Linear and Nonlinear FEL-SEW Spectroscopic Characterization of Nanometer-Thick Films

Abstract

The conditions of the existence and transformations of surface electromagnetic waves (SEWs) on metals (surface plasmons) and dielectrics (phonon-polaritons) are discussed. Interferometric SEW experiments provide the possibility for the direct determination of the real and imaginary parts of the dielectric constants at the frequencies in the tuning range of a free electron laser (FEL) without any preliminary models. The important role of the outstanding facilities of FEL—namely, the broad tuning range, high power, narrow bandwidth of emission, and well-collimated beam—in SEW experiments is outlined. It is demonstrated by the examples of the infrared absorption spectra of a Langmuir-Blodgett film on metal, of a metal oxide film, and of polymeric films of nanometer thicknesses on metals. Free surfaces of single-crystal CaF2 and the thin polymeric film were studied by an interferometric experiment for the optical constant determination. Nonlinear spectroscopic applications of the SEW-FEL technique to studies of a second harmonic generation (SHG)—the frequency dependence of efficiency, the angle dependence of SHG, and the influence of a thin-film deposition on a quartz surface—are described.

Metal Films with Arrays of Tiny Holes: Spectroscopy with Infrared Plasmonic Scaffolding

“…Van Duyne and co-workers have compared enhancements of localized IR SPs on metal nanoparticles and metal island films . Enhanced IR spectra have been recorded with wavelength-scanned SP ATR configurations. ,, Techniques described as surface electromagnetic wave (SEW) spectroscopy − are based on the propagation of nonradiative SP modes. Prism (or grating) coupling excites SPs out of a prism (or grating) along a smooth air/metal interface (usually with lasers), and vibrational spectra are recorded by dips in measured SP propagation lengths vs wavelength.…”

Analysis of the propagation of terahertz surface plasmon polaritons on semiconductor groove gratings

“…The emitted THz radiation was collimated and focused onto an aperture to generate SPPs. [25][26][27][28] The aperture was formed by the surface of the sample and a razor blade edge placed at a distance of 300 m above the surface. As reported in Ref.…”

Optically switchable mirrors for surface plasmon polaritons propagating on semiconductor surfaces

“…We use the aperture excitation technique to couple the free space THz radiation to SPPs and to couple back SPPs to free space THz radiation after propagating on the surface of the semiconductor. 26 This technique has the important advantage that it allows broadband coupling. Figure 1͑b͒ illustrates the SPP coupling section of our experimental setup, including SPP incoupling, SPP propagation along the Bragg reflector, and SPP outcoupling.…”