A flow device intended for a two-phase flow processing enclosure of the natural counter-flow type, in which an ascending gaseous flow and a descending liquid flow circulate. The support member is movable between an accommodated position within the main casing and a pulled-out position outside the main casing, the support member being formed with cartridge accommodating sections. Each one-turn portion of the first helical part has a peripheral length of M times a wavelength \u03bb of use, where M is a positive natural number. A large portion of the lightwave signal propagated between the first optical propagation means and the second optical propagation means is allowed to pass through the optical branching means, however, a portion of the lightwave signal is reflected in a given direction by the optical branching means. 6 nm, and a gate electrode layer on the gate insulating layer, and the gate electrode layer is composed of polycrystalline silicon which has an average grain size falling within a range between 10 nm and 150 nm in the vicinity of the gate insulating layer.