The dependence of the output of an external-cavity laser on the relative phases of inputs from five gain elements

Five diode lasers that each have one facet antireflection (AR) coated are fiber coupled into an external-cavity and operated as a coherent ensemble. The external-cavity laser output power and spectrum are functions of the relative phases of the inputs from the optical fibers. The phases can be adjusted for an optimum single-mode spectrum simultaneous with maximum output power. In this case, the residual reflections from the AR-coated facets are also properly phased. Dephasing reduces the output power and tunes the wavelength through a series of discrete, lower-power maxima. These maxima occur at wavelengths for which the fiber inputs to the cavity are again in phase but the reflections from the AR-coated facets are not in phase.<>