Direct spatiotemporal manipulation mechanism to generate spatiotemporally coupled ultrafast light fields

Abstract

Manipulation of spatiotemporally coupled (STC) light fields has gathered considerable interest over the last decade. The manipulation is generally performed in spectrum-space domain rather than time-space domain for the Fourier correlated natures of the time and spectrum domains because ultrafast light fields evolve so rapidly that no light modulator can keep pace with them. Spectrum-space manipulation using a 4-f pulse shaper has proved particularly successful, but suffers from limited spectral and pixel resolutions, plus information crosstalk from the spectral modulation in spectrum-space plane. To overcome these flaws, an innovative mechanism is proposed for direct time-space manipulation of an ultrafast light field, which involves introducing a space-dependent time delay and then performing spatial manipulation by a geometrical transformation. As an experimental verification, based on this mechanism, a high-quality STC light spring has been experimentally generated with a topological charge bandwidth as broad as 11.5 and a tunable central topological charge from 2 to − 11. Furthermore, the light spring can propagate with a stable spatiotemporal intensity structure and a basically invariant rotation period from the near field to the far field, which is critically important for its further manipulation and applications. This work provides an efficient way to generate complex spatiotemporal beams such as light springs, which have applications including information encryption, optical communication, and laser-plasma acceleration.