Generation of copper nanoparticles induced by fs-laser irradiation in borosilicate glass

Abstract

Glasses containing metallic nanoparticles are promising materials for technological applications in optics and photonics. Although several methods are available to generate nanoparticles in glass, only femtosecond lasers allow controlling it three-dimensionally. In this direction, the present work investigates the generation of copper nanoparticles on the surface and in the bulk of a borosilicate glass by fslaser irradiation. We verified the formation of copper nanoparticles, after heat treatment, by UV-Vis absorption, transmission electron microscopy and electron diffraction. A preferential growth of copper nanoparticles was observed in the bottom of the irradiated region, which was attributed to self-focusing in the glass. in borosilicate glasses using ultrafast laser irradiation," J. ©2012 Optical Society of America

Ultrafast Laser Pulses for Structuring Materials at Micro/Nano Scale: From Waveguides to Superhydrophobic Surfaces

“…Thus, if low repetition rate lasers are applied, annealing is required, configuring a two-step processing. Figure 12 clarifies the effects of high and low repetition rate lasers on the precipitation of copper and silver NPs in borosilicate glass [107,109]. The absorption spectra of pristine samples are represented by solid curve, while dotted and dashed curves display the absorbance after the irradiation using fs-lasers of 5 MHz (800 nm, 50 fs) and 1 kHz (775 nm, 150 fs) of repetition rate, respectively.…”

“…Cations in the glass matrix can react with these free electrons resulting in their reduction. Therefore, if the glass is doped with, for instance, Ag + , Au 3+ , Cu 2+ ions, photoreduction reactions promote the formation of neutral atoms that further aggregate on account of the atomic mobility provided by the increase of temperature [35,36,107]. This procedure is summarized through Equations (1)- (3), which elucidate the formation of metallic silver nanoparticles by femtosecond-laser micromachining [36,108].…”

Metallic nanoparticles grown in the core of femtosecond laser micromachined waveguides

“…In this case, the irradiation resulted in an increase of the absorbance for the visible region of the spectrum (a ¼ 1.6 cm À1 ) due to the formation of color center and reduction of silver ions. 10,11,18 A small plasmon band was observed only after a heat treatment, preformed at 400 C for 1 h. The effect of color centers caused by the irradiation using the MHz laser can be ruled out, since the absorbance due to the plasmon band overcomes any absorption caused by the color center.…”

“…10,24 Such behaviour might be due to the non-uniform laser intensity distribution as a consequence of the spherical aberration caused by high numerical aperture lens, 9 or because of the self-focusing effect, that happens when materials with n 2 > 0 are exposed to high laser intensities. 10 However, although the dark regions present a higher amount of nanoparticles, it is reasonable to assume that in the rim outside such region, nanoparticles are also present, but in a smaller concentration, since Ag atoms could diffuse to the boundary regions due to fs-laser induced temperature gradient. 25,26 Independently on the NP distribution, both structures were able to guide light at 632.8 nm, indicating a refractive index change at the irradiated regions.…”

“…8 For instance, the spatially controlled growth of metallic nanoparticles in glass using femtosecond laser irradiation has been demonstrated. [9][10][11][12] The control of such properties in a confined region makes possible the development of photonic devices, as waveguides, splitters, resonators, and microfluidic channels. 7,8 Fabrication of waveguides in materials with promising optical nonlinearities has been the subject of several studies aiming at integrated photonic devices.…”