Anisotropic photonic time interfaces via isotropic spacetime modulations

TL;DR

This paper proposes a novel spacetime modulation method using isotropic-to-isotropic interfaces to emulate anisotropic photonic time interfaces, enabling real-time control of wave propagation.

Contribution

It introduces a new approach to emulate anisotropic time interfaces through isotropic-to-isotropic spacetime modulations in multilayered media.

Findings

Theoretical demonstration of changing energy propagation direction in real time.

Numerical simulations support the feasibility of emulating anisotropic time interfaces.

Potential to control wave propagation in four-dimensional space-time.

Abstract

The engineering of the optical properties of materials in space and time is opening further directions and possibilities to control wave propagation in four dimensions (x,y,z,t). A key example of such modulations are time interfaces where the permittivity of the medium is changed in time from isotropic to another isotropic value. Recently, isotropic-to-anisotropic time interfaces in a homogeneous, unbounded medium have also been proposed, demonstrating their potential for redirecting waves in real time. However, the challenge relies on accessing/creating permittivity tensors in time. To address this, here we propose isotropic-to-isotropic spacetime modulations inspired by spacetime effective media to emulate such isotropic-to-anisotropic time interfaces. Specifically, we consider that subwavelength spatially periodic multilayers, arranged either horizontally or vertically, are created in time using simultaneous isotropic-to-isotropic time interfaces applied in discrete spatial regions. The theory behind this approach is presented in detail demonstrating that, indeed, it is possible to change the direction of energy propagation in real time and emulate permittivity tensors. All the results are supported by numerical simulations, demonstrating the potential of the proposed spacetime approach to emulate photonics isotropic-to-anisotropic time interfaces.