共查询到20条相似文献,搜索用时 250 毫秒
1.
Schumacher AB Dodge JS Carnahan MA Kaindl RA Chemla DS Miller LL 《Physical review letters》2001,87(12):127006
We present the first study of nonlinear optical third-harmonic generation (THG) in the strongly correlated charge-transfer insulator Sr(2)CuO(2)Cl(2). For fundamental excitation in the near infrared, the THG spectrum reveals a strongly resonant response for photon energies near 0.7 eV. Polarization analysis reveals this novel resonance to be only partially accounted for by three-photon excitation to the optical charge-transfer exciton, and indicates that an even-parity state at 2 eV, with a(1g) symmetry, participates in the third-harmonic susceptibility. 相似文献
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We characterize experimentally the influence of sample structure and beam focusing on signal level in third-harmonic generation (THG) microscopy. In the case of a homogeneous spherical sample, the dependence of the signal on the size of the sphere can be controlled by modifying the Rayleigh length of the excitation beam. More generally, the influence of excitation focusing on the signal depends on sample geometry, allowing one to highlight certain structures within a complex system. We illustrate this point by focusing-based contrast modulation in THG images of Drosophila embryos. 相似文献
4.
W. Wang X. Zhang S. Zhao W. Han J. Wang H. Jia F. Li B. Feng F. Wang K. Li Y. Xiang L. Wang W. Zhong 《Laser Physics》2010,20(8):1721-1724
By using the cascaded KDP crystals, the third harmonic generation (THG) of temporal phase modulated broadband laser is experimentally demonstrated in this paper. The spectral characteristic of the generated third harmonic waves is investigated in detail. The experimental results show that the cascaded crystals method is able to satisfy the acceptance bandwidth of broadband laser beam. In addition, the influence on the THG spectrum and THG conversion efficiency of the air spacing between the two cascaded crystals is experimentally studied and it is remarkable on THG spectrum but insignificant for THG conversion efficiency. The relatively ideal THG spectrum is obtained by the optimal parameter of air spacing and the stability of THG spectrum is very good in our experiment. 相似文献
5.
Kim EM Elovikov SS Murzina TV Nikulin AA Aktsipetrov OA Bader MA Marowsky G 《Physical review letters》2005,95(22):227402
Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than 2 orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to a local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a two-dimensional random array of silver nanoparticles. 相似文献
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G. Filippidis E.J. Gualda M. Mari K. Troulinaki C. Fotakis N. Tavernarakis 《Micron (Oxford, England : 1993)》2009,40(8):876-880
We present the detailed imaging of structures and processes of the nematode Caenorhabditis elegans (C. elegans) using non-linear microscopy. Complementary information about the anatomy of the nematode was collected by implementing a combination of two photon excitation fluorescence (TPEF), second and third harmonic generation (SHG and THG) image contrast modes on the same microscope. Three-dimensional (3D) reconstructions of TPEF, SHG and THG images were also performed. Moreover, THG imaging technique has been tested as a potential, novel, non-destructive diagnostic tool for monitoring cellular processes in vivo, such as neuronal degeneration. 相似文献
8.
Third-harmonic generation (THG) from silicon crystals excited by femtosecond pulses has been studied. THG as a function of
probe pulse delay from linear and circularly polarized probe pulses was examined. Both polarizations exhibit a fast, 300 fs
drop in THG when the Si is pumped by pulses with fluence above the melting threshold. This drop for both polarizations indicates
that electronic effects dominate THG in laser-melted Si since structural effects should principally influence THG from linearly
polarized probes, suggesting that care needs to be exercised in interpreting THG signal as an ultrafast probe of crystalline
structure in semiconductors. 相似文献
9.
This paper reports a facile and effortless method to realize three-dimensional (3D) molecular third-harmonic-generation (THG) microscopy through the technique of resonance enhancement with absorbing dye. Hematoxylin, a popular absorbing stain, is applied as an example to verify the multiphoton resonant enhancement based on the 1230 nm excitation light and can selectively enhance THG yield at cell nuclear sites in the studied specimens, serving as a cell nucleus contrast agent. It is concluded that combining THG microscopy with the mature staining technique can readily achieve 3D molecular imaging without using fluorescence. 相似文献
10.
H. Xu W. Chu Y. Liu W. Liu H. Xiong Y. Fu J. Yao B. Zeng J. Ni S. L. Chin Y. Cheng Z. Xu 《Applied physics. B, Lasers and optics》2011,104(4):909-912
We experimentally demonstrate third-harmonic generation (THG) by intense femtosecond laser pulse at a central wavelength of ??800?nm superposed by its second harmonic in air. The third-harmonic signal shows a periodic modulation with a period of ??0.67?fs when the delay between fundamental and second-harmonic wave is continuously changed. The periodic modulation of THG can be attributed to the interference of third-harmonic signals generated from a direct THG channel (3??=??+??+??) and a four-wave mixing (FWM) channel (3??=2??+2?????). With high pump intensity, the fitting of the measured TH spectrum as a function of delay implies that the pump pulse undergoes a strong pulse splitting and self-phase modulation at the focus. 相似文献
11.
