Single State Absorption Spectra of Novel Nonlinear Optical Materials

1999 ◽  
Vol 597 ◽  
Author(s):  
Sean M. Kirkpatrick ◽  
Casey Clark ◽  
Richard L. Sutherland
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Transient Absorption ◽  
Short Pulse ◽  
Measurement Techniques ◽  
Excited State Absorption ◽  
Leading Edge ◽  
Photon Absorption ◽  
Two Photon ◽  
Pulse Pump

AbstractDuring the absorption of a laser pulse of moderate length, the leading edge can experience excited state absorption out of the first singlet state. The measurement of this excited state absorption spectrum can only be accurately probed using short pulse pump-probe techniques. Specifically, we examine the excited state absorption of AF-380 in THF using ultrafast transient white light absorption spectroscopy (TWLA). This material has been the focus of several investigations due to it's purported large two-photon absorption cross-section, the discrepancies between long and short pulse measurements, and it's use in holographic twophoton induced photopolymerization. It is believed that a substantial excited state absorbance can account for the difference in two-photon cross section measurements. It is also possible that this excited state exhibits coherence for time scales that can affect further absorption of longer pump pulses. We examine the transient absorption of this species, as well as polarization and free carrier effects and discuss the possible implications with regards to measurement techniques.

scholarly journals Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

2019 ◽  
Vol 15 ◽  
pp. 2438-2446 ◽  
Author(s):  
Alessandro Iagatti ◽  
Baihao Shao ◽  
Alberto Credi ◽  
Barbara Ventura ◽  
Ivan Aprahamian ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Transient Absorption ◽  
Solvent Polarity ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon

In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch, belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible two-photon absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main emission component in the 500–520 nm spectral range, attributed to the Z-isomer, and a very short living blue-shifted emission, attributed to the E-isomer. Finally, transient absorption measurements performed upon far-red excitation are employed as an alternative method to determine the two-photon absorption cross-section of the molecule.

scholarly journals Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

2019 ◽  
Author(s):  
Alessandro Iagatti ◽  
Baihao Shao ◽  
Alberto Credi ◽  
Barbara Ventura ◽  
Ivan Aprahamian ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Transient Absorption ◽  
Solvent Polarity ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon

In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch, belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible two-photon absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime decreases with increasing solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time resolved luminescence measurements evidence the presence of a main emission component in the 500-520 nm spectral range, attributed to the Z isomer, and a very short living blue-shifted emission, attributed to the E isomer. Finally, transient absorption measurements performed upon far-red excitation are employed as an alternative method to determine the two-photon absorption cross-section of the molecule.

Broadband Excited State Dynamics of Common Reverse Saturable Absorbing Dye Media.

1994 ◽  
Vol 374 ◽  
Author(s):  
Kenneth J. McEwan ◽  
Richard C. Hollins
Keyword(s):  
Excited State ◽  
Organic Liquid ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Excited State Lifetime ◽  
Absorption And Emission ◽  
Two Photon Absorption ◽  
Two Photon ◽  
State Response ◽  
Photon Excitation

AbstractIn this paper we describe a technique by which the broadband excited state absorption/emission and dynamics can be measured for materials with either linear or two photon absorption. The technique is applied to two different dyes in solution and to a cyano-biphenyl organic liquid. The ratio of σex/σgr for HITCI in methanol is greater than 1 from 400 to 570nm and at 532nn is determined to be 25; the excited state lifetime is 800ps. For CAP in methanol σex/σgr is greater than 1 from 400–650nm and is 14 at 532nm. Dimer absorption and emission are found to contribute to the excited state response in this material. In the organic liquid broadband (400–570nm) excited state absorption is measured following two photon excitation at 588nm.

