| Summary: | Light that can carry orbital angular momentum (OAM) has found a variety of applications in super-resolution microscopy, optical communications, and laser machining, bringing up the need for pure OAM light generation at on-demand power levels and wavelengths. Parametric four-wave mixing is a promising platform for such source generation, and while investigations of higher-order fiber modes have revealed enhanced phase-matching possibilities, the role of the angular momentum of light in this process has not yet been substantially considered. Here, with a specially designed ring-core fiber in which over 16 OAM modes can be stably guided, we demonstrate the first experiments, to our knowledge, investigating nonlinear four wave mixing between OAM modes in an optical fiber. The large modal space as well as spin and OAM conservation rules enable a high diversity of phase matching conditions while also providing high selectivity. We report parametric wavelength translations of over 438 nm and the ability to obtain kilowatt peak-power level ∼ nanosecond pulses of pure OAM beams at user defined colors.
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