Wavelength-adaptable effective q-plates with passively tunable retardance

Abstract

Wave retarders having spatially varying optical axes orientations, called q-plates are extremely efficient devices for converting spin to orbital angular momentum of light and for the generation of optical vortices. Most often, these plates are designed for a specific wavelength and have a homogeneous constant retardance. The present work provides a polarimetric approach for overcoming both these limitations. We theoretically propose and experimentally demonstrate q-plates with tunable retardance, employing a combination of only standard q-plates and waveplates. A clear prescription is provided for realizing wavelength indepedent q-plates for a desired retardance, with a potential for ultrafast switching. Apart from the potential commercial value of the proposed devices, our results may find applications in quantum communication protocols, astronomical coronography, angular momentum sorting and in schemes that leverage optical vortices and spin to orbital angular momentum conversion.

Taming the swirl of self-structured liquid crystal q-plates

“…Starting from the fact that the occurrence of the swirled UQPs cannot the avoided (figure 1) we propose a compensation scheme to get rid of it owing to the arithmetic of geometric phase optical elements. Latter has already received attention in the context of generating phase singularities with topological charges that differs from q 2 [27,28] or passive tuning the retardance of q-plates [29]. In all cases, an effective behavior is obtained by an appropriate combination of q-plates and homogeneous optical retarders.…”

Vortex plate retarder-based approach for the generation of sub-20 fs light pulses carrying orbital angular momentum

“…On the other hand, generating ultrashort vortices presents challenges, given that most techniques designed for monochromatic vortices encounter limitations when applied to broadband light sources [21][22][23]. Despite the proposal and application of polychromatic methods for ultrashort pulse vortex generation [24][25][26][27][28], these approaches are intricate to implement, retaining the attractiveness of monochromatic techniques but limiting their application to continuous wave beams or long pulses where the variation in pulse temporal duration is less critical. Notably, achieving optimal performance from phase-modulation components, such as spatial light modulators [29], for ultrafast optical vortex generation necessitates complex calibration procedures and is impeded by the low conversion efficiency and low damage threshold of these elements.…”