Ellipsometric determination of permittivity in a negative index photonic crystal metamaterial

Principia Dardano,Vito Mocella,Massimo Gagliardi,Stefano Cabrini,Ivo Rendina

doi:10.1038/lsa.2012.42

Abstract

In this work, we present the first experimental evidence of negative dielectric susceptibility in a two-dimensional silicon photonic crystal (PhC) with negative refractive index behavior. In the frequency range in which the effective refractive index neff is equal to −1, the incident light couples efficiently to the guided modes in the top surface layer of the PhC metamaterial. These modes resemble surface plasmon polariton resonances. This finding was confirmed by ellipsometric measurements, demonstrating the isotropy of the PhC resonances. Such negative index PhC materials may be of use in biosensing applications. Researchers have realized a device that exhibits negative effective refractive index on the surface of a silicon chip. The ability to control light on a semiconductor chip is important for applications that involve the interaction of electronics with light. The approach developed by Vito Mocella and colleagues from the Consiglio Nazionale delle Ricerche in Italy is based on the use of photonic crystals—in this case, a periodic array of holes etched into silicon. The holes change the way light propagates along the surface of the chip such that the structure has a negative refractive index at its resonance wavelength, which means that light bends in a direction opposite to what would usually be expected when passing from one medium to another. This effect could be used for highly sensitive biosensing applications.

Highlights

Photonic crystals (PhCs) have reshaped the landscape of photonic devices[1] with such early applications as waveguides[2,3] and resonant cavities,[4] as well as multiplexing.[5]
The power of PhCs and their unusual properties arises from the optical bandgap, which can be tailored by design
PhCs have been used more widely as a metamaterial with an effective negative refractive index.[6,7,8,9,10]. Light propagating in such a metamaterial can undergo a drastic change in group velocity, causing the light to bend away from the usual direction that is observed with a conventional refracting medium

Summary

Introduction

Photonic crystals (PhCs) have reshaped the landscape of photonic devices[1] with such early applications as waveguides[2,3] and resonant cavities,[4] as well as multiplexing.[5]. Owing to the fine control over the optical bandgap of the PhC, the effective refractive index can exhibit optical antimatter behavior.[7] For example, a set of circular holes etched vertically into a silicon slab in a hexagonal arrangement can produce an effective resonant refractive index of neff[521] for light propagating along the length of the slab (perpendicular to the direction of the holes). Such a metamaterial strongly couples incoming light and can be used to transmit data with minimum losses over millimeter distances for lab-on-a-chip applications.[8]

Methods

Results

Conclusion