  Narrow linewidth laser(NLL) of high frequency stability and small form factor
is essential to enable applications in long range sensing, quantum information
and atomic clocks. Various high performance NLL have been demonstrated by
Pound-Drever Hall(PDH) lock or self injection lock(SIL) of a seed laser to a
vaccum-stabilized FP cavity of ultrahigh quality factor(Q). However they are
often complicated lab setups due to the sophisticated stabilizing system and
locking electronics. Here we report a compact NLL of 68mL volume, realized by
SIL of a diode laser to a miniature FP cavity of 7.7x108 Q and 0.5mL volume,
bypassing table-size vaccum, thermal and vibration isolation. We characterized
the NLL with a self-delayed heterodyne system, the Lorentzian linewidth reaches
60mHz, and the integrated linewidth is ~80Hz. The frequency noise performance
exceeds that of commercial NLLs and the best reported hybrid-integrated NLL
realized by SIL to high Q on-chip ring resonators. Our work marks a major step
toward a field-deployable NLL of superior performance utilizing ultra-high Q FP
cavity.
