共查询到20条相似文献,搜索用时 15 毫秒
1.
Yu. P. Strokach T. M. Valova Z. O. Golotyuk V. A. Barachevsky V. N. Yarovenko M. A. Kalik M. M. Krayushkin 《Optics and Spectroscopy》2005,99(5):714-718
A comparative spectral-kinetic study of the photochromism of a series of synthesized thienyl derivatives of perfluorocyclopentene dihetarylethenes is performed. A relation between the photochromic properties of these compounds (the absorption spectra of the initial and photoinduced forms, the photosensitivity, the interconversion constants of both forms, and the photodegradation) and their structure is established. For some compounds experiencing reversible and irreversible phototransformations, photoinduced fluorescence was observed. The data obtained give grounds to suggest that the compounds synthesized can be used in developing recording media for two-photon 3D main and archival storage. 相似文献
2.
Ogasawara T Ashida M Motoyama N Eisaki H Uchida S Tokura Y Ghosh H Shukla A Mazumdar S Kuwata-Gonokami M 《Physical review letters》2000,85(10):2204-2207
We report strong instantaneous photoinduced absorption in the quasi-one-dimensional Mott insulator Sr2CuO3 in the IR spectral region. The observed photoinduced absorption is to an even-parity two-photon state that occurs immediately above the absorption edge. Theoretical calculation based on a two-band extended Hubbard model explains the experimental features and indicates that the strong two-photon absorption is due to a very large dipole coupling between nearly degenerate one- and two-photon states. Room temperature picosecond recovery of the optical transparency suggests the strong potential of Sr2CuO3 for all-optical switching. 相似文献
3.
Ning CZ 《Physical review letters》2004,93(18):187403
We propose to make a two-photon laser based on intersubband (sublevel) transitions in semiconductor nanostructures. The advantages and feasibility of such a two-photon laser are analyzed in detail using the density matrix approach. Both one-photon and two-photon gains in a three subband quantum well structure are studied on the same footing to show how the two-photon gain can be maximized, while the competing one-photon gain is minimized. The results show that a sufficient two-photon gain can be achieved to overcome one-photon competition and the loss of a conventional semiconductor cavity, making intersubband transitions one of the very few feasible approaches to two-photon lasing. 相似文献
4.
J. H. Li X. X. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):563-569
We theoretically investigate the features of two-photon absorption
in a five-level atomic system with interacting dark resonances. It
is found that two-photon absorption can be completely suppressed
at two different frequencies due to the application of two
coherent coupling fields and the atomic system exhibits double
electromagnetically induced transparency windows against
two-photon absorption. The position and width of the double
two-photon transparency windows can be controlled via properly
adjusting the frequency detuning and the intensities of the two
coupling fields. In addition, one enhanced narrow central line can
be observed in the two-photon absorption spectra, which may find
applications in high-precision spectroscopy. Form a physical point
of view, we explicitly explain these results in terms of quantum
interference induced by three different two-photon excitation
channels in the dressed-state picture. 相似文献
5.
C.R. Mendonca D.S. Correa T. Baldacchini P. Tayalia E. Mazur 《Applied Physics A: Materials Science & Processing》2008,90(4):633-636
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.
PACS 42.65.-k; 78.40.Me; 42.70.Jk; 81.05.Lg 相似文献
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J. Peřina Jr. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):235-242
The dependence of one- and two-photon characteristics of pulsed entangled two-photon fields generated in spontaneous parametric
down-conversion on the pump-pulse properties (shape of the pump-pulse spectrum and its internal structure) is examined. It
is shown that entangled two-photon fields with defined properties can be generated. A general relation between the spectra
of the down-converted fields is established. As a special case the interference of two partially overlapping pulsed two-photon
fields is studied. The fourth-order interference pattern of entangled two-photon fields is investigated in the polarization
analog of the Hong-Ou-Mandel interferometer.
Received: 23 December 1998 / Received in final form: 14 April 1999 相似文献
9.
We analyse the fluctuations at steady state in the good quality cavity case in two-photon lasers with running wave and two-photon absorptive optical bistability in a ring cavity. In the case of two-photon laser we do not find any nonclassical effect, contrary to expectations. On the other hand, in two-photon optical bistability we find squeezing and antibunching in the low transmission branch. The maximum reduction of fluctuations that can be obtained is slightly larger than by a factor of two. 相似文献
10.
Joseph R. Lakowicz Ignacy Gryczynski Józef Kuśba Eva Danielsen 《Journal of fluorescence》1992,2(4):247-258
We measured the fluorescence intensity and anisotropy decays of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled membranes resulting from simultaneous two-photon excitation of fluorescence. Comparison of these two-photon data with the more usual one-photon measurements revealed that DPH displayed identical intensity decays, anisotropy decays, and order parameters for one- and two-photon excitation. While the anisotropy data are numerically distinct, they can be compared by use of the factor 10/7, which accounts for the two-photon versus one-photon photoselection. The increased time 0 anisotropy of DPH can result in increased resolution of complex anisotropy decays. Global analysis of the one- and two-photon data reveals consistency with a single apparent angle between the absorption and the emission oscillators. The global anisotropy analysis also suggests that, except for the photoselection factor, the anisotropy decays are the same for one-and two-photon excitation. This ideal behavior of DPH as a two-photon absorber, and its high two-photon cross section, makes DPH a potential probe for confocal two-photon microscopy and other systems where it is advantageous to use long-wavelength (680- to 760-nm) excitation. 相似文献
11.
