lsurf.materials.sellmeier_refractive_index

lsurf.materials.sellmeier_refractive_index(wavelength, B1=1.03961212, B2=0.231792344, B3=1.01046945, C1=0.00600069867, C2=0.0200179144, C3=103.560653)

Compute refractive index using Sellmeier equation.

The Sellmeier equation is an empirical formula that accurately models the dispersion of optical glasses.

Parameters:

• wavelength (float) – Wavelength in meters.

• B1 (float) – Sellmeier B coefficients (dimensionless). Defaults are for N-BK7 glass.

• B2 (float) – Sellmeier B coefficients (dimensionless). Defaults are for N-BK7 glass.

• B3 (float) – Sellmeier B coefficients (dimensionless). Defaults are for N-BK7 glass.

• C1 (float) – Sellmeier C coefficients in μm². Defaults are for N-BK7 glass.

• C2 (float) – Sellmeier C coefficients in μm². Defaults are for N-BK7 glass.

• C3 (float) – Sellmeier C coefficients in μm². Defaults are for N-BK7 glass.

Returns:

n – Refractive index at given wavelength.

Return type:

float

Notes

Sellmeier equation:

n² - 1 = B₁λ²/(λ² - C₁) + B₂λ²/(λ² - C₂) + B₃λ²/(λ² - C₃)

where λ is in micrometers.

Default coefficients are for Schott N-BK7 glass, valid 300-2500 nm.

References

[1]

Sellmeier, W. (1871). Ann. Phys. Chem., 143, 271.

[2]

Schott AG. Technical Information TIE-29.

Examples

>>> n_589nm = sellmeier_refractive_index(589e-9)
>>> print(f"n = {n_589nm:.6f}")  # ~1.5168