Vortex algebra by multiply cascaded four-wave mixing of femtosecond optical beams

Abstract

Experiments performed with different vortex pump beams show for the first time the algebra of the vortex topological charge cascade, that evolves in the process of nonlinear wave mixing of optical vortex beams in Kerr media due to competition of four-wave mixing with self-and cross-phase modulation. This leads to the coherent generation of complex singular beams within a spectral bandwidth larger than 200nm. Our experimental results are in good agreement with frequency-domain numerical calculations that describe the newly generated spectral satellites.

White light generated by femtosecond optical vortex beams

“…Extensive numerical simulations confirm the physical mechanisms of the processes involved. New results here in addition to these in [26] are: i) The single-beam pumping experiment serving as a proof for the main findings obtained with the two-beam pumping scheme;…”

“…The main results [26] are worth mentioning: If the two pump beams (e.g. at frequencies ω 5 and ω 6 ) carry OVs with opposite unit charges, the generated signals at frequencies ω 4 and ω 7 carry charge-three vortices of different signs which, eventually, decay into three charge-one vortices with highly overlapping cores.…”

“…In this work we report in details on the first [26] successful experimental studies of the generation of SC light by OVs. In two different experimental setups we use short femtosecond pump pulses with embedded singly-and doubly-charged vortex beams.…”

Cascade Raman sideband generation and orbital angular momentum relations for paraxial beam modes

“…In these experiments, topological charge measurements verified a predicted orbital angular momentum algebra (OAM-algebra). This OAM-algebra was later verified in experiments given in [16,17]. In [16] the authors employed two optical parametric amplifiers to produce two spectrally separated beams that were crossed in a Raman active crystal, and in [17] the authors utilized a dichroic beam splitter and spectral filters.…”

“…Recently a number of investigations involving the nonlinear interaction of optical vortices with matter appeared in the literature [15][16][17]. In experiments presented in [15], the authors crossed time-delayed chirped pulses in a lead tungsten PbWO 4 crystal and demonstrated for the first time the coherent transfer of optical angular momentum in the generation of cascaded Raman sidebands.…”