Scalable harmonic laser source and method

A method for generating, from an array of laser fiber amplifiers, a high power coherent output beam at a desired wavelength in the visible or ultraviolet regions of the spectrum, the method comprising the steps of:

• generating in a master oscillator a pump signal at a fundamental frequency;
• coupling the pump signal to each of element of the array of fiber amplifiers;
• coupling the amplified pump signal from the array of fiber amplifiers into corresponding elements of an array of nonlinear crystals functioning as harmonic generators;
• generating in each element of the array of nonlinear crystals an output signal with a frequency that is a desired harmonic of the fundamental frequency, to provide an array of output sub-beams;
• detecting phase differences in the output sub-beams comprising:
• splitting off a sample of each of the output sub-beams;
• frequency shifting a selected one of the output sub-beam samples;
• and
• interfering each one of the sub-beam samples with the selected frequency-shifted sample in a detector array, to generate a phase difference signal;
• wherein the selected output sub-beam is used as phase reference and the other sub-beams are adjusted to be phase coherent with the selected sub-beam;
• and
• adjusting the phases of the laser amplifier input signals in response to the detected phase differences.