Two photon fluorescence sensors based on resonant grating waveguide structures

We use novel high-finesse polymeric resonant grating waveguide structures (GWS) for strong enhancement of two photon fluorescence (TPF). At a specific wavelength and angular orientation of the incident beam, the grating waveguide structure resonates. This resonance results in a field enhancement at the surface that can be exploited for TPF spectroscopy, without the need for highly focused laser excitation light. We compare the TPF obtained from a thin layer of tetramethylrhodamine (TMR) deposited on top of a GWS at resonance and off-resonance. Our procedure and results indicate that the detection of TPF can indeed be improved with the resonant GWS by at least fifteen times. These results have been also demonstrated using a GWS and a 2 μm thick layer of TMR aqueous solution.