On the Digital Holographic Interferometry of Fibrous Material, I. Optical Properties of Polymer and Optical Fibers

TL;DR

This paper demonstrates the use of digital holographic interferometry to accurately measure optical properties such as refractive index and birefringence in polymer and optical fibers, overcoming manual focusing limitations.

Contribution

It introduces a method combining phase-shifting interferometry and digital holography for precise optical property measurement of fibers.

Findings

Refractive index measured with 4×10^-4 accuracy.

Accurate determination of birefringence and index profile.

Numerical focusing improves measurement precision.

Abstract

The digital holographic interferometry (DHI) was utilized for investigating the optical properties of polymer and optical fibers. The samples investigated here were polyvinylidene fluoride (PVDF) polymer fiber and graded-index (GRIN) optical fiber. The phase shifting Mach-Zehnder interferometer was used to obtain five phase-shifted holograms, in which the phase difference between two successive holograms is pi/2, for each fiber sample. These holograms were recorded using a CCD camera and were combined to gain a complex wavefield, which was numerically reconstructed using the convolution approach into amplitude and phase distributions. The reconstructed phase distribution was used to determine the refractive index, birefringence and refractive index profile of the studied samples. The mean refractive index has been measured with accuracy up to 4 {\times} 10-4. The main advantage of DHI is to overcome the manual focusing limitations by means of the numerical focusing. The results showed accurate measurements of the optical properties of fibers.