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Cancellation of photoinduced absorption in metal nanoparticle composites through a counterintuitive consequence of local field effects

1997; Optica Publishing Group; Volume: 14; Issue: 7 Linguagem: Inglês

10.1364/josab.14.001625

1520-8540

David D. Smith, George L. Fischer, Robert W. Boyd, Don A. Gregory,

Spectroscopy and Quantum Chemical Studies

By applying the Maxwell Garnett model to gold nanoparticles in water we deduce a value of Im χi(3)=1.1×10-7 esu for the imaginary part of the cubic susceptibility for gold corresponding to a Fermi smearing mechanism. We also demonstrate a sign reversal in the nonlinear absorption for gold particles in 1, 1′, 3, 3, 3′, 3′-hexamethylindotricarbocyanine iodide. Although the imaginary part of χ(3) is positive for each component by itself, remarkably the imaginary part of χ(3) is negative for the colloid as a whole. We show that the nonlinearity of the host must be considered and that the sign reversal in χ(3) is a result of the fact that at the surface plasmon resonance the local field factor has an imaginary component that arises from a phase shift between the applied field and the local field inside the particle.