Laboratoire neurophotonique
UFR des Scicences Fondamentales et Biomédicales
benoit.forget@parisdescartes.fr
For example, a sound wave : $$f=1000\,{\rm Hz} \; ;\; c=330\,{\rm m.s^{-1}} \quad\to\; \lambda = 0,33\,\textrm{m}$$
One particular "point" of phase \(\varphi_0\) travels along the axis \(Ox\) at speed \(c\).
In 2D (3D) a given path (surface) of same phase form a "wavefront"
The wave vector indicates the (local) direction of propagation of the wave.
For the "locally plane" wavefront : $$ \vec k\cdot \vec r = \rm{cst} $$
The wave vector is normal to the wave front
Diffrent thickness \(\to\) different phase shift (retardation).
$$ \Delta \varphi(x) = 2\pi (n-1) \frac{x \tan \alpha}{\lambda}$$
For any point (x,y) of the incoming wavefront we want to add independantly the appropriate phase delay