High-power erbium-doped waveguide amplifier by modal manipulation on thin-film lithium niobate

Abstract

Erbium-doped thin-film lithium niobate waveguide amplifiers have attracted growing interests due to their compatibility with on-chip high-speed electro-optical modulation. Subject to the high coupling and propagation losses the off-chip output powers of such on-chip amplifiers are rather limited, impeding their deployment in telecommunication networks and free-space optical communications. In this work, a high-power erbium doped thin-film lithium niobate waveguide amplifier was fabricated by the photolithography assisted chemo-mechanical etching (PLACE) technique. Optimized modal manipulation of the on-chip light fields enabled the efficient amplification of high-power input signals (>10 dBm), with the maximum on-chip (off-chip) output powers of 19 dBm (16 dBm) observed at the signal wavelength around 1532 nm, corresponding to the on-chip power conversion efficiency as high as 15%. Besides, the small-signal fiber-to-fiber net gains above 15 dB with noise figures of 5 dB, as well as a broad gain bandwidth covering the full telecom C-band were also revealed in the experiment, which showed a flat gain spectrum in the deep saturation regime for high-power input signals.