An optoelectronic device includes a first reflector and a second reflector, which define an optical path on a substrate. A gain medium is disposed on the optical path between the first and second reflectors and configured to amplify laser radiation within a given gain band. A comb filter is disposed on the optical path between the first and second reflectors and configured to pass a set of distinct wavelength sub-bands within the gain band, the set of distinct wavelength sub-bands defining a comb. A bandpass filter is disposed on the optical path between the first and second reflectors in series with the comb filter. The bandpass filter has a passband encompassing a subset of the wavelength sub-bands in the comb.