The Experts below are selected from a list of 1785 Experts worldwide ranked by ideXlab platform
Rainer Hillenbrand - One of the best experts on this subject based on the ideXlab platform.
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terahertz nanofocusing with cantilevered terahertz Resonant Antenna tips
Nano Letters, 2017Co-Authors: Stefan Mastel, Mark B Lundeberg, Pablo Alonsogonzalez, Kenji Watanabe, Takashi Taniguchi, James Hone, Frank H L Koppens, Alexey Yu Nikitin, Rainer HillenbrandAbstract:We developed THz-Resonant scanning probe tips, yielding strongly enhanced and nanoscale confined THz near fields at their tip apex. The tips with length in the order of the THz wavelength (λ = 96.5 μm) were fabricated by focused ion beam (FIB) machining and attached to standard atomic force microscopy (AFM) cantilevers. Measurements of the near-field intensity at the very tip apex (25 nm radius) as a function of tip length, via graphene-based (thermoelectric) near-field detection, indicate their first and second order geometrical Antenna resonances for tip length of 33 and 78 μm, respectively. On resonance, we find that the near-field intensity is enhanced by one order of magnitude compared to tips of 17 μm length (standard AFM tip length), which is corroborated by numerical simulations that further predict remarkable intensity enhancements of about 107 relative to the incident field. Because of the strong field enhancement and standard AFM operation of our tips, we envision manifold and straightforward f...
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Resonant Antenna probes for tip enhanced infrared near field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent...
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Resonant Antenna probes for tip-enhanced infrared near-field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices.
Jung-woo Baik - One of the best experts on this subject based on the ideXlab platform.
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a slot loaded composite right left handed transmission line for a zeroth order Resonant Antenna with improved efficiency
IEEE Transactions on Microwave Theory and Techniques, 2009Co-Authors: Jung-woo BaikAbstract:In this paper, a new composite right/left-handed transmission line (CRLH-TL) with equilateral slots is proposed for efficiency-improved zeroth-order Resonant Antennas. A 1-D infinitesimal equivalent transmission line circuit model is derived, and the characteristic impedance and dispersive relation are theoretically computed. Based on the isotropic arranged unit cells of the slot-loaded composite right/left-handed transmission line (SL CRLH-TL), 2-D zeroth-order resonators are designed for planar magnetic monopole Antenna applications. The SL CRLH-TL provides the zeroth-order resonance with some degradation of the quality factor. Therefore, a highly efficient radiating resonator can be designed with higher gain at the zeroth-order frequency. The theoretical approach was verified by the experimental results. The radiation efficiency was improved by up to 45.6% for the nine-rectangular zeroth-order Resonant Antenna and 21.4% for the seven-hexagonal zeroth-order Resonant Antenna without degrading the radiating performance. Moreover, the Antenna gains of these two Antennas were enhanced by 7.56 and 6.31 dB, respectively, due to the increase of the radiation efficiency.
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A Slot-Loaded Composite Right/Left-Handed Transmission Line for a Zeroth-Order Resonant Antenna With Improved Efficiency
IEEE Transactions on Microwave Theory and Techniques, 2009Co-Authors: Jung-woo BaikAbstract:In this paper, a new composite right/left-handed transmission line (CRLH-TL) with equilateral slots is proposed for efficiency-improved zeroth-order Resonant Antennas. A 1-D infinitesimal equivalent transmission line circuit model is derived, and the characteristic impedance and dispersive relation are theoretically computed. Based on the isotropic arranged unit cells of the slot-loaded composite right/left-handed transmission line (SL CRLH-TL), 2-D zeroth-order resonators are designed for planar magnetic monopole Antenna applications. The SL CRLH-TL provides the zeroth-order resonance with some degradation of the quality factor. Therefore, a highly efficient radiating resonator can be designed with higher gain at the zeroth-order frequency. The theoretical approach was verified by the experimental results. The radiation efficiency was improved by up to 45.6% for the nine-rectangular zeroth-order Resonant Antenna and 21.4% for the seven-hexagonal zeroth-order Resonant Antenna without degrading the radiating performance. Moreover, the Antenna gains of these two Antennas were enhanced by 7.56 and 6.31 dB, respectively, due to the increase of the radiation efficiency.
