Dynamically controlling local field enhancement at an epsilon-near-zero/dielectric interface via nonlinearities of an epsilon-near-zero medium

Alexander Baev,Robert W Boyd,M Zahirul Alam,Paras N Prasad

doi:10.1515/nanoph-2020-0490

Abstract

Abstract For p-polarized light incident on an interface between an ordinary dielectric and an epsilon-near-zero (ENZ) material, an enhancement of the component of the electric field, normal to this interface, has been shown to occur. This local field enhancement holds great promise for amplifying nonlinear optical processes and for other applications requiring ultrastrong local fields in epsilon-near-zero based technologies. However, the loss associated with the imaginary part of the dielectric constant of an epsilon-near-zero material can greatly suppress the field enhancement factor. In this study, we analyze, using density matrix formalism, the field enhancement factor for a saturable two-level system that exhibits second- and third-order nonlinearities. We show that, in such a system, an almost lossless ENZ response can arise as a consequence of saturable nonlinearity and that the local field enhancement factor can be readily controlled dynamically by adjusting the intensity of the incident electromagnetic wave. Our findings provide for the first time a pathway to design a material exhibiting an external field responsive epsilon-near-zero behavior for applications in nonlinear photonics.

Highlights

An epsilon-near-zero (ENZ) material is a natural or engineeredmaterial with the real part of the dielectric permittivity approaching zero
We analyze, using density matrix formalism, the field enhancement factor for a saturable two-level system that exhibits second- and third-order nonlinearities. In such a system, an almost lossless ENZ response can arise as a consequence of saturable nonlinearity and that the local field enhancement factor can be readily controlled dynamically by adjusting the intensity of the incident electromagnetic wave
We showed, using the density matrix formalism, that local field enhancement at the interface between a lossless dielectric and a lossy Lorentz– Drude-type medium with large carrier density can be readily manipulated via adjusting the incident field strength

Summary

Introduction

Δε 2√ε and the change in refractive index (Δn) for a given change in permittivity (Δε) has a pole under ENZ condition It seems that in an ENZ material, even a very lowpower optical field would produce a large nonlinear response, and local field enhancement would be one of the sources contributing to this effect. With a few tens of GW/cm of incident peak intensity, this effect may prove significant and needs a thorough investigation We believe that this knowledge can help interpret experimental results and can aid in the design of ENZ (meta)materials with huge local field enhancement at a prespecified wavelength for various applications in nonlinear photonics.

Model be roughly fulfilled for laser pulses as short as a few nanoseconds

Results and discussion

Findings

Conclusion