The optical loss suppression in thin gold film within mid-IR range

Novel experimental mechanism of suppression losses in plasmonic subsystem in noble metal is demonstrated. This mechanism is based on the so-called parametric two-wave coherent coupling irradiation. The ratio of the frequency of the probe mode to the support mode corresponds to parametric resonance condition ω_p: ω_s = 2 : 1. The support mode is generated by the CO₂ pulsed laser, and the probe mode was obtained due to the second harmonic generation (SHG) of the support mode. By adjusting the parameters phase shift, between the two waves, and their amplitudes, the optical losses can be dramatically reduced to near zero. A highly dispersive Au thin film were analyzed. When the specific conditions are satisfied, the losses, in the probe wave, were shown to be reduced significantly.