Grating-coupled excitation and detection of surface plasmon polariton waves (SPPW) on Cu(111) using periodic density patterns of rare gas monolayers.

Using periodic density profiles of xenon (Xe) as thin as 1 $\sim $ 5 monolayers, we have excited and detected grating-coupled surface plasmon polariton waves (SPPW) on Cu(111) in ultrahigh vacuum. The periodic density profiles are formed by laser-induced thermal desorption with a pair of coherent laser pulses at vacuum wavelength of 0.532 $\mu $m. The periodicity of the profiles is 5.45 $\mu $m. By illuminating the xenon-density-grating-covered Cu(111) with a converging He-Ne laser covering a span of incidence angles from 66.4$^{\circ}$ to 74.4$^{\circ}$ and detecting the oblique-incidence reflectivity difference r$_{p}$/r$_{p0}$ -- r$_{s}$/r$_{s0}$ vs. incidence angle with a multiple-element photodiode array, we observed the surface-plasmon resonance (SPR) peaked at $\phi _{SPR}$ = 70.4$^{\circ}$ with a full-width at half-maximum $\delta \phi _{SPR}$ = 0.29$^{\circ}$. From the resonance angle $\phi _{SPR}$ and $\delta \phi _{SPR}$, we have determined the optical dielectric constant of single crystalline Cu at 633 nm to be $\varepsilon _{Cu}$ = -9.53 + $i$ 0.142, markedly different from the literature values for evaporated Cu films. At elevated temperatures such that a xenon density grating on Cu(111) decays in contrast, the surface plasmon resonance as measured by r$_{p}$/r$_{p0}$ -- r$_{s}$/r$_{s0}$ diminishes, reflecting the kinetic of surface diffusion of xenon on Cu(111).