Passive stability of the laser emission near 608 THz. (a) Laser frequency near 608 THz with the initial frequency set to zero. The measured laser drift over \(\approx 10^4\) s is of order the systematic frequency uncertainty of the wavemeter. (b) Allan deviation calculated for the data set (a) treating the wavemeter as a stable reference. The self-injection locked WGM laser is stable over short and long timescales.