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Linear and nonlinear absorption of a series of new donor-pi-acceptor polymethines with different lengths of conjugation are investigated and include quantum chemical analysis. Two-photon absorption cross-sections as large as 11,000 GM and solvatochromism are observed.
We report multi-carrier dynamics and two-photon absorption in lead-salt quantum dots. Inter and intra-band relaxation as well as Auger recombination is observed, along with breaking of the one and two-photon transition selection rules.
Temperature dependent two-photon and free-carrier absorption spectra of InSb are measured using a tunable picosecond source via temperature controlled Z-scan experiments and show good agreement with theoretical predictions. Three-photon absorption is also observed.
The optical properties of gold nanorods suspended in toluene are studied as a function of orientation by aligning them with a low frequency electric field. The nonlinear optical response is consistent with a 2-level saturation model.
We investigate the fluorescence properties of dye molecules embedded in core-shell plasmonic nanoparticles. The absorption and emission dynamics of the dyes may be modified by engineering the plasmonic resonance of the core-shell structure.
The three-photon absorption (3PA) spectrum of ZnSe was measured using femtosecond Z-scans and theoretically verified using a Kane 4-band model including nonparabolicity and nonzone-center wave functions. Several other semiconductors with various bandgap energies are presented.
Large excited-state-absorption (ESA) spectra and lifetime dynamics for a new series of NIR cyanine-like dyes are compared to similar visible dyes. Strongly red-shifted (200-300 nm) and increased ESA are observed and explained through quantum-chemical calculations.
We investigate the nonlinear optical response of gold thin films of different thicknesses. Field enhancement effects lead to counterintuitive results which we interpret in terms of the excitation of plasmonic resonances at the metal-dielectric interfaces.
We report studies of multi-carrier dynamics in PbS quantum dots. Nanosecond recombination times are observed for the 1Sel-1S3/2 transition and evidence of direct radiative recombination from 1Pel-1P3/2 is observed on picoseconds time scales.
Excited state absorption spectra for a series of near IR symmetric polymethine, squaraine and tetraone dyes were measured by the femtosecond pump - white light continuum probe technique. Structure-property relationships were revealed and explained with quantum- chemical analysis.
In this presentation, we describe another promising organic material that enables all-optical switching in an extremely wide time scales spanning sub-nanoseconds to cw regime - a nonlinear neat organic liquid (L34) in bulk or wave-guided [fiber core] structure. In the visible spectrum [400-700 nm], quantitative z-scan and pump-probe techniques have shown that in the sub-nanosecond time scales, the...
To understand the effects of electron accepting bridges on the nonlinear absorption, we characterized both two-photon and excited-state absorption spectra of three cyanine dyes of increasing electron acceptor strength.
We report theoretical and experimental results of nonlinear absorption and refraction in a series of colloidal CdSe quantum-dots. A two-level-model is used to describe the nonlinearities when quantum-dots are excited close to their first resonance.
We compare two-photon absorption spectra of polymethines and squaraines experimentally and quantum-chemically. Squaraines display two-photon cross-sections considerably larger (7times103GM) than polymethines, due to an extra band introduced by the squaraine structure in the conjugated chain.
We measured nondegenerate two-photon absorption spectra of single-crystal polydiacetylene (PTS) with white-light continuum nonlinear optical spectroscopy. We observed an intermediate state resonance enhancement in qualitative agreement with a three-level model
We present a rapid characterization technique for nonlinear absorption and refraction: the white-light continuum z-scan. The broadband nature of this pump permits us to measure the two-photon absorption spectrum of ZnSe using only one beam.
Summary form only given. Passive optical limiters are used to protect human eyes or sensitive optical elements from laser damage. Excited-state absorption (ESA) evoked transitions from one excited state to a higher one is a prerequisite for efficient optical limiting. Numerous parameters of the system as well as laser pulse characteristics make it difficult to determine optimum conditions for efficient...
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