Photoelectronic mapping of the spin-orbit interaction of intense light fields

Abstract

The interaction between a quantum particle's spin angular momentum' and its orbital angular momentum(2) is ubiquitous in nature. In optics, the spin-orbit optical phenomenon is closely related with the light-matter interaction(3) and has been of great interest(4,5). With the development of laser technology(6), the high-power and ultrafast light sources now serve as a crucial tool in revealing the behaviour of matter under extreme conditions. A comprehensive knowledge of the spin-orbit interaction for intense light is of utmost importance. Here, we report the in situ modulation and visualization of the optical orbital-to-spin conversion in the strong-field regime. We show that, through manipulating the morphology of femtosecond cylindrical vector vortex pulses(7) by a slit, the photon's orbital angular momentum can be controllably transformed into spin after focusing. By employing a strong-field ionization experiment, the orbital-to-spin conversion can be imaged and measured through the photoelectron momentum distributions. Such detection and consequent control of the spin-orbit dynamics of intense laser fields has implications for controlling photoelectron holography and coherent extreme-ultraviolet radiations(8).