ABSTRACT
The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of dimethoxycurcumin and bis-dehydroxycurcumin dissolved in several solvents differing in polarity and H-bonding capability are presented. The singlet oxygen generation efficiency of the two compounds relative to curcumin is estimated. The photodegradation quantum yield of the former compound in acetonitrile and methanol is determined. The dimethoxycurcumin and bis-dehydroxycurcumin decay mechanisms from the S (1) state are discussed and compared with those of curcumin, dicinnamoylmethane and bis-demethoxycurcumin.
Subject(s)
Curcumin/chemistry , Curcumin/analogs & derivatives , Fluorescence , Hydrogen Bonding , Molecular Structure , Photochemical ProcessesABSTRACT
Three-dimensional holographic images of extended diffusing objects are simultaneously recorded and reconstructed by optical cross correlation in a second-order nonlinear crystal. An interaction geometry in which the phase-matched object and reference fields propagate slightly noncollinearly is particularly convenient for producing these second-harmonic-generated holograms.
ABSTRACT
Second-harmonic-generated holograms directly provide the outputs of logical gates AND and NAND operating on optical bits encoded as amplitude modulations in the object and reference wave fronts. By use of a Nd:YAG laser and a beta-barium borate crystal, we realized a real-time half-adder of two one-digit binary numbers. The feasibility of highly parallel operation is also discussed.
ABSTRACT
A model of three-wave parametric interactions is presented, in both type I and type II noncollinear phase-matching conditions, in which the group velocities of the interacting pulses are suitably linked to each other. We consider two conditions for group velocities that are significant in the parametric generation/amplification of femtosecond pulses and determine the interaction geometry required to fulfill them in uniaxial crystals. The results are compared with those for collinear phase matching and are used to interpret the behavior of ultrabroadband parametric sources.
