absorption_effective#
- optika.sensors.absorption_effective(wavelength, n_substrate, direction_substrate)[source]#
The absorption coefficient per unit perpendicular depth for a wave refracted into the (absorbing) light-sensitive region at oblique incidence.
This is the rigorous generalization of \(4 \pi \, \text{Im}(n) / \lambda\) to oblique incidence: it uses the complex refracted cosine
direction_substrateso that the geometric \(\sec\theta\) path-length factor is no longer needed downstream. Reduces to the normal-incidence coefficient whendirection_substrateis 1.- Parameters:
wavelength (Quantity | AbstractScalar) – The wavelength of the incident light in vacuum.
n_substrate (complex | AbstractScalar) – The complex index of refraction of the light-sensitive region.
direction_substrate (complex | AbstractScalar) – The (generally complex) cosine of the refracted angle inside the light-sensitive region, e.g. from
optika.materials.snells_law_scalar().
- Return type:
Notes
For a wave refracted from a transparent ambient medium into an absorbing medium, the planes of constant amplitude remain parallel to the interface, so the intensity attenuates along the surface normal with coefficient
\[\alpha_\perp = \frac{4 \pi}{\lambda} \, \text{Im}(n_2 \cos\theta_2),\]where \(n_2\) is the complex index of the light-sensitive region and \(\cos\theta_2\) is its (complex) refracted cosine.