Generation and Enhancement of Persistent Nanoscale Magnetization in All-Dielectric Metasurfaces by Optically Injected and Localized Free Carriers

TL;DR

This paper demonstrates how optically injected free carriers in dielectric metasurfaces can generate persistent nanoscale magnetization by creating time-varying resonances and localized magnetic fields, enabling advanced control of optical waves.

Contribution

It introduces a method to produce long-lasting nanoscale magnetization in dielectric metasurfaces through localized free carrier injection and time-varying resonances, a novel approach in the field.

Findings

Generation of frequency-shifted infrared MGWs via free carriers.

Creation of large, localized quasistatic magnetic fields within metasurfaces.

Persistence of nanoscale magnetization for several optical cycles after excitation.

Abstract

Time-varying dielectric metasurfaces that support sharp optical resonances with nontrivial electromagnetic field distributions constitute a unique platform for realizing temporal interfaces for metasurface-guided waves (MGWs). Rapidly changing metasurface resonance enables frequency conversion and temporal scattering of a concurrently propagating MGW. Using analytical methods and electromagnetic simulations, free carriers are generated locally to create frequency-shifted infrared MGWs. Such time interfaces can be utilized to generate large, highly localized quasistatic magnetic fields within the metasurfaces. The resulting nanoscale magnetization, supported by the residual circulating currents, persists for several optical cycles after the departure of the time-scattered MGWs. During the rectification process, the initial electromagnetic energy of the injected MGWs is partitioned between the temporally scattered MGWs, the residual motion of the free carriers, and a quasistatic magnetic field.