Chip-sized diode lasers with ultra-narrow spectral linewidth are of high interest for many applications, e.g. for phase encoding in optical communications and precision metrology [1,2]. Recently, a record-narrow intrinsic linewidth of 290 Hz was achieved with hybrid integration of an InP semiconductor optical amplifier (SOA) and a low-loss dielectric waveguide feedback circuit with a Vernier spectrally selective feedback filter that significantly extends the on-chip cavity length . However, increasing the cavity length also reduces the cavity mode spacing, which causes undesired instabilities in the form of mode hops and power fluctuations when tuning the laser wavelength.
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