Abstract-Terahertz radiation, circular dichroism, and optical activity of a Rashba quantum ring subjected to a static electric field

Omid Sharifi Sedeh and MirFaez Miri

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.235434

We study a Rashba quantum ring subjected to an in-plane static electric field. Due to the violation of the rotational symmetry, the system radiates at the Rabi frequency upon interaction with a strong electromagnetic field. With a proper choice of the driving amplitude, the radiation frequency is in the range of $0.1-10\mathrm{THz}$. Due to the Rashba spin-orbit interaction which splits the spin-up and spin-down states and affects the transitions between the ground and excited states, the system exhibits circular dichroism and optical activity. The static electric field and gate-voltage-dependent Rashba parameter strongly influence the system. In other words, the Rashba quantum ring may serve as an electrically tunable terahertz emitter, absorption modulator, dichroic element, and polarization rotator.

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Abstract-Electric and Magnetic Hotspots via Hollow InSb Microspheres for Enhanced Terahertz Spectroscopy

Mahdiyeh Sadrara,  MirFaez Miri

https://www.nature.com/articles/s41598-018-35833-2

We study electric and magnetic hotspots in the gap between hollow InSb microspheres forming dimers and trimers. The outer radius, core volume fraction, distance, and temperature of the microspheres can be chosen to achieve field enhancement at a certain frequency corresponding to the transition between energy levels of a molecule placed in the gap. For example, utilizing 80 μm radius spheres at a gap of 2 μm held at a temperature of 295 K, allow electric field intensity enhancements of 10–2880 and magnetic field intensity enhancements of 3–61 in the frequency window 0.35–1.50 THz. The core volume fraction and the ambient temperature affect the enhancements, particularly in the frequency window 1.5–2 THz. Electric and magnetic hotspots are promising for THz absorption and circular dichroism spectroscopy.