Abstract
Measurements of weak, embedded index structures are important for material characterization of photopolymers, glass and other optical materials as well as for characterization of fabricated structures such as waveguides. We demonstrate an optical diffraction tomography system capable of measuring deeply-buried, weak, fabricated index structures written in a homogeneous volume. High-fidelity cross sections of these weak index structures are constructed by replicating the structure to be measured to form a diffraction grating. The coherent addition of scattering from each of these objects increases the sensitivity of the imaging system. Measurements are made in the far field, without the use of lenses, eliminating phase aberration errors through thick volumes.
Highlights
Quantitative, high-resolution images of weak index structures are important for a wide variety of applications
We demonstrate an optical diffraction tomography system capable of measuring deeply-buried, weak, fabricated index structures written in a homogeneous volume
We demonstrate an optical diffraction tomography system capable of quantitative imaging of weak index structures written in a 3D volume
Summary
Quantitative, high-resolution images of weak index structures are important for a wide variety of applications. We demonstrate an optical diffraction tomography system capable of quantitative imaging of weak index structures written in a 3D volume. This is accomplished by making many identical, -spaced copies of the object to be measured in order to increase the sensitivity of the imaging system. The low signal-to-noise problem is addressed by duplicating the object of interest on a regular grid so that the scatter from each object adds coherently to the others, giving a stronger signal for the reconstruction This method of duplicating the object of interest and reconstructing the object from discrete samples in the far field is similar to that used for x-ray diffraction measurements of crystals [22].
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