dodge_1984#
M. J. Dodge, “Refractive properties of magnesium fluoride”, Appl. Opt. 23, 1980 (1984)
Source record · Catalogue · Review register
DOI: 10.1364/ao.23.001980
Source kind: measurement
Recorded technique: Minimum deviation on the NBS modified Gaertner precision spectrometer (Fig. 1; the instrument of Rodney and Spindler), for the ordinary (O) and extraordinary (E) rays at 45 wavelengths from 0.2025 to 7.04 um (‘0.2026’ in the abstract), ‘at a temperature near 19 C’ (p. 1980). One commercial single-crystal MgF2 prism, cut with the optic axis perpendicular to the triangular faces and bisecting the refracting angle (about 68 degrees; faces 4.1 x 2.9 cm, flat to half a fringe). Sources: Hg, Cd, He and Zn lamps; beyond 2.0 um absorption bands of atmospheric H2O and CO2 and of polystyrene with a Globar, interference filters to identify wavelengths at 3.5-6.5 um. Polarizers to tell the rays apart: wire grid (IR), Polaroid sheet (visible), MgF2 Nicol (UV), usually removed for the measurement itself. Detectors: photomultiplier (UV), thermocouple with a CsI window (visible and IR) (pp. 1980-1981).
Materials in structured entries: MgF2
Dataset quantities: refractive_index
Contents: 2 datasets; 2 formulas.
Curation notes#
Journal pages 1980-1985 are pdf pages 1-6 (p. 6 also carries an unrelated news item). Identity checked against the first page.
WHAT IS TABULATED. The measured indices are NOT printed. Table I gives the two Sellmeier formulas fitted to them (45 values per ray; average absolute residual 1.4e-5 for O and 1.8e-5 for E; largest residuals +8.2e-5 for O at 4.224 um, CO2 bands, and -8.5e-5 for E at 6.486 um, H2O bands; p. 1981). Table II gives n_O, n_E and the birefringence computed from the formulas at regular wavelengths, 0.20-7.00 um: ‘The three-term Sellmeier equation was then used to calculate the refractive index at regular wavelength intervals ... The quality of the fit of the experimental data would indicate that the overall accuracy of the calculated values is better than 2 x 10^-5’ (p. 1981). ‘The systematic errors are considered negligible’ (p. 1982). The Table II indices are recorded as this paper’s data (no other representation of the measurements exists), with that accuracy as a bound.
AIR OR VACUUM. Not stated. The measurements were made near 19 C on the NBS instrument of Rodney and Spindler and Malitson, in the room (no enclosure is described), with wavelengths of emission lines and of atmospheric absorption bands; as for those papers (TC-323, TC-399; malitson_1963, where Daimon and Masumura state ‘in air’), the index is taken as relative to the room air at 19 C (pressure not stated) and the wavelengths as standard-air wavelengths. This is an inference from the method and the laboratory, not a statement of the paper.
AXES. ‘Magnesium fluoride is a positive uniaxial crystal’ (p. 1980); O is the ordinary ray (axis o), E the extraordinary (axis e), the birefringence beta = n_E - n_O > 0 (p. 1982). The prism’s optic axis is perpendicular to its triangular faces, so both rays travel perpendicular to the axis and E is the principal extraordinary index.
BIREFRINGENCE (Table II, fourth column; no quantity): n_E - n_O of the two printed columns, to the last digit (all 36 rows, checked 2026-09-27), from 0.01348 at 0.20 um to 0.00569 at 7.00 um.
dn/dT. Not measured here: ‘The temperature coefficient of index, dn/dT, was reported by Feldman et al. [NBS Tech. Note 993 (1979), p. 63] at several temperatures from -180 to 200 C and at wavelengths from 0.4579 to 3.39 um for both polarizations. The temperature coefficient of refractive index dn/dT is <= 2 x 10^-6 C^-1 in all cases’ (p. 1983). Not recorded as data (a bound quoted from another report). Homogeneity (Rosberry): maximum variation per cm 3.7e-5 (p. 1983).
COMPARISONS (figures, not digitised). Fig. 3: other single crystals minus this study, O and E: the NBS 1966 data (Handbook of Optics, 0.21-1.08 um), Duncanson and Stevenson (1958), and Teska (unpublished, ‘generally higher by about 2 x 10^-4 at all wavelengths for both polarizations’, attributed to annealing, pp. 1982-1984); the other three agree ‘to within a few parts in 10^-5’ (p. 1984). Fig. 2 also shows two hot-pressed MgF2 specimens (Buckner et al.; Irtran-I, Herzberger and Salzberg), 4e-4 apart. Fig. 4: beta, with Chandrasekharan and Damany’s VUV values (whose sign Dodge corrects, p. 1982) and Teska’s; Figs. 5-7: -dn/dlambda (O ray, minimum near 1.3 um), the dispersion of beta and beta/lambda. The birefringence changes sign below 0.1194 um (p. 1984, from ref. 13).
REFRACTIVEINDEX.INFO (main/MgF2/nk/Dodge-o.yml and Dodge-e.yml, compared 2026-09-27): formula 1 with the Table I constants (O: 0.48755108, 0.04338408, 0.39875031, 0.09461442, 2.3120353, 23.793604; E: 0.41344023, 0.03684262, 0.50497499, 0.09076162, 2.4904862, 23.771995), identical; range 0.2-7.0 um; comment ‘19 C’; temperature 292 K. No mention of air. solprop’s MgF2 (ordinary ray only) uses the O coefficients as an absolute index at vacuum wavelengths: about 3.7e-4 low (n x 2.7e-4 of air) if the index is relative to air, as inferred here.
