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[IEEE 2019 IEEE SENSORS - Montreal, QC, Canada (2019.10.27-2019.10.30)] 2019 IEEE SENSORS - Evanescent field waveguide particle detector : Simulations concerning size and shape dependence
摘要： The midinfrared (MIR) spectral region (3–5 μm), which penetrates most haze layers in the atmosphere and is less sensitive to variations in atmospheric water vapor, seems to be appropriate for retrieving land surface temperature (LST). However, there are currently few studies of LST retrieval with MIR data because it is difficult to eliminate solar irradiance from the total energy measured in the MIR during the daytime. This paper proposes a physics-based method to retrieve LST from MODIS daytime MIR data. The bidirectional reflectivity describing the reflected solar direct irradiance is determined using the method by Tang and Li. The directional emissivity, representing the surface emitted radiance, is determined by a kernel-driven bidirectional reflectance distribution function model, i.e., RossThick-LiSparse-R. Intercomparisons using the MODIS-derived LST product MYD11_L2, for the Baotou experimental site in Urad Qianqi, Inner Mongolia, China, have a maximum root-mean-square error (RMSE) of 1.69 K and a minimum RMSE of 1.31 K, for four scenes of MODIS images. Furthermore, in situ LSTs measured at the Hailar field site in northeastern Inner Mongolia, China, were also used to validate the proposed method. Comparisons of the LSTs retrieved from MODIS daytime MIR data and those calculated using in situ measurements have a bias and RMSE of ?0.17 K and 1.42 K, respectively, which indicates that the proposed method can accurately retrieve LST from MODIS daytime MIR data.
关键词： MODIS,midinfrared (MIR),Daytime,land surface temperature (LST)
更新于2025-09-23 15:19:57
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Laser-driven tunneling photocurrent as a source of midinfrared to microwave multidecade supercontinua yoked to high-order harmonics
摘要： Electron tunneling induced by a strong-field laser driver can lead to an ultrafast stepwise buildup of the photoelectron density ρ. When the laser field is strong enough, each such step in the temporal profile of ρ is confined well within the field cycle, providing an ultrabroadband, multidecade force that drives the photoelectron current j. However, whether or not the photocurrent can emit electromagnetic radiation with such an extraordinarily broad spectrum depends on the damping, which defines the low-frequency cutoff in the spectrum of this radiation. We show that, with a suitable choice of the gas pressure and parameters of the laser driver, the laser-induced tunneling photocurrent can serve as a source of a remarkably broadband electromagnetic radiation with a multidecade spectrum stretching from the vacuum ultraviolet all the way down to the microwave range. We demonstrate that the supercontinuum fields emitted by individual photocurrent steps, induced by different field half cycles, can coherently combine, giving rise to well-resolved high-order harmonics on the high-frequency end of the spectrum yoked to a bright midinfrared to microwave supercontinuum, dominating the long-wavelength part of the multidecade radiation output.
关键词： high-order harmonics,photocurrent,supercontinua,microwave,midinfrared,laser-driven tunneling
更新于2025-09-19 17:13:59
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Attomolar Detection of Low-Molecular Weight Antibiotics Using Midinfrared-Resonant Toroidal Plasmonic Metachip Technology
摘要： Plasmonic metamaterials can be used to enhance midinfrared sensors and detectors for immunosensing applications. The major challenge with them is to integrate these technologies in low-cost, compact, and promising platforms. As an emerging technique, we utilize toroidal resonant plasmonic metamaterials to develop an ultrasensitive label-free analytical platform for the detection of specific antibiotics in the midinfrared spectra. Taking advantage of the unique sensitivity of robustly squeezed electromagnetic fields in the toroidal plasmonic meta-atoms, we demonstrate that our proposed approach based on toroidal metastructures provides recognition of extremely-low-weight (approximately 0.6 KDa) biological targets at attomolar densities. We envisage that this understanding extends the capabilities of plasmonic metamaterials to analyze the presence of specific biological molecules and organisms with ultrahigh precision.
关键词： midinfrared sensors,Plasmonic metamaterials,ultrasensitive label-free analytical platform,antibiotics detection,toroidal resonant plasmonic metamaterials
更新于2025-09-11 14:15:04
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Broadband Linear-to-Circular Polarization Conversion Enabled by Birefringent Off-Resonance Reflective Metasurfaces
摘要： Due to the scarcity of circular polarization light sources, linear-to-circular polarization conversion is required to generate circularly polarized light for a variety of applications. Despite significant past efforts, broadband linear-to-circular polarization conversion remains elusive particularly in the terahertz and midinfrared frequency ranges. Here we propose a novel mechanism based on coupled mode theory, and experimentally demonstrate at terahertz frequencies that highly efficient (power conversion efficiency approaching unity) and ultrabroadband (fractional bandwidth up to 80%) linear-to-circular polarization conversion can be accomplished by the judicious design of birefringent metasurfaces. The underlying mechanism operates in the frequency range between well separated resonances, and relies upon the phase response of these resonances away from the resonant frequencies, as well as the balance of the resonant and nonresonant channels. This mechanism is applicable for any operating frequencies from microwave to visible. The present Letter potentially opens a wide range of opportunities in wireless communications, spectroscopy, and emergent quantum materials research where circularly polarized light is desired.
关键词： linear-to-circular polarization conversion,midinfrared,birefringent metasurfaces,terahertz,broadband
更新于2025-09-11 14:15:04
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Ultrathin Yttria-Stabilized Zirconia as a Flexible and Stable Substrate for Infrared Nano-Optics
摘要： Infrared (IR) technologies have become increasingly relevant as they offer a wide range of applications, from thermal imaging to chemical and biological vibrational spectroscopy. Substrate materials, such as calcium fluoride and zinc selenide, are commonly used for IR optics. Unfortunately, they are typically fragile or hygroscopic, thus potentially producing problems during device fabrication and in the long-term functional operation. Here, yttria-stabilized zirconia (YSZ) ceramic is introduced as a flexible and stable platform for IR nano-optics. In particular, the YSZ substrate is combined with metallic nanostructures and graphene to demonstrate new plasmonic, polarizing, and transparent heating devices, which, at the same time, enable high-temperature processing and withstand harsh environments thanks to the high YSZ thermal and chemical stability. In addition, it is shown that the YSZ substrate is mechanically flexible, ideally suited for making foldable or bendable devices, and for low-cost large-scale roll-to-roll fabrication processes. The combination of all the aforesaid features, which are not available from other alternative materials, and this work offers compelling evidence that ultrathin YSZ is a unique substrate for IR applications.
关键词： zirconia,transparent,graphene,midinfrared,flexible plasmonics
更新于2025-09-10 09:29:36