what is divergence vs. coherent light
Coherent Light. Coherence is a property of light that enables waves to form temporary or stationary interference patterns. Coherence is defined to two waves. If two waves are monochromatic (having the same wavelength) and are of the same phase, these two waves are defined as coherent waves. Sources generating such waves are known as coherent sources.
Divergence is the increase in laser beam diameter with distance from the aperture from which the beam emerges in any plane that intersect the beam axis. What this means is that the diameter of the beam expands over distance at an angle (the divergence in milliradians or mrad ).