Direct coupling of photonic modes and surface plasmon polaritons observed in 2-photon PEEM

Abstract

We report the direct microscopic observation of optical energy transfer from guided photonic modes in an indium tin oxide (ITO) thin film to surface plasmon polaritons (SPP) at the surfaces of a single crystalline gold platelet. The photonic and SPP modes appear as an interference pattern in the photoelectron emission yield across the surface of the specimen. We explore the momentum match between the photonic and SPP modes in terms of simple waveguide theory and the three-layer slab model for bound SPP modes of thin metal films. We show that because the gold is thin (30-40 nm), two SPP modes exist and that momentum of the spatially confined asymmetric field mode coincides with the dominant mode of the ITO waveguide. The results demonstrate that photoemission electron microscopy (PEEM) can be an important tool for the observation of photonic to SPP interactions in the study of integrated photonic circuits.

Light propagation and interaction observed with electrons

“…The image clearly shows photoemission from the nanowire, and the spatial pattern of the photoemission yield is nicely in registry with the light diffraction pattern in the ITO, i.e. there is no discernible phase mismatch between emission from the wire and from the ITO (18). The missing phase shift indicates that there is no independent plasmon propagation in the wire, which is in agreement with the strong attenuation in gold in the 400nm wavelength region (15).…”

Two-color multiphoton emission for comprehensive reveal of ultrafast plasmonic field distribution

“…Since the amount of electron emission at the position of the excited plasmons is significantly increased due to strong near-field enhancement, the plasmon-mediated photoelectrons from the nanostructures has been used to image the plasmonic near-field distribution [17][18][19]. Photoemission electron microscopy (PEEM), an instrument that use light as an excitation source to image the near-field of a nanostructure by means of the photoelectrons, has the advantage of high spatial resolution, fast, non-invasive and temporally resolved accessibility, and it has become a powerful tool in advancing near-field characterization of plasmonics [18,[20][21][22][23].…”

Probing Polaritons in 2D Materials

“…Incident photons with properly low energy can generate (multiple) plasmonic modes via light absorption and a photoelectron will be ejected when these plasmonic modes interact with another incident photon or photoexcited plasmon and will ultimately be recorded by a CCD camera. PEEM is suitable for investigating nonlinear photoemissions and can help characterize the plasmonic properties of the sample . While the resolution of PEEM as an electron microscope is limited by electron optics, this method provides a new approach for dynamically probing polaritons with the desired high spatial and temporal resolution if an ultrafast optical pulse is introduced.…”

“…PEEM is suitable for investigating nonlinear photoemissions and can help characterize the plasmonic properties of the sample. [140,164] While the resolution of PEEM as an electron microscope is limited by electron optics, this method provides a new approach for dynamically probing polaritons with the desired high spatial and temporal resolution if an ultrafast optical pulse is introduced. However, PEEM currently can only operate in the X-ray spectra to near infrared range and plasmon polaritons have been only investigated on metal films [164][165][166][167] and nanostructures.…”