Plasmon-Assisted Two-Slit Transmission: Young’s Experiment Revisited

Abstract

We present an experimental and theoretical study of the optical transmission of a thin metal screen perforated by two subwavelength slits, separated by many optical wavelengths. The total intensity of the far-field double-slit pattern is shown to be reduced or enhanced as a function of the wavelength of the incident light beam. This modulation is attributed to an interference phenomenon at each of the slits, instead of at the detector. The interference arises as a consequence of the excitation of surface plasmons propagating from one slit to the other. DOI: 10.1103/PhysRevLett.94.053901 PACS numbers: 42.79.Dj, 73.20.Mf, 78.66.Bz Recently, there has been a surge of interest in the phenomenon of light transmission through subwavelength apertures in metal plates. This followed the observation by Ebbesen et al. [1] that the transmission through a twodimensional hole array can be much larger than predicted by conventional diffraction theory [2]. This discovery has rekindled the interest in a similar but simpler problem, viz., the transmission of a one-dimensional array of subwavelength slits in a metal film, i.e., of a metal grating [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In many cases the enhanced transmission of hole or slit arrays has been explained in terms of the excitation of (coupled) surface plasmons on the metal film [3][4][5][6], an explanation that has recently been challenged [16]. It has been shown that, for slit arrays, Fabry-Pérot-type waveguide resonances can also give rise to a considerably enhanced transmission [5,7,9,10,12].In the present Letter we study an even more fundamental system than the metallic grating, namely, a thin metal layer perforated by just two parallel subwavelength slits. In contrast to the systems that have recently attracted so much attention, our slits are separated by many optical wavelengths. Thus we study the light transmission of a setup that lies at the heart of wave physics, namely, that of Thomas Young. We do, however, not focus on the wellknown interference pattern named after him, but on the angle-integrated power transmission coefficient of the perforated screen, i.e., the transmission integrated over many interference orders. We show that this transmission coefficient is strongly modulated as a function of the wavelength of the incident light for the case that that light is TMpolarized, i.e., with the electric field aligned perpendicular to the slits. In contrast, there is no such modulation when the incident light is TE-polarized, or when the ''wrong'' metal is chosen. All our observations can be explained in terms of a model involving the coherent transport of electromagnetic energy between the slits by surface plasmons.Our samples consist of a 200 nm thick gold film, evaporated on top of a 0.5 mm thick fused quartz substrate with a 10 nm thick titanium adhesion layer between the gold and the glass. In such a sample a two-slit pattern is written using a focussed ion beam, each slit being 50 m long and 0:2 m wide. The slits are separated by a dis...

Optical response of nanostructured surfaces: experimental investigation of the composite diffracted evanescent wave model

“…Interferometry measurements of the surface waves on "output side" slit-groove structures (not reported here) confirm the value of n surf in Table I, and we believe that conventional, infinite-plane SPP theory [4] is not adequate to explain these results. We note that persistent surface waves over ∼ 10 µm distances have also been reported in a double slit experiment [16] and interpreted as SPPs [17].…”

Plasmon Enhanced Photoemission

“…The assumption that the performance of these types of systems can be modeled on the basis of a single unit has also been followed in a number of other studies [49,51,52]. However, it is well known that collective e↵ects can play an important role in determining the behavior of some types of plasmonic systems [25,[53][54][55][56][57]. The analysis of a single resonant NG narrower then the metal skin depth can be connected to the collective excitation of the subwavelength grating in a simple relationship between the NG width w, height h, and period p required to achieve complete light absorption at the metal surface.…”

Mechanisms for photon sorting based on slit–groove arrays

“…3 (b). In order to explain the optical response of the Double-Pixel, it is compared with two simpler systems: a Double-Slit (DS) for which all grooves are removed and only a single slit remains in each pixel (see [6,32,33,34,35,36,37,38] for a full discussion of its optical response), and the Pixel-Slit (PS) structure, where the grooves of one pixel are removed leaving only a single slit, while the other pixel is not changed. A schematic representation of the three systems is given in the inset of Fig.…”