F. Guinea A. H. Castro Neto N. M.R. Peres 《The European physical journal. Special topics》2007,148(1):117-125
We discuss the excitation spectrum, electronic susceptibilities,
and possible electronic instabilities in graphene and graphene stacks. The
corrections due interactions of Landau levels in graphene are analyzed. At
low dopings, and for
sufficiently low couplings, single layer graphene is stable against
ferromagnetism. On the other hand, a graphene bilayer, and
infinite graphite, are unstable towards ferromagnetism and
antiferromagnetism. 相似文献
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In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method (FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation (SHG) and third-harmonic generation (THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot. 相似文献
13.
The third-harmonic-generation (THG) spectrum was measured for a NiBr-chain compound, which is a one-dimensional Mott insulator, in a reflection configuration. A sharp peak and a shoulder structure in the THG spectrum are attributed to three-photon resonance to an exciton and a continuum, respectively. The band-edge energy, the exciton binding energy, and the spectral weights for the exciton and the continuum were determined from comparative studies of linear absorption, THG, and electroreflectance spectra. The excitonic effect is more pronounced in the NiCl chain than in the NiBr chain. 相似文献
14.
In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method(FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation(SHG) and third-harmonic generation(THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot. 相似文献
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Recently, experimental studies of the spin excitation spectrum revealed a strong temperature dependence in the normal state and a resonance feature in the superconducting state of several Fe-based superconductors. Based on these findings, we develop a model of electrons interacting with a temperature dependent magnetic excitation spectrum and apply it to angle resolved photoemission in Ba(1-x)K(x)Fe(2)As(2). We reproduce in quantitative agreement with experiment a renormalization of the quasiparticle dispersion both in the normal and the superconducting state, and the dependence of the quasiparticle linewidth on binding energy. We estimate the strength of the coupling between electronic and spin excitations. Our findings support a dominantly magnetic pairing mechanism. 相似文献
16.
利用紧致密度矩阵近似方法,研究了一个特殊量子点量子阱中的三阶非线性光学特性(三次谐波产生),得到了量子点量子阱系统的三次谐波产生系数的解析表达式,而且考虑了量子点量子阱系统中的两种电子束缚态-壳层阱内与阱外两种束缚态。对CdS/HgS构成的典型的量子点量子阱进行了数值计算,得到了10^-15(m/v)^2量级的三次谐波产生系数,并且绘出了三次谐波产生系数作为量子点量子阱的尺寸和泵浦光子能量的函数曲线,最后对曲线的特征及其形成的原因进行了解析。 相似文献
17.
W. Xu Z. Zeng F. Lu C. Zhang 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):272
We examine how the Rashba spin-orbit interaction (SOI) affects the fast-electron optical spectrum of a two-dimensional electron gas (2DEG). It is found that for a spin-split 2DEG, the spectrum of optical absorption is mainly induced by plasmon excitation via inter-SO electronic transition. From the width and position of the spectrum, the Rashba spin-splitting can be identified optically and, therefore, important spintronic properties can be measured though optical experiments. 相似文献
18.
ZHANGLi XIEHong-Jing 《理论物理通讯》2003,40(5):614-618
Within the framework of the compact density matrix approach, the third-harmonic generation (THG) in an electric-field-biased semi-parabolic quantum well (QW) has been deduced and investigated. Via variant of displacement harmonic oscillation, the exact electronic states in the semi-parabolic QW with an applied electric field have also been obtained and discussed. Numerical results on typical GaAs material reveal that, electric fields and confined potential frequency of semi-parabolic QW have obvious influences on the energy levels of electronic states and the THG in the semi-parabolic QW systems. 相似文献
19.
I. I. Shafranyosh V. V. Stetsovich N. N. Chavarga M. I. Sukhoviya 《Optics and Spectroscopy》2012,112(2):155-158
We have measured the luminescence spectra of isolated uracil molecules in the wavelength range of 200–500 nm that were excited
by slow electrons. The spectrum contains more than 20 spectral bands and lines. We show that the luminescence spectrum of
uracil is formed by processes of dissociative excitation of molecules, dissociative excitation with ionization, and excitation
of electronic states of the initial molecule and molecular ion. 相似文献
20.
G.J. Tserevelakis G. Filippidis A.J. Krmpot M. Vlachos C. Fotakis N. Tavernarakis 《Micron (Oxford, England : 1993)》2010,41(5):444-447
In this study, third-harmonic generation (THG) imaging measurements were performed to characterize different developmental stages of the nematode Caenorhabditis elegans (C. elegans) embryos. Femtosecond laser pulses (1028 nm) were utilized for excitation. THG image contrast modality proved as a powerful diagnostic tool, providing valuable information and offering new insights into the complex developmental process of C. elegans embryogenesis. 相似文献