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## Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

Fonte: AMER PHYSICAL SOC
Publicador: AMER PHYSICAL SOC

Tipo: Artigo de Revista Científica

ENG

Relevância na Pesquisa

78.46412%

#ELECTRON-SPIN POLARIZATION#EUROPIUM CHALCOGENIDES#HARMONIC-GENERATION#2ND-HARMONIC GENERATION#TUNNEL-JUNCTIONS#FARADAY-ROTATION#ABSORPTION-EDGE#EUS#MICROSCOPY#BARRIERS#Physics, Condensed Matter

EuTe possesses the centrosymmetric crystal structure m3m of rocksalt type in which the second-harmonic generation is forbidden in electric dipole approximation but the third-harmonic generation (THG) is allowed. We studied the THG spectra of this material and observed several resonances in the vicinity of the band gap at 2.2-2.5 eV and at higher energies up to 4 eV, which are related to four-photon THG processes. The observed resonances are assigned to specific combinations of electronic transitions between the ground 4f(7) state at the top of the valence band and excited 4f(6)5d(1) states of Eu(2+) ions, which form the lowest energy conduction band. Temperature, magnetic field, and rotational anisotropy studies allowed us to distinguish crystallographic and magnetic-field-induced contributions to the THG. A strong modification of THG intensity for the 2.4 eV band and suppression of the THG for the 3.15 eV band was observed in applied magnetic field. Two main features of the THG spectra were assigned to 5d(t(2g)) and 5d(e(g)) subbands at 2.4 eV and 3.15 eV, respectively. A microscopic quantum-mechanical model of the THG response was developed and its conclusions are in qualitative agreement with the experimental results.; DFG - Deutsche Forschungsgemeinschaft[YA65/4-1]; RFBR Russian Foundation for Basic Research; FoNE of the European Science Foundation; FAPESP; CNPq; (DAAD) Deutscher Akademischer Austausch Dienst...

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## Optical third harmonic generation in the magnetic semiconductor EuSe

Fonte: AMER PHYSICAL SOC; COLLEGE PK
Publicador: AMER PHYSICAL SOC; COLLEGE PK

Tipo: Artigo de Revista Científica

ENG

Relevância na Pesquisa

88.21464%

#ELECTRON-SPIN POLARIZATION#EUROPIUM CHALCOGENIDES#2ND-HARMONIC GENERATION#TUNNEL-JUNCTIONS#BARRIERS#FIELD#ZERO#EUO#PHYSICS, CONDENSED MATTER

Third harmonic generation (THG) has been studied in europium selenide EuSe in the vicinity of the band gap at 2.1-2.6 eV and at higher energies up to 3.7 eV. EuSe is amagnetic semiconductor crystalizing in centrosymmetric structure of rock-salt type with the point group m3m. For this symmetry the crystallographic and magnetic-field-induced THG nonlinearities are allowed in the electric-dipole approximation. Using temperature, magnetic field, and rotational anisotropy measurements, the crystallographic and magnetic-field-induced contributions to THG were unambiguously separated. Strong resonant magnetic-field-induced THG signals were measured at energies in the range of 2.1-2.6 eV and 3.1-3.6 eV for which we assign to transitions from 4 f(7) to 4 f(6)5d(1) bands, namely involving 5d(t(2g)) and 5d(e(g)) states.; Deutsche Forschungsgemeinschaft [YA65/4-1]; Deutsche Forschungsgemeinschaft; Russian Foundation for Basic Research; Russian Foundation for Basic Research [10-02-01008]; Russian Academy; Russian Academy; FoNE of the European Science Foundation; FoNE of the European Science Foundation; FAPESP; FAPESP; CNPq; CNPq; Deutscher Akademischer Austausch Dienst (DAAD); Deutscher Akademischer Austauschdienst (DAAD); FWF, Vienna, Austria [I80-N20]; FWF...

