Optically driven photoconductive switches are one of the predominant sources currently used in terahertz im-aging systems.However,owing to their low average powers,only raster-based images can be taken,resulting in sl...Optically driven photoconductive switches are one of the predominant sources currently used in terahertz im-aging systems.However,owing to their low average powers,only raster-based images can be taken,resulting in slow acquisition.In this work,we show that by placing a photoconductive switch within a cavity,we are able to generate absolute average THz powers of 181μW with the frequency of the THz emission centered at 1.5 THz-specifications ideally adapted to applications such as non-destructive imaging.The cavity is based on a metal-insulator-metal structure that permits an en hancement of the average power by almost 1 order of magnitude compared to a standard structure,while conserving a broadband spectral response.We demonstrate proof-of-principle real-time imaging using this source,with the broadband spectrum permitting to eliminate strong diffraction artifacts.展开更多
This application note discusses the preliminary results of paleomagnetics studies of several incisions of the Paleozoic period the territory of Armenia and neighboring regions （Minor Caucasus）. It is supposed that b...This application note discusses the preliminary results of paleomagnetics studies of several incisions of the Paleozoic period the territory of Armenia and neighboring regions （Minor Caucasus）. It is supposed that before the Permian period the Armenian-lranian Mezocontinent was uniform with Afro-Arabia and only at the end of the late Paleozoic the formed Mesozoic ocean separated these areas from each other. A result of application of the complex laboratory investigations were identified from samples of primary magnetization the direction of which corresponds to the time of formation of the studied rocks. On the basis of paleomagnetic researches of Triassic, Permian, Devonian, Carbonian rocks a preliminary conclusion has been made about the dipole configuration of the geomagnetic field throughout Paleozoic. The comparison of the obtained data to paleomagnetic definitions of African, Arabian plates, Europe and the Siberian platform leads to the conclusion that the Minor Caucasus existed separately from the present general lithosphere blocks of Greater Caucasus and Europe.展开更多
Epitaxial VO_(2)films grown by pulsed laser deposition(PLD)method with superior phase transition related switching characteristics are successfully embedded to SAW devices using concept of the“impedance loaded SAW se...Epitaxial VO_(2)films grown by pulsed laser deposition(PLD)method with superior phase transition related switching characteristics are successfully embedded to SAW devices using concept of the“impedance loaded SAW sensor”.A resistance of VO2 sensor abruptly drops from 0.7 MΩto 90Ωwhen it is heated above~65℃and shows a narrow hysteresis loops when switching.Two designs of SAW devices are examined in which RF signal is reflected back from interdigital transducer(IDT)or a surface acoustic waves(SAW)is transferred through a coupler and the RF response is altered 2 and 3 times correspondingly upon the phase transition in VO2.In the proposed devices with external load,a SAW does not propagate via VO2 film and therefore is not attenuated which is beneficiary for wireless applications.Additionally,a SAW phase shift as great as 50°is induced to the SAW transferred through the coupler due to the phase transition in VO2.The proposed approach may boost the development of remotely controlled autonomous sensors,including those based on VO2 metamaterials and hybrid plasmonic structures for near IR/middle IR and sub-THz/THz applications.展开更多
A tunable high-Q surface acoustic wave(SAW)resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied.The worki...A tunable high-Q surface acoustic wave(SAW)resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied.The working frequency range was 90-2450 MHz.A method of calculating such resonators,considering losses in the metal film as well as losses due to the propagation of SAWs and transformations into bulk waves is proposed.Such a design allows one to obtain a quality factor over 5000 in the frequency range 2400-2483 MHz.The resonant frequency shifts by 600 kHz when the capacitance changes by±25%of the value of 21 pF(or 32 ppm/pF)and has an almost linear character.展开更多
Let is the Walsh generalized system. In the paper constructed a weighted space , and series in the Walsh generalized system with monotonically decreasing coefficient such that for each function in the space one can fi...Let is the Walsh generalized system. In the paper constructed a weighted space , and series in the Walsh generalized system with monotonically decreasing coefficient such that for each function in the space one can find a subseries that converges to in the weighted and almost everywhere on [0,1].展开更多
基金H2020 Future and Emerging Technologies(MIRBOSE 737017)French RENATECH network.
