The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Yifu Zhu - One of the best experts on this subject based on the ideXlab platform.
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Perfect Photon Absorption in the nonlinear regime of cavity quantum electrodynamics
Physical Review A, 2016Co-Authors: Girish S. Agarwal, Liyong Wang, Yifu ZhuAbstract:It has been shown that perfect Photon Absorption can occur in the linear excitation regime of cavity quantum electrodynamics (CQED), in which Photons from two identical light fields coupled into two ends of the cavity are completely absorbed and result in excitation of the polariton state of the CQED system. The output light from the cavity is totally suppressed by destructive interference and the polariton state can only decay incoherently back to the ground state. Here we analyze perfect Photon Absorption and the onset of optical bistability in the nonlinear regime of the CQED and show that perfect Photon Absorption persists in the nonlinear regime of the CQED below the threshold of optical bistability. Therefore perfect Photon Absorption is a phenomenon that can be observed in both linear and nonlinear regimes of CQED. Furthermore, our study reveals that optical bistability is influenced by input-light interference and can be manipulated by varying the relative phase of the two input fields.
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Suppression of two-Photon Absorption by quantum interference
Physical Review A, 2001Co-Authors: Min Yan, E. Rickey, Yifu ZhuAbstract:Electromagnetically induced transparency may lead to suppression of two-Photon Absorption in a four-level atomic system. This phenomenon is manifested by destructive quantum interference among multiple excitation paths created by a coherent coupling field. We report an experimental observation of such suppression of two-Photon Absorption in cold ${}^{87}\mathrm{Rb}$ atoms.
Cleber Renato Mendonça - One of the best experts on this subject based on the ideXlab platform.
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Two-Photon Absorption in oxazole derivatives: An experimental and quantum chemical study
Optical Materials, 2012Co-Authors: D. L. Silva, Daniel S. Correa, Sérgio Carlos Zílio, L. De Boni, S.c.s. Costa, A.a. Hidalgo, Sylvio Canuto, Cleber Renato MendonçaAbstract:Abstract Experimental and theoretical studies on the two-Photon Absorption properties of two oxazole derivatives: 2,5-diphenyloxazole (PPO) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) are presented. The two-Photon Absorption cross-section spectra were determined by means of the Z-scan technique, from 460 up to 650 nm, and reached peak values of 84 GM for PBD and 27 GM for PPO. Density Functional Theory and response function formalism are used to determine the molecular structures and the one- and two-Photon Absorption properties and to assist in the interpretation of the experimental results. The Polarizable Continuum Model in one-Photon Absorption calculations is used to estimate solvent effects.
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Broadband three-Photon Absorption spectra of platinum acetylide complexes
Optical Materials Express, 2011Co-Authors: Marcelo G. Vivas, Erick Piovesan, Daniel L. Silva, Thomas M. Cooper, Leonardo De Boni, Cleber Renato MendonçaAbstract:We investigate the three-Photon Absorption spectra of four platinum acetylides complexes employing femtosecond pulses. We observed strong three-Photon Absorption cross-section in the near-infrared region (from 850 nm to 1200 nm). The three-Photon Absorption (3PA) spectra present resonance enhancement effect as two Photons of the excitation wavelength approach the lower two-Photon allowed states of the molecules as well as a 3PA allowed band around 1180 nm. The 3PA cross-section spectra were interpreted using the sum-over-essential-states approach, considering a three-energy-level diagram.FAPESPCNPqCAPESAFOSR (FA9550-07-1-0374
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Optical birefringence induced by two-Photon Absorption in polythiophene bearing an azochromophore
Polymer, 2008Co-Authors: Daniel S. Correa, Luca Boni, Marcos Roberto Cardoso, Vanessa C. Gonçalves, Débora Terezia Balogh, Cleber Renato MendonçaAbstract:We carried out experiments of induced birefringence via two-Photon Absorption in spin-coated films of the conjugated polymer poly[2-[ethyl-[4-(4-nitro-phenylazo)-phenyl]-amino]-ethane (3-thienyl)ethanoate], PAzT, at 680 and 775 nm. This process allows recording in the bulk because of the spatial confinement of the birefringence provided by the two-Photon Absorption. The induced birefringence is associated with molecular reorientation caused by the two-Photon induced isomerization of the azochromophores attached to the polymer backbone. In addition, the two-Photon Absorption spectrum of PAzT was measured to help selecting the excitation wavelength for two-Photon Absorption induced birefringence.
