Giant Enhancement of Nonlinear Optical Response in Nd:YAG Single Crystals by Embedded Silver Nanoparticles.

We report on the enhancement and modulation of nonlinear optical response in an Nd:YAlO (Nd:YAG) laser crystal through embedded silver nanoparticles (NPs) fabricated by Ag ion implantation. The linear absorption spectrum of the sample clearly reveals a localized surface plasmon resonance (SPR) band from 350 to 700 nm correlated to the Ag NPs. By using the Z-scan technique with femtosecond pulses at a wavelength of 515 nm, which is considered as an optical excitation within the SPR band, the nonlinear refraction index reaches values as high as ∼10 cm/W, enhanced by ∼4 orders of magnitude in comparison to that of unimplanted Nd:YAG (without Ag NPs). In addition, it has been shown that embedded Ag NPs in the Nd:YAG host reveal saturable absorption signifying the nonlinear responses. We have also observed that the nonlinear absorption coefficients depend significantly on the excitation energy and can be modulated by varying the fluence of Ag ions.