Liquid Crystals for Fast Infrared Laser Switching and Optical Limiting Application

1997 ◽  
Vol 479 ◽  
Author(s):  
I. C. Khoo ◽  
M. V. Wood ◽  
Brett D. Guenther
Keyword(s):  
Excited State ◽  
Liquid Crystals ◽  
Chlorophyll A ◽  
Nonlinear Optical ◽  
Transient Absorption ◽  
Measurement Techniques ◽  
Excited State Absorption ◽  
Transient Absorption Spectroscopy ◽  
Optical Effects ◽  
Nonlinear Optical Effects

AbstractThe nonlinear optical effects of chlorophyll ‘a’ have been determined using an array of measurement techniques. Regions of spectral interest exhibiting induced excited state absorption were identified with transient absorption spectroscopy measurements. At specific wavelengths within these regions, the dye was characterised using the Z-scan technique. Additional measurements were made to complement the latter results including a focused aperture experiment in which thermal defocusing and scattering mechanisms were identified.

Reverse Saturable Absorption and Induced Thermal Effects in Chlorophyll ‘A’

1997 ◽  
Vol 479 ◽  
Author(s):  
J. M. Robertson ◽  
G. Bourhill
Keyword(s):  
Chlorophyll A ◽  
Thermal Effects ◽  
Transient Absorption ◽  
Measurement Techniques ◽  
Excited State Absorption ◽  
Transient Absorption Spectroscopy ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
Optical Effects ◽  
Nonlinear Optical Effects

AbstractThe nonlinear optical effects of chlorophyll ‘a’ have been determined using an array of measurement techniques. Regions of spectral interest exhibiting induced excited state absorption were identified with transient absorption spectroscopy measurements. At specific wavelengths within these regions, the dye was characterised using the Z-scan technique. Additional measurements were made to complement the latter results including a focused aperture experiment in which thermal defocusing and scattering mechanisms were identified.

Nonlinear Optical Effects in Polymer Dispersed Liquid Crystals

1990 ◽  
Vol 179 (1) ◽  
pp. 269-275 ◽  
Author(s):  
Gabriella Cipparrone ◽  
Cesare Umeton ◽  
Giulia Arabia ◽  
Giuseppe Chidichimo ◽  
Francesco Simoni
Keyword(s):  
Liquid Crystals ◽  
Nonlinear Optical ◽  
Optical Effects ◽  
Polymer Dispersed Liquid Crystals ◽  
Nonlinear Optical Effects ◽  
Polymer Dispersed

Laser-induced thermal, orientational, and density nonlinear optical effects in nematic liquid crystals

1990 ◽  
Vol 42 (2) ◽  
pp. 1001-1004 ◽  
Author(s):  
I. C. Khoo ◽  
J. Y. Hou ◽  
G. L. Din ◽  
Y. L. He ◽  
D. F. Shi
Keyword(s):  
Liquid Crystals ◽  
Nonlinear Optical ◽  
Nematic Liquid Crystals ◽  
Optical Effects ◽  
Nonlinear Optical Effects

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.

The geometry relaxation and photodeactivation from the S2 state of dibenzofuran studied by ultrafast spectroscopy

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1495-1506 ◽  
Author(s):  
Lian Wang ◽  
Song Zhang ◽  
Ye Wang ◽  
Bing Zhang
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Excited State Absorption ◽  
Transient Absorption Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Pharmaceutically Active Compound ◽  
S2 State ◽  
Franck Condon ◽  
T State

AbstractDibenzofuran (DBF) has attracted much attention from scientists recently since it is applied as a photoluminescence material and pharmaceutically active compound. Since the polychlorinated derivatives are highly toxic and manifest photostability in the environment. Femtosecond transient absorption spectroscopy associated with quantum chemical calculations are employed to investigate the ultrafast excited state dynamics of dibenzofuran from the S2 state in 1,4-dioxane and ethanol, respectively. Following excitation at a wavelength of 266 nm, the S2 state is firstly populated in the Franck–Condon region and preserves the planar molecular structure of the ground state. The observed increase of the transient absorption spectra of the excited state within the first several picoseconds indicates a geometry relaxation occurring on the S2 potential energy surface. The subsequent kinetic traces of excited state absorption show that the S2 state in the adiabatic region decays to the S1 state through a fast internal conversion, followed by intersystem crossing to the T1 state with a decay time of tens and hundreds of picoseconds in ethanol and 1,4-dioxane, respectively. Finally, the deactivation processes from the S1 or T state are slow and take place on a time scale of about 20 ns.

Laser-Induced Reorientation In Liquid Crystals: A New Class Of Nonlinear Optical Effects.

1987 ◽  
Author(s):  
E. Santamato ◽  
G. Abbate ◽  
R. Bruzzese ◽  
P. Maddalena ◽  
A. Sasso
Keyword(s):  
Liquid Crystals ◽  
Nonlinear Optical ◽  
New Class ◽  
Optical Effects ◽  
Nonlinear Optical Effects
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