Refractive index and geometrical thickness measurement of a transparent pellicle in air by Gaussian beam defocusing.
We demonstrate that it is possible to measure the local geometrical thickness and the refractive index of a transparent pellicle in air by combining the diffractive properties of a Gaussian beam with the analytical equations of the light that propagates through a thin layer. We show that our measurement technique is immune to inherent piston-like vibrations present in the pellicle. As our measurements are based on characterizing properly the Gaussian beam in a plane of detection, a homodyne technique for this purpose is devised and described. The feasibility of our proposal is confirmed by measuring local geometrical thicknesses and the refractive index of a commercially available stretch film.
Octavio
O
Olvera-R
Moisés
M
Cywiak
Joel
J
Cervantes-L
Arquímedes
A
Morales