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Details of Refractive Indices

Measurement of refractive indices of solid

Measuring method, range of wavelength measurable, and the accuracy will be different according to the size and the shape of the test piece.

1-1  For bulk shaped materials


Chart 1 : Examples of measurements and the methods

Material characteristics Measuring materials Measuring method
Isotropic materials Optical glass, Silica glass, etc. Refractometer (V-Block method)
or
Spectrometer (Minimum deviation method)
Crystals of cubic system(CaF2,Si,ZnS,ZnSe,etc)
Plastics (without birefringence) Refractometer (V-Block Method)
Porous Glasses (n1.03) Spectrometer (Minimum deviation method)
Anisotropy materials Uniaxial crystals(Quartz,TiO2,Sapphire,LBO,Ice, etc) Spectrometer (Minimum deviation method)
Refractometer (V-Block method)
Plastics with birefringence Refractometer (V-Block method)
Please refer Chart 2 for spectral lines measurable and the accuracy of the measurements.

Chart 2 : Spectral lines measurable and the accuracy
Spectral lines Measuring Equipment
MÖLLERWEDEL Carl Zeiss
Jena
Wavelength Symbols Symbols
of lumps
(Light
source)
Super
Precision
Spectrometer
Type1
Precision
Spectr
ometer
Type 2
Refracto
meter
Type
PR-2
Ultra precision Precision Standard Standard
in air
(nm)
in
vacuum
(nm)
Measuring
Accuracy
(10-6)
Measuring
Accuracy
(10-5)
Measuring
Accuracy
(10-5)
Measuring
Accuracy
(10-5)
2325.42 2326.05   Hg ±5 ±1 × ×
2058.09 2058.65   He ±5 ±1 × ×
1970.09 1970.63   Hg ±5 ±1 × ×
1813.07 1813.57   Hg ±5 ±1 × ×
1529.58 1530.00   Hg ±5 ±1 × ×
1128.64 1128.95   Hg ±3 ±1 × ×
1013.98 1014.26 t Hg ±1 ±1 ±3 ±5
852.110 852.344 s Cs ±1 ±1 ±3 ±5
780.023 780.237   Rb ±1 ±1 ±3 ±5
706.519 706.714 r He ±1 ±1 ±3 ±5
656.273 656.454 C H2 ±1 ±1 ±3 ±3
643.847 644.025 C' Cd ±1 ±1 ±3 ±3
632.82 632.99   He-Ne ±1 ±1 ±3 ±3
587.562 587.725 d He ±1 ±1 ±3 ±3
546.075 546.227 e Hg ±1 ±1 ±3 ±3
486.133 486.269 F H2 ±1 ±1 ±3 ±3
479.992 480.126 F' Cd ±1 ±1 ±3 ±3
435.835 435.957 g Hg ±1 ±1 ±3 ±3
404.656 404.770 h Hg ±1 ±1 ±3 ±5
388.865 388.975   He ±1 ±1 ±3 ×
365.015 365.119 i Hg ±1 ±1 ±3 ×
340.365 340.463   Cd ±3 ±1 × ×
334.148 334.244   Hg ±3 ±1 × ×
312.566 312.657   Hg ±3 ±1 × ×
296.728 296.814   Hg ±3 ±1 × ×
289.360 289.444   Hg ±3 ±1 × ×
253.652 253.728   Hg ±3 ±1 × ×
228.802 228.872   Cd ±3 ±1 × ×
226.502 226.572   Cd ±3 ±1 × ×
214.438 214.506   Cd ±3 ±1 × ×
213.856 213.923   Zn ±3 ±1 × ×
206.200 206.266   Zn ±3 ±1 × ×
202.548 202.613   Zn ±3 ±1 × ×
- 194.227   Hg ±5 ±1 × ×
- 184.950   Hg ±5 ±1 × ×

1-2  For surface layers

Chart 3 : Examples of measurements and the methods
Condition of test materials Example of measurement Measuring method
Thin film
(Several microns in thickness needed)
Thin film coated on glass substrates
Silicon oxide film on silicon wafer
By refractometer
(Critical angle method,
Prism coupling method, etc.)
Surface layer
(Several microns in thickness needed)
Chemically strengthened surface layer
Wavelengths used for the measurements:633nm, d, e, & g
Measuring accuracy:±1×10-3~±1×10-4

1-3  For powder

Chart 4 : Examples of measurements and the methods
Particle diameter Example of measurement Measuring method
Several microns ~ 30 microns White powder of glasses and rocks Becke method
Wavelengths used for the measurements:633nm, D, e, & g
Available measurement range:nD=1.43~1.73
ng=1.43~1.78
Measuring accuracy:±1×10-3
 

Measurement of refractive indices of liquid

Chart 5 : Examples of measurements and the methods
Condition of test material Example of measurement Measuring method
Liquid like Oil, Alcohol, Water, Gasoline, etc. Refractometer
(V-Block method)
Greasy Greasy oil
Jelly Adhesive
Wavelengths used for the measurements:795nm, 780nm, C, C', 633nm, d, e, F, F', & g
Measuring accuracy:±3×10-4~±5×10-5