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## Técnica de varredura-Z com pulsos de femtossegundo e geração de terceiro harmônico; Z-scan tecnique with femtosecond pulse and third-harmonic generation

Fonte: Biblioteca Digitais de Teses e Dissertações da USP
Publicador: Biblioteca Digitais de Teses e Dissertações da USP

Tipo: Dissertação de Mestrado
Formato: application/pdf

Publicado em 09/02/2012
PT

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98.575205%

#Geração de terceiro harmônico#Nonlinear optics#Óptica não linear#Pulsos ultracurtos#Técnica de varredura-Z#Third-harmonic generation#Ultrashort pulses#Z-scan technique

Neste trabalho fizemos um estudo da geração de terceiro harmônico (GTH) usando pulsos de femtossegundos (fs). A GTH é uma importante técnica que permite estudar propriedades ópticas não lineares de terceira ordem de materiais. Estudamos a GTH aplicando as técnicas de franjas de Maker e a de varredura-Z em diferentes materiais levando em conta as contribuições de suas interfaces. A técnica de franjas de Maker com GTH permite a determinação de propriedades ópticas lineares e não lineares de volume, mas não de interface, portanto, a técnica de varredura-Z na condição de focalização forte foi implementada para estudar a influência da interface na GTH. Estudamos diversos vidros ópticos (sílica, K10, SK11, LLF1 e LLF6) e também diferentes soluções (acetona, clorofórmio, DMSO e tolueno) em uma cubeta. Em termos de número de interfaces, usando uma lâmina de vidro temos duas, no caso de um sanduíche de dois vidros temos três (entrada, meio e saída) e temos quatro interfaces para a cubeta. Observamos que elas contribuem tanto nas intensidades quanto nos espectros dos terceiros harmônicos (TH) gerados. Dependendo do tipo de interface e do sentido de propagação, tanto a intensidade quanto o espectro do TH são diferentes. Observamos que a reflexão de Fresnel atua significativamente nas diferenças de intensidades da GTH nas interfaces entre dois meios com índices de refração lineares diferentes. Uma interferência construtiva ocorre quando o feixe de laser propaga de um material com índice de refração mais alto para outro com índice mais baixo...

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## Microscopias de óptica não linear : fluorescência excitada por absorção de dois fótons, geração de segundo harmônico e geração de terceiro harmônico; Non linear optical microscopies : two photon excited fluorescence, second harmonic generation and third harmonic generation

Fonte: Biblioteca Digital da Unicamp
Publicador: Biblioteca Digital da Unicamp

Tipo: Dissertação de Mestrado
Formato: application/pdf

Publicado em 21/12/2010
PT

Relevância na Pesquisa

99.09416%

#Microscopia#Ótica não-linear#Fluorescência excitada por dois fótons#Geração de segundo harmônico#Geração de terceiro harmônico#Microscopy#Nonlinear optics#Two photon excited fluorescence#Second harmonic generation#Third harmonic generation

Biologia celular é um novo mundo promissor com enorme impacto social, econômico e na saúde. Organismos vivos são capazes de, produzir a própria energia a partir da luz do sol, se reproduzir, de se auto-reparar, sinalizar e navegar por sinais bioquímicos, biomecânicos, luminosos, térmicos, e outros, e produzir materiais à temperatura ambiente. As possibilidades abertas por essa área incluem, desde bactérias e protozoários usados para destruir células de câncer, regeneração de órgãos inteiros, produção de etanol a partir de algas, e outros. Entretanto, para o entendimento da biologia em seu nível mais profundo, ferramentas de observação não destrutivas fazem-se necessária para seguir os processos celulares durante seu tempo de vida. A óptica tem a única onda não destrutiva capaz de fornecer informações em tempo real com suficiente resolução espacial de eventos acontecendo internamente à célula. Ademais, porque feixes de luz não colidem, a óptica permite a integração de diferentes técnicas capazes de reunir informações simultâneas de processos celulares. Óptica não linear é especialmente adequada para tal, pois não requer marcação ou processamentos especiais de amostras que poderiam destruir...

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## Investigation of Second- and Third-Harmonic Generation in Few-Layer Gallium Selenide by Multiphoton Microscopy

Fonte: Nature Publishing Group
Publicador: Nature Publishing Group

Tipo: Artigo de Revista Científica

Publicado em 19/05/2015
EN

Relevância na Pesquisa

68.571396%

Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390 nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes.

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## Third-harmonic generation via broadband cascading in disordered quadratic nonlinear media

Fonte: http://www.osa.org/
Publicador: http://www.osa.org/

Tipo: Journal article; Published Version; Optical Society of America
Formato: 7 pages

Relevância na Pesquisa

88.21464%

#nonlinear optics#nonlinear optics: nonlinear optics, transverse effects in#harmonic generation and mixing

We study parametric frequency conversion in quadratic
nonlinear media with disordered ferroelectric domains. We demonstrate
that disorder allows realizing broadband third-harmonic generation via
cascading of two second-order quasi-phase matched nonlinear processes.
We analyze both spatial and polarization properties of the emitted radiation
and find the results in agreement with our theoretical predictions.

