ONE-MIX · Mid-infrared optical dual-comb generation and spectroscopy with one unstabilized semiconductor laser

ONE-MIX proposes to develop single-source dual-comb lasers for mid-infrared (2-5 μm wavelength)spectroscopy, potentially enabling many new applications in science and industry, such as environment, safety,pharma, and health. This proposal extends our recent demonstration of a dual-comb MIXSEL (ModelockedIntegrated eXternal-cavity Surface Emitting Lasers) in the near-infrared, validated by measuring weak waterabsorption at 968 nm. Many more relevant gas absorption lines, however, are in the mid-infrared, wheresensitivities of parts-per-billion can be achieved.Dual-comb mid-IR spectroscopy applications are currently limited by the cost, complexity, and size ofconventional optical comb systems, based on two modelocked lasers with four active stabilization loops. Thesingle-source dual-comb MIXSEL, however, substantially reduces the complexity of existing systems to asingle compact free-running laser. In comparison to other competing new approaches such as quantum cascadelasers or micro resonator combs, the MIXSEL provides substantially more power per comb line with lowlinewidth and noise, and is ideally suited for a 1 to 5 GHz comb spacing, which is optimal for many molecularspectroscopy applications, allowing for fast, accurate, and sensitive absorption measurements.This proposal leverages our know-how in MIXSEL design combined with III-V semiconductor epitaxy todemonstrate this new class of lasers in the mid-IR, enabling simpler, lower-cost systems with sufficient speedand sensitivity for many relevant and commercially interesting applications in the 2 to 5 μm spectral region,such as CO2 , CH4, or NOx trace gas detection. We propose to extend the near-IR MIXSELs to the mid-IR bycombining two validated semiconductor approaches – using type-II gain quantum wells combined with a type-I saturable absorber quantum wells, fabricated with existing GaSb (gallium-antimonide) molecular beamepitaxy systems operated out of the FIRST lab at ETH Zurich.