Evolution from Periodic Oscillation to Chaos in Q-switched Vortex Lasers of a Unit Topological Charge

Recently direct vortex lasing from azimuthal symmetry breaking resonator were demonstrated both in continuous wave [1] and in Q-switched [2] operations. Regarding to the investigation of laser dynamics we rebuild the Q-switched vortex laser system following the same configuration reported in REF [2]. Produced Q-switched laser emits annular intensity pattern and its positive unit topological charage is quantified by spiral phase pattern sensed using a interferometer. Clear transition from periodic oscillation of every 2 pulses, 4 pulses and 6 pulses to completely disorders in pulse sequences can be identified in delay maps using the pulse-to-pulse duration as an observable. This spatial-temporal dynamic can be explained by Tang-Statz-DeMars model that describes the coherent coupling and nonlinear interactions of the off-axis multiple pass resonance modes. Moreover pumping a KTP crystal by this Q-switched vortex laser at the wavelength of 1064 nm, second harmonic wave at 532 nm exhibits unconventional intensity distribution other than a vortex with doubling topological charges because of the interactions among the resonating off-axis modes in fundamental wave.
[1] Yuan-Yao Lin, et al., J. Opt 20 075203 (2018).
[2] Yuan-Yao Lin, et al., J. Opt. 21, 085201 (2019).