Discrete spectrum of anti-Stokes emission from metal particle-adsorbate complexes in a microcavity

Abstract

This report presents the discovery of greatly enhanced, broad-range, multiphoton excited emission from Ag aggregate-adsorbate complexes seeded into a cylindrical microcavity. The emission spectrum contains descrete peaks spanning the wavelength range from the 632 nm HeNe laser exciting wavelength down to 200 nm. Observation of multiphoton processes at the low exciting light intensity (20 W/cm2) became possible due to using a fractal-microcavity composite, where coupling the localized plasmon modes in fractal aggregates with microcavity resonances is provided. The important role of the multiphoton resonant transitions between discrete states of a finite-size metal particle in enhanced local fields is shown. Analysis, based on the model of a spherical potential well, shows that the observed spectra contain fingerprints of the quantum size effet.

Whispering-gallery nanocavity plasmon-enhanced Raman spectroscopy

“…However, the intrinsically high ohmic losses of metal result in low resonance quality factors, thus limiting their enhancement and sensitivity. Therefore, combining SERS with special optical structures (for example: multihole capillaries, photonic crystals and WGM cavities) for optimizing comes as a preferred method 23 24 25 26 . Optical cavities with WGMs, which confine light to small volumes by resonant photon circulation could greatly enhance the light-matter interaction 27 28 29 30 31 32 33 .…”

SERS-based detection in an optofluidic ring resonator platform

“…The use of resonating WGMs for SERS has been investigated theoretically and experimentally [14][15][16]. We previously used a microsphere ring resonator to show experimentally a gain of over two orders of magnitude compared to a SERS system in which the excitation light makes a single or non-resonant pass through the sample volume [15].…”