  Frequency combs, broadband light sources whose spectra consist of coherent,
discrete modes, have become essential in many fields. Miniaturizing frequency
combs would be a significant advance in these fields, enabling the deployment
of frequency-comb based devices for diverse measurement and spectroscopy
applications. We demonstrate diode-laser based frequency comb generators. These
laser diodes are simple, electrically pumped, inexpensive and readily
manufactured. Each chip contains several dozen diode-laser combs. We measure
the time-domain output of a diode frequency comb to reveal the underlying
frequency dynamics responsible for the comb spectrum, conduct dual comb
spectroscopy of a molecular gas with two devices on the same chip, and
demonstrate that these combs can be battery powered.
