Keywords

Neural Network; Beam Shaping; Bessel Beams; Multiphoton Lithography

Abstract

Multiphoton lithography (MPL) is a method of laser-based 3D-printing for fabricating micron-scale structures point-by-point in a photopolymerizable medium. MPL’s high-resolution capabilities have made it a powerful method for the fabrication of many devices, such as microelectromechanical systems (MEMS) and tissue scaffolds.  The throughput of MPL processes can be increased by using spatially shaped laser beams that expose large areas or volumes simultaneously. A laser beam can be reshaped by passing it through a spatial light modulator (SLM) displaying a pre-designed phase mask. One type of laser beam profile used for this purpose is the Bessel beam, a type of structured beam known for its propagation-invariant characteristics. Limited forms of volumetric-MPL have been reported based on axially extended Bessel beams. Nonetheless, generalized volumetric-MPL remains elusive, and no methods are known for designing phase masks based on non-idealized Bessel functions. In this thesis, a convolutional neural network (CNN) was used to design phase masks that form a wide range of radially symmetric and asymmetric 3D forms. The CNN was trained using annular phase-profiles that form Bessel-like conical sections. To assess CNN performance, image similarity metrics such as MSE, SSIM and CW-SSIM were implemented to compare beam profiles generated from CNN produced phase masks to targeted beam profiles within in-silico experiments. Additionally, CNN performance was evaluated in a physical optical system by using CNN designed phase masks for beam shaping. The CNN could design single-annulus phase masks needed to produce a variety of symmetrical Bessel beam profiles, as well as partial-annulus phase masks needed to produce asymmetric beam profiles.

Thesis Completion Year

2026

Thesis Completion Semester

Spring

Thesis Chair

Kuebler, Stephen

College

College of Sciences

Department

Chemistry

Thesis Discipline

Optics & Photonics

Language

English

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

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Optics Commons

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