On second harmonic generation and multiphoton-absorption induced luminescence from laser-reshaped silver nanoparticles embedded in glass

Controlled metallization of ion-exchanged glasses by thermal poling

We present studies of the formation of silver nanoparticles (NPs) in silver-sodium ion-exchanged glasses by a combination of thermal poling and nanosecond pulsed laser irradiation at 355 nm. In poling, silver ions drift deeper into the glass and become separated from the glass surface by a poled layer depleted in cations. Performed measurements have indicated poling-induced broadening of silver ions depth distribution. Laser irradiation reduces silver ions to atomic silver via breaking silver-non-bridging oxygen (NBO) bonds, extraction of electrons from the NBO atoms and capturing these electrons and electrons generated via multi-photon absorption in the glass by silver ions. The depleted layer limits diffusion of silver atom towards glass surface and, as a consequence, formation of silver NPs on the surface of poled glasses. It is shown that thermal poling mode allows one to control formation of silver NPs of glass surface.

Giant Second-Harmonic Generation in Cantor-like Metamaterial Photonic Superlattices

We present a nonlinear transfer matrix method for studying the second-harmonic generation (SHG) in nonperiodic metamaterial photonic superlattices. A large enhancement of up to 5 orders of magnitude in SHG efficiency was observed for superlattices made with a Cantor-like quasiperiodic assembly of a nonlinear material and a metamaterial. The enhancement was found to depend much more on the electric field amplitude along the structure because of self-similarity effects than on the amount of nonlinear material, which opens the way to design superlattices for tailored applications in broad-band tunable lasers.

Ag nanoparticles embedded in Nd:YAG crystals irradiated with tilted beam of 200 MeV Xe ions: optical dichroism correlated to particle reshaping

We report on the fabrication of reshaped Ag nanoparticles (NPs) embedded in a Nd:YAG crystal by combining Ag ion implantation and swift heavy Xe ion irradiation. The localized surface plasmon resonance (LSPR) effect is proved to be efficiently modulated according to the phenomenon of polarization-dependent absorption. The LSPR peak located at 448 nm shows red shift and blue shift at 0° and 90° polarization, respectively, which is in good agreement with calculation by discrete dipole approximation. Based on the near-field intensity distribution, the interaction between reshaped NPs shows a non-ignorable effect on the optical absorption. Furthermore, the polarization-dependence of the photoluminescence (PL) intensity is analyzed, which is positively related to the modulated LSPR absorption. It demonstrates the potential of the enhancement of PL intensity by embedded plasmonic Ag NPs. This work breaks the conventional view of the quenching effect of NPs by ion irradiation and opens a new way to realize the modulation of optical dichroism.

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

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.