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Two-Photon Absorption spectrum of the photoinitiator Lucirin TPO-L
Applied Physics A, 2007Co-Authors: Cleber Renato Mendonça, Prakriti Tayalia, Daniel S. Correa, Tommaso Baldacchini, Eric MazurAbstract:Two-Photon Absorption induced polymerization provides a powerful method for the fabrication of intricate three-dimensional microstructures. Recently, Lucirin TPO-L was shown to be a photoinitiator with several advantageous properties for two-Photon induced polymerization. Here we measure the two-Photon Absorption cross-section spectrum of Lucirin TPO-L, which presents a maximum of 1.2 GM at 610 nm. Despite its small two-Photon Absorption cross-section, it is possible to fabricate excellent microstructures by two-Photon polymerization due to the high polymerization quantum yield of Lucirin TPO-L. These results indicate that optimization of the two-Photon Absorption cross-section is not the only material parameter to be considered when searching for new photoinitiators for microfabrication via two-Photon Absorption.
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Two-Photon Absorption in azoaromatic compounds
Chemical Physics Letters, 2002Co-Authors: Luca Boni, José J. Rodrigues, Lino Misoguti, Osvaldo N. Oliveira, Carlos Henrique Tomich De Paula Da Silva, Sérgio Carlos Zílio, Débora Terezia Balogh, D.s. Dos Santos, Cleber Renato MendonçaAbstract:Abstract We report on the two-Photon Absorption (2PA) cross-section for eight azoaromatic compounds in dimethyl sulfoxide solutions, using the Z-scan technique with femtosecond laser pulses at 775 nm. The 2PA cross-sections of these molecules are of the order of (1–6)×10 −50 cm 4 s Photon −1 . A correlation was established between the molecular structure and the two-Photon Absorption process, which makes it possible to develop molecular design strategies to create structures with suitable two-Photon Absorption coefficients.
Eric W Van Stryland - One of the best experts on this subject based on the ideXlab platform.
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Nondegenerate two-Photon Absorption in zinc blende semiconductors
Journal of The Optical Society of America B-optical Physics, 1992Co-Authors: D. C. Hutchings, Eric W Van StrylandAbstract:An algorithm is presented for the calculation of the nondegenerate two-Photon Absorption coefficient by using second-order perturbation theory and a Kane band-structure model, including the effects of nonparabolicity and nonzone-center wave functions. The polarization dependence is included by correctly accounting for the symmetry of the electronic wave functions. A comparison is made with degenerate two-Photon Absorption data in various zinc blende semiconductors, and excellent agreement is found without the use of fitting parameters. Comparisons are also made with nondegenerate two-Photon Absorption spectra measured in ZnSe and ZnS by using a picosecond continuum and with some polarization-dependent measurements obtained by a two-color Z-scan measurement.
Hans Ågren - One of the best experts on this subject based on the ideXlab platform.
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Two-Photon Absorption of Metal-Assisted Chromophores
Journal of Chemical Theory and Computation, 2014Co-Authors: Xin Li, Zilvinas Rinkevicius, Hans ÅgrenAbstract:Aiming to understand the effect of a metal surface on nonlinear optical properties and the combined effects of surface and solvent environments on such properties, we present a multiscale response theory study, integrated with dynamics of the two-Photon Absorption of 4-nitro-4'-amino-trans-stilbene physisorbed on noble metal surfaces, considering two such surfaces, Ag(111) and Au(111), and two solvents, cyclohexane and water, as cases for demonstration. A few conclusions of general character could be drawn: While the geometrical change of the chromophore induced by the environment was found to notably alter (diminish) the two-Photon Absorption cross section in the polar medium, the effects of the metal surface and solvent on the electronic structure of the chromophore surpasses the geometrical effects and leads to a considerably enhanced two-Photon Absorption cross section in the polar solvent. This enhancement of two-Photon Absorption arises essentially from the metal charge image induced enlargement of the difference between the dipole moment of the excited state and the ground state. The orientation-dependence of the two-Photon Absorption is found to connect with the lateral rotation of the chromophore, where the two-Photon Absorption reaches its maximum when the polarization of the incident light coincides with the long-axis of the chromophore. Our results demonstrate a distinct enhancement of the two-Photon Absorption by a metal surface and a polar medium and envisage the employment of metal-chromophore composite materials for future development of nonlinear optical materials with desirable properties.
