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.

Up-Conversion Luminescence in Colloidal CdTe Nanocrystals

2002 ◽  
Vol 737 ◽  
Author(s):  
S. A. Filonovich ◽  
M. J. M. Gomes ◽  
Yu. P. Rakovich ◽  
J. F. Donegan ◽  
D. V. Talapin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Excited State Absorption ◽  
Spectral Shift ◽  
Excitation Intensity ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Cdte Nanocrystals ◽  
Intermediate States ◽  
Gap States

ABSTRACTWe report on the efficient photoluminescence up-conversion in colloidally synthesized CdTe nanocrystals. We demonstrate that the efficiency of photon energy up-conversion and magnitude of spectral shift can be controlled: (i) by the size of the nanocrystals; (ii) by the temperature dependence of the excited state absorption coefficient; (iii) by the dependence on excitation intensity. From the analysis of the experimental data we can suggest that intrinsic gap states are involved as intermediate states in the photoluminescence up-conversion rather than nonlinear two-photon absorption or Auger processes.

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.

DENDRITIC FLUORENE OLIGOMERS FOR NONLINEAR ABSORPTION IN THE VISIBLE RANGE

2005 ◽  
Vol 14 (03) ◽  
pp. 311-318 ◽  
Author(s):  
CYRIL BARSU ◽  
CHANTAL ANDRAUD ◽  
NADIA AMARI ◽  
SYLVIE SPAGNOLI ◽  
PATRICE L. BALDECK
Keyword(s):  
Nonlinear Absorption ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Visible Range ◽  
Absorption Process ◽  
Time Duration ◽  
Absorption Properties ◽  
Two Photon Absorption ◽  
Two Photon ◽  
At Resonance

We report here the nonlinear absorption properties of dendritic molecules of oligofluorenes. Measurements were performed in chloroform between 450 and 650 nm for nanosecond time duration pulses. The nonlinear absorption is attributed to a three-photon absorption process involving first a two-photon absorption (TPA) step followed by an excited state absorption (ESA) process. The corresponding three-photon absorption coefficient α3 presents at resonance high values (α3 > 10000 cm 3/ GW 2 for 2G1 the first dendrimer generation bearing a bifluorene at a concentration of 50 g/L). These values are strongly enhanced with respect to those obtained in the same conditions for analog linear oligofluorenes.

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

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.

Concentration-dependent two-photon absorption and subsequent excited-state absorption in 4-methoxy-2-nitroaniline

2009 ◽  
Vol 106 (3) ◽  
pp. 033511 ◽  
Author(s):  
Bing Gu ◽  
Wei Ji ◽  
Xiao-Qin Huang ◽  
P. S. Patil ◽  
S. M. Dharmaprakash
Keyword(s):  
Excited State ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon

Two-photon absorption and excited state absorption properties of an organic dye PSPI

2004 ◽  
Vol 241 (1-3) ◽  
pp. 215-219 ◽  
Author(s):  
Guangyong Zhou ◽  
Dong Wang ◽  
Xiaomei Wang ◽  
Zongshu Shao ◽  
Minhua Jiang
Keyword(s):  
Excited State ◽  
Excited State Absorption ◽  
Organic Dye ◽  
Photon Absorption ◽  
Absorption Properties ◽  
Two Photon Absorption ◽  
Two Photon

APPLICATION OF ADOMIAN'S METHOD TO NONLINEAR ABSORPTION

2006 ◽  
Vol 15 (02) ◽  
pp. 219-225 ◽  
Author(s):  
F. SANCHEZ ◽  
H. LEBLOND ◽  
M. BRUNEL ◽  
K. AÏT AMEUR
Keyword(s):  
Experimental Data ◽  
Nonlinear Equation ◽  
Plane Wave ◽  
Absorption Coefficient ◽  
Nonlinear Absorption ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Two Photon Absorption Coefficient ◽  
Good Agreement

We use the method of Adomian to investigate the solution of the nonlinear equation giving the evolution of a plane wave in a medium exhibiting linear, two- and three-photon absorption. The second-order solution is in good agreement with numerical simulations. An effective two-photon absorption coefficient is conveniently defined to fit experimental data.

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