Toward a robust design of nanodimer type structures addressed to high harmonic generation

F.VIDELA; E. NEYRA; G.A. TORCHIA

Pucón

Conferencia; Reunion Iberomericana de Optica y Laser; 2016

Universidad de Concepcion-ICO-OSA-SPIE-

We have studied the field enhancement effect when a metallic triangular or trapezoidal nanodimer (bow ties) was irradiated with intense laser pulses at various wavelengths near from 800nm. Given that these nanostructures can be implemented in high harmonic generation (HHG) experiments,we have focused our attention in the resonance behaviour and some geometrical parameter of the triangles and trapezoids (dimensions established former by Kim et al., and achievable by mean of e-beam lithography or focused ion beam ). Their height, width, thickness and the separation between apices was analysed . The process of high harmonic generation requires intensities of 1013 W/cm2 if some noble gas like Argon sourronding nanostructures is irradiated with a focusing femtosecond laser pulses. However by mean of field enhancement produced by interaction between laser pulses and matallic nanostructures (ie: nano dimers) high intensities can be achieved starting from modest intensities about 1011 W/cm2 Such intensities are generated in the output power of fs laser oscillator systems, so an amplifier stage is not required. Different fields distributions considering space and intensity were observed fromsimulations with an FDTD based software. In consequence could be established the influence of each parameter in the enhanced field. In addition trapezoidal core shell were simulated in order to study the same field enhancement characteristics. Complemenraty imulations of bare gold and silver ablated nanostructures were made in order to explore their effect in the field enhancement. Because the high intensities developed in nanostructures is necessary to consider that melting temperature depends on its dimension, due to higher value of surface to volume ratio. In this work, we have simulated different bow ties geometries for two materials gold and silver and study quantitatively the field enhancement considering the intensity and spatial distribution, for both cases with and without shell ofTi was employed as a coverl material in both cases due to their high melting point and mechanical properties that ensure high resistance to mechanical deformations.The effect of the field distributions in HHG yielld has been explored by integrated the classical Newton Loretz equation since from this analysis could be determined the maximum kinetic energy of the recombination electrons.