PICOSECOND-INDUCED NONLINEAR ABSORPTION IN LIQUID CRYSTAL MEDIA

1995 ◽  
Vol 04 (01) ◽  
pp. 245-260 ◽  
Author(s):  
K. J. McEWAN ◽  
R. C. HOLLINS
Keyword(s):  
Experimental Data ◽  
Liquid Crystal ◽  
Excited State ◽  
Nonlinear Absorption ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Isotropic Phase ◽  
Pump Probe ◽  
Two Photon Absorption ◽  
Two Photon

The contributions to the nonlinear absorption of liquid crystal media in their isotropic phase are measured using a picosecond pump/probe technique at 587 nm. Good agreement between the experimental data and theory is obtained by assuming that two-photon absorption and excited state absorption dominate the nonlinear optical response. The important parameters are extracted from the experimental data and it is shown that the nonlinear absorption depends strongly on the molecular structure. The lifetime of the excited state is measured and found to compare well with the fluorescence lifetime.

Two-photon absorption and two-photon assisted excited-state absorption in CdSe0.3S0.7quantum dots

2009 ◽  
Vol 11 (6) ◽  
pp. 065206 ◽  
Author(s):  
Feng Wu ◽  
Guilan Zhang ◽  
Wei Tian ◽  
Wenju Chen ◽  
Guofeng Zhao ◽  
...  
Keyword(s):  
Excited State ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon

Comparative photophysics of sapphyrin derivatives: effects of confused and fused pyrrole rings

2011 ◽  
Vol 15 (09n10) ◽  
pp. 858-864 ◽  
Author(s):  
Jong Min Lim ◽  
Iti Gupta ◽  
Hiroyuki Furuta ◽  
Dongho Kim
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Photophysical Properties ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Nonradiative Decay ◽  
Two Photon Absorption ◽  
Two Photon

We have investigated the photophysical properties of [22] π-conjugated pentapyrrolic systems, sapphyrin, N-confused and N-fused sapphyrins, with a particular focus on the effects of confused and fused pyrrole rings on their electronic structures using steady-state and time-resolved spectroscopic methods, two-photon absorption cross-section (σ(2)) measurements and quantum mechanical calculations. The absorption spectra of N-confused and N-fused sapphyrins exhibit relatively red-shifted features compared to sapphyrin. In parallel with these spectral features, the reduced HOMO–LUMO gaps were observed in going from sapphyrin to N-fused sapphyrin. In the analysis of the anisotropy of the induced current density (AICD), N-confused and N-fused sapphyrins show that extra π-electrons in confused and fused pyrrole rings contribute to the extension of their π-conjugation pathways. Slightly larger twophoton absorption cross-section values of N-confused and N-fused sapphyrins (3250 and 3900 GM) than that of sapphyrin (2900 GM) also reflect an enhanced π-conjugation effect due to bicyclic and endocyclic extensions in π-conjugation pathways, respectively. The excited singlet and triplet state lifetimes of N-confused sapphyrin were determined to be 60 ps and 1 μs, respectively, due to conformational change and acceleration of nonradiative decay processes, being in a sharp contrast with those of sapphyrin (2.4 ns and 13 μs, respectively). In the case of N-fused sapphyrin, very short singlet excited-state lifetime of 5 ps was detected probably due to the excited-state NH-tautomerization process which enhances nonradiative decay processes.

Red to Green Upconversion in Er3+-Doped BaTiO3 Nanorods

2008 ◽  
Vol 8 (12) ◽  
pp. 6564-6568 ◽  
Author(s):  
Márcio A. R. C. Alencar ◽  
Glauco S. Maciel ◽  
Cid B. de Araújo ◽  
Amitava Patra
Keyword(s):  
Excited State ◽  
Excitation Spectrum ◽  
Ground State ◽  
Laser Power ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Absorption Process ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Upconversion Emissions

We investigated the frequency upconversion (UC) process in BaTiO3:Er3+ nanocrystals for excitation wavelengths in the range 638 to 660 nm. Green upconversion emissions at 526 and 547 nm corresponding to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 to transitions of the Er3+ were observed. The excitation spectrum for UC emissions presented three bands, due to ground state and excited state absorption of Er3+ ions. The UC intensity as a function of the laser power was investigated and it was found this a two-photon absorption process.

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