Application of the photoelastic tomography to three-dimensional measurement of birefringence in anisotropic microobjects

Abstract

In the paper we present method for three-dimensional measurement of birefringence distribution in photonics components. The tool we used in this work is automated digital photoelasticity combined with tomography, namely photoelastic tomography. Till now the photoelasticity procedures have been applied for objects with significant dimensions and therefore the diffraction phenomena could be neglected. In this paper we verify the correctness of this method for measurement of small objects. In order to identify this error we simulate the measurement process starting from integrated retardation determination and ending on 3D distribution evaluation. Computations are performed using full vectorial propagation method based on Maxwell-curl equations (finite difference time domain method FDTD). The results of simulations are compared with actual measurement results derived from physical setup. The result of experimental and numerical analysis allow optimizing the measurement setup and minimizing the errors. The correctness of the photoelastic tomography for analysis of microobjects has been proven on an example of birefringent optical fibers.

Interferometric and tomographic investigations of polymer microtips fabricated at the extremity of optical fibers

“…This setup has been described in [13,16]. The light coming from a light source first passes through the polarizer (P) and quarterwave plate (λ/4).…”

“…In order to minimize the coupling losses between optical fibre and components, it is essential to know the detailed optical characteristics of the microlenses and especially the distribution of local values of the refractive index and birefringence that may be created by the polymerization process, mechanical stress or a presence of impurity. The measurement techniques which are able to deliver 3D distribution of these quantities in microlenses or other microelements are interferometric [12] and elastooptics [13] tomography.…”

Tomographic studies of 3D refractive index and birefringence distribution in M-O elements replicated by hot embossing technology

“…Under assumption, that main anisotropy axis is known and constant the complicated problem of tensor field tomography is reduced to the problem of scalar field tomography of birefringence. This method has been successfully applied to polarization maintaining fibre optics [16,17], however here we have more general case in which it may in future require solution of full complicated problem of tensor field tomography tensor. At the moment we simplify the problem to linear operation.…”

“…However it is very troublesome, as it requires careful cutting of a sample with frozen stresses. Therefore here we propose to apply more convenient and nondestructive method for determination of anisotropic properties of HE sample, namely photoelastic tomography [16]. Under assumption, that main anisotropy axis is known and constant the complicated problem of tensor field tomography is reduced to the problem of scalar field tomography of birefringence.…”

“…Photoelastic tomography is the measurement method, which combines automated polariscopy [15] with tomographic 3D reconstruction methods [16].In the second stage tomographic algorithm is applied to the projections which represents 2D retardations obtained in the polariscope. The measurement procedure consists of the following stages, which are similar to the procedure described in Section 3.3 and Fig.…”