  Thin-film lithium niobate (TFLN) has emerged as a promising platform for the
realization of high performance chip-scale optical systems, spanning a range of
applications from optical communications to microwave photonics. Such
applications rely on the integration of multiple components onto a single
platform. However, while many of these components have already been
demonstrated on the TFLN platform, to date, a major bottleneck of the platform
is the existence of a tunable, high-power, and narrow-linewidth on-chip laser.
Here, we address this problem using photonic wire bonding to integrate optical
amplifiers with a thin-film lithium niobate feedback circuit, and demonstrate
an extended cavity diode laser yielding high on-chip power of 78 mW, side mode
suppression larger than 60 dB and wide wavelength tunability over 43 nm. The
laser frequency stability over short timescales shows an ultra-narrow intrinsic
linewidth of 550 Hz. Long-term recordings indicate a high passive stability of
the photonic wire bonded laser with 58 hours of mode-hop-free operation, with a
trend in the frequency drift of only 4.4 MHz/h. This work verifies photonic
wire bonding as a viable integration solution for high performance on-chip
lasers, opening the path to system level upscaling and Watt-level output
powers.
