A system of two waveguides coupled laterally through a small window is cons
idered. The asymptotics (in the width of window) of resonance (quasibound s
tate) close to the second threshold is obtained. The cases of two different
and two identical waveguides are considered. The technique is matching the
asymptotic expansions of the solutions. (C) 2000 American Institute of Phy
sics. [S0022-2488(00)03804-4].