| Popis: |
In this work we demonstrate, for the first time, the second harmonic generation (SHG) of a spatiotemporal optical vortex (STOVs) and its orbital angular momentum conservation. We use transient-grating single-shot supercontinuum spectral interferometry (TG-SSSI, [1] , [2] ) to measure the spatiotemporal phase and amplitude of the fundamental and SHG STOVs. A STOV [1] , [3] is an electromagnetic structure with orbital angular momentum (OAM) and optical phase circulation defined in space-time and is supported by a polychromatic pulse. In a STOV, the OAM vector is perpendicular to the direction of propagation, in contrast to a conventional space-defined optical vortex, which can be supported by a monochromatic beam, and where the OAM vector is parallel/anti-parallel to the direction of propagation. In second harmonic generation ( ω → 2 ω ) of conventional OAM beams, the second harmonic photons carry twice the OAM of fundamental beam photons ( lħ → 2 lħ ), where l is the OAM beam topological charge [4] . |
