Multicore fibre laser phase locking by an external mirror

A theory of phase locking of radiation emitted by individual fibres of a multicore fibre laser with the help of an external mirror is developed. The Talbot effect in radiation from an annular set of emitters is described analytically. The theoretical results are compared with the results of experiments and numerical calculations. The method of collective mode selection in the multicore set with the help of a spherical mirror producing a nearly concentric cavity is analysed.