Orbital angular momentum mode detection of the combined vortex beam generated by coherent combining technology

Coherent beam combining (CBC) technology has distinct advantages in generating high power vortex beam. In this paper, a circularly arranged coherent beam array (CBA) with discrete vortex phases is constructed to generate vortex beams. We demonstrated that the combined vortex beam (CVB) generated by the CBA is a multiplexing vortices optical field, which sidelobe is the coaxial interference pattern of these spiral harmonic components. Using the designed Dammam vortex grating (DVG), the orbital angular momentum (OAM) spectrum of the CVB is detected. Moreover, taking the target OAM mode purity of the CVB as the evaluation function of active phase control system, we realized the closed-loop phase control of the CBA and obtained the phase-locked output of the CVB.