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## Third Harmonic Generation from Aligned Single-Wall Carbon Nanotubes

Fonte: Universidade Rice
Publicador: Universidade Rice

ENG

Relevância na Pesquisa

78.47149%

#Applied sciences#Pure sciences#Single-walled carbon nanotubes#Third harmonics#Non-linear optics#Electrical engineering#Condensed matter physics#Optics

Optical properties of single-wall carbon nanotubes (SWCNTs) have been extensively studied during the last decade, and much basic knowledge has been accumulated on how light emission, scattering, and absorption occur in the realm of linear optics. However, their nonlinear optical properties remain largely unexplored. Here, we have observed strong third harmonic generation from highly aligned SWCNTs with intense mid-infrared radiation. Through power dependent experiments, we have determined the absolute value of the third-order nonlinear optical susceptibility, ‡ (3) , of our SWCNT film to be 6.92 Ã— 10 -12 esu, which is three orders of magnitude larger than that of the fused silica reference sample we used. Furthermore, through polarization-dependent third harmonic generation experiments, all the nonzero tensor elements of ‡ (3) have also been extracted. The contribution of the weaker tensor elements to the overall ‡ (3) signal has been calculated to be approximately 1/6 of that of the dominant [Special characters omitted.] component. These results open up new possibilities for application of carbon nanotubes in optoelectronics.

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## Simultaneous fs pulse spectral broadening and third harmonic generation in highly nonlinear fibre: experiments and simulations

Fonte: Springer
Publicador: Springer

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

88.21464%

#Keywords: Computer simulation#Harmonic generation#Laser pulses#Nonlinear equations#Spectrum analysis#Pump pulses#Spectral broadening#Fibers

Experiments and numerical simulations are used to study non-phasematched single-mode third harmonic generation occurring simultaneously with fs pulse spectral broadening in highly nonlinear fibre. Pump pulses around 100 fs at 1560 nm injected into sub-5 c

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## Cascaded third harmonic generation in hybrid graphene-semiconductor waveguides

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/07/2015

Relevância na Pesquisa

68.643525%

We study cascaded harmonic generation of hybrid surface plasmons in
integrated planar waveguides composed of a graphene layer and a
doped-semiconductor slab. We derive a comprehensive model of cascaded third
harmonic generation through phase-matched nonlinear interaction of fundamental,
second harmonic and third harmonic plasmonic modes supported by the structure.
We show that hybrid graphene-semiconductor waveguides can simultaneously
phase-match these three interacting harmonics, increasing the total
third-harmonic output by a factor of 5 compared to the non-cascaded regime.

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## Symmetry selective third harmonic generation from plasmonic metacrystals

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/03/2014

Relevância na Pesquisa

68.552207%

Nonlinear processes are often governed by selection rules imposed by the
symmetries of the molecular configurations. The most well-known examples
include the role of mirror symmetry breaking for the generation of even
harmonics, and the selection rule related to the rotation symmetry in harmonic
generation for fundamental beams with circular polarizations. While the role of
mirror symmetry breaking in second harmonic generation has been extensively
studied in plasmonic systems, the investigation on selection rules pertaining
to circular polarization states of harmonic generation has been limited to
crystals, i.e. symmetries at the atomic level. Here we demonstrate the
rotational symmetry dependent third harmonic generation from nonlinear
plasmonic metacrystals. We show that the selection rule can be imposed by the
rotational symmetry of meta-crystals embedded into an isotropic organic
nonlinear thin film. The results presented here may open new avenues for
designing symmetry-dependent nonlinear optical responses with tailored
plasmonic nanostructures.; Comment: 13 pages, 3 figures

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## Nonlinear optics from an ab-initio approach by means of the dynamical Berry phase: Application to second- and third-harmonic generation in semiconductors

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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We present an ab-initio real-time-based computational approach to study
nonlinear optical properties in condensed matter systems that is especially
suitable for crystalline solids and periodic nanostructures. The equations of
motion and the coupling of the electrons with the external electric field are
derived from the Berry-phase formulation of the dynamical polarization [Souza
et al., Phys. Rev. B 69, 085106 (2004)]. Many-body effects are introduced by
adding single-particle operators to the independent-particle Hamiltonian. We
add a Hartree operator to account for crystal local effects and a scissor
operator to correct the independent particle band structure for quasiparticle
effects. We also discuss the possibility of accurately treating excitonic
effects by adding a screened Hartree-Fock self-energy operator. The approach is
validated by calculating the second-harmonic generation of SiC and AlAs bulk
semiconductors: an excellent agreement is obtained with existing ab initio
calculations from response theory in frequency domain [Luppi et al., Phys. Rev.
B 82, 235201 (2010)]. We finally show applications to the second-harmonic
generation of CdTe and the third-harmonic generation of Si.; Comment: 10 pages, 9 figures

