On the mechanism of optical discharge stop in the tapered region of a fibre cladding

Two mechanisms are considered which lead to the recently discovered [E.M. Dianov, I.A. Bufetov, A.A. Frolov Opt. Lett., 29 (16), 476 (2004)] effect of optical discharge stop in the tapered region of a fibre cladding. One of the mechanisms is related to the increase in the plasma temperature in the tapered region due to heat removal weakening, while another is caused by the increase in the displacement of the inner radius of the cladding with decreasing its outer radius. It is shown that the second mechanism is more important.