This article demonstrates the design of dielectric terahertz (THz) attenuators comprising of periodically placed x-cut and z-cut ion-sliced lithium niobate dielectric layers. Changes introduced in the propagating wave due to alternating refractive indices of a ferroelectric material have been exploited for the design of an effective attenuator. The electrical and optical properties gathered from experimental investigations have been used to study the influence of different crystalline orientations on the design. The conduit comprising the periodically placed dielectric slabs has been configured as a tristate switch by modulating the amplitude of the traversing THz wave by altering its angle of incidence. Full-wave finite-element simulations have been conducted over a series of parametric configurations to come up with the optimized design. A modulation depth as high as 94.76% is achieved. The proposed low-cost, easily configurable THz dielectric attenuators operating around 0.625 THz can be potentially used as an external modulator for THz quantum cascade lasers.
Magneto-Elasto-Electroporation (MEEP) is a magnetically controlled acoustic-electroporation observed while core-shell Magneto-electric nanoparticles interact with Biological Cells. The surface polarity change of the piezoelectric coating (BaTiO3) due to absorption of pressure created due magneto-striction of core (CoFe2O4) in AC magnetic field results in electric field (Uext) change at the external vicinity of the cell membrane when nanoparticles are nearby. This results in transmembrane Voltage (Um) change which is basically the difference in Cell’s internal potential (Uint) and external potential. The nonlinear permeability change of cell membrane due to change in Um opens the nano-pores on the membrane. The magnetic moment of the nanoparticles further helps in penetration of the Magneto-electric nanoparticles inside the cell through these magneto-electrically controlled newly opened nano-pores on cell’s membrane. MEEP is analyzed through in-vitro analysis and Mathematical equations are formulated for numerically expressing its fundamental effect. TEM imaging, XRD analysis, Zeta-potentiometer measurement and AFM imaging are confirming the coating of the piezoelectric layer on Magneto-stricitve nanoparticles, Acoustic measurements confirms the photo-acoustic and magneto-acoustic property of CoFe2O4 nanoparticles and Fluorescence microscopy as well as Confocal microscopy are confirming the penetration of particle inside the Human Epithelial cells (HEP2). Further on application of repulsive magnetic field, nanoparticles are observed to transport a group of cells in controlled boundary conditions in microfluidic chamber. Hence these nanoparticles can be used for accurate and efficient drug delivery as well as cell transport applications
Ultrashort THz pulses overlap with resonances through which magnetism or ferroelectricity can be probed or controlled. Low energy modes like soft mode phonons associated with the atomic displacements that result in ferroelectricity, or spin waves in magnetically ordered systems which can be either magnetic dipole active, in the case of the magnons, or electric dipole active in the case of electromagnons can be controlled using THz pulses. The interesting thing about multiferroics is that these modes can potentially be used for ultrafast magnetoelectric control. In common ferroics and multiferroics these modes often overlap well with the spectra of typical ultrashort THz pulses. In this work we exploit that unique feature of Terahertz ultrashort pulses to report on the multiferroic domain characterization of Bismuth Ferrite and Lead Iron Niobate correlating its ferroic behaviors, enhanced or reduced,with its varying doping concentration in the terahertz regime.The material properties like index of refraction and absorption coefficient thus derived using optical interferometry can be further explored for ultrafast device configuration.
We report an experimental study, where Cobalt Ferrite (CoFe2O4) nanoparticles exhibit Photoacoustic (PA) emission peak intensity of 235.2V/J when analyzed under the Opto-Acoustic measurement setup. PA emission peak intensity decreases to 210V/J when AC Magnetic field is applied and further when Barium Titanate coated cobalt ferrite nanoparticles were analyzed, the PA peak further reduces to 68.76667V/J and with application of AC magnetic field the peak completely disappears. The measurement depicts the Photoacoustic and magnetoelastic behavior of cobalt ferrite nanoparticles.
A study of Terahertz response of single crystal LiNbO3 thin films subjected to different structural and experimental configuration has been conducted in this work. In this work z-cut and x-cut ion-sliced Lithium Niobate thin films with and without embedded electrodes have been studied employing both Transmission and Reflection mode of Terahertz Spectroscopy along with z-cut single crystal in bulk form. The measurements have been performed in room temperature to probe distinctive THz-material interactions in the frequency range of 0.1-3 THz (3.34cm-1 - 100cm-1). The information thus obtained from the experimental investigation has been used to deduce a conclusive study on the influence of different polar domains on electrical and optical properties in THz frequency regime. Single Lorentzian oscillator model has also been used to define the THz signature thus acquired.
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