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Integrated silicon photonics has sparked a significant ramp-up of investment in both academia and industry as a
scalable, power-efficient, and eco-friendly solution. At the heart of this platform is the light source, which in itself, has
been the focus of research and development extensively. This paper sheds light and conveys our perspective on the
current state-of-the-art in different aspects of application-driven on-chip silicon lasers. We tackle this from two perspectives:

Lasers with hertz linewidths at time scales of seconds are critical for metrology, timekeeping, and manipulation of
quantum systems. Such frequency stability relies on bulk-optic lasers and reference cavities, where increased size
is leveraged to reduce noise but with the trade-off of cost, hand assembly, and limited applications. Alternatively,
planar waveguide–based lasers enjoy complementary metal-oxide semiconductor scalability yet are fundamentally