Hybrid-Integrated Full S-Band Tunable External Cavity Laser With a Trident-Tapered Coupler

We demonstrate a hybrid-integrated external-cavity laser (ECL) based on an ultra-low-loss Si3N4platform for the full S-band (1460–1530 nm) operation. A trident-shaped spot-size converter relaxes the horizontal alignment tolerance. Compared with a conventional inverse taper, it improves the coupling efficiency by 1.59 dB at a 2 μm lateral offset. The laser delivers a continuous 116.02-nm tuning range (1429.26–1545.28 nm), fully covering the S-band, a maximum fiber-coupled output power of 13.54 dBm, a peak side-mode suppression ratio of 68.74 dB, a minimum intrinsic linewidth of 503 Hz, and relative intensity noise (RIN) values ranging from −170.98 to −151.97 dBc/Hz across the measured wavelengths throughout the tuning range. These results support the potential of the laser for broadband S-band and multi-band wavelength division multiplexing (WDM) systems.