Florian Huth - One of the best experts on this subject based on the ideXlab platform.
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Resonant Antenna probes for tip enhanced infrared near field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent...
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Resonant Antenna probes for tip-enhanced infrared near-field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices.
K.l. Sheeja - One of the best experts on this subject based on the ideXlab platform.
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Design and optimisation of a zeroth order Resonant Antenna along with experimental verification for wireless applications
International Journal of Signal and Imaging Systems Engineering, 2015Co-Authors: K.l. Sheeja, Prasanna Kumar Sahu, Santanu Kumar BeheraAbstract:In this paper, optimisation and experimental verification of a compact zeroth order Resonant Antenna is presented. It is observed that an Antenna can be tuned to a desired working frequency by adjusting the inductive via radius. The Antenna is subsequently optimised using HFSS simulation software. Pattern search optimisation is carried out to determine the optimum via radius to achieve minimum reflection coefficient with enhanced bandwidth. Using optimisation we achieved dual band backward wave with a bandwidth of about 2% at 4.28 GHz. After designing and optimisation the Antenna is analysed for its performance. The proposed Antenna is measured at Antenna Measurement Facility (AMF), ISRO, Ahmedabad. A good agreement between the measured and the simulated results validates the design. The simulated bandwidth at 3.695 GHz covers the IEEE 802.11 wireless local–area network (WLAN) standards. The designed compact Antenna is most suitable for precise wireless applications having good radiation characteristics with wide coverage area.
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CPW fed elliptical zeroth order Resonant Antenna for WiMax applications
Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, 2012Co-Authors: K.l. Sheeja, P.k. SahuAbstract:In this paper, a new compact coplanar waveguide (CPW) fed elliptical zeroth order Resonant (ZOR) Antenna based on Composite Right/Left Handed (CRLH) transmission line is proposed. The performance of the Antenna is designed and simulated by Ansoft HFSS. The reflection coefficient, gain and Antenna efficiency of the proposed Antenna are observed to be - 38.3108dB, 2.1930dB and 77.286% respectively at the zeroth mode of 4.89GHz. In this paper an effort is made to circumvent the narrow bandwidth problem and fabrication complexity as exhibited by popular microstrip based ZOR Antennas with vias. It is observed that an extended bandwidth of about 6.6% at the zeroth mode is obtained. Since the proposed Antenna is implemented by using a combination of open ended spiral and anti-spiral inductors using CPW feeding technique, so vias are not required which enables the fabrication of this Antenna simple and easy. The proposed Antenna also has an additional advantage of being a very low profile one exhibiting an omni-directional radiation pattern typical of monopole Antennas. Hence the Antenna is suitable for modern wired and wireless systems and also suitable for Worldwide interoperability for Microwave Access (WiMax) applications (IEEE 802.11a standard).
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Comparative study of a CRLH TL based Zeroth Order Resonant Antenna
2012 National Conference on Communications (NCC), 2012Co-Authors: K.l. Sheeja, Prasanna Kumar Sahu, Santanu Kumar BeheraAbstract:In this paper, a comparative study between a compact microstrip Zeroth Order Resonant Antenna with another coplanar waveguide (CPW) based vialess ZOR Antenna is presented. But the drawback of this microstrip based CRLH TL is that a narrow bandwidth of about 0.75% with an improved gain of about 3.6256dB is achieved. In order to circumvent this drawback we demonstrate a vialess CPW fed structure using the same substrate, RT Duroid (5880) (e R = 2.2, h = 1.57mm) and compare the performance of both these Antennas. In the CPW fed case we obtain a bandwidth enhancement of about 7.84% with a dumb-bell shaped radiation pattern at phi=90deg (E-radiation pattern). The zeroth order mode obtained in this case is at 2.14GHz while with the microstrip based ZOR Antenna, the zeroth order freq is at 3.995GHz with a monopolar radiation pattern at phi=90deg. The CPW fed Antenna is easy to fabricate as it is based on a single layer. The drawback of this CPW fed Antenna is that the gain reduces to 1.6949dB as the structure is electrically much smaller than the microstrip based ZOR Antenna. Simulated results for both the cases are shown. The operational bandwidth of the CPW based ZOR Antenna at 2.14 (2.06 to 2.2195) GHz covers the required bandwidths of the IEEE 802.11 for wireless local-area networks (WLAN) applications while in case of the microstrip ZOR Antenna, the operational bandwidth at 3.995Ghz and at 3.095 GHz encompasses worldwide interoperability for microwave access (WiMax) standards suitable for point to point multiband applications.
