Transversely pumped dye-doped slab waveguides are investigated. II set of c
oupled-rate equations for the excited-state population and for the amplifie
d spontaneous emission (ASE) power, at all wavelengths, is presented. The e
quations are solved numerically for the steady-state case. The results desc
ribe the dependence of ASE output power on pumping power, the spectral narr
owing process, and the effect of waveguiding, The theoretical calculations
are compared with the results of experiments, and good agreement is found.