arXiv subjects

Roney Thomas

Publications and source records attributed to Roney Thomas.

3 recordsLinked to original sources

arXiv2018

Unidirectional Photonic Circuit with Phase-Change Fano Resonator

We demonstrate that the integration of a phase-change material (PCM) in one of the two microresonators of a photonic metamolecule, coupled to a bus waveguide, can lead to unidirectional Fano resonances and to the emergence of a unidirectional transmission window. The phase change is caused by light-induced heating and is accompanied by an abrupt increase in the extinction coefficient of the PCM resonator. Due to the photonic circuit asymmetry, the critical value of the input light intensity triggering the phase change is strongly dependent on the input light direction. The latter determines the unidirectional nature of the emerging transmission window. This effect can be utilized in on-chip magnetic-free isolators and Q-switches.

physics.optics↗

arXiv2017

Self-Regulated Transport in Photonic Crystals with Phase-Changing Defects

Phase changing materials (PCM) are widely used for optical data recording, sensing, all-optical switching, and optical limiting. Our focus here is on the case when the change in the transmission characteristics of the optical material is caused by the input light itself. Specifically, the light-induced heating triggers the phase transition in the PCM. In this paper, using a numerical example, we demonstrate that incorporating the PCM in a photonic structure can lead to a dramatic modification of the effects of light-induced phase transition, as compared to a stand-alone sample of the same PCM. Our focus is on short pulses. We discuss some possible applications of such phase-changing photonic structures for optical sensing and limiting.

physics.optics↗

arXiv2017

Giant Non-reciprocity Near Exceptional Point Degeneracies

We show that gyrotropic structures with balanced gain and loss that respect anti-linear symmetries exhibit a giant non-reciprocity at the so-called exact phase where the eigenfrequencies of the isolated non-Hermitian set-up are real. The effect occurs in a parameter domain near an exceptional point (EP) degeneracy, where mode-orthogonality collapses. The theoretical predictions are confirmed numerically in the microwave domain, where a non-reciprocal transport above 90dB is demonstrated, and are further verified using lump-circuitry modeling. The analysis allows us to speculate the universal nature of the phenomenon for any wave system where EP and gyrotropy can co-exist.

physics.class-ph↗