Laser-written nanogratings for spatial structuring in the near-infrared

Abstract

The objective of this study was to characterize laser-written nanograting half-wave plates for spatial structuring of light at 800 nm and 1030 nm wavelengths. The fabrication of vector beams, i.e. the spatial structuring of the polarization field, was of great interest for the study.

Wave plates were fabricated by focusing a high powered femtosecond pulse laser into a glass plate. Moving the glass in the x − y -plane wave plates with different characteristics, such as retardance and optical axis orientation, were fabricated by varying the laser parameters. The parameters studied were: pulse duration, repetition rate and energy, movement speed of glass plate and separation of lines where laser was focused.

The effect of different fabrication parameters on the retardance of the wave plates was studied using normalized transmission measurements. Additionally, the vector beam created by the wave plates was studied using polarization tomography.

Wave plates with retardance close to that of a half-wave plate, were found for a 800 nm beam. However, for the 1030 nm beam optimal fabrication parameters for a half-wave plate were not found on the studied pulse energy region. We were able to construct accurate and complex vector beams using the fabricated wave plates, especially using the wave plates with lower movement speeds.