Femtosecond laser direct-write waveplates based on stress-induced birefringence

TL;DR

This paper presents a method to create tunable, stress-induced birefringent waveplates in silica glass using femtosecond laser writing combined with chemical etching, enabling precise polarization control for various wavelengths.

Contribution

It introduces a novel direct-write technique for fabricating stress-induced birefringent waveplates with tailored retardance levels in silica glass.

Findings

Successfully fabricated quarter-wave plates with controlled retardance

Analyzed and modeled stress distribution for design guidance

Achieved clear aperture devices free of laser modifications

Abstract

The use of femtosecond lasers to introduce controlled stress states has recently been demonstrated in silica glass. We use this technique, in combination with chemical etching, to generate and control stress-induced birefringence over a well-defined region of interest, demonstrating direct-write wave plates with precisely tailored retardance levels. This tailoring enables the fabrication of laser-written polarization optics that can be tuned to any wavelength for which silica is transparent and with a clear aperture free of any laser modifications. Using this approach, we achieve sufficient retardance to act as a quarter-wave plate. The stress distribution within the clear aperture is analyzed and modeled, providing a generic template that can be used as a set of design rules for laser-machined polarization devices.