Enhanced transmission of terahertz radiation through a periodically modulated slab of layered superconductor (original) (raw)
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Physical Review B, 2018
We study theoretically the optic transmission through a slab of layered superconductor separated from two dielectric leads by spatial gaps. Based on the transfer matrix formalism along with the Josephson plasma electrodynamic approach, we derive analytic expressions for the transmittance and identify the conditions for the perfect transmission. The special interest of the study is focused on the resonant transmission, which occurs when the wave does not propagate in the spatial gaps. Far from the resonance, the transmittance is exponentially small due to the total internal reflection from the lead-gap interface. However, the excitation of electromagnetic modes localized on the layered superconductor gives rise to a remarkable resonant enhancement of the transmission. Moreover, this phenomenon is significantly modified for the layered superconductors in comparison with usual dielectrics or conductors. The dispersion curves for the modes localized on the layered superconductor are proved to be nonmonotonic, thus resulting in the specific dependence of the transmittance T on the incidence angle θ. In particular, we predict the onset of two resonant peaks in the T (θ) dependence and their subsequent merge into the broadened single peak with increasing of the wave frequency. Our analytical results are demonstrated by numerical data.
Layered superconductors as nonlinear waveguides for terahertz waves
Physical Review B, 2007
We show that unusual nonlinear self-sustained waves, called nonlinear waveguide modes ͑NWGMs͒, can propagate along thin slabs of layered superconductors. We show that these waves are stable in the main approximation for extremely anisotropic superconductors if the nonlinear wave amplitude is smaller than a critical value. These modes have no analogs among linear Josephson plasma waves and do not exist in thick samples. The magnetic field of the NWGM is distributed symmetrically with respect to the middle of the slab, decays far from the sample, and can change its sign inside. The impedance ratio of the tangential electric-and magnetic-field amplitudes for NWGMs can be of the order of unity, resulting in a nonmonotonic dispersion relation, ͑k͒, strongly sensitive to the NWGM amplitudes. Thus, the "stopping light" phenomenon, now controlled by the magnetic-field amplitude, can be observed. Resonance excitations of the NWGMs should produce anomalies in the amplitude dependence of the reflectivity and transmissivity of the incident terahertz waves, which could be useful for terahertz devices.
The possibility of enhancing the radiation power and monochromaticity by optically induced photonic crystal in the superconducting cavity is proposed and investigated. In such a structure, by periodically irradiating the stacked Josephson junctions and consequently partially suppression of the superconductivity in the irradiated positions due to depairing, a periodic optical configuration is formed. This leads to photonic band gap opening in the range of the terahertz radiation emitted from the layered superconductor. We show that such a photonic band gap significantly enhances the impedance matching at the boundary of the cavity and the waveguide. Since the weak optical coupling of the outer and inner space of layered superconductor samples is a serious reason of reducing radiated power especially in the experiments, the proposed configuration is capable of extremely enhancement in the emitted power along with attenuation of the undesired harmonics.
Physical Review Letters, 2012
We predict a complete TM↔TE transformation of the polarization of terahertz electromagnetic waves reflected from a strongly anisotropic boundary of a layered superconductor. We consider the case when the wave is incident on the superconductor from a dielectric prism separated from the sample by a thin vacuum gap. The physical origin of the predicted phenomenon is similar to the Wood anomalies known in optics, and is related to the resonance excitation of the oblique surface waves. We also discuss the dispersion relation for these waves, propagating along the boundary of the superconductor at some angle with respect to the anisotropy axis, as well as their excitation by the attenuated-total-reflection method.
Physical Review B, 2021
We show that layered superconductors, due to their peculiar nonlinear response to a weak dc magnetic field, behave as tunable hyperbolic media within a wide terahertz range. Thereby, various attractive phenomena intrinsic in hyperbolic materials can be controlled by dc magnetic field. In particular, in this work a resonant transparency of a layered superconductor induced by the excitation of localized waves with nonmonotonic dispersion, is studied. We reveal the dc magnetic field is able to adjust the electromagnetic properties of a layered superconductor in order to observe specific twin peaks in the transmittance-vs-angle dependence. In addition, solving the problem by the transfer-matrix method, we succeed in deriving the matrix responsible for the effect of dc magnetic field. It is notable that this specific matrix depends neither on the size of the layered superconductor, nor on the parameters of surroundings.
THz transmittance in one-dimensional superconducting nanomaterial-dielectric superlattice
Materials Chemistry and Physics, 2009
Electromagnetic wave transmission at THz in a one-dimensional superconducting metallo-dielectric superlattice has been theoretically investigated based on the transfer matrix method together with superconductor electromagnetics. The results of transmittance spectra show the existence of a cutoff frequency in such a bilayer periodic structure. Electromagnetic wave is allowed to propagate through the structure when its frequency is higher than cutoff frequency. However, it will be totally reflected at a frequency below cutoff frequency. This cutoff frequency is strongly dependent on thicknesses of the superconductor and dielectric layers, and the temperature as well. In temperature-dependent transmittance, strong oscillations can be seen at higher temperatures.
Response of High-Tc Superconductor Metamaterials to High Intensity THz Radiation
2012
We report the observation of a nonlinear terahertz response of splitring resonator arrays made of high-temperature superconducting films. Intensitydependent transmission measurements indicate that the resonance strength decreases dramatically (i.e. transient bleaching) and the resonance frequency shifts as the intensity is increased. Pump-probe measurements confirm this behaviour and reveal dynamics on the few-picosecond timescale.
Extraordinary terahertz transmission in superconducting subwavelength hole array
Optics Express, 2011
We report the extraordinary terahertz (THz) transmission through subwavelength hole array in superconducting NbN film. As the temperature drops below the superconducting transition temperature, the transmission spectra experience distinct changes. The extraordinary transmission is greatly enhanced in superconducting state due to the enhancement of surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). We have also observed temperature-dependent resonance frequency shift, which mainly depends on the coupling between SPPs and LSPs.
Terahertz superconductor metamaterial
Applied Physics Letters, 2010
We characterize the behaviour of split ring resonators made up of high-transition temperature YBCO superconductor using terahertz timedomain spectroscopy. The superconductor metamaterial shows sharp change in the transmission spectrum at the fundamental inductive-capacitive resonance and the dipole resonance as the temperature dips below the transition temperature. Our results reveal that the high performance of such a metamaterial is limited by material imperfections and defects such as cracks, voids and secondary phases which play dominant role in partially impeding the flow of current causing dissipation of energy and electrical resistance to appear in the superconductor film.