Dynamic mode evolution and phase transition of twisted light in nonlinear process

TL;DR

This paper investigates how orbital angular momentum (OAM) light evolves during sum frequency generation in nonlinear optics, revealing phase transfer and mode transformations useful for OAM mode control.

Contribution

It provides new insights into the phase transfer and mode evolution of OAM light in nonlinear processes, including the behavior of superposition modes and opposite OAM interactions.

Findings

Non-diffractive spatial patterns observed in superposition modes.

Opposite OAM pump beams evolve into quasi-Gaussian modes.

Pump phases are coherently transferred to the SFG beam.

Abstract

We report on studying the dynamic evolution of orbital angular momentum (OAM) carrying light in sum frequency generation (SFG). Dynamic evolution of the SFG beam is studied in different cases, in which the two pump beams are either a single OAM mode or OAM superposition mode. For the cases when the two pumps are both in superposition mode, two kinds of spatial patterns and evolution behaviors are observed, one set of spatial pattern is non-diffractive and unchanged with propagating. In addition, SFG of two pump beams with opposite OAM will evolve into a kind of quasi-Gaussian mode. These observations show that the pumps phases are coherently transferred to SFG beam in the conversion process. Our findings give insights to physical picture of OAM light transformation in nonlinear processes, which can be used in OAM mode engineering and de-multiplexing of different OAM modes.