Temporal dynamics of light-written waveguides in unbiased liquid crystals

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