More white light interference on the end facet of an optical fibre
This one has been shot 48 times with a 1.21 W CO2 laser to produce a Gaussian-shaped hole in the surface. Interference in the white light falling on different heights within the hole produces a kind of contour map of the dent. The picture is around 200 micrometres in diameter. The radius of curvature right at the bottom of the hole is around 350 micrometres.