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If Specify absolute refractive index (the default) is selected, the Refractive index, real part can be taken From material, or it can be entered directly. The default value is 1. This index is considered absolute, that is, relative to vacuum.
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If Specify relative refractive index is selected, the Refractive index, real part can be taken From material, or it can be entered directly. The default value is 1. Then enter the Reference temperature Tref,rel (SI unit: K, default 293.15 K) and the Reference pressure Pref,rel (SI unit: Pa, default 0). The given refractive index is understood to be relative to air; that is, the absolute refractive index is the product of the specified value with the refractive index of air at the reference temperature and pressure.
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If Get dispersion model from list is selected, choose an option from the Optical dispersion model list. The following options are available:
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If Get dispersion model from material is selected, the dispersion model in each domain is automatically deduced from the Material nodes and their selections. This allows different optical dispersion models to be used in different domains in the geometry, using only a single Medium Properties node.
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For the built-in optical dispersion models, the wavelength is always assumed to be in units of microns (μm). For example, in the Schott (polynomial) model, the coefficients A0, A1, A2, A3, and so on have units of 1, μm, μm2, μm3, and so on. If another source were to provide these coefficients using nanometers instead of microns, then some manual conversion would be required.
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For Extinction coefficient, specify the value of κ directly. This can be taken From material or User defined; if User defined the default is 0. The Geometrical Optics interface only recognizes isotropic κ where the absorption rate does not depend on ray polarization.
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For Attenuation coefficient, specify the value of the Attenuation coefficient α (SI unit: 1/m) which is related to κ by α = 4πκ/λ0. The default is 1 1/m.
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For Internal transmittance, 2 mm sample thickness, enter a value or expression for the internal transmittance of a 2 mm thick sample of the material, neglecting Fresnel losses. Internal transmittances are dimensionless and are denoted τi,d, where d is replaced with the sample thickness, for example, τi,2. The default is 0.9. The relationship between τi,d and κ is κ = -(λ0 log τi,d)/(4πd).
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The remaining options are internal transmittances at other values of the sample thickness. Options for 5 mm, 10 mm, and 25 mm samples are available. Otherwise the settings are the same as the Internal transmittance, 2 mm sample thickness option.
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Locate the default Medium Properties node.
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From the Refractive index of domains list, select Get dispersion model from material. If the glasses loaded in step 1 also provide thermo-optic coefficients, it is important to specify an accurate value of the Temperature as well.
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None (the default): no offset will be applied.
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Schott thermo-optic: this is the only built-in thermo-optic dispersion model available. The coefficients used to compute a temperature dependent offset in the refractive index can either be taken From material (the default), or User defined. A reference temperature is also required. This may also be taken From material (the default), or User defined.
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