Research

Tailoring Evanescent Light on Surface

Surface Phonon Polaritonic Metasurfaces

Gradient optical metasurfaces have been used to demonstrate a wavefront control of light in free space and in optical waveguides by imposing spatially varying optical responses to the light. However, the control of light localized and propagating on surface has been challenging because the surface waves scatter intensively to the metallic metasurfaces causing the optical loss. Can we find new metasurfaces platform to tailor the surface waves of light? Our group addresses the challenge by understanding fundamentally the near-field interaction between surface waves of light and surface charge oscillations confined in gradient metasurfaces. The research project will deal with the technologically important long-wavelength infrareds and result in producing active flat optical components, perfect infrared absorbers, narrow-band thermal emitters and detectors, optical isolators, and phase modulators in mid and far infrared.

Selected Publications & Presentations

[1] Coupled surface plasmon-phonon polariton nanocavity arrays for enhanced mid-infrared absorption, S. Kachiraju, I. Nekrashevich, I. Ahmad, H. Farooq, L. Chang, S. Kim, and M.-H. Kim, Nanophotonics vol. 11 no. 20 pp. 4489-4498 (2022), https://doi.org/10.1515/nanoph-2022-0339.

Mid-Far Infrared Magneto-Transport

Magnetic Weyl Semimetals

: chiral electrons with magnetism

Topological materials are new type of quantum materials which phases of matter are classified by surface states produced by the topology of the bulk band structure. Among them, topological Weyl semimetals have received a lot of attention because of quantum anomalies such as a topological Fermi arc and chiral anomaly from Weyl fermions, which allow quantum control of topologies electrically and optically. Recent material survey extends to rare-earth based magnetic non-centrosymmetric Weyl semimetals showing a rich topological tunability of Weyl fermions at the low-energy band structures below 100 meV. The simplest investigation of Weyl fermions is to measure anomalous Hall conductivity. We are interested in probing and understanding low-energy infrared magneto-transport fingerprints of Weyl fermions in magnetic Weyl semimetals under broken time-reversal symmetry. Hall measurement at finite frequencies near dc to infrared has rarely been considered because the mid-far infrared magneto-polarimetry measurement has still been challenged so far. Our group addresses the challenge by developing mid-far infrared Hall spectrometer at Texas Tech University which aims to access the under-explored low-energy infrared anomalous Hall conductivity close to dc.

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