Direct measuring of single-cycle mid-IR light bullets path length in LiF by the laser coloration methodSergey Chekalin, Victor Kompanets, Andrey Kuznetsov, Alexander Dormidonov and Valerii KandidovEPJ Web Conf., 161 (2017) 02011DOI: https://doi.org/10.1051/epjconf/201716102011