A chirp signal source includes first and second lasers formed on a solid-state chip or substrate. Each of the lasers has a resonator or cavity which incorporates or includes electrooptic material which changes refractive index in response to an electric field. The lasers are pumped, and the resulting laser beams are coupled to a light-to-electric converter which combines the light beams to generate an electrical difference frequency. The change in refractive index allows the lasers to be swept or chin,ed at a much higher rate than thermal or piezoelectrically operated lasers. This structure has the advantages of tending to reduce temperature effects on the difference frequency. It has the further advantage of a high sweep rate, which can be used to improve the signal-to-noise ratio. A radar or lidar ranging system according to an aspect of the invention uses multiple solid-state lasers, which are thermally coupled together.