Single-Mode Laser Diode Pumped Yb:CaF2 Dual-Comb Oscillator

Dual optical frequency combs offer excellent performance in delay-swept laser measurements such as high precision spectroscopy, optical ranging and equivalent time sampling. Approaches where both combs are generated in a single oscillator make it possible to avoid the complexity of two fully stabilized but physically separate frequency comb sources [1] . One way to achieve a single-cavity dual-comb operation is by using a birefringent crystal inside the cavity, where it introduces a round-trip delay difference between the two polarization states of the cavity, while also separating them spatially on the active intra-cavity elements. We first demonstrated this technique with a semiconductor disk laser [2] , and more recently with a Yb:CaF 2 femtosecond solid-state laser pumped by a spatially multimode laser diode [3] . Here, by using a single-spatial-mode laser diode for pumping, we demonstrate a femtosecond dual-comb with a further reduced complexity as compared to [3] . This configuration offers a compact and low-noise solution to dual-comb generation.