Quantitative near-field characterization of surface plasmon polaritons on monocrystalline gold platelets

Abstract

Near-field microscopy allows for visualization of both the amplitude and phase of surface plasmon polaritons (SPPs). However, their quantitative characterization in a reflection configuration is challenging due to complex wave patterns arising from the interference between several excitation channels. Here, we present near-field measurements of SPPs on large monocrystalline gold platelets in the visible. We study systematically the influence of the incident angle of the exciting light on the SPPs launched by an atomic force microscope tip. We find that the amplitude and phase signals of these SPPs are best disentangled from other signals at grazing incident angle relative to the edge of the gold platelet. Furthermore, we introduce a simple model to extract the wavelength and in particular the propagation length of the tip-launched plasmons. Our experimental results are in excellent agreement with our theoretical model. The presented method allows the quantitative analysis of polaritons occurring in different materials at visible wavelengths.

Extremely confined gap plasmon modes: when nonlocality matters

“…While our experiments cannot totally dismiss such alternative explanations, they appear less obvious for our samples fabricated using high-quality materials. Indeed, SNOM measurements on single Au flakes 33 , 34 —where the bare surface plasmons exhibit the local-response dynamics, since there are no small spatial sample features to promote significant effects from the large wavevector response of the plasmons—appear well-explained by the Olmon data for crystalline Au 66 , while more recent experiments conclude even lower bulk damping 82 , 83 in better accordance with the McPeak data 22 .…”

Ultimate Limit for Optical Losses in Gold, Revealed by Quantitative Near-Field Microscopy

“…During the final stage of the preparation of this manuscript, a similar, recent publication was brought to our attention. 43 There, the authors use similar gold monocrystals to study SPPs excited with a 632.8 nm He−Ne laser, and they employ the same s-SNOM, but in reflection mode, where the top parabolic mirror is used for both illumination and collection of scattering from the tip. This makes the near-field maps less intuitive to understand, and data processing is more sophisticated, but at the end the authors arrive at the same conclusion: that the SPP propagation losses correspond to the theoretical value determined from the gold permittivity of McPeak et al 17 The data that support the findings of this study are available from the corresponding authors upon reasonable request.…”

“…During the final stage of the preparation of this manuscript, a similar, recent publication was brought to our attention . There, the authors use similar gold monocrystals to study SPPs excited with a 632.8 nm He–Ne laser, and they employ the same s-SNOM, but in reflection mode, where the top parabolic mirror is used for both illumination and collection of scattering from the tip.…”

Observation of multiple bulk bound states in the continuum modes in a photonic crystal cavity

“…They could be identified by observing far-field radiation patterns of the modes [ 30 ]. Also, near-field patterns of modes could be obtained by near-field microscopy [ 44 ]. Both methods need a precise optical setup and an efficiency improvement of the setup and will be investigated in further studies.…”