Nonlinear absorption and nonlinear refraction: Maximizing the merit factors

Both nonlinear absorption and nonlinear refraction are effects that are potentially useful for a plethora of applications in photonics, nanophotonics and biophotonics. Despite substantial attention given to these phenomena by researchers studying the merits of disparate systems such as organic materials, hybrid materials, metal-containing molecules and nanostructures, it is virtually impossible to compare the results obtained on different materials when varying parameters of the light beams and different techniques are employed. We have attempted to address the problem by studying the properties of various systems in a systematic way, within a wide range of wavelengths, and including the regions of onephoton, two-photon and three-photon absorption. The objects of our studies have been typical nonlinear chromophores, such as π-conjugated molecules, oligomers and polymers, organometallics and coordination complexes containing transition metals, organometallic dendrimers, small metal-containing clusters, and nanoparticles of various kinds, including semiconductor quantum dots, plasmonic particles and rare-earth doped nanocrystals. We discuss herein procedures to quantify the nonlinear response of all of these systems, by defining and comparing the merit factors relevant for various applications

Solvent effects on the optical properties of PEG-SH and CTAB capped gold nanorods

Cetyltrimethylammonium bromide (CTAB) and (11-mercaptoundecyl)tetra(ethylene glycol) (PEG-SH) capped gold nanorods were prepared and dispersed in water and dimethyl sulfoxide (DMSO). Transmission electron microscopy images reveal that changing the solvent from water to DMSO cause that nanoparticles tend to organize (PEG-SH ligand) or aggregate (CTAB ligand). UV-vis absorbance spectra reveal that ligand as well as solvent exchange cause positive solvatochromic shifts and changes in the relative extinction values. After the transfer of nanorods from a solvent of lower to higher refraction index a red shift of the longitudinal surface plasmon resonance band is observed. This effect is more pronounced in the case of PEG-SH capped nanorods. Time resolved pump-probe measurements revealed that both ligand and solvent exchange influence the excited state relaxation times, however, a more pronounced change is induced by the ligand exchange. Two-photon excited fluorescence spectra of PEG-SH covered nanorods showed a slight intensity increase when moving from water to DMSO solvent

End-to-end self-assembly of gold nanorods in isopropanol solution: experimental and theoretical studies

International audienc

Nonlinear absorption and nonlinear refraction: maximizing the merit factors

Both nonlinear absorption and nonlinear refraction are effects that are potentially useful for a plethora of applications in photonics, nanophotonics and biophotonics. Despite substantial attention given to these phenomena by researchers studying the merits of disparate systems such as organic materials, hybrid materials, metal-containing molecules and nanostructures, it is virtually impossible to compare the results obtained on different materials when varying parameters of the light beams and different techniques are employed. We have attempted to address the problem by studying the properties of various systems in a systematic way, within a wide range of wavelengths, and including the regions of onephoton, two-photon and three-photon absorption. The objects of our studies have been typical nonlinear chromophores, such as π-conjugated molecules, oligomers and polymers, organometallics and coordination complexes containing transition metals, organometallic dendrimers, small metal-containing clusters, and nanoparticles of various kinds, including semiconductor quantum dots, plasmonic particles and rare-earth doped nanocrystals. We discuss herein procedures to quantify the nonlinear response of all of these systems, by defining and comparing the merit factors relevant for various applications