Ultra-broadband tunable GaSb-silicon hybrid laser for gas spectroscopy

Wavelength-tunable laser sources operating in the 2–3 μm spectral range are of significant interest for applications such as gas sensing, remote sensing, and laser spectroscopy. In this work, we demonstrate a chip-scale hybrid laser source with a record 125 nm quasi-continuous tuning range around the 2.4 μm wavelength. This is achieved by integrating a GaSb-based reflective semiconductor optical amplifier (RSOA) with a low-loss silicon photonics circuit incorporating a broadband optical filter. The filter design employs only two cascaded silicon micro-ring resonators, engineered to provide an ultra-wide free spectral range (FSR) that enables precise wavelength control and exceptional spectral purity. By dynamically tuning the micro-ring resonators and the gain chip, quasi mode-hop-free operation can be achieved across the entire bandwidth. The device exhibits a side-mode suppression ratio (SMSR) exceeding 60 dB and delivers 11 mW output optical powers at room temperature. To underscore its practical utility, the laser is deployed in tunable diode laser absorption spectroscopy (TDLAS) for the detection of methane in different absorption lines with picometer wavelength resolution, demonstrating its capability for broadband gas analysis. This work establishes a scalable platform for compact, high-performance short-wave mid-infrared laser systems with applications in environmental monitoring, industrial safety, and medical diagnostics.