Near-field imaging and spectroscopy of plasmonic cavities (Conference Presentation)

Abstract

Photoemission electron microscopy (PEEM) is an attractive and advantageous technique in the field of plasmonics. Whilst surface plasmons are excited at the metal dielectric interface by light, it is the near-field photoelectron distribution that is imaged, with <40 nm resolution, and thereby the optical diffraction limit is overcome. Additionally parallel acquisitioning makes time-resolved (TR) PEEM1 possible. PEEM therefore allows us to investigate light-matter interactions in localized, propagating and hybridized surface plasmons leading to advances in fundamental research and technological applications. In addition to near-field imaging it is also possible to perform near-field spectroscopy. A tunable short pulse optical parametric oscillator (OPO) light source can be combined with PEEM. We demonstrate this technique with arrays of whispering gallery mode (WGM) cavities2 fabricated with focused ion beam milling (FIB) on gold surfaces. Characteristic spectral peaks and near-field mode distributions result from the coherent excitation of different plasmon resonances. This near-field interference of modes allows us to control the emission from these WGM cavities3. Additionally recent advances in ultrafast near-field microscopy and spectroscopy will be discussed. [1] M. Bauer, C. Wiemann, J. Lange, D. Bayer, M. Rohmer and M. Aeschlimann, Appl. Phys. A 88 473 (2007) [2] E. J. Vesseur, F. J. Garcia de Abajo and A. Polman Nano Letters 9 3147 (2009) [3] P. Melchior, D. Kilbane, E. J. Vesseur, A. Polman and M. Aeschlimann Optics Express 23, 31619 (2015)