Molecular Wave Plate for the Control of Ultrashort Pulses Carrying Orbital Angular Momentum

Ultrashort laser pulses carrying orbital angular momentum (OAM) have become essential tools in atomic, molecular, and optical studies, particularly for investigating strong-field light-matter interactions. However, controlling and generating ultrashort vortex pulses presents significant challenges, since their broad spectral content complicates manipulation with conventional optical elements, while the high peak power inherent in short-duration pulses risks damaging optical components. To address these challenges, we demonstrate a "molecular wave plate" as a promising way for generating and controlling broadband ultrashort vortex beams. By exploiting the nonadiabatic alignment of linear gas-phase molecules induced by vector beams, the interaction between the vector beam and the gas-phase molecules results in spatially varying polarizability, imparting a phase modulation to a probe laser. This process effectively creates a tunable molecular wave plate that adapts naturally to a broad spectral range. By leveraging this approach, we can generate ultrashort vortex pulses across a wide range of wavelengths. Under optimized gas pressure and interaction length conditions, this method allows for highly efficient, near unity, conversion of circularly polarized light into the desired OAM pulse, thus enabling the generation of few-cycle, high-intensity vortex beams. This molecular wave plate, which overcomes the limitations imposed by conventional optical elements, opens up new possibilities for exploring strong-field physics, ultrafast science, and other applications that require high-intensity vortex beams.