Passively modelocked, optically pumped semiconductor disk lasers, commonly referred to as VECSELs or MIXSELs, offer a unique combination of wavelength versatility, wafer scalability, high beam quality, and substantial average output power. While V-shaped cavities are typically used for SESAM-modelocked VECSELs, MIXSELs utilize a simplified straight cavity, integrating the saturable absorber into the VECSEL chip. Here, we demonstrate a dual-comb modelocked MIXSEL in the Short-Wave Infrared (SWIR) regime, employing InGaSb quantum well gain and saturable absorber layers. The free-running dual-comb MIXSEL generates distinct microwave comb lines based on a few interferograms, eliminating the need for stabilization. Two distinct repetition rates enable sampling without aliasing while maintaining rapid acquisition times. Moreover, the phase of the heterodyne beat interferograms can be tracked, allowing for the application of coherent averaging algorithms. This breakthrough lays the foundation for dual-comb spectroscopy in the 2-μm regime providing direct access to CO2 spectroscopy.
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