Experimental investigation of twist conservation in nonlinear optical three-wave mixing

We conduct an experimental investigation into the conservation of the twist phase in twisted Gaussian Schell model (TGSM) beams during both up- and down-conversion three-wave-mixing nonlinear processes. Independently generated TGSM beams, prepared with varying twist parameters, are used to pump and seed the nonlinear interactions. The resulting beams are then analyzed to determine their twist properties. Our findings demonstrate that the twists of the up- and down-converted beams depend on those of the pump and seed beams. Additionally, the results indicate that the twist phase is conserved throughout the process, in qualitative agreement with theoretical predictions. This study is motivated by the increasing potential applications of TGSM beams in various fields.