  The control of light by light is one of the main aims in modern photonics. In
this context, a fundamental cornerstone is the realization of light-written
waveguides in real time, resulting in all-optical reconfigurability of
communication networks. Light-written waveguides are often associated with
spatial solitons, that is, non-diffracting waves due to a nonlinear
self-focusing effect in the harmonic regime. From an applicative point of view,
it is important to establish the temporal dynamics for the formation of such
light-written guides. Here we investigate theoretically the temporal dynamics
in nematic liquid crystals, a material where spatial solitons can be induced
using continuous wave (CW) lasers with few milliWatts power. We fully address
the role of the spatial walk-off and the longitudinal nonlocality in the
waveguide formation. We show that, for powers large enough to induce light
self-steering, the beam undergoes several fluctuations before reaching the
stationary regime, in turn leading to a much longer formation time for the
light-written waveguide.
