Frequency stabilisation of a diode laser by a whispering-gallery mode

A model for stabilisation of a laser frequency is considered which takes into account the spectral splitting of the mode and the dependence of its Q factor on coupling with the laser. It is shown that the stabilisation regime is optimal when the coupling coefficient with a whispering-gallery mode is greater than the critical coefficient at which the mode is split. The presence of the amplitude – phase correlation in the active region of the laser determines the maximum value of the stabilisation parameter caused by the dynamic restriction of the feedback level. The single-mode lasing disappears in the case of a strong feedback. It is shown that the appropriate choice of the feedback-phase level suppresses the dynamic instability, which provides in principle a strong feedback with a high-Q external resonator.