In the paper we present interferometric and photoelastic tomography methods applied for the 3D studies of refractive
index (n) and birefringence (B) in photonics components such as optical fibres and microelements produced or replicated
by a variety of novel technologies including deep proton writing (DPW) and hot embossing technology. The enhanced
automated measurement and data analysis procedures are described and the experimental results obtained for microobjects
working in transmission are given. Also the methodology to combine the tomographic data for full
characterization of internal structure of 3D photonics elements is provided. The main samples under test are: microlens
fabricated by DPW, Panda fibre and massive waveguide microinterferometer in the form of cuboids produced by hot
embossing process.
In this paper we present the improved interferometric tomography method for determination of 3D refractive index
distribution. The improvement relies on numerical correction of experimental results obtained for strongly refractive
objects based on the a priori, approximate knowledge about the refractive index distribution in the object under test. The
complete correction methodology is presented and discussed. The applicability of the method is shown through the
numerical simulations of the reconstruction process and the experiments including reconstruction of refractive index
distribution in a grin lens.
In the paper we present the method for 3D measurement of birefringence in photonics components by means of automated photoelasticity combined with tomography. The enhanced measurement procedure is described and the experimental results obtained for an exotic phase object, namely glass capillary infilled with liquid crystals are presented. The sources of errors are discussed for the cases of different object models and the numerical experiments aiming in determination of limitations of the experimental procedures are performed. Finally the possibility of reduction of these errors by an introduction of additional numerical focusing priori the tomographic reconstruction algorithmis shown and its applicability is proven by numerical simulations.
We discuss on-going reliability studies of micro-optical components and assemblies as conducted in the EU FP6 Network of Excellence on Micro-Optics "NEMO". We focus on three case studies including first biaxial fatigue testing of micro-optical components, second reliability testing and quality control of MEMS and third micro-interferometric tomography for measuring optical fibre refractive index changes. For each of these case studies we discuss the dedicated measurement and characterization methods as well as first results and the perspectives for future research.
In the paper we present method for three-dimensional measurement of birefringence distribution in anisotropic objects. The tool, which we used is combination of classic polariscopy with tomographic reconstruction method. Tomographic reconstruction is performed using the filtered backpojection algorithm. The results of measurement of
glass capillary infilled with licquid crystal are presented together with the results of numerical simulation of measurement process. Simulations include polarized light propagation performed by means of finite difference time domain method combined with Jones calculus. The numerical simulations are performed for various birefringence values and allow for determination of relative errors of birefringence distribution. Additionally the absolute refractive
indices are determined experimentally through the measurement of capillary with polarization sensitive microinterferometric tomography.
In this paper we report on the measurement of the refractive index profile of optical fibers exposed to the
gamma radiation. The tool we used for determining the refractive index distribution is microinterferometric
tomography. Nuclear radiation is known to affect the guiding properties of optical fibers and it is therefore essential to
characterize these effects to assess the applicability of fiber-optic technology for communication and sensing in space
applications and in nuclear industry. We show that the fibres exhibit a slight refractive index increase which confirms
results reported earlier.
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.
Microinterferometric tomography allows for determination of three-dimensional refractive index distributions in phase isotropic microelements. In this paper we present the measurement of the refractive index profile of the optical fibers exposed to the gamma radiation. Nuclear radiation is known to affect the guiding properties of optical fibers and it is therefore essential to characterize these effects to assess the applicability of fiber-optic technology for communication and sensing in nuclear industry. It is already well known that radiation affects the absorption of the fiber. Here, we investigated whether we could quantify the effect of radiation on the refractive index of core and cladding of an optical fiber.
Tomographic microinterferometry allows for a fast determination of the 3D refractive index distribution in optical elements. In this paper the limitations of this method due to diffraction effects at the edges of microelements or the steps in refractive index distribution inside objects with dimensions comparable to the wavelength are experimentally analyzed and by FDTD based simulations of reconstruction process. The other limitation considered refers to the deviation from a straight light propagation condition assumed in tomographic reconstruction. This problem is analyzed on the base of an experimental analysis of a 3D refractive index distribution in gradient index fiber optics and grin lens. The further modifications of tomographic microinterferometry in order to decrease these limitations are discussed.
This paper presents tomographic microinterferometry as a tool for determination of 3D refractive index distribution in optically transparent elements. Principles of method and exemplary results are obtained in laboratory system are given. Concept of insensitive for ambient influence field tomograph dedicated for fast determination of refractive index distribution is given. Decreasing of acquisition and computing time is achieved by reduction of number of views, for which measurements are taken. The influence of decreasing number of projection is analyzed in order to determine a certain compromise between the quality of n(x,y,z) reconstruction and time of measurement.
The paper gives a review of interferometric tomography with focus on their necessary modification when applied to 3D refractive index determination in micro-objects. Specifically the influence of diffraction phenomenon and radial run-out occurring during measurement are analyzed. The analysis is confirmed by results of measurements of 3D refractive index distribution in a multimode and single mode fibers. Additionally the discussion of future work at photoelastic tomography applied for microobjects is given.
The paper gives a review of interferometric and photoelastic tomography with focus on their necessary modification when applied to 3D refractive index determination in micro-objects. Specifically the influence of diffraction phenomenon and radial run-out occurring during measurement are analyzed. The analysis are confirmed by results of measurements of 3D refractive index distribution in a multimode and single mode fibres.
The development of low cost shape measurement system built on base of LCD display and cheap internet webcam is presented. Design of optomechanical system is described. Measurement methods (including calibration mode) are explained.
Microinterferometric tomography method for determination of 3D refractive index distribution in phase elements is described. Applications of this method to measurement of gradient index fibers, fiber splices and single mode fiber are presented. Initial results of holey fiber testing are given and future trends in development of this method (applications to photonic structures) are discussed.
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