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Two‐Photon Absorption Cross‐Sections of Reference Dyes: A Critical Examination
ChemPhysChem, 2008Co-Authors: Yan-hua Wang, Hans ÅgrenAbstract:The electronic structure and one- and two-Photon Absorption spectra of four fluorophores, p-bis(o-methoxystyryl)benzene (Bis-MSB), coumarin 307, fluorescein and rhodamine B, commonly used as reference compounds for two-Photon Absorption spectra, have been theoretically calculated and compared with available experimental data. The possible reasons for the wide discrepancies in two-Photon Absorption cross-sections reported in the literature are discussed on the basis of the theoretical findings. The role of a solvent environment on the electronic one- and two-Photon Absorption spectra is also studied. We highlight some necessary precautions that one needs to take when comparing literature results of two-Photon Absorption cross-sections.
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Multi-Photon Absorption of Molecules
Response Theory and Molecular Properties (A Tribute to Jan Linderberg and Poul Jørgensen), 2005Co-Authors: Peter Cronstrand, Yi Luo, Hans ÅgrenAbstract:Abstract Recent applications of response theory formulations of Olsen and Jorgensen on multi-Photon Absorption of molecules have been briefly reviewed. The connection between the calculated microscopic and experimentally measured macroscopic properties is derived. The performance of various computational approaches ranging from Hartree–Fock and Coupled Cluster to Density Functional theory for these spectral properties is analyzed. Using analytic response theory results as reference, the validity of the commonly applied few-states models for two- and three-Photon Absorption of molecules have been examined. A design strategy for three-dimensional charge-transfer multi-Photon Absorption systems is presented.
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Few-states models for three-Photon Absorption
The Journal of chemical physics, 2004Co-Authors: Peter Cronstrand, Patrick Norman, Yi Luo, Hans ÅgrenAbstract:Few-states models are derived for the calculation of three-Photon Absorption matrix elements. Together with earlier derived few-states models for two-Photon Absorption, the models are evaluated aga ...
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Spectral profiles of two-Photon Absorption: Coherent versus two-step two-Photon Absorption
MRS Proceedings, 2004Co-Authors: Sergey Polyutov, Kenji Kamada, Ivaylo Minkov, Faris Gel'mukhanov, Alexander Baev, Hans ÅgrenAbstract:ABSTRACTWe present a theory of two-Photon Absorption in solutions which addresses the formation of spectral shapes taking account of the vibrational degrees of freedom. The theory is used to rationalize observed differences between spectral shapes of one- and two-Photon Absorption. We elaborate on two underlying causes, one trivial and one non-trivial, behind these differences. The first refers simply to the fact that the set of excited electronic states constituting the spectra will have different relative cross sections for one-and two- Photon Absorption. The second reason is that the two-step and coherent two-Photon Absorption processes are competing, making the one-and two-Photon spectral bands different even considering a single final state. The theory is applied to the N-101 molecule [di-phenyl-amino-nitro-stilbene] which was recently studied experimentally in the paper [ T.-C. Lin, G.S. He, P.N. Prasad, and L.-S. Tan, J. Mater. Chem., 14, 982, 2004.]
D. C. Hutchings - One of the best experts on this subject based on the ideXlab platform.
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Theory of anisotropy of two-Photon Absorption in zinc-blende semiconductors
Physical review. B Condensed matter, 1994Co-Authors: D. C. Hutchings, Brian S. WherrettAbstract:The influence of the higher ${\mathrm{\ensuremath{\Gamma}}}_{15}^{\mathit{c}}$ conduction-band set on the strength of the two-Photon-Absorption coefficient, the two-Photon linear/circular dichroism, and the two-Photon-Absorption anisotropy is calculated across the spectral region below the fundamental Absorption edge, for the cubic materials GaAs and InSb. The anisotropy is entirely due to the higher band and is predicted to produce up to a 70% variation in the two-Photon-Absorption coefficient of GaAs as the relative orientation of the optical polarization to the crystal axes is altered. This is in good agreement with recent experiments.
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Nondegenerate two-Photon Absorption in zinc blende semiconductors
Journal of The Optical Society of America B-optical Physics, 1992Co-Authors: D. C. Hutchings, Eric W Van StrylandAbstract:An algorithm is presented for the calculation of the nondegenerate two-Photon Absorption coefficient by using second-order perturbation theory and a Kane band-structure model, including the effects of nonparabolicity and nonzone-center wave functions. The polarization dependence is included by correctly accounting for the symmetry of the electronic wave functions. A comparison is made with degenerate two-Photon Absorption data in various zinc blende semiconductors, and excellent agreement is found without the use of fitting parameters. Comparisons are also made with nondegenerate two-Photon Absorption spectra measured in ZnSe and ZnS by using a picosecond continuum and with some polarization-dependent measurements obtained by a two-color Z-scan measurement.