Speaker
Description
Qualification of spiral phase plates for high power laser systems The application of light beams exhibiting Orbital Angular Momentum (OAM), commonly known as optical vortices (OV), has led to notable progress in various fields, such as optical metrology and the exploration of new interactions between light and matter. Despite the emergence of several techniques for generating and detecting structured light beams, including those with OAM, accurately characterizing these beams—especially in terms of their amplitude, wavefront, and mode content—remains a challenging and unresolved issue. The high-power laser system (HPLS) at ELI-NP [1] will be able to produce focused intensities of up to few I0 ∼ 1×1023Wcm−2. Therefore, increase availability and access to such spatially and temporally ultra-intense laser solutions provides an opportunity to produce and inevitable to implement in any experiment optical vortices. In this research, we introduce a method for precisely measuring full aperture phase discontinuities using a Shack-Hartmann wavefront sensor. OV beams were generated by employing spiral phase plates (SPPs), already used in the first user experiments campaign at ELI-NP [2]. The wavefront was characterized by measuring the transmitted or reflected wavefront with the detector positioned in the relay imaging plane across a 70mm aperture, utilizing a flat mirror with a central hole. The experimental setup demonstrated the capability to distinguish between the 16 steps of the helical phase plate, and reconstruct the low order aberrations introduced by the wavefront. The obtained results were combined with measurements from a non-contact optical profilometer, thus offering an alternative to conventional measurement methods. The approach based on the characterized large aperture helical phase plate make possible continuous operation of HPLS to deliver hollow ultra-short laser pulses [2], for ion acceleration experiments [3].
