GaSb–TFLN Hybrid Integrated Pockels Laser for Ultrafast Spectroscopy in the 2 μm Waveband

Abstract High-speed wavelength-tunable lasers in the 2 μm waveband are important for laser spectroscopy, optical communication, and frequency-modulated continuous-wave LiDAR. Here, we demonstrate a hybrid integrated Pockels laser that combines a GaSb reflective semiconductor optical amplifier with a thin-film lithium niobate (TFLN) photonic external cavity incorporating a distributed Bragg reflector (DBR). The low-coupling-coefficient DBR provides narrowband optical feedback and increases the photon lifetime, enabling narrow-line width lasing near 1.95 μm. At room temperature, the laser delivers an on-chip output power of 6.5 mW, a side-mode suppression ratio of 39 dB, and an intrinsic line width of 31.6 kHz estimated from the white frequency-noise floor. Benefiting from the Pockels effect in TFLN, the device achieves fast and linear electro-optic wavelength tuning, with a mode-hop-free tuning range of 3.4 GHz, a tuning rate of 2.8 × 1015 Hz/s, and a tuning nonlinearity of 1.6%. We further apply the laser to tunable diode laser absorption spectroscopy and demonstrate MHz-rate scanning of a CO2 absorption line. The measured spectrum agrees well with HITRAN-based simulation, highlighting the potential of this platform for ultrafast spectroscopy and integrated tunable laser systems in the 2 μm waveband.