Erbium-doped lithium niobate waveguide amplifier enhanced by an inverse-designed on-chip reflector.

This study presents a 3.6-cm-long erbium-doped lithium niobate waveguide amplifier enhanced by an inverse-designed on-chip reflector. Integrating a reflector to reflect signal light (1531.6 nm) at the waveguide end yielded an internal net gain of 40.5 dB, achieving a 17.3 dB gain improvement compared to a comparable reflector-free amplifier under small signal conditions. These results highlight a novel strategy, to the best of our knowledge, for optimizing integrated optical amplifiers, combining high gain with simplified architecture. The approach holds promise for advancing high-density photonic integrated systems, demonstrating the efficacy of inverse design in tailoring photonic device performance for practical applications.