Polarization-resolved two-photon luminescence microscopy of V-groove arrays

Using two-photon luminescence (TPL) microscopy and local reflection spectroscopy we investigate electromagnetic field enhancement effects from a mu m-sized composition of 450-nm-deep V-grooves milled by focused ion beam in a thick gold film and assembled to feature, within the same structure, individual V-grooves as well as one- and two-dimensional 300-nm-period arrays of, respectively, parallel and crossed V-grooves. We analyze TPL signal levels obtained at different spatial locations and with different combinations of excitation and detection polarizations, discovering that the TPL emitted from the V-grooves is polarized in the direction perpendicular to that of the V-grooves. This feature implies that the TPL occurs solely in the form of (p-polarized) surface plasmon modes and originates therefore from the very bottom of V-grooves, where no photonic modes exist. Implications of the results obtained to evaluation of local field enhancements using TPL microscopy, especially when investigating extended structures exhibiting different radiation channels, are discussed. (C)2011 Optical Society of America