Indeed, under the assumption that doping dense glasses with the NP precursors and controlling the NP growth under laser irradiation are possible, one can imagine such an experiment where NPs are created in the pre-doped fiber core after its drawing, by exposing it to the laser beam. The local precipitation of NPs in a fiber core may itself be useful in laser technology, where
NPs can act for example as emitters (Figure 1a) or saturable absorbers. Another example of application idea was given in a patent deposited by Alcatel [15] in 2004. It consists in creating a Bragg grating by doping periodic zones with NPs (Figure 1b), then using the enhanced Kerr optical effect of the composite zones to optically control either the reflection wavelength or the filter contrast, two parameters depending on the effective PRIMA-1MET manufacturer refractive index. 3-Methyladenine This prospect, as well as the one related to other applications like photochromic display systems [16], has substantially increased the interest in using laser irradiation to generate particles in a glass and also in a xerogel matrix. What is called a xerogel here can be presented as a porous glassy phase with interconnected pores [17]. Hence, atoms of NP precursors have a higher mobility than in a dense glass, facilitating
the NP formation without any specific heat treatment, contrary to the case of dense glasses. Indeed, concerning metal nanoparticles, since the pioneer work of Qiu et al. [18] in 2002, many other studies have dealt with precipitating gold, silver, and even copper buy VX-661 nanocrystals in dense melted glasses [19, 20]. The principle is first to reduce metal cations by extracting electrons from the matrix using infrared femtosecond (fs) pulses. The high electric field of the
pulses creates nonbridging oxygen holes and free electrons that can be trapped by metal ions [21]. A subsequent heat treatment is however necessary to give the metal atoms a sufficient mobility in the vitreous matrix, allowing their migration to the existing clusters [22] and yielding Erastin purchase the formation of nanoparticles. In theory, the energy needed for this diffusion is much weaker in the case of a porous medium. Figure 1 Examples of new-generation optical device concepts using NP in a fiber core. (a) Quantum dot-based laser consisting in a NP-doped core region inside an optical cavity using Bragg gratings (BG). The pump light at any wavelength lower than the exciton wavelength can be guided in the inner cladding, interacting with the QD by leaking modes. (b) All-optical control of the properties of a Bragg grating containing periodic arrangement of NP. Alkoxide-derived inorganic xerogels have been recently shown as a much cheaper alternative to chemical vapor deposition methods for providing pure silica rods.
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