Program Interface

(require 'fresnel-equations)

Function: combine-layers th_i w layers

layers is a list of lists of index-of-refraction and thickness. The index-of-refraction may be a complex number or a procedure of wavelength (w) in meters returning a complex number.

Layers with negative thickness are modeled as incoherent (with positive thickness); otherwise as coherent (with inteference fringing).

The index-of-refraction of the top and bottom media are given by the first and last layers, which must have thickness 0. w is probe wavelength. th_i is the angle of the incident ray in radians.

Combine-layers returns a list of three non-negative real numbers:

• the ratio of transmitted power to incident power;
• the ratio of reflected power (from the top) to incident power; and
• the ratio of reflected power (from the bottom) to incident power.

The transmitted and forward ratios sum to 1.0 if layers are all dielectric (lossless). The transmitted and reverse ratios sum to 1.0 if layers are all dielectric (lossless).

Negative w computes the S-polarization, else the P-polarization.

Function: snell-law x1 x2 th-i

Real numbers x1 and x2 are the indexes of refraction of the incident and opposite side of the boundary plane between two dielectric materials. Real number th-i is the angle of incidence (from the normal of the boundary plane).

snell-law returns the exit angle (from normal) of an incident ray impinging at th-i from normal. If the ray undergoes total internal reflection, then the returned angle will not be real and should be ignored.

(snell-law 2.8 1.3 .1) => 216.71826868463917e-3
(snell-law 2.8 1.3 .3) => 689.9583515921762e-3
(snell-law 2.8 1.3 .4) => 994.9783891781343e-3
(snell-law 2.8 1.3 .5) => 1.5707963267948965-254.68865153727376e-3i

Function: snells-law z1 z2 th-i

Complex numbers z1 and z2 are the indexes of refraction of the incident and opposite side of the boundary plane between two dielectric materials. Real number th-i is the angle of incidence (from the normal of the boundary plane).

snells-law returns the exit angle (from normal) of an incident ray impinging at th-i from normal. If the ray undergoes total internal reflection, then the returned angle is bogus and should be ignored.