Transport-of-intensity-based phase imaging to quantify the refractive index response of 3D direct-write lithography

Precise direct-write lithography of 3D waveguides or diffractive structures within the volume of a photosensitive material is hindered by the lack of metrology that can yield predictive models for the micron-scale refractive index profile in response to a range of exposure conditions. We apply the t...

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Bibliographic Details
Published in:Optics express 2018-01, Vol.26 (2), p.1851-1869
Main Authors: Glugla, David J, Chosy, Madeline B, Alim, Marvin D, Sullivan, Amy C, McLeod, Robert R
Format: Article
Language:English
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Summary:Precise direct-write lithography of 3D waveguides or diffractive structures within the volume of a photosensitive material is hindered by the lack of metrology that can yield predictive models for the micron-scale refractive index profile in response to a range of exposure conditions. We apply the transport of intensity equation in conjunction with confocal reflection microscopy to capture the complete spatial frequency spectrum of isolated 10 μm-scale gradient-refractive index structures written by single-photon direct-write laser lithography. The model material, a high-performance two-component photopolymer, is found to be linear, integrating, and described by a single master dose response function. The sharp saturation of this function is used to demonstrate nearly binary, flat-topped waveguide profiles in response to a Gaussian focus.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.26.001851