Ultrafast focus control in laser processing using liquid acoustic lenses: modeling, methods, and applications

Abstract

Lasers are widely used in material processing, additive manufacturing, high-resolution imaging, and diagnostics. Increasing the precision and functionality of ultrafast laser-based material processing requires fine control of beam characteristics. Instead of defining the beam parameters in advance, the recent development of varifocal optical elements has enabled flexible beam shaping to effectively and responsively deliver energy to any three-dimensional location on the fly. This dissertation explores an innovative laser focus control method using a liquid acoustics lens called the TAG lens, which uses acoustic pressure waves to modulate its refractive index. Research work is presented on the modeling, methods, and applications of ultrafast laser focus control using the TAG lens. We first build a 2D axisymmetric model and employ analytical solutions and finite element simulations to understand the mechanics of acoustic lenses. Next, we explore two axial scanning methods, continuous axial scanning and synchronous axial scanning, with their applications in laser material processing. Furthermore, we develop a dynamic axial scanning method for optical detection applications and present a novel approach to auto-focusing.