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:CaF2 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:CaF2 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.

An unstabilized femtosecond semiconductor laser for dual-comb spectroscopy of acetylene.

Dual-comb systems based on two optical frequency combs of slightly different line spacing emerge as powerful tools in spectroscopy and interferometry. Semiconductor lasers have a high impact in continuous-wave tunable laser spectroscopy. Here we demonstrate the first dual-comb interferometer based on a single femtosecond semiconductor laser: a dual-comb modelocked optically pumped external-cavity surface-emitting laser (MIXSEL) ideally suited for a 1 to 10 GHz comb spacing. At a center wavelength of 1.03 µm (9709 cm-1) we measured acetylene gas transmittance with a resolution of 2.7 GHz in 100 ms with residual errors of less than 3% using thousand comb lines without aliasing effects.

Calibration of high-accuracy spectrometers using stabilized 11-GHz femtosecond semiconductor laser.

We demonstrate for the first time the calibration of the wavelength scale of high-performance spectrometers using a fully stabilized optical frequency comb from an ultrafast optically pumped semiconductor disk laser (SDL) as a traceable reference. The SDL is a modelocked integrated external-cavity surface-emitting laser (MIXSEL) with the gain and saturable absorber layers fully integrated into one wafer chip, which forms one end mirror of the simple straight cavity with a pulse repetition rate of 11 GHz. This MIXSEL comb is actively stabilized and opens new possibilities for easier and more accurate frequency calibrations of standard laboratory instruments.