Imaging of terahertz surface plasmon waves excited on a gold surface by a focused beam

Raimund Mueckstein,Oleg Mitrofanov

doi:10.1364/oe.19.003212

Abstract

Surface plasmon polariton (SPP) waves formed near a tightly focused THz beam on a metallic surface are detected by an integrated sub-wavelength aperture THz near-field probe. The probe allows mapping the electric field pattern of the SPP wave and tracking the SPP propagation from the center of the focal spot. The SPP nature of the observed wave is confirmed by time-resolved measurements. Analysis of the detected patterns leads to an explanation of how THz SPP waves can be detected by the integrated sub-wavelength aperture probe.

Highlights

Detection of surface plasmon polaritons (SPPs), the electro-magnetic waves confined to metallic surfaces, often presents experimental challenges [1,2]
In this study we demonstrate the possibility of time-resolved high spatial resolution imaging of THz Surface plasmon polariton (SPP) waves by using an integrated sub-wavelength aperture THz near-field probe
This work demonstrates that the integrated sub-wavelength aperture probe allows mapping THz SPP waves, despite the fact that the electric field of the SPP wave is normal to the metallic surface of the probe

Summary

Introduction

Detection of surface plasmon polaritons (SPPs), the electro-magnetic waves confined to metallic surfaces, often presents experimental challenges [1,2]. In the THz range, in contrast, imaging methods are not as versatile and only a few examples of SPP mapping have been reported: surface waves propagating along metallic wires, waveguides, and metallic surfaces have been detected by near-field electro-optic probes, photoconductive antennas, and scattering probes [8,9,10,11,12,13,14,15]. The integrated design of the probe makes it sensitive to a SPP wave excited directly on its metallic surface Taking advantage of this property we mapped the SPP wave near a THz beam focused on a metallic surface, a phenomenon that has not been observed at THz frequencies. The ability to detect the electric field of the SPP wave, ESPP, rather than the intensity, can improve an understanding of SPP phenomena by providing the amplitude and phase information, which is hard to obtain in the optical domain

Experimental results

SPP coupling into the probe

Conclusions