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Comparative study of a CRLH TL based Zeroth Order Resonant Antenna
2012 National Conference on Communications (NCC), 2012Co-Authors: K.l. Sheeja, P.k. Sahu, S.k. BeheraAbstract:In this paper, a comparative study between a compact microstrip Zeroth Order Resonant Antenna with another coplanar waveguide (CPW) based vialess ZOR Antenna is presented. But the drawback of this microstrip based CRLH TL is that a narrow bandwidth of about 0.75% with an improved gain of about 3.6256dB is achieved. In order to circumvent this drawback we demonstrate a vialess CPW fed structure using the same substrate, RT Duroid (5880) (εR = 2.2, h = 1.57mm) and compare the performance of both these Antennas. In the CPW fed case we obtain a bandwidth enhancement of about 7.84% with a dumb-bell shaped radiation pattern at phi=90deg (E-radiation pattern). The zeroth order mode obtained in this case is at 2.14GHz while with the microstrip based ZOR Antenna, the zeroth order freq is at 3.995GHz with a monopolar radiation pattern at phi=90deg. The CPW fed Antenna is easy to fabricate as it is based on a single layer. The drawback of this CPW fed Antenna is that the gain reduces to 1.6949dB as the structure is electrically much smaller than the microstrip based ZOR Antenna. Simulated results for both the cases are shown. The operational bandwidth of the CPW based ZOR Antenna at 2.14 (2.06 to 2.2195) GHz covers the required bandwidths of the IEEE 802.11 for wireless local-area networks (WLAN) applications while in case of the microstrip ZOR Antenna, the operational bandwidth at 3.995Ghz and at 3.095 GHz encompasses worldwide interoperability for microwave access (WiMax) standards suitable for point to point multiband applications.
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Resonant Antenna based on CRLH TL
2010 International Conference on Mathematical Methods in Electromagnetic Theory, 2010Co-Authors: K.l. Sheeja, P.k. Sahu, Nabil Dakhli, S.k. BeheraAbstract:In this paper, a study of the compact microstrip Antenna based on composite right/left handed (CRLH) metamaterial transmission line is presented. The physical size and operational frequencies of the Antenna are determined by the CRLH metamaterial's unit cell. The Antenna exhibits monopolar radiation at its fundamental mode of Resonant frequency. As it is well known that the composite right/left-handed (CRLH) transmission line (TL) has unique property of an infinite-wavelength wave at specific non-zero frequency because of zero permittivity and permeability. Generally, CRLH includes both LH series C/shunt L and parasitic RH series L/shunt C in its circuit model, resulting in a structure which is LH at lower frequencies and RH at higher frequencies. The operation bandwidth cover the required band widths of the IEEE 802.11 wireless local-area networks (WLAN) standards and worldwide interoperability for microwave access (WiMax) in the 2.97 GHz, 3.345GHz and 3.79 GHz (3.49-3.79 GHz). The zeroth order Resonant frequency was found to be at 3.79GHz.
Andrey Chuvilin - One of the best experts on this subject based on the ideXlab platform.
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Resonant Antenna probes for tip enhanced infrared near field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent...
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Resonant Antenna probes for tip-enhanced infrared near-field microscopy
Nano Letters, 2013Co-Authors: Florian Huth, Martin Schnell, Roman Krutokhvostov, Sergei Lopatin, I. Amenabar, Andrey Chuvilin, Rainer HillenbrandAbstract:We report the development of infrared-Resonant Antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical Antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as Resonant Antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices.