REPRODUCTIONS. adair_1989’s ‘n (1.06 um)’ of MgF2 (o), 1.3735, cites Dodge in the Handbook of Laser Science and Technology (CRC, 1986), not this paper. It is not this paper’s value: the O formula gives 1.37322 at 1.06 um (1.37359 made absolute with the air’s index), and Table II 1.37358 at 1.00 um and 1.37134 at 1.40 um (checked 2026-09-27). The handbook is not in the library.
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
dodge_1984/n_o_19C#
{
"id": "n_o_19C",
"material": "MgF2",
"file": "MgF2/dodge_1984__n_o_19C.csv",
"table": "tbl_722b5ecebf2e",
"quantity": "refractive_index",
"abscissa_unit": "um",
"wavelength_medium": "standard_air",
"use": "primary",
"parameters": {
"axis": "o",
"temperature_k": 292.15,
"form": "bulk",
"technique": "minimum deviation",
"index_medium": "air",
"air_temperature_k": 292.15
},
"uncertainty": {
"absolute": 2e-05,
"level": "bound"
}
}
Table II, n_O: the ordinary index at 36 regular wavelengths, 0.20-7.00 um, 19 C, computed from the Table I formula fitted to the (unprinted) measurements; ‘the overall accuracy of the calculated values is better than 2 x 10^-5’ (p. 1981). Relative to the room air (inferred; see the source notes).
dodge_1984/n_e_19C#
{
"id": "n_e_19C",
"material": "MgF2",
"file": "MgF2/dodge_1984__n_e_19C.csv",
"table": "tbl_722b5ecebf2e",
"quantity": "refractive_index",
"abscissa_unit": "um",
"wavelength_medium": "standard_air",
"use": "primary",
"parameters": {
"axis": "e",
"temperature_k": 292.15,
"form": "bulk",
"technique": "minimum deviation",
"index_medium": "air",
"air_temperature_k": 292.15
},
"uncertainty": {
"absolute": 2e-05,
"level": "bound"
}
}
Table II, n_E: the extraordinary index at 36 regular wavelengths, 0.20-7.00 um, 19 C, computed from the Table I formula; accuracy ‘better than 2 x 10^-5’ (p. 1981). Relative to the room air (inferred).
Formulas#
dodge_1984/sellmeier_o#
{
"id": "sellmeier_o",
"form": "n2_sellmeier_wavelength",
"terms": {
"B": [
"0.48755108",
"0.39875031",
"2.3120353"
],
"L": [
"0.04338408",
"0.09461442",
"23.793604"
]
},
"wavelength_medium": "standard_air",
"index_medium": "air",
"air_temperature_k": 292.15,
"range_nm": [
202.57,
7041.92
],
"material": "MgF2",
"parameters": {
"axis": "o",
"temperature_k": 292.15
},
"equation": "The equation of p. 1981 (unnumbered) with Table I (p. 1981), O ray",
"printed": "n^2 - 1 = Sum_j A_j lambda^2/(lambda^2 - lambda_j^2); O ray: A_1 = 0.48755108, A_2 = 0.39875031, A_3 = 2.3120353, lambda_1 = 0.04338408, lambda_2 = 0.09461442, lambda_3 = 23.793604",
"variable": "lambda: wavelength in um (air, inferred; see the source notes)",
"range": "0.2025-7.04 um measured (45 wavelengths); Table II computed at 0.20-7.00 um; 'near 19 C'",
"coefficients": {
"A1": "0.48755108",
"A2": "0.39875031",
"A3": "2.3120353",
"lambda1": "0.04338408",
"lambda2": "0.09461442",
"lambda3": "23.793604"
},
"check": "Reproduces Table II's n_O at all 36 wavelengths to its five printed decimals (rounded; largest difference 4.8e-6). Checked 2026-09-27 against the printed coefficients."
}
Fitted by least squares (Sutton and Stavroudis) to the 45 measured O-ray indices; the parameters ‘are not considered as having any real physical significance but are used only for interpolation’ (p. 1981). Average absolute residual 1.4e-5. Relative to the room air at 19 C (inferred). Identical to refractiveindex.info main/MgF2/nk/Dodge-o and to solprop’s MgF2.
dodge_1984/sellmeier_e#
{
"id": "sellmeier_e",
"form": "n2_sellmeier_wavelength",
"terms": {
"B": [
"0.41344023",
"0.50497499",
"2.4904862"
],
"L": [
"0.03684262",
"0.09076162",
"23.771995"
]
},
"wavelength_medium": "standard_air",
"index_medium": "air",
"air_temperature_k": 292.15,
"range_nm": [
202.57,
7041.92
],
"material": "MgF2",
"parameters": {
"axis": "e",
"temperature_k": 292.15
},
"equation": "The equation of p. 1981 (unnumbered) with Table I (p. 1981), E ray",
"printed": "n^2 - 1 = Sum_j A_j lambda^2/(lambda^2 - lambda_j^2); E ray: A_1 = 0.41344023, A_2 = 0.50497499, A_3 = 2.4904862, lambda_1 = 0.03684262, lambda_2 = 0.09076162, lambda_3 = 23.771995",
"variable": "lambda: wavelength in um (air, inferred; see the source notes)",
"range": "0.2025-7.04 um measured (45 wavelengths); Table II computed at 0.20-7.00 um; 'near 19 C'",
"coefficients": {
"A1": "0.41344023",
"A2": "0.50497499",
"A3": "2.4904862",
"lambda1": "0.03684262",
"lambda2": "0.09076162",
"lambda3": "23.771995"
},
"check": "Reproduces Table II's n_E at all 36 wavelengths to its five printed decimals (rounded; largest difference 5.0e-6). Checked 2026-09-27 against the printed coefficients."
}
As sellmeier_o, for the extraordinary ray; average absolute residual 1.8e-5. Identical to refractiveindex.info main/MgF2/nk/Dodge-e.
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.