In the process of optical second-harmonic generation an X-wave, travelling at the group velocity of the fundamental frequency, spontaneously forms. Its parameters, as well as the angular spectrum, are directly correlated to the group velocity mismatch and to the wavevector mismatch between the two harmonics. A novel mechanism for spatio-temporal localized waves generation is thus proposed. ∗Ele...

In this paper, we perform a detailed study of the spectral response of the gold U-shaped nano-structures for different geometrical parameters and polarizations in order to obtain significant localization factor in the wavelength 1.55 μm. The obtained near-field distribution of electric fields reveals that resonances in these nano-structures correspond to the even and odd plasmonic modes dependi...