Fluorescence quenching in tip-enhanced nonlinear optical microscopy

We describe the theoretical treatment of fluorescence quenching in tip-enhanced nonlinear optical microscopy (TENOM). Finite difference time domain simulations demonstrate that while sharp pyramidal probes yield fluorescence signal enhancement that decays monotonically as a function of probe-fluorophore distance, more commonly used conical probes cause more complex image contrast. Fluorescence quenching can thus explain the halo-type images that are sometimes observed in TENOM. Formation of a dielectric spacer layer on the TENOM probe should alleviate the complications associated with quenching.