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

Area of Science:

• Photonics and optical physics
• Metamaterials science
• Nanophotonics

Background:

• Optical vortices are crucial in various photonic applications.
• Spatiotemporal optical vortex (STOV) pulses, characterized by space-time phase helicity and donut shapes, are a recent area of interest.
• Controlling STOV pulse properties is essential for advancing optical technologies.

Purpose of the Study:

• To investigate the molding of spatiotemporal optical vortex (STOV) pulses.
• To explore the use of epsilon-near-zero (ENZ) metamaterials for STOV generation.
• To demonstrate high-order STOV generation using cascaded metamaterial structures.

Main Methods:

• Transmission of femtosecond pulses through a thin ENZ metamaterial slab composed of a silver nanorod array in a dielectric host.
• Leveraging the strong optical nonlocality of ENZ metamaterials to induce interference between optical waves.
• Utilizing cascaded metamaterial structures for generating higher-order STOV pulses.

Main Results:

• Successfully molded STOV pulses by controlling phase helicity in space-time coordinates.
• Observed the appearance of phase singularities in transmission spectra due to wave interference within the ENZ metamaterial.
• Demonstrated the feasibility of generating high-order STOV pulses with a cascaded metamaterial design.

Conclusions:

• Epsilon-near-zero (ENZ) metamaterials offer a viable platform for molding spatiotemporal optical vortex (STOV) pulses.
• The interference mechanism within ENZ metamaterials is key to generating phase singularities and STOV characteristics.
• Cascaded metamaterial structures provide a pathway for generating complex, high-order STOV pulses for advanced photonic applications.