In Volume Fresnel Lenses

This study explores the application of Femtosecond Laser Direct Writing (FLDW) in the fabrication of micro lenses, with a particular emphasis on crafting Fresnel lenses from bulk Fused Silica. By employing an NKT Laser, we meticulously fine-tuned the laser parameters through a series of square-writing experiments.

These experiments were critical for identifying the precise threshold between type 1 and type 2 modifications in the material. Progressing from these initial findings, we successfully created cubes within the Fused Silica substrate and accurately measured the resulting phase shifts using a Michelson interferometer.

These critical insights informed the design and production of Fresnel lenses with various focal lengths. The culmination of our efforts was the fabrication of a lens achieving a 2π phase shift and a focal length of 105mm. This lens was subsequently integrated into a microscope setup, where it demonstrated its efficacy by producing high-quality imaging results. Our project not only highlights the flexibility and potential of FLDW in microlens and grating production but also suggests that the use of Fused Silica could open up avenues for its application across a wide range of projects.

Impressions