Size-dependent nonlinear absorption and refraction of Ag nanoparticles excited by femtosecond lasers

Abstract

Silver (Ag) nanoparticles with different average sizes are prepared, and the nonlinear absorption and refraction of these nanoparticles are investigated with femtosecond laser pulses at 800 nm. The smallest Ag nanoparticles show insignificant nonlinear absorption, whereas the larger ones show saturable absorption. By considering the previously reported positive nonlinear absorption of 9 nm Ag nanoparticles, the nonlinear absorptions of Ag nanoparticles are found to be size-dependent. All these nonlinear absorptions can be compatibly explained from the viewpoints of electronic transitions, energy bands and electronic structures in the conduction band of Ag nanoparticles. The nonlinear refraction is attributed to the effect of hot electrons arising from the intraband transition in the s—p conduction band of Ag nanoparticles.

Transformation from Self-Focusing to Self-Defocusing of Silver Nanoparticles

“…The UV-Vis absorption spectrum of AgNPs is shown in Figure 2. It can be seen from Figure 2 that AgNPs have a strong absorption band at about 410 nm, which can be attributed to the SPR of AgNPs [12,13,26]. The TEM image of AgNPs is shown in Figure 3 and it can be determined that the average diameter of AgNPs is about 10 nm.…”

“…The NLO effect of noble metal nanoparticles is greatly enhanced due to their unique localized surface plasmon resonance (LSPR) behaviour [7][8][9][10]. The nonlinear refractive properties of gold, silver and other noble metal nanoparticles have been widely studied [10][11][12][13][14][15][16][17][18][19][20]. It has been reported that the nonlinear refractive index of composite materials with noble metal nanoparticles is greatly enhanced due to the effect of noble metal nanoparticles [9,10].…”

Pulse Duration and Wavelength Effects of Laser Ablation on the Oxidation, Hydrolysis, and Aging of Aluminum Nanoparticles in Water

“…However, the chemical reactions are very different once one considers the nano- and macro-scale structures [17,18,19]. In the case of nanoscale, studies have shown that morphology [20,21] and sizes of particles [22,23,24] have an impact on their chemical properties. Therefore, it is worth studying the dynamics of morphology and particle sizes of Al, aluminum oxide, and hydrolysates at the nanometer level.…”

Interaction of Pulses of Different Duration with Chemically Prepared Silver Nanoparticles: Analysis of Optical Nonlinearities

“…The analysis of the nonlinear absorption coefficients and nonlinear refractive indices of Ag NPs, as well as the exploration of their potential applications, was reported in a few studies [17][18][19]. There are experimental studies showing that particle size, morphology, and surrounding medium of noble metal NPs have great influence on their nonlinear optical properties [20][21][22][23]. For example, Ag NPs with smaller particle sizes demonstrated weak nonlinear optical response, while larger particles were characterized by strong saturable absorption (SA) [20].…”

“…There are experimental studies showing that particle size, morphology, and surrounding medium of noble metal NPs have great influence on their nonlinear optical properties [20][21][22][23]. For example, Ag NPs with smaller particle sizes demonstrated weak nonlinear optical response, while larger particles were characterized by strong saturable absorption (SA) [20]. With the increase of particle sizes, nonlinear absorption has shown a shift from two-photon absorption (2PA) to SA, while nonlinear refraction was transformed from self-defocusing to self-focusing [21].…”