Complementary-Tuning-Enabled Hybrid III-V/Si₃N₄ Dual External Cavity Laser Combines Wide Tunability and Frequency Agility

Integrated external cavity lasers (ECLs) are emerging as a promising chip-scale implementation of tunable lasers, promoting system miniaturization and functionality expansion with the booming of silicon photonics. In spite of the extensive exploration and great progresses on ECLs, challenge remains in the combination of wide tunability and frequency agility. Here we address this problem by proposing a hybrid III-V/Si₃N₄dual external cavity laser (DECL) with complementary tuning. The hybrid DECL consists of two Si₃N₄-based external cavities butt-coupled with a semiconductor optical amplifier at each side. On the two external cavities, complementary high-efficiency thermal-optic tuning and fast photoelastic tuning are employed, respectively. The experimentally demonstrated hybrid DECL leverages a combination of a tuning range of 27.4 nm in the C-band, a linear frequency modulation at a speed of 200 kHz, a wavelength-switching time below 900 ns, and an ultra-low intrinsic linewidth down to 33.1 Hz. With the unification of wide tunability, frequency agility and ultra-low linewidth, this hybrid DECL holds promise for many applications in telecommunications, interconnects and light detection and ranging.