wahlstrand_2012b#

J. K. Wahlstrand, Y.-H. Cheng and H. M. Milchberg, “High Field Optical Nonlinearity and the Kramers-Kronig Relations”, Phys. Rev. Lett. 109, 113904 (2012)

Source record · Catalogue · Review register

DOI: 10.1103/PhysRevLett.109.113904

Source kind: measurement

Recorded technique: Single-shot supercontinuum spectral interferometry (as wahlstrand_2012): 40-fs, 3.5-mJ, 800-nm Ti:sapphire pump; supercontinuum probe (120 nm bandwidth, generated in SF6) and reference 2 ps apart; thin gas flow (L_eff ~ 200-400 um depending on gas) in a vacuum chamber; 1000 interferograms averaged (phase shifts down to 5e-3 rad). ‘An auxiliary spatial interferometry beam [7] allowed extraction of the absolute linear phase shift of the Ar stationary gas flow; all other gases were referenced to Ar’; the absolute index shift is ‘calibrated by a measurement in a backfilled vacuum chamber at low pressure, as in [7]’ (p. 1). Delta n measured against peak intensity up to the ionization threshold of each gas, and compared with a Kramers-Kronig calculation from the PPT-type ionization rate of Popruzhenko et al. (pp. 2-4).

Materials in structured entries: Ar, He, Kr, Ne, Xe

Dataset quantities: nonlinear_index

Contents: 5 datasets; 0 formulas.

Curation notes#

Journal pages 113904-1 to -5 = PDF pages 1-5. Identity checked against the first page. He, Ne, Ar, Kr, Xe.

DEFINING EQUATIONS (p. 1, quoted): ‘The nonlinear refractive index shift is Delta n(x, t) = (k0 L_eff)^-1 Delta Phi(x, t)’ ... ‘Below the ionization threshold, we write Delta n(x, t) = 2 n2 I(x, t), where I(x, t) is determined directly from the pump pulse energy and from I(x, t) proportional to Delta Phi(x, t) at low intensity in Ar. The factor of 2 recognizes that Delta n describes cross-phase modulation and n2 is the nonlinear self-refractive index.’ p. 4: ‘The experimentally measured values of n2 = Delta n / 2I are in good agreement with previous estimates using harmonic generation [25 = Shelton and Rice]’. So the tabulated n2 is the SELF coefficient. Kramers-Kronig, Eq. (1): Delta n(omega, E) = (c/pi) P int Delta alpha(Omega, E) / (Omega^2 - omega^2) dOmega (Delta alpha here an absorption coefficient); average-frequency approximation, Eq. (2). No chi(3) or gamma is defined. Gaussian conventions.

VALUES. The n2 values exist only as labels printed in the panels of Fig. 3 (p. 4; the figure is a raster image, its text is not in the pdf text layer), read from the figure image: He (3.1 +- 0.4) x 1e-21, Ne (8.7 +- 1.1) x 1e-21, Ar (9.7 +- 1.2) x 1e-20, Kr (2.2 +- 0.4) x 1e-19, Xe (5.8 +- 1.1) x 1e-19 cm2/W. Each is the slope of a linear fit of Delta n to 2 n2 I over the measured points below the ionization threshold (Fig. 3 caption). Horizontal error bars are the intensity calibration, vertical the phase extraction; the meaning of the +- on n2 is not stated. The Ar value equals wahlstrand_2012’s Ar value (same calibration).

REFERENCE STATE. Not stated in this Letter; the calibration is ‘as in [7]’ (wahlstrand_2012, 1 atm). Recorded as 101325 Pa, 290.9 K: the density of that N2 flow calibration (wahlstrand_2012 notes; TC-316). Pump 800 nm (1.55 eV, p. 2), vacuum assumed; probe wavelength not stated here (the supercontinuum of wahlstrand_2012, ~550-635 nm).

PART. Noble gases: electronic. The response is linear in intensity up to the measured ionization threshold of each gas (Fig. 3, dotted lines; not tabulated; note [24]: the Ar threshold here is ~20 % lower than in Wahlstrand et al. PRL 107, 103901 (2011), because that experiment overestimated the peak intensity). This contradicts the saturating and inverting higher-order Kerr series of Bree et al. (and Loriot et al.): Fig. 3 overlays Bree et al.’s self index and the probe index obtained by multiplying their n_2k by k + 1 (Supplemental Material [18], not in the library).

Recorded bibliographic identity status: VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.