The frequency estimation of an optical cavity field suffering from an unavoidable dissipative environment is investigated. Generally, dissipative noise significantly reduces the precision. Here, it is found that two-photon driving can improve measurement precision by resisting the noise. Moreover, over a long duration, the frequency uncertainty can be minimized with the right magnitude of the parametric two-photon drive, which is in sharp contrast to the uncertainty tending to infinity without two-photon driving. The results show that two-photon driving can achieve ultrasensitive measurement in a dissipative environment under the long-encoding-time condition. 相似文献
12.
This work demonstrates that the detuning of the fs-laser spectrum from the two-photon absorption band of organic materials can be used to reach further control of the two-photon absorption by pulse spectral phase manipulation. We investigate the coherent control of the two-photon absorption in imidazole-thiophene core compounds presenting distinct two-photon absorption spectra. The coherent control, performed using pulse phase shaping and genetic algorithm, exhibited different growth rates for each sample. Such distinct trends were explained by calculating the two-photon absorption probability considering the intrapulse interference mechanism, taking into account the two-photon absorption spectrum of the samples. Our results indicate that tuning the relative position between the nonlinear absorption and the pulse spectrum can be used as a novel strategy to optimize the two-photon absorption in broadband molecular systems. 相似文献
13.
We show that light pulses propagating in two-photon absorbing systems may present time delays like slow light produced via coherent population oscillations in one-photon interactions. Two regimes are numerically studied for a simplified two-level system: (a) a light pulse at frequency ω/2 undergoes two-photon absorption (TPA) and is delayed by the absorbing system (two-photon slow light) and (b) a light pulse at frequency ω is delayed in a system prepared by TPA of a light pulse at frequency ω/2 (two-photon-assisted slow light). The study carried out in solutions of dyes and dendrites shows significant delays, low distortion, and good transmission for easily reachable experimental conditions. The working principle can be applied to other media and can be used in telecommunications technology. 相似文献
14.
We study the cooperative two-photon spontaneous decay of an excited atomic system in a microcavity whose size is of the order
of several wavelengths of atomic radiation. We show that a thermalized electromagnetic field in the microcavity strongly affects
the two-photon cooperative spontaneous emission of radiation. The increase in the rate of spontaneous cooperative decay is
due to the presence of a small number of thermalized photons in a microcavity mode. At low temperatures, the two-photon absorption
probability is found to be a linear function of the two-photon flux, and photon superbunching is observed.
Zh. éksp. Teor. Fiz. 115, 1153–1167 (April 1999) 相似文献
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It is shown that two-photon Bell states can be prepared by “spreading” of a two-photon wave packet (biphoton) in a dispersive medium without compensating for group delays between photons with orthogonal polarizations or using narrow-band filters but by selecting the time correlation function. This is possible because two-photon interference effects are manifested in the shape of the time correlation function of intensity due to its spreading. 相似文献
17.
We investigate theoretically two-photon absorption spectroscopy modified by a control field in a confined Y-type four-level system. Dicke-narrowing effect occurs both in two-photon absorption lines and the dips of transparency against two-photon absorption due to enhanced contribution of slow atoms. We also find that the suppression and the enhancement of two-photon absorption can be modified by changing the strength of the control field and the detuning of three laser fields. This control of two-photon absorption may have some applications in information processing and optical devices. 相似文献
18.
《Optics Communications》2004,229(1-6):291-303
I develop the theory of molecular orientation induced by two-photon isomerization. Phenomenologically, two-photon isomeric orientational hole burning and reorientation induce molecular orientation while rotational diffusion tends to randomize it. Using the formalism of Legendre polynomials solves the general equations of the theory, and analytical solutions are derived for actual physical cases at the early time evolution and the steady state of two-photon excitation. The theory explains the observed results of two-photon molecular orientation, and predicts additional experiments in this direction. The isomerization parameters and the movement of the isomers during polarized two-photon excitation can be quantified by the analytical theory. A theoretical study on the creation of molecular orientation by competing orientational Kerr effect and two-photon orientation is also presented. 相似文献
19.
Soumitra Satapathi Lian Li Haibin Huo Mengyan Shen Jayant Kumar 《Optics Communications》2011,284(14):3612-3614
Two-photon-induced fluorescence from a soluble polythiophene containing urethane side groups has been investigated using femto-second laser pulses at 800 nm. Strong two-photon fluorescence was measured in polymer solution. The quadratic dependence of the fluorescence on the excitation laser intensity confirmed the two-photon process. The measured two-photon absorption cross-section is larger as compared to those of other reported polythiophenes. This polymer can be readily hydrolyzed to yield a water soluble polythiophene which could be useful in biological imaging. 相似文献
20.
理论研究分子结构与双光子吸收性质之间的关系对于指导实验者设计与合成功能分子材料具有重要意义. 在杂化密度泛函水平上, 利用响应函数方法, 计算了一类以二乙烯硫/砜基为中心的新型电荷转移分子的双光子吸收截面, 并在相同计算水平上, 与联苯乙烯类强双光子吸收分子做了比较; 以新型电荷转移分子为基础, 利用异构效应, 设计出了可以增强双光子吸收强度的分子结构. 研究表明, 在可应用波长范围内, 该系列分子表现出较强的双光子吸收响应, 与相似共轭长度的强双光子吸收分子具有相同量级的双光子吸收截面; 二乙烯硫/砜基在分子中心作为吸电子基团可以形成有效的电荷转移分子; 改变咔唑基的连接方式可以有效提高双光子吸收截面. 该研究为实验合成新型双光子吸收分子材料提供了理论依据. 相似文献