We investigate persistent spectral hole burning (SHE) in a 120-nm-thick polymer film doped with chlorin molecules superimposed as a cover layer on a commercial single-mode planar glass waveguide. Transmission spectral holes and time-domain picosecond pulse propagation is studied by excitation via the evanescent part of the guided TEO-mode at liquid-helium temperature. We show that single-mode waveguide with SHE cover layer can act as integrated sub-gigahertz narrow-band filter.