文摘Optically driven photoconductive switches are one of the predominant sources currently used in terahertz im-aging systems.However,owing to their low average powers,only raster-based images can be taken,resulting in slow acquisition.In this work,we show that by placing a photoconductive switch within a cavity,we are able to generate absolute average THz powers of 181μW with the frequency of the THz emission centered at 1.5 THz-specifications ideally adapted to applications such as non-destructive imaging.The cavity is based on a metal-insulator-metal structure that permits an en hancement of the average power by almost 1 order of magnitude compared to a standard structure,while conserving a broadband spectral response.We demonstrate proof-of-principle real-time imaging using this source,with the broadband spectrum permitting to eliminate strong diffraction artifacts.
文摘This application note discusses the preliminary results of paleomagnetics studies of several incisions of the Paleozoic period the territory of Armenia and neighboring regions （Minor Caucasus）. It is supposed that before the Permian period the Armenian-lranian Mezocontinent was uniform with Afro-Arabia and only at the end of the late Paleozoic the formed Mesozoic ocean separated these areas from each other. A result of application of the complex laboratory investigations were identified from samples of primary magnetization the direction of which corresponds to the time of formation of the studied rocks. On the basis of paleomagnetic researches of Triassic, Permian, Devonian, Carbonian rocks a preliminary conclusion has been made about the dipole configuration of the geomagnetic field throughout Paleozoic. The comparison of the obtained data to paleomagnetic definitions of African, Arabian plates, Europe and the Siberian platform leads to the conclusion that the Minor Caucasus existed separately from the present general lithosphere blocks of Greater Caucasus and Europe.
基金supported by Southern Federal University research project No.07/2020-06-MM and 10th Anniversary International Conference on“Physics and Mechanics of New Materials and Their Applications”(PHENMA 2021-2022).
文摘Epitaxial VO_(2)films grown by pulsed laser deposition(PLD)method with superior phase transition related switching characteristics are successfully embedded to SAW devices using concept of the“impedance loaded SAW sensor”.A resistance of VO2 sensor abruptly drops from 0.7 MΩto 90Ωwhen it is heated above~65℃and shows a narrow hysteresis loops when switching.Two designs of SAW devices are examined in which RF signal is reflected back from interdigital transducer(IDT)or a surface acoustic waves(SAW)is transferred through a coupler and the RF response is altered 2 and 3 times correspondingly upon the phase transition in VO2.In the proposed devices with external load,a SAW does not propagate via VO2 film and therefore is not attenuated which is beneficiary for wireless applications.Additionally,a SAW phase shift as great as 50°is induced to the SAW transferred through the coupler due to the phase transition in VO2.The proposed approach may boost the development of remotely controlled autonomous sensors,including those based on VO2 metamaterials and hybrid plasmonic structures for near IR/middle IR and sub-THz/THz applications.
基金This research work is supported by the Russian Ministry of Science and Higher Education under the project No.16.5405.2017/8.9。
文摘A tunable high-Q surface acoustic wave(SAW)resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied.The working frequency range was 90-2450 MHz.A method of calculating such resonators,considering losses in the metal film as well as losses due to the propagation of SAWs and transformations into bulk waves is proposed.Such a design allows one to obtain a quality factor over 5000 in the frequency range 2400-2483 MHz.The resonant frequency shifts by 600 kHz when the capacitance changes by±25%of the value of 21 pF(or 32 ppm/pF)and has an almost linear character.
文摘Let is the Walsh generalized system. In the paper constructed a weighted space , and series in the Walsh generalized system with monotonically decreasing coefficient such that for each function in the space one can find a subseries that converges to in the weighted and almost everywhere on [0,1].
