Coherent combination techniques

A second approach to summing the power emitted by several laser sources is optical interference summation. Given the coherence of most laser sources, this is often the only feasible option, since the superposition of highly coherent laser beams from identical lasers (same wavelength and polarization) inevitably leads to the creation of an interference pattern between these beams. The smooth spatial profile of the laser beam, usually Gaussian on emission, then becomes modulated by the light lobes of the interference pattern, where the resulting light intensity is strong, and the dark lobes, where the light intensity cancels out.

Two main geometric configurations are possible for the laser beams in this case (figure 8 ):

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