shaw_1993#

M. J. Shaw, C. J. Hooker and D. C. Wilson, Opt. Commun. 103, 153 (1993)

Source record · Catalogue · Review register

Source kind: measurement

Recorded technique: Self-phase modulation of about 10 ps pulses at 248.6 nm (tripled 746 nm Ti:sapphire oscillator pulses amplified in a dye amplifier and a double-passed KrF discharge amplifier to 2 mJ, 180 MW, 8 Hz) focused by a 2 m lens into a 3 m pressure cell; spectra on an echelle spectrometer (0.2 cm^-1) against pressure (Baratron gauge) in both directions; the B integral of each spectrum fitted with a modelled asymmetric pulse shape (sech^2 oscillator pulse cubed and passed through a saturated amplifier, Eqs. 9-11); relative n2 from the slopes of B against pressure (Eq. 8, Fig. 4).

Materials in structured entries: Ar, CH4, He, N2, Ne, O2

Dataset quantities: nonlinear_index_ratio

Contents: 6 datasets; 0 formulas.

Curation notes#

Defining equations (p. 2): n = n0 + n2 <E^2> = n0 + Gamma I (Eq. 1), ‘I is the intensity (watt/cm^2) and Gamma = 4.2 x 10^-3 (n2/n0) (n2 in e.s.u.)’; B(t) = k Gamma int_0^L I dl (Eqs. 4-5); B = B1 + alpha gamma P with alpha = k int I dl and gamma = Gamma/P, ‘n2 is usually specified at a pressure of 760 Torr’ (p. 3). Gamma is the single-beam (self) coefficient of SPM. The absolute scale needs int I dl, estimated as 6.8 +- 2.4 TW/cm (from 4.5, 7.6 and 9.2 TW/cm by three assumptions, p. 3), so the absolute values are uncertain by +-33 %; the ratios to air are better than 10 % (Conclusion, p. 7-8). Only the ratios (Table 1) are for curated gases; the only absolute value is for air: ‘n2 for air at 248 nm, 760 Torr and 300 K of 2.9 +- 1.0 x 10^-16 esu’ (p. 5), not a curated species. B1 = 1.3 with the cell evacuated (window and lens material).

Table 1 (‘Relative values of nonlinear refractive index at 248 nm. Errors shown are calculated from the standard errors in the slopes of the fitted lines’; tbl_d1f5f8c27975, image checked): air 1.00, N2 0.62 +- 0.03, O2 2.50 +- 0.25, Ar 0.24 +- 0.01, CH4 0.94 +- 0.07, Ne 0.005 +- 0.001, He -0.002 +- 0.001. Extracted as nonlinear_index_ratio against ‘air’ (reference_material = air, not a curated species; same pressure, 760 Torr and 300 K for the absolute value). The uncertainties are standard errors of slopes (1 sigma). - O2 is not measured: ‘calculated using the results obtained for air, nitrogen and argon, assuming that oxygen makes a 21 % contribution to the total nonlinear index of air while nitrogen contributes 78 % and argon 1 %’ (p. 5). Check: (1 - 0.78 x 0.62 - 0.01 x 0.24)/0.21 = 2.45 against 2.50 printed (2 %, presumably unrounded slopes). - CH4: stimulated Raman scattering above about 250 Torr raised the slope; only the data below 250 Torr were used (p. 5). - Ne (just observable at 7000 Torr) and He (no broadening; a slight narrowing, 50 spectra): the authors write ‘It seems plausible that our values for helium and probably also neon were affected by ionization in the focal region’ (p. 8), with an MPI estimate giving B of about -0.1 (p. 7): both excluded. - Molecules: ‘at our pulselength of 10 ps there is some reduction of the susceptibility of the molecular gases due to the freezing out of the nuclear motions’ (p. 6; rovibrational response times 1-2 ps estimated). Recorded as part = total (the nuclear response is largely adiabatic at 10 ps), with that caveat. The ratio N2/Ar disagrees with Hellwarth et al.’s calculation (p. 6).

Wavelength: 248.6 nm (the KrF gain peak, p. 3; medium not stated). Pulse: ‘about 10 ps’ (streak camera), modelled as an asymmetric pulse of about 11 ps FWHM (p. 4).

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

Datasets#

shaw_1993/ratio_N2#

{
  "id": "ratio_N2",
  "material": "N2",
  "file": "N2/shaw_1993__ratio_N2.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "primary",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "total",
    "pulse_fs": 10000
  }
}

Table 1: n2(N2)/n2(air) at 248.6 nm, SPM of 10 ps pulses, slope standard error.

shaw_1993/ratio_O2#

{
  "id": "ratio_O2",
  "material": "O2",
  "file": "O2/shaw_1993__ratio_O2.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "check",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "total",
    "pulse_fs": 10000
  }
}

Table 1: n2(O2)/n2(air), not measured but derived from air, N2 and Ar with volume fractions 0.21/0.78/0.01 (p. 5); marked check because it is a combination of the other ratios.

shaw_1993/ratio_Ar#

{
  "id": "ratio_Ar",
  "material": "Ar",
  "file": "Ar/shaw_1993__ratio_Ar.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "primary",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "electronic",
    "pulse_fs": 10000
  }
}

Table 1: n2(Ar)/n2(air) at 248.6 nm (numerator electronic, reference air total), up to 3500 Torr of Ar.

shaw_1993/ratio_CH4#

{
  "id": "ratio_CH4",
  "material": "CH4",
  "file": "CH4/shaw_1993__ratio_CH4.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "primary",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "total",
    "pulse_fs": 10000
  }
}

Table 1: n2(CH4)/n2(air) at 248.6 nm from the slope below 250 Torr (SRS above).

shaw_1993/ratio_Ne#

{
  "id": "ratio_Ne",
  "material": "Ne",
  "file": "Ne/shaw_1993__ratio_Ne.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "excluded",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "electronic",
    "pulse_fs": 10000
  }
}

Table 1: n2(Ne)/n2(air). Excluded: the authors think neon ‘probably also’ affected by ionisation in the focus (p. 8); broadening only just observable at 7000 Torr.

shaw_1993/ratio_He#

{
  "id": "ratio_He",
  "material": "He",
  "file": "He/shaw_1993__ratio_He.csv",
  "table": "tbl_d1f5f8c27975",
  "quantity": "nonlinear_index_ratio",
  "abscissa_unit": "nm",
  "use": "excluded",
  "uncertainty": {
    "column": true,
    "level": "1 sigma"
  },
  "parameters": {
    "reference_material": "air",
    "part": "electronic",
    "pulse_fs": 10000
  }
}

Table 1: n2(He)/n2(air) = -0.002 +- 0.001, a slight spectral narrowing; excluded: the authors attribute it to free electrons from multiphoton ionisation in the focus (p. 7-8). An upper limit on He’s n2 at best.

Formulas#

No formulas are recorded.

Corrections#

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.