Search

We report the broadband nonlinear optical (NLO) properties of CsPbBr_3 perovskite films achieved from colloidal nanocrystals prepared following a room temperature and open atmosphere anti-solvent precipitation method. The NLO studies were performed on the films of nanocubes (NCs) and nanorods (NRs) using the Z-scan technique with 1 kHz femtosecond pulses at 600, 700, and 800 nm. Large two-photon absorption cross sections (∼10^5  GM) were retrieved by fitting the open-aperture Z-scan data. Strong third-order NLO susceptibility (∼10^−10  esu) was observed in these films. At higher peak intensities a switching of sign (in both NCs and NRs) in the real and imaginary parts of the NLO susceptibility was observed from the studies on these CsPbBr_3 nanocrystals. The obtained NLO coefficients clearly suggest that these materials are promising for ultrafast photonic applications.

Plasmonic based hybrid noble metal nanoclusters (NCs) have gained much interest in various technological applications such as optoelectronics, photonic devices and nonlinear media including biomedical applications due to their tunable optical properties. Here, Ag NCs are grown as embedded in glass using simple ion‐exchange process and effect of various parameter including post thermal treatment is studied on tunability of their optical behavior (plasmonic, optical nonlinearity, and photoluminescence properties) in view of their potential applications in nanophotonics devices and as nonlinear media. The tunable optical, structural and thermodynamic properties associated with the rapid growth and agglomeration of Ag NCs in the glass is also studied under the post thermal treatment process. The various techniques such as XRD, RBS, Z‐scan and UV‐vis, XPS, PL and TEM are used for characterizing ion exchanged samples. A blue shift of 15 nm is observed significantly in optical absorbance as a function of post thermal treatment. Open and closed aperture Z‐scan experiments show strong nonlinear absorption coefficients for the Ag NCs. The thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS) and Gibbs energy (ΔG) for the nucleation and growth of the Ag NCs in the glass matrix are calculated at different temperatures with an activation energy of 59 kJ mol−1obtained by the Arrhenius linear equation and a model is suggested. In addition, these Ag NCs embedded glasses exhibit good antimicrobial activities (against E. colibacteria) with a change in antibacterial behavior at higher annealing temperature indicating their multifunctional applications. Ag nanoclustersare grown as embedded in glass using a simple ion‐exchange process and the effect of various parameters including post thermal treatment is studied on the tunability of their optical behavior (plasmonic, optical nonlinearity, and photoluminescence properties) in view of their potential applications in nanophotonics devices and as nonlinear media.

The article reports on the use of raman spectroscopy and laser induced breakdown spectroscopy (LIBS) for explosives detection by applying filamentation techniques. Topics discussed include use of plasma filamentation for detection of explosives; use of Schmidt-Cassegrain telescope (SCT) for collecting light that transmits the plasma emission to a spectrometer; and use of complex combinations and ratios of carbon (C), nitrogen (N), oxygen (O), and hydrogen (H) elements for detection system.