Analyzing the coupling coefficients between emitters of a diode laser array phase locked in an external cavity

Expressions describing couplings between different emitters of a diode laser array (DLA), positioned in an external cavity (EC), have been deduced. The results show that: the increase of the EC length reduce the differences between these coupling coefficients, which is favorable to achieve the so called “parallel coupling” at the expense of the effectiveness of the EC; decreasing the reflection coefficient at the front facet of the DLA is favorable to achieve phase locking in EC; the more parallelly coupled the emitters are, the lower the allowed reflection coefficient at the front facet of the DLA is.