arXiv subjects

Shriganesh Prabhu

Publications and source records attributed to Shriganesh Prabhu.

6 recordsLinked to original sources

arXiv2025

Unveiling nonlinearities of electromagnetically induced transparency in a THz metamaterial

Electromagnetically induced transparency (EIT) in terahertz (THz) metamaterials relies on the coherent coupling between a radiative (bright) mode and a subradiant (dark) mode. Understanding the dynamic interplay between the bright and dark modes holds the key to manipulate the mutual interference and hence the transparency. Here, we use nonlinear 2D-THz spectroscopy to scrutinize the dynamics through nonlinearities of the EIT-like phenomenon in a metamaterial platform that comprises of two coupled resonators. From the temporal profiles of the nonlinear pump-probe and photon-echo signals, we found that the bright mode relaxation time is almost twice the time for the coherent exchange of energy between the two coupled resonators. The multi-peak nature of photon-echo signal and the corresponding temporal signatures further provides a direct visualization of the interference between the dressed states that drives the transparency window in our THz metamaterial. A time-resolved density matrix model accurately describes the observed features, including the cross-peak behavior and the temporal dynamics, establishing the coherent mode coupling as the origin of the transparency window.

physics.optics↗

arXiv2025

Phonon-polariton mediated dual electromagnetically induced transparency-like response in a THz metamaterial

Light and matter can intertwine to create entirely new quantum states in the so-called strong-coupling regime, allowing unprecedented control over electromagnetic waves. In this work, strong-coupling mediated polaritonic states are exploited to demonstrate tunable dual electromagnetically induced transparency (EIT) like response in the terahertz (THz) frequency range using a micron-sized metamaterial system coupled with the phonon mode of a lead halide perovskite film. This architecture allows us to reversibly switch between the single and the dual EIT-like behavior without modifying the metamaterial structures. The dual EIT-like nature is further confirmed through the in-plane electric field distributions and the slow-light effects. The specific structural symmetry further allowed us to effectively switch between the dual EIT-like response and the conventional strong-coupling responses. Such tunability bears potential implications for developing metamaterial-phonon-based tunable THz devices such as switches, filters, and slow-light devices.

physics.optics↗

arXiv2023

Ultrafast Carrier Relaxation and Second Harmonic Generation in a Higher-Fold Weyl Fermionic System PtAl

In topological materials, shielding of bulk and surface states by crystalline symmetries has provided hitherto unknown access to electronic states in condensed matter physics. Interestingly, photo-excited carriers relax on an ultrafast timescale, demonstrating large transient mobility that could be harnessed for the development of ultrafast optoelectronic devices. In addition, these devices are much more effective than topologically trivial systems because topological states are resilient to the corresponding symmetry-invariant perturbations. By using optical pump probe measurements, we systematically describe the relaxation dynamics of a topologically nontrivial chiral single crystal, PtAl. Based on the experimental data on transient reflectivity and electronic structures, it has been found that the carrier relaxation process involves both acoustic and optical phonons with oscillation frequencies of 0.06 and 2.94 THz, respectively, in picosecond time scale. PtAl with a space group of $P$$2_{1}$3 allows only one non-zero susceptibility element i.e. $d_{14}$, in second harmonic generation (SHG) with a large value of 468(1) pm/V, which is significantly higher than that observed in standard GaAs(111) and ZnTe(110) crystals. The intensity dependence of the SHG signal in PtAl reveals a non-perturbative origin. The present study on PtAl provides deeper insight into topological states which will be useful for ultrafast optoelectronic devices.

cond-mat.mes-hall↗

arXiv2022

A detailed study on novel metamaterial absorber at WR3 band

Frequency band of 30 to 300 GHz, which is termed as mm wave band offers 100 times bandwidth as compared to sub 6 GHz band. In this study, we propose a novel design which acts as a near unity absorber at 258 GHz or 0.258 THz in Y polarization and 292 GHz or 0.292 THz in X polarization. The study also includes effect of change in parameters on resonance frequency in both X and Y polarization which allows us to use same design with modified parameters to get near unity absorptivity in frequency of 205 to 345 GHz. Further, we also discuss on higher frequency mode which particularly appears in Y polarization and on changing the inner square dimension of the design.

physics.optics↗

arXiv2022

Dualband and Tripleband Metamaterial absorber in WR1 band and Lower TeraHertz frequencies

Frequency Band of 0.5 THz to 1.1 THz (WR1.5 and WR1) is one of the promising bands when it comes to 6G. In this paper, we propose a novel metamaterial absorber suitable to be used at lower WR1 frequencies in TE mode. Alternatively, the design can be used as a strong absorber at lower Terahertz frequencies. In addition, when used in TM mode the absorber works as a perfect absorber at higher WR1 band.

physics.optics↗

arXiv2022

Terahertz Optical Properties and Birefringence in Single Crystal Vanadium doped [100] \b{eta}-Ga2O3

We report the Terahertz optical properties of the Vanadium doped [100] \b{eta}-Ga2O3 using Terahertz Time-Domain Spectroscopy (THz-TDS). The V-doped \b{eta}-Ga2O3 crystal shows strong birefringence in the 0.2-2.4 THz range. Further, phase retardation by the V-doped \b{eta}-Ga2O3 has been measured over the whole THz range by Terahertz Time-Domain Polarimetry (THz-TDP). It is observed that the V-doped \b{eta}-Ga2O3 crystal behaves both as a quarter waveplate (QWP) at 0.38, 1.08, 1.71, 2.28 THz, and a half waveplate (HWP) at 0.74 and 1.94 THz, respectively.

cond-mat.mtrl-sci↗