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## Highly Nonlinear Dynamics of Third-Harmonic Generation by Focused Beams

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/11/2003

Relevância na Pesquisa

68.399824%

Beams that experience third-harmonic generation (THG) also experience Kerr
effects. With Kerr effects, beams do not take simple Gaussian shapes, but
exhibit nonlinear dynamics. These nonlinear dynamics have an effect on the THG
accumulated by focusing and then diverging beams. We formulate a
self-consistent and complete set of nonlinear Schroedinger equations for a pair
of coupled beams -- a fundamental and its third-harmonic. Numerical simulations
show that the Kerr nonlinearities allow some third-harmonic to propagate to the
far-field even for zero or negative phase-mismatch. This is because the
nonlinear dynamics break the beams' reflection symmetry about the focal plane
and therefore increases far-field THG by changing some of the interference from
destructive to constructive. THG conversion efficiencies are computed as
functions of several beam parameters.; Comment: About 6 pages. 7 Figures. Accepted to Physical Review A

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## Third Harmonic Generation at 223nm in the Metallic Regime of GaP

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 02/11/2010

Relevância na Pesquisa

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We demonstrate second and third harmonic generation from a GaP substrate
500{\mu}m thick. The second harmonic field is tuned at the absorption resonance
at 335nm, and the third harmonic signal is tuned at 223nm, in a range where the
dielectric function is negative. These results show that a phase locking
mechanism that triggers transparency at the harmonic wavelengths persists
regardless of the dispersive properties of the medium, and that the fields
propagate hundreds of microns without being absorbed even when the harmonics
are tuned to portions of the spectrum that display metallic behavior.

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## Third Harmonic Generation in Cuprous Oxide: Efficiency Determination

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 27/12/2013

Relevância na Pesquisa

68.52025%

The efficiency of third harmonic generation in cuprous oxide was measured.
Intensities followed a non-cubic power law which indicates nonperturbative
behavior. Polarization anisotropy of the harmonic generation was demonstrated
and related to the third order susceptibility. The results will influence the
understanding of harmonic generation in centrosymmetric materials and are
potentially relevant to device design and the interpretation of exciton
behavior.

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## Verification of generalized Kramers-Kronig relations and sum rules on experimental data of third harmonic generation susceptibility on polymers

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/02/2003

Relevância na Pesquisa

68.52025%

#Physics - Optics#Condensed Matter - Materials Science#Physics - Atomic Physics#Physics - Chemical Physics

We present the first analysis of harmonic generation data where the full
potential of the generalized nonlinear Kramers-Kronig (K-K) relations and sum
rules is exploited. We consider two published sets of wide spectral range
experimental data of third harmonic generation susceptibility on different
polymers, the polysilane (frequency range: $0.4-2.4$ $eV$) and the
polythiophene (frequency range: $0.5-2.0$ $eV$). We show that, independent
truncated dispersion relations connect the real and imaginary part of the
moments of the third harmonic generation susceptibility
$\omega^{2\alpha}\chi^{(3)}(3\omega; \omega, \omega ,\omega)$, with $\alpha$
ranging from 0 to 3, in agreement with the theory, while there is no
convergence if we choose $\alpha=4$. We repeat the same analysis for
$\omega^{2\alpha}[\chi^{(3)}(3\omega; \omega, \omega ,\omega)]^{2}$ and show
that a larger number of independent K-K relations connect the real and the
imaginary part of the function under examination. We also compute the sum rules
for the suitable moments of the real and imaginary parts, and observe that only
considering higher powers of the susceptibility the correct vanishing sum rules
are more precisely obeyed. Sum rules providing explicit information about
structural properties of the material seem to require wider spectral range.
These constraints are expected to hold for any material and provide fundamental
tests of self-consistency that any experimental or model generated data have to
obey.; Comment: 37 pages...

