  We demonstrated a continuously tunable laser system by butt coupling a
reflective semiconductor optical amplifier (RSOA) chip with a thin-film lithium
niobate (TFLN) based multi-channel interference (MCI) cavity chip. This hybrid
integrated lasers allows for fine-tuning of the laser wavelength from 1538 nm
to 1560 nm with a resolution of 0.014 nm and a side-mode suppression ratio
(SMSR) exceeding 30 dB. The MCI cavity chip is fabricated using the
photolithography assisted chemo-mechanical etching (PLACE) technique. The
developed laser has an output power of approximately 10 {\mu}W, which can be
further amplified to 70 mW using a commercial erbium-doped fiber amplifier
(EDFA) without significant broadening of the laser linewidth.
