Space-time non-separable dynamics of ultrashort vortex pulse with power exponential spectrum

Abstract: Ultrashort optical pulses with orbital angular momentum (OAM) owing to their applications in classical as well as quantum domains attract a lot of research attention. The evolution of their spatio-temporal dynamics is of particular interest. In the present work, the spatio-temporal evolution of ultrashort Laguerre Gauss (LG) vortex with power exponential spectrum, also called power exponential (PE) pulse is numerically explored, in dispersive and nonlinear media. The evolution of space-time non-separable ultrashort vortex pulse is specifically addressed. The study reveals the asymmetric spatio-temporal evolution and splitting in the spatio-temporal plane. Compression at the trailing edge of the pulse is observed with increase in the strength of the nonlinearity. The study further reveals that the temporal, spectral, and chirp evolution patterns of the pulse vary uniquely across different spatial regions and these variations depend upon the strength of nonlinearity and propagation distance. In weak nonlinear regime, a redshift in the spectrum is observed as one moves radially outward from the bright caustic of the ultrashort LG vortex, while a blueshifted spectrum emerges as one approaches the phase singularity. Interestingly, as the pulse furthers in the medium, nonlinearity induced spectral shift is witnessed and with stronger nonlinearity, a complex spectral evolution is observed.