Two photon versus one photon fluorescence excitation in whispering gallery mode microresonators

We investigate the feasibility of both one photon and two photons fluorescence excitation by using whispering gallery mode microresonators. We report the linear and non linear fluorescence real-time detection of labeled IgG covalently bonded to the surface of a silica whispering gallery mode resonator (WGMR). The immunoreagents have been immobilized onto the surface of the WGMR sensor after being activated with an epoxy silane and an orienting layer. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of immunoreactions. We also investigate the potential of microbubbles as nonlinear enhancement platform. The dyes used in these studies are tetramethyl rhodamine isothiocyanate, Rhodamine 6G and fluorescein. All measurements were performed in a modified confocal microscope