Nonlocality-mediated spatiotemporal optical vortex generation in nanorod-based epsilon-near-zero metamaterials

Optical vortices have myriad applications in photonics. Very recently, promising concepts of spatiotemporal opti-cal vortex (STOV) pulses based on the phase helicity in the space-time coordinates have attracted much attention owing to their donut shape. We elaborate on the molding of STOV under the transmission of femtosecond pulses through a thin epsilon-near-zero (ENZ) metamaterial slab based on a silver nanorod array in a dielectric host. At the heart of the proposed approach is the interference of the so-called main and additional optical waves enabled by strong optical nonlocality of these ENZ metamaterials, which leads to the appearance of phase singularities in transmission spectra. The cascaded metamaterial structure is proposed for high -order STOV generation.(c) 2023 Optica Publishing Group

Automated summary

Optical vortices with donut shapes, known as spatiotemporal optical vortices (STOV) pulses, have attracted much attention in photonics due to their promising applications. In this study, STOV pulses were generated by transmitting femtosecond pulses through a thin epsilon-near-zero (ENZ) metamaterial slab containing a silver nanorod array. The interference of main and additional optical waves in these ENZ metamaterials, enabled by their strong optical nonlocality, led to the appearance of phase singularities in the transmission spectra. A cascaded metamaterial structure was proposed for high-order STOV generation.