Fluorescent clusters in chloride photo-thermo-refractive glass by femtosecond laser bleaching of Ag nanoparticles

Abstract

We report photoluminescence in bulk chloride photo-thermo-refractive glass under irradiation with femtosecond laser pulses. The fluorescence originates from the bleaching of silver nanoparticles precipitating in the glass. Similarly to the conventional process of the femtosecond re-shaping of metal inclusions with diameter tens of nanometers, irradiation of the smaller nanoparticles results in a fast shrinking size with an ellipsoidal shape via photofragmentation. Under UV excitation, remaining sub-nanometer silver molecular clusters show visible and near IR fluorescence, which increases with chlorine concentration. The observed bleaching of silver nanoparticles in bulk glass-metal nanocomposite can find applications in data storage and bleaching of volume Bragg gratings.

Volume Bragg gratings in chloride photo-thermo-refractive glass after femtosecond laser bleaching

“…However, the particle species cannot move far from the origin due to limited space. Figure 2 shows that initially metallic nanoparticle is surrounded by NaAgCl shell with larger refractive index [9,11]. The femtosecond bleaching transforms AgNPs into closely spaced silver clusters, which can be bought back and restore the nanoparticle via thermal treatment within several minutes [11,16].…”

“…We have recently proposed, synthesized and characterized a novel PTR glass composition, which provides positive refractive index change [9,10]. X-ray diffraction analysis revealed the precipitation of the NaAgCl nanocrystalline phase which is responsible for the positive refractive index change with magnitude of as high as 8.7 × 10 −4 [9,11]. It has been shown that this glass open a way to fabricate the volume mix type Bragg gratings, which possess both refractive index and absorption coefficient modulation.…”

“…This process was studied extensively during last two decades in different glass matrix including classic PTR glass [15][16][17][18][19]. We have recently shown that the absorption can be significantly reduced by means of the intense femtosecond laser radiation without noticeable effect on the NaAgCl volume fraction [11,20]. In addition it have been demonstrated that fluorescent silver nanoclusters remain in the glass volume after femtosecond bleaching of the AgNPs [11].…”

Femtosecond Laser Micro/Nano-manufacturing: Theories, Measurements, Methods, and Applications

“…Then, Royon et al [141] created silver clusters through a femtosecond laser shot inside a femtophotoluminescent glass, which can store information precisely. Klyukin et al [142] observed the presence of fluorescent clusters in chloride photothermorefractive glass under femtosecond laser irradiation. Birefringent [130] structures were obtained by means of multiple femtosecond laser pulses in nanoporous glass, where the minimum distance between dots was as small as 1.4 μm [143].…”

Features of Volume Holograms in Fluoride and Chloride Photothermorefractive Glass

“…The absorption of ultrashort pulse energy leads to local heating and the explosion of the metallic particle [31]. In Figure 9, process of AgNPs surrounded by NaCl-AgCl shell, destruction, is shown schematically [32]. The femtosecond bleaching transforms AgNPs into silver clusters.…”