The Refractive index, real part,
n (dimensionless) may be expressed as a function of both wavelength and temperature by using an expression of the form
The wavelength-dependent (non-temperature-dependent) component of this equation, n(
λ), might be any one of the optical dispersion models discussed above, or it could be specified by other means. The change in refractive index as a function of temperature,
Δn(
λ,Τ) can be computed using a thermo-optic dispersion model.
An expression for the change in refractive index as a function of temperature, Δn(
λ,T) is given in
Ref. 5. It may be derived by integrating the dispersion formula for the thermo-optic coefficient (
dn/dT). That is,
In the above formula T0 is the reference temperature against which the temperature difference
ΔT =
T − T0 is computed and
D0,
D1,
D2,
E0,
E1, and
λTK, are glass specific coefficients.