Dispersion measurement of inert gases and gas mixtures at 800 nm

The higher-order Kerr effect (HOKE) has been recently advocated to explain measurements of the saturation of the nonlinear refractive index in gases. Here we show that cascaded third-harmonic generation results in an effective fifth order nonlinearity that is negative and significant. Higher-order harmonic cascading will also occur from the HOKE, and the cascading contributions may significantly modify the observed nonlinear index change. At lower wavelengths cascading increases the HOKE saturation intensity, while for longer wavelengths cascading will decrease the HOKE saturation intensity.Comment: Optics Letters, in pres

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“…When Δk 1m L ≫ 2π, Table 1. Material [1,2] a Calculated using Sellmeier equations [17,18]. All units are SI (i.e., Δk 13 m −1 , n 2 m 2 ∕W etc.).…”

mentioning

confidence: 99%

Higher-order Kerr effect and harmonic cascading in gases

2012

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“…The refraction coefficient δ 1 , depending on the pressure and temperature of the gas medium, is obtained from the Sellmeier equation [108,109]. The nonlinear refractive index η 2 , also depending on pressure of the gas medium, can be calculated through third-order susceptibility χ (3) , which can be measured from experiments [110,111].…”

Section: Maxwell's Wave Equation 231 Fundamental Laser Fieldmentioning

confidence: 99%

Theory of Nonlinear Propagation of High Harmonics Generated in a Gaseous Medium

Jin

2013

Springer Theses

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In this thesis, we establish the theoretical tools to investigate high-order harmonic generation (HHG) by intense infrared lasers in a gaseous medium. The macroscopic propagation of both the fundamental and the harmonic fields is taken into account by solving Maxwell's wave equations, while the single-atom (or single-molecule) response is obtained by quantitative rescattering theory. The initial spatial mode of the fundamental laser is assumed either a Gaussian or a truncated Bessel beam. On the examples of Ar, N 2 and CO 2 , we demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N 2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO 2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continuous harmonic spectrum of Xe due to the reshaping of the fundamental laser field can be used to produce an isolated attosecond pulse by spectral and spatial filtering in the far field. For on-going application of using HHG to ionize aligned molecules, we present the photoelectron angular distribution from aligned N 2 and CO 2 in the laboratory frame, which can be compared directly with future experiments. demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N 2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO 2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continu...

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“…For hollow-core waveguides with a diameter that is much larger than the laser wavelength, the transverse laser fields are decomposed into EH 1m modes that propagate with different propagation constants β m (ω) using the Hankel transform [22,23]. It should be noted that the analytical expression of β m (ω) takes into account the boundary conditions imposed by the HCF and non-modal dispersion of the filled gases based on the refractive index of the dielectric cladding and gas at specific temperature and pressure [24]. The plasma generation is described by the Ammosov-Delone-Krainov (ADK) formula [25], which gives a good quantitative description of the ionization process in the tunneling regime.…”

Section: Numerical Modelmentioning

confidence: 99%

Wavelength scaling of optimal hollow-core fiber compressors in the single-cycle limit

Chen¹,

Lai²,

Hong³

et al. 2012

Opt. Express

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Abstract:We systematically investigate supercontinuum generation using three-dimensional numerical simulations of nonlinear femtosecond pulse propagation in hollow-core fibers (HCF) at different pump wavelengths ranging from 400 nm to 2 μm. A general design strategy for HCF compressors is presented, maximizing the spectral broadening while preserving high beam quality for given pump pulse energy, duration and wavelength. We show close fitting of the modeled results with simple analytical formulas, enabling the construction of high-energy pulse compressors at the wavelength range of interest. Based on the presented wavelength scaling study, we propose an orthogonally polarized two-color pumping scheme in a single HCF compressor for the coherent synthesis of the electric fields in the sub-cycle regime with mJ level energies.

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Dispersion measurement of inert gases and gas mixtures at 800 nm

Cited by 176 publications

References 39 publications

Higher-order Kerr effect and harmonic cascading in gases

Higher-order Kerr effect and harmonic cascading in gases

Theory of Nonlinear Propagation of High Harmonics Generated in a Gaseous Medium

Wavelength scaling of optimal hollow-core fiber compressors in the single-cycle limit

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