the quantum critical point. To understand the sensitivity of its ground state, the effects of subtle aliovalent chemical disorder on the static and high frequency dynamic conductivity in the coherently strained structures were explored. The Ce-doped Ca1?xCexRuO3 (0 ? x ? 0.1) thin films were deposited on LaAlO3 (1 0 0) and SrTiO3 (1 0 0) substrates and studies for low-energy terahertz (THz) carrier dynamics, dc transport and Hall effect. These compositions exhibited a very effective and unusual Hall-carrier switching in both compressive and tensile strain induced epitaxial thin films. The dc resistivity depicts a switching from a non-Fermi liquid to a Fermi liquid behavior without any magnetic phase transition. A discernible and gradual crossover from Drude to Drude–Smith THz dynamic optical conductivity was observed while traversing from pure to 10% Ce-doped CaRuO3 films. Overall, a nearly Fermi liquid behavior, effective carrier switching and unusual features in THz conductivity, were all novel features realized for the first time in physically and/or chemically modified CaRuO3. These new phases highlight the novel subtleties and versatility of the systems lying near the quantum critical point.
关键词： epitaxial strain,terahertz,allovalent doping,Hall carrier switching
更新于2025-09-23 15:23:52
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Ruler equation for precisely tailoring the resonance frequency of terahertz U-shaped metamaterials
摘要： Artificially controlling the spectral response of metamaterials is important for the applications of functional devices. Here, we identify a simple ruler equation for describing the direct relation between the resonance frequencies and geometric parameters in terahertz U-shaped metamaterials. Utilizing this ruler equation, we demonstrate the switching of the multi-band resonator which can be customized to work at expectant frequency bands. This ruler equation provides a practical guidance on tailoring the resonance frequency and paves the way for the development of metamaterial-based terahertz functional devices.
关键词： terahertz,surface plasmon,metamaterials
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Moving Target Detection for THz SAR Systems Based on Multilook Processing
摘要： Compared with conventional X-band synthetic aperture radar (SAR) systems, THz SAR is more sensitive to Doppler vibration and has better detection performance for moving targets. In this paper, a moving target detection scheme is designed for terahertz SAR systems based on multilook processing. The Doppler spectrum is divided into several sub-looks and focused separately to generate corresponding sub-images. Moving targets are indicated through sharpness detection of the sub-images. The effectiveness of the proposed algorithm is veri?ed by simulated data.
关键词： terahertz,multilook processing,moving target detection,Synthetic aperture radar
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Intelligent Informatics and Biomedical Sciences (ICIIBMS) - Bangkok (2018.10.21-2018.10.24)] 2018 International Conference on Intelligent Informatics and Biomedical Sciences (ICIIBMS) - Computational Study of Frozen Tissue Melanoma Imagining at Terahertz Frequencies
摘要： Terahertz radiation is highly absorbed by liquid water, with less than 0.0001% of the signal surviving to a depth of 1.0 millimeter at 0.45 terahertz, limiting the potential for imaging of human tissues. On the other hand, 90% of the terahertz signal survives in ice in the 0.1 to 1.0 terahertz band, opening the possibility of in-vivo imaging of skin lesions, particularly melanomas, to a depth of 5.0 millimeters by first freezing the skin in situ. Computational modelling of THz-frozen skin imaging indicates that contrast exists to differentiate melanomas from normal frozen skin on the basis of water content alone. If the melanin content of melanomas is a significant absorber of terahertz radiation, then melanin becomes the main contrast element. The modelling results justify the further exploration of the imaging technique with the study of ex-vivo frozen melanoma samples before progressing to in-vivo clinical trials.
关键词： terahertz,melanoma,skin,freezing,imaging
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A 300GHz Monolithic Integrated Amplifier in 0.5-μm InP Double Heterojunction Bipolar Transistor Technology
摘要： We present a compact, 6-stage terahertz monolithic integrated circuit (TMIC) amplifier with an operating frequency of 275-310GHz, formed by common-base configured 0.5 um InP Double Heterojunction Bipolar Transistor (DHBT) and a multilayer thin-film microstrip (TFM) wiring environment. The amplifier small signal gain exhibits >7.4dB at 300GHz. The peak gain is 12.5dB at 280GHz. This is the first time reported InP DHBT TMIC amplifier operating in H-band employing TFM in china. The total size of this 6-stage amplifier is only 1.7 mm ╳0.9 mm.
关键词： thin-film microstrip (TFM),Indium phosphide (InP),H-band,Amplifier,Heterojunction bipolar transistors (HBTs),Terahertz monolithic integrated circuit (TMIC)
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Sheffield (2018.7.8-2018.7.11)] 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Multi-Layer Terahertz Imaging of Non-Overlapping Contents
摘要： This paper considers terahertz (THz) imaging of multi-layer non-overlapping contents with compressed measurements. One issue here is the shadow effect from front layers to deep layers due to the non-uniform penetrating illumination. In the case of non-overlapping contents in layered structures, the shadow effect can be utilized to improve recovery performance and reduce the number of measurements. To this end, we propose several approaches based on the total variation (TV) minimization principle and take into account individual-layer sparsity, group sparsity over layers, and hierarchical group sparsity over layers to reduce the number of measurements. Numerical evaluation confirms the effectiveness of the proposed approaches.
关键词： compressed measurements,content extraction,Terahertz,multi-layer structure
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - A High Frequency Vibration Compensation Approach in Terahertz SAR Based on Wavelet Multi-Resolution Analysis
摘要： The use of terahertz wave in SAR imaging can solve the difficulties of frame rate and detection of slow moving targets in conventional SAR imaging. The most important difference between terahertz SAR (THz-SAR) and conventional SAR is the treatment on motion compensation. For reason that the wavelength of terahertz SAR is much shorter than that of conventional microwave SAR, the tiny vibration of SAR platform will blur SAR images, especially high frequency components. The high frequency vibration will result in paired echoes in SAR imaging, which can't be focused with traditional SAR imaging algorithms. Thus the vibration parameters can't be estimated precisely enough to construct the reference function to compensate the sinusoidal modulation phase. So we first get focused paired echoes in terahertz SAR imaging through Doppler keystone transform (DKT), then we propose a frequency estimation method based on wavelet multi-resolution analysis, along with parametric space projection method, to complete the high frequency vibration estimation of terahertz SAR. At last, the numerical tests using the point target echoes validate the proposed method.
关键词： synthetic aperture radar,high frequency vibration error,Terahertz,wavelet multi-resolution analysis,vibration estimation
更新于2025-09-23 15:22:29
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Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
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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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Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application
摘要： In recent years, tremendous advances have been made in the choice of materials used in the industry. With weight reduction as the goal, composite and polymer materials are more and more popular but they are almost transparent to X-ray. Because of this, interest has grown in other wavelengths like terahertz (THz). Due to a difference in how X-ray and THz propagate, X-ray CT algorithms cannot be directly used. For example, THz induces refraction making the reconstruction problem nonlinear. In this paper, we present a new algorithm which complies with beam profile intensities, refraction, and reflection. It is based on linearizing the reconstruction process around a computer-aided design (CAD) model of the object to be reconstructed. The method we propose computes the deviation between the object and this model.
关键词： Terahertz computed tomography,Inverse problem,Nondestructive testing,Modeling,Monte Carlo,Refraction,Nonlinear problem,Projection simulation
更新于2025-09-23 15:22:29