Goos–Hänchen shift of a mid-infrared femtosecond filament visualized by the laser coloration method

We present the results of investigation of total internal reflection of a femtosecond light filament in a LiF crystal in the regime of anomalous group velocity dispersion. We measure the Goos–Hänchen shift of the filament in the vicinity of the critical angle for a single femtosecond pulse using the laser coloration method. The obtained experimental values are compared to several existing theoretical models. (letter)