Broadband InP-based 2-μm semiconductor optical amplifier enabling hybrid integrated external-cavity lasers

Optoelectronic devices and photonic integrated circuits (PICs) operating in the 2-μm wavelength region are attracting increasing interest for gas sensing, optical communications, and light detection and ranging (LiDAR). Here, we demonstrate a broadband InP-based semiconductor optical amplifier (SOA) as a gain platform for 2 μm photonic systems. The SOA achieves a small-signal gain exceeding 20 dB, a maximum output power of 13 dBm, and a 3-dB gain bandwidth of more than 100 nm. Using this broadband gain material, we further realize hybrid integrated external-cavity lasers by coupling a reflective SOA with a low-loss silicon nitride PIC. The lasers exhibit single-mode wavelength coverage of 82 nm, with an on-chip output power of 5.0 mW and a side-mode suppression ratio of 45 dB.