المؤلفون: Murtunge, Yamuna, Patil, Vidhyadhar, Puranik, Ruturaj, S, Jayakrishnan S, Bansal, D, Maity, Arijit, Venkatramani, Ravindra, Kulkarni, S. B., Thamizhavel, A, Prabhu, S. S.

مصطلحات موضوعية: Physics - Optics

الوصف: An optically high-quality single crystal of sodium mesitylene sulfonate crystal was successfully grown by a slow evaporation method using methanol as solvent at room temperature. Single-crystal XRD has characterized the material and belongs to a monoclinic structure with a C2 space group. Functional groups were determined using Fourier-transformed infrared spectroscopy. The optical quality of the generated crystal was evaluated using UV-Vis NIR spectral analysis, which is transparent in the range of 300-1500 nm. We report the optical properties using terahertz time-domain spectroscopy (THz-TDS) and THz generation using crystal.

الوصول الحر: http://arxiv.org/abs/2407.04564Test

المؤلفون: Mohan Rao, S. Jagan, Sarkar, Rakesh, Punjal, Ajinkya, Ghindani, Dipa, Roy Chowdhury, Dibakar, Prabhu, S. S., Kumar, Gagan

المساهمون: Tampere University, Physics

مصطلحات موضوعية: 114 Physical sciences

الوصف: We demonstrate a metamaterial (MM) design capable of showing linear broadband polarization conversion over the terahertz (THz) frequency range. The building block of the proposed MM structure is composed of a strip and four split ring resonators (SRRs), which are coupled through their near fields. To examine co- and cross-polarization transmission amplitudes, we gradually increase the distance between the strip and SRRs. When the SRRs are near (S = 2 μm) the strip, maximum cross-polarization conversion is attained with a resonance mode hybridization effect in the co-polarization transmission due to strong near-field coupling between the strip and SRRs. When the SRRs moved away from the strip (S = 22 μm), minimum cross-polarization conversion is attained due to weak coupling between the strip and SRRs. This MM system exhibits a transition from a strongly coupled state to a weakly coupled state with the rise in displacement between the strip and SRRs. The ability to tune the linear polarization conversion can be useful in the improvement of efficient THz polarization rotation devices. The proposed MM structure can be used in other frequency domains, like the microwave and visible range, by scaling up/down the structure. ; Peer reviewed

وصف الملف: fulltext

العلاقة: 123102; 12; 133; https://trepo.tuni.fi/handle/10024/155745Test; URN:NBN:fi:tuni-202304133686

الإتاحة: https://doi.org/10.1063/5.0143796Test
https://trepo.tuni.fi/handle/10024/155745Test

المؤلفون: Nayak, Banoj Kumar, Prabhu, S. S., Achanta, Venu Gopal

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Optics

الوصف: Hot carrier dynamics in a dispersionless plasmonic structures over a broad wavelength are studied by pump-probe measurements with 45 fs time resolution. The role of direct excited as well as plasmon generated hot carriers on low energy probe plasmons are studied by simultaneous measurement of differential transmittance and reflectance. While the pump fluence dependence on the decay times is linear for hot electrons and plasmon generated hot electrons, when pump is near resonant with the X- symmetry point, decay time varied as square of pump fluence. Decay times of 800 nm degenerate pump-probe measurements highlight the difference in surface (reflection) and the bulk (transmission) mechanisms. Decay time corresponding to the hot carrier relaxation is in the 1 -3 ps range for different excitation energies. Rise time, governed by the plasmon to hot carrier conversion and electron - electron scattering processes, is about 200 fs for the hot carrier and hot plasmon excitation cases which increased to about 485 fs for when pump is resonant with interband transition at X- symmetry point.
Comment: 15 pages, 7 figures, 3 tables

الوصول الحر: http://arxiv.org/abs/1905.01050Test

المؤلفون: Shukla, R A, Achanta, V G, Barbaro, P D, Dugad, S R, Heering, A, Gupta, S K, Mirza, I, Prabhu, S S, Rumerio, P

مصطلحات موضوعية: Physics - Instrumentation and Detectors, High Energy Physics - Experiment

الوصف: The CMS hadron Calorimeter is made of alternating layers of scintillating tiles and metals, such as brass or iron. The original photo detectors were hybrid units with a single accelerating gap called Hybrid Photo Diodes (HPD). Scintillating light was transmitted to the HPDs by means of optical fibers. During data taking at the Large Hadron Collider (LHC), the signal strength of scintillator tiles of detector units in the forward region degraded significantly due to the damage related to the amount of radiation to which the scintillator was exposed to. Scintillators suffer damage when exposed to radiation, however, the amount of damage observed was more than originally estimated. Several HPDs were removed during a detector shut down period. Microscopic scans of relative quantum efficiencies for few of these HPDs were made. The damage of the photocathode was determined to vary with the amount of optical signal transmitted by optical fibers to the HPD. Imprints of each fiber (1 mm) on the photocathode with varying damage within the same pixel were observed. Most of the observed reduction of the calorimeter signal can be attributed to localised damage of the photocathode.
Comment: Article to be submitted to Review of Scientific Instruments

الوصول الحر: http://arxiv.org/abs/1806.09887Test

المؤلفون: Mohan Rao, S. Jagan, Sarkar, Rakesh, Punjal, Ajinkya, Ghindani, Dipa, Roy Chowdhury, Dibakar, Prabhu, S. S., Kumar, Gagan

المصدر: Journal of Applied Physics; 3/28/2023, Vol. 133 Issue 12, p1-9, 9p

مصطلحات موضوعية: TERAHERTZ materials, METAMATERIALS, LINEAR polarization, RESONATORS, RESONANCE

