Gouy Phase Shift

1. Apr 18, 2012

vivek91m

Hello friends,
Could you please explain me Gouy Phase Shift, i have gone through the wikipedia article and i know that it occurs because of the focusing although i am not able to get a physical picture of the same, so it would be really nice if anyone can explain me in simple words about this phenomenon.

Regards,
Vivek.

2. Apr 18, 2012

DrDu

That's a general phenomenon occuring at caustics. Usually, it is a good approximation to assume that the wave is a plane wave with wavevector given as k=nw/c, where w is the frequency, n the refractive index and c the speed of light in vacuum. Usually the intensity of that wave A varies slowly on a scale 1/k. This assumption breaks down near a caustic or a focal point and the intensity becomes very large over a distance $\Delta x\approx \lambda/2=\pi/k$. This intensity bump thus shifts the phase of the wave after the focal point.
A more careful analysis starts from the short wavelength asymptotics of the wave equation (WKB approximation), see e.g.:

3. Apr 21, 2012