Nonlinear orbital angular momentum conversion with spatial-amplitude independence

Abstract

Nonlinear optics with structured light can provide a host of important functions for shaping spatail and temproal structure of light, and the most common used one is frequency conversion. In this work, we propose and demonstrate a novel nonlinear toolkit capable of tuning frequency and orbital angular momentum (OAM) of signal beams simultanously, more importantly, it does not change the spatial ampulitude structure of signal. This unique frequency interface is enabled by using a special structured pump called vortex super-Gaussian beam that has a flattop amplitude distribution and tunable vortex wavefront. This technique provides a dual interface of frequency and OAM, and may inspire many potential applications involving OAM beams.

Digital generation of super-Gaussian perfect vortex beams via wavefront shaping with globally adaptive feedback

“…It is noticed that the conventional Gaussian model-defined target intensity should be further optimized when trying to excite a flat-top PVB. To address this problem, a super-Gaussian apodization is employed for the flat-top PVB generation as defined in the following equations [47] :…”