Nonlinear refraction of gold island films

Giant nonlinear refraction has been experimentally observed in gold island films. The complex third-order nonlinear susceptibility χ (3) (ω;ω,-ω,ω) reaches a value of -8×10 -5 esu (λ = 532 nm, ι = 10 ns) and (+5×10 -7 + i0.3×10 -7 ) esu (λ = 800 nm, ι = 85 fs). The mechanism of nonlinearity of the refractive index can be associated with the resonance enhancement of the factor of the local optical field at the pump wavelength due to the excitation of surface plasmons, as well as with the contribution of the heating of conduction electrons in an ensemble of metal particles.