مستخلص: We demonstrate a metamaterial (MM) design capable of showing linear broadband polarization conversion over the terahertz (THz) frequency range. The building block of the proposed MM structure is composed of a strip and four split ring resonators (SRRs), which are coupled through their near fields. To examine co- and cross-polarization transmission amplitudes, we gradually increase the distance between the strip and SRRs. When the SRRs are near (S = 2 μ m) the strip, maximum cross-polarization conversion is attained with a resonance mode hybridization effect in the co-polarization transmission due to strong near-field coupling between the strip and SRRs. When the SRRs moved away from the strip (S = 22 μ m), minimum cross-polarization conversion is attained due to weak coupling between the strip and SRRs. This MM system exhibits a transition from a strongly coupled state to a weakly coupled state with the rise in displacement between the strip and SRRs. The ability to tune the linear polarization conversion can be useful in the improvement of efficient THz polarization rotation devices. The proposed MM structure can be used in other frequency domains, like the microwave and visible range, by scaling up/down the structure. [ABSTRACT FROM AUTHOR]

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المؤلفون: Sangala, Bagvanth Reddy, Nagarajan, Arvind, Deshmukh, Prathmesh, Surdi, Harshad, Rana, Goutam, Gopal, Achanta Venu, Prabhu, S. S.

المصدر: Pramana - J Phys 94, 2 (2020)

مصطلحات موضوعية: Physics - Optics

الوصف: We report single and multiband linear polarizers for terahertz (THz) frequencies using cut-wire metamaterials (MM). The MMs are designed by finite element method, fabricated by electron beam lithography, and characterized by THz time-domain spectroscopy. The MM unit cells consist of single or multiple length cut-wire pads of gold on semi-insulating Gallium Arsenide for single or multiple band polarizers. The dependence of the resonance frequency of the single band polarizer on the length of the cut-wires is explained based a transmission line model.
Comment: 6 pages, 3 figures

الوصول الحر: http://arxiv.org/abs/1502.03657Test

المؤلفون: Thilagavathy, G, Vishnu, V., Prabhu, S. S. Niranjan

المصدر: Journal of Association of Pulmonologist of Tamil Nadu ; volume 7, issue 2, page 81-83 ; ISSN 2772-6355 2772-6363

الإتاحة: https://doi.org/10.4103/japt.japt_2_24Test

المؤلفون: Rana, Rakesh, Pandey, Parul, Prabhu, S. S., Rana, D. S.

المصدر: Phys. Rev. B 97, 045123 (2018)

مصطلحات موضوعية: Condensed Matter - Strongly Correlated Electrons

الوصف: Formation of charge-density-waves in ordered electronic phases (such as charge-order) is an emergent phenomenon in the perovskite class of correlated oxides. This scenario is visualized to prevail in exotic RNiO3 (R=rare-earth) nickelates in which the structure controls the incipient charge-order to form in weak localization limit. However, any consequent effect demonstrating these nickelates in rare category of charge-density-waves conductors with controlled charge-lattice interactions has been a fundamental challenge so-far. Here, we present first evidence of the charge-density-waves in a prototypical NdNiO3 system employing terahertz time-domain spectroscopy along selective crystal axes. A finite peak structure at 5meV in the terahertz conductivity displays all the characteristics of a charge-density-wave condensate. Contrasting charge-dynamics of collective charge-density-waves mode and Drude conductivity emerging, respectively, from orthorhombic and cubic symmetries disentangle charge-ordering from the insulating state, establish a novel structure-property cause-effect relationship, and present opportunities to harness these diverse attributes in oxide electronics.

الوصول الحر: http://arxiv.org/abs/1412.3244Test

المؤلفون: Sangala, Bagvanth Reddy, Surdi, Harshad, Gopal, Achanta Venu, Prabhu, S. S.

مصطلحات موضوعية: Physics - Optics

الوصف: We demonstrate a THz metamaterial with broadband dipole resonance originating due to the hybridization of LC resonances. The structure optimized by finite element method simulations is fabricated by electron beam lithography and characterized by terahertz time-domain spectroscopy. Numerically, we found that when two LC metamaterial resonators are brought together, an electric dipole resonance arises in addition to the LC resonances. We observed a strong dependence of the width of these resonances on the separation between the resonators. This dependence can be explained based on series and parallel RLC circuit analogies. The broadband dipole resonance appears when both the resonators are fused together. The metamaterial has a stopband with FWHM of 0.47 THz centered at 1.12 THz. The experimentally measured band features are in reasonable agreement with the simulated ones. The experimental power extinction ratio of THz in the stopbands is found to be 15 dB.
Comment: 13 pages, 4 figures, 1 table

الوصول الحر: http://arxiv.org/abs/1411.6464Test

المؤلفون: Singh, Abhishek, Pal, Sanjoy, Surdi, Harshad, Prabhu, S. S., S., Mathimalar, Nanal, Vandana, Pillay, R. G., Dohler, G. H.

مصطلحات موضوعية: Condensed Matter - Materials Science, Physics - Optics

الوصف: We report here a photoconductive material for THz generation and detection with sub-picosecond carrier lifetime made by C12 (Carbon) irradiation on commercially available semi-insulating (SI) GaAs. We are able to reduce the carrier lifetime of SI-GaAs down to sub-picosecond by irradiating it with various irradiation dosages of Carbon (C12) ions. With an increase of the irradiation dose from ~1012 /cm2 to ~1015 /cm2 the carrier lifetime of SI-GaAs monotonously decreases to 0.55 picosecond, resulting in strongly improved THz pulse detection compared with normal SI-GaAs.

الوصول الحر: http://arxiv.org/abs/1409.5940Test