Enhanced non-linear optical properties of Eu3+ activated glasses by embedding silver nanoparticles

Tri-positive lanthanide ion (Eu3+) activated glasses doped with different concentrations of silver (Ag0) nanoparticles obtained using thermal reducing agent were fabricated by applying the method of melt quench. The formation of Ag0 nanoparticles in glasses was revealed by the surface plasmon resonance (SPR) peak in the absorption spectra. Transmission electron microscopic measurements confirmed the presence of spherically shaped Ag0 nanoparticles of different size distribution. The absorption spectra showed a red-shift of the SPR peak with an increase in AgNO3 concentration occurring through Ostwald's ripening process because of the growth of particle size (as evidenced from microscope images). The non-linear optical (NLO) and optical limiting measurements were performed in the near infrared spectral region and femtosecond pulse excitation. The non-linear parameters were found to increase as the AgNO3 concentration increased to 0.6 mol %, however, the parameters subsequently decreased at higher doping level. The optical limiting threshold values demonstrated a reverse trend. The increase in non-linear optical properties regarding Ag nanoparticles concentration attributed to the enhancement of polarizabilities of glasses that occurred through local field stimulated by SPR of Ag nanoparticles when exposed to laser radiation of high energy. The increase in NLO coefficients (particularly the non-linear absorption coefficient) and the decrease in optical limiting threshold values with AgNO3 concentration (up to 0.6 mol %) indicated that these glasses containing 0.6 mol % AgNO3 are useful for the construction of the power optical limiters that function at the infrared region in the femtosecond pulse regime.