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Title: On the evolution of cured voxel in bulk photopolymerization upon focused Gaussian laser exposure

Unconstrained depth photopolymerization is emerging as a promising technique for fabrication of several polymer microstructures such as self propagating waveguides, 3D freeform structures by bulk lithography, and polymer nanoparticles by flash exposure. Experimental observations reveal governing physics beyond Beer Lambert's law and scattering effects. This paper seeks to model unconstrained depth photopolymerization using classical nonlinear Schrödinger equation coupled with transient diffusion phenomenon. The beam propagation part of the proposed model considers scattering effects induced due to spatial variation of the refractive index as a function of the beam intensity. The critical curing energy model is used to further predict profile of polymerized voxel. Profiles of photopolymerized voxel simulated using proposed model are compared with the corresponding experimental results for several cases of exposure dose and duration. The comparison shows close match leading to conclusion that the experimentally observed deviation from Beer Lambert's law is indeed due to combined effect of diffusion of photoinitiator and scattering of light because of change in the refractive index.
Authors:
;  [1] ;  [2]
  1. Suman Mashruwala Advance Microengineering Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076 (India)
  2. Department of Physics, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076 (India)
Publication Date:
OSTI Identifier:
22308919
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIFFUSION; LAMBERT LAW; LASER RADIATION; MICROSTRUCTURE; NANOPARTICLES; NONLINEAR PROBLEMS; POLYMERIZATION; POLYMERS; REFRACTIVE INDEX; SCATTERING; SCHROEDINGER EQUATION; SIMULATION; TRANSIENTS; VISIBLE RADIATION; WAVEGUIDES