  The additional degree of freedom as introduced by the orbital angular
momentum (OAM) of light has revolutionized the various technological
applications. Optical pulses with OAM have applications in the generation of
twisted attosecond pulses, ultrafast spectroscopy, telecommunication, high
harmonic generation and in many other areas of physics as well. In this paper,
we present a numerical investigation of the propagation dynamics of ultrashort
Laguerre Gauss (LG) vortices using nonlinear envelope equation (NEE) in a
dispersive and nonlinear medium. Asymmetric splitting of ultrashort LG vortices
in time at its bright caustic are observed above a certain pulse power. The
asymmetric splitting owes its origin to spacetime focussing. We also observe
that spatial evolution at pulse center (t=0 in pulse frame) and temporal
evolution at bright caustic of the ultrashort LG vortex are quite similar. In
the spectral domain, oscillatory structures are formed and above a certain peak
power, we observe the generation of new frequency components with more intense
lower frequency components.
