Very narrow, with the width smaller than a wavelength, solitons in (1 + 1)-
dimensional and (2 + 1)dimensional versions of cubic-quintic and full satur
able models are studied, starting with the full system of the Maxwell's equ
ations rather than the paraxial (nonlinear Schrodinger) approximation. For
the solitons with both TE and TM polarizations it is shown that there alway
s exists a finite minimum width, and the solitons cease to exist at a criti
cal value of the propagation constant, at which their width diverges. Full
similarity of the results obtained for both nonlinearities suggests that th
e same general conclusions apply to narrow solitons in any non-Kerr model.
(C) 2001 Optical Society of America.