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## Quantum Theory of the Third-Harmonic Generation in Graphene

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/07/2014

Relevância na Pesquisa

68.399824%

A quantum theory of the third-harmonic generation in graphene is presented.
An analytical formula for the nonlinear conductivity tensor
$\sigma^{(3)}_{\alpha\beta\gamma\delta}(\omega,\omega,\omega)$ is derived.
Resonant maxima of the third harmonic are shown to exist at low frequencies
$\omega\ll E_F/\hbar$, as well as around the frequency $\omega=2E_F/\hbar$,
where $E_F$ is the Fermi energy in graphene. At the input power of a CO$_2$
laser ($\lambda\approx 10$ $\mu$m) of about 1 MW/cm$^2$ the output power of the
third-harmonic ($\lambda\approx 3.3$ $\mu$m) is expected to be $\simeq 50$
W/cm$^2$.; Comment: 5 pages, 3 figures

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## Continuous third harmonic generation in a terahertz driven modulated nanowire

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/03/2013

Relevância na Pesquisa

68.341025%

We consider the possibility of observing continuous third-harmonic generation
using a strongly driven, single-band one-dimensional metal. In the absence of
scattering, the quantum efficiency of frequency tripling for such a system can
be as high as 93%. Combining the Floquet quasi-energy spectrum with the Keldysh
Green's function technique, we derive the semiclassical master equation for a
one-dimensional band of strongly and rapidly driven electrons in the presence
of weak scattering by phonons. The power absorbed from the driving field is
continuously dissipated by phonon modes, leading to a quasi-equilibrium in the
electron distribution. We use the Kronig-Penney model with varying effective
mass to establish growth parameters of an InAs/InP nanowire near optimal for
third harmonic generation at terahertz frequency range.; Comment: 16 pages, 7 figures

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## Third harmonic generation in graphene and few-layer graphite films

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/01/2013

Relevância na Pesquisa

68.61326%

#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Physics - Optics

We observe optical third harmonic generation from graphene and few-layer
graphite flakes produced by exfoliation. The emission scales with the cube of
the intensity of the incident near-infrared femtosecond pulses and has a
wavelength that is one-third of the incident wavelength, both consistent with
third harmonic generation. We extract an effective third-order susceptibility
for graphene that is on the order of 1e-16 square meter per square volt, which
is comparable to that for materials that are resonantly excited, but larger
than for materials that are transparent at the fundamental and third harmonic
wavelengths. By measuring a set of flakes with different numbers of atomic
layers, we find that the emission scales with the square of the number of
atomic layers, which suggests that the susceptibility of graphene is
independent of layer number, at least for a few layers.; Comment: 5 pages, 3 figures

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## Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides

Fonte: Nature Publishing Group
Publicador: Nature Publishing Group

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

68.341025%

Slow light has attracted significant interest recently as a potential solution for optical delay lines and time-domain optical signal processing. Perhaps even more significant is the possibility of dramatically enhancing nonlinear optical effects due to the spatial compression of optical energy. Two-dimensional silicon photonic-crystal waveguides have proven to be a powerful platform for realizing slow light, being compatible with on-chip integration and offering wide-bandwidth and dispersion-free propagation. Here, we report the slow-light enhancement of a nonlinear optical process in a two-dimensional silicon photonic-crystal waveguide. We observe visible third-harmonic-generation at a wavelength of 520nm with only a few watts of peak power, and demonstrate strong third-harmonic-generation enhancement due to the reduced group velocity of the near-infrared pump signal. This demonstrates yet another unexpected nonlinear function realized in a CMOS-compatible silicon waveguide.

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## Third-harmonic generation and laser-induced continuum structure in sodium

Fonte: Institute of Physics Publishing
Publicador: Institute of Physics Publishing

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

88.59278%

#Keywords: Laser-induced continuum structures (LICS)#Quantum interference#Third harmonic generation#Electron energy levels#Harmonic generation#Laser beam effects#Nonlinear optics#Sodium#Quantum optics

Observation of laser-induced continuum structure (LICS) in sodium due to the coupling of a bound state to the continuum by a strong laser field has been reported elsewhere. Such experiments have mostly employed a single laser photon to probe the structured continuum from the ground state. Other experiments have used multiphoton (third harmonic) probe schemes, but only one of these has successfully observed LICS, in agreement with theoretical predictions. We report here a very similar experiment generating third-harmonic radiation in sodium to probe the anticipated LICS produced by coupling the 5s state to the p continuum. However, under no conditions was any continuum structure observed, in agreement with in a number of other experiments, but at variance with theoretical predictions.

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