Involvement of plasmons in a frequency conversion process [36] increases the overlap integral [40], [43] several orders of magnitude because both the excited and the converted modes are strongly localized compared to the incident plane waves [8]. In the far field, one observes the damping of the plasmon due to radiation reaction or recombination of the pairs into which plasmon decays [44]. Far-field Raman signal is proportional to the number of Stokes-shifted plasmons.