Time-varying materials for analog optical computing

Abstract

Subject of study. In this study, a new class of artificial electromagnetic media, known as time-varying materials, is explored. These materials are characterized by a rapid modulation of their optical parameters on ultrashort timescales that are comparable to or shorter than the wave period. Aim of study. The aim of this study was to develop a new platform for implementing analog optical computers. Specifically, we investigated the dependence of the amplitudes and frequencies of waves, formed through interaction with a time-varying medium, on the permittivity switching time and magnitude of spectral dispersion. Method. The amplitudes of reflected and refracted electromagnetic waves were calculated using the time-domain finite-element method. A Lorentz model with a time-dependent plasma frequency was employed to analyze the time-varying medium with spectral dispersion. The optical response of the medium, which exhibited noninstantaneous switching, was studied by considering a sigmoidal switching profile. Main results. Our findings show that a dispersive time-varying medium can generate several spectral components that are shifted from the frequency of the incident light. By controlling the speed and depth of permittivity switching, the amplitudes and frequencies of the time-reflected/refracted waves can be adjusted. To observe the reflected wave, the duration of switching should be comparable to or less than the period of the incident wave. Practical significance. The results of this study are valuable for developing next-generation optical devices. The ability to flexibly control the amplitude and frequency of light waves through the temporal modulation of homogeneous media offers new opportunities for the realization of analog optical computers.