Abstracts - Dipartimento di Elettronica Applicata

Meta 2010 & FEM 2010 – Rome, 13-15 December 2010
Optimized second harmonic generation in gold
square rod chains
Marco Centini, Alessio Benedetti, Concita Sibilia, Mario Bertolotti
Dipartimento di Scienze di Base e Applicate per l'Ingegneria- Sez Fisica. Sapienza
Università di Roma. Via A. Scarpa 16 00161 Roma – Italy
E-mail: marco.centini@uniroma1.it
Thanks to the development of nanotechnologies and nanoscience, nonlinear properties
of metallic nanostructures have been deeply investigated both theoretically and
experimentally in the last years. SHG enhancement from nanoantennas and nanodimers
has been observed both in near and far fields[1,2]. In a recent work we studied
SHG in gold nanowires pointing out the possibility to tailor the properties of the
generated signal by proper design of the system [3]. The same method developed in
[3] has been used to investigate SHG by a chain of gold rods. Here we report the
results of our calculations by considering, as an example, a chain made of five gold
rods (figure 1a). We show that strong field localizations are obtained in the region
between the rods resulting from interference of localized surface plasmons when the
fundamental field is tuned on a coupled resonance (figure 1a). This effect provides a
more efficient coupling of the pump energy to plasmon modes and is responsible of
the enhancement of second harmonic generated signal (figure 1b).
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c) b)
Figure 1: (a) modulus of the magnetic field H normalized with respect to the amplitude of the incident
field. Fundamental field wavelength is 770 nm, rod sections are 120x120 nm2 and gaps between rods
are 15 nm. (b) polar plot of the nonlinear differential scattering cross section for the generated second
harmonic field. Typical values of the nonlinear scattering cross section by a gold flat surface at the
same wavelength are of the order of 10 -20 cm 2 /W.
References
[1] B. K. Canfield et al., Nano Letters, 7, 5, 1251-1255 (2007)
[2] T. Hanke et al., Phys. Rev. Lett. 103, 257404 (2009).
[3] A. Benedetti et al., JOSA B 27, 3, 408-416 (2010)).
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