Widely Tunable (2.47–2.64 µm) Hybrid Laser Based on GaSb/GaInAsSb Quantum-Wells and a Low-Loss Si3N4 Photonic Integrated Circuit

Photonic integrated circuits fabricated using a Si3N4 waveguide platform exhibit low losses in a wide wavelength region extending from visible to beyond 2 µm. This feature is exploited to demonstrate a high-performance integrated laser exhibiting broad wavelength tuneability near a 2.6 µm wavelength region. The laser is based on a Si3N4 photonic integrated circuit incorporating a tunable reflector and a AlGaInAsSb/GaSb quantum-well gain element. A tuning range of 170 nm (2474–2644 nm) and single-mode CW operation with a maximum power of 6.4 mW at room temperature are demonstrated. The performance is enabled by exploitation of several essential building blocks realized in Si3N4, namely low-loss Y-branches, inverse tapers, and a double-ring resonator with a free spectral range of ≈160 nm. Moreover, the limits of wavelength coverage are explored using Si3N4 waveguides and show that the platform supports low propagation loss up to 3.5 µm. Finally, the possibility to achieve improved mode matching between Si3N4 and GaSb waveguides is analyzed, further enabling enhancing the performance of such a hybrid laser platform and supporting wavelength extension beyond a 3 µm range.