Dual-comb ranging with frequency combs from single cavity free-running laser oscillators.

Laser ranging (LIDAR) with dual optical frequency combs enables high-resolution distance measurements over long ranges with fast update rates. However, the high complexity of stabilized dual optical frequency comb systems makes it challenging to use this technique in industrial applications. To address this issue, here we demonstrate laser ranging directly from the output of both a free-running dual-comb diode-pumped semiconductor and solid-state laser oscillator. Dual-comb operation from a single cavity is achieved via polarization duplexing with intracavity birefringent crystals. We perform ranging experiments with two implementations of this scheme: a modelocked integrated external cavity surface-emitting laser (MIXSEL) and a Yb:CaF solid-state laser. For these proof of principle demonstrations, we measure the distance to a moving mirror mounted on a home-made shaker. The MIXSEL laser has a repetition rate of 2.736 GHz and a repetition rate difference of 52 kHz, and yields a measurement resolution of 1.36 µm. The Yb:CaF laser has a repetition rate of 137 MHz and a repetition rate difference of 952 Hz, and yields a measurement resolution of 0.55 µm. In both cases the resolution is inferred by a parallel measurement with a HeNe interferometer. These results represent the first laser ranging with free-running dual-comb solid-state oscillators. With further optimization, resolution well below 1 µm and range well above 1 km are expected with this technique.