Coherent combining of fiber arrays using passive phasing

Passive phasing is a promising method for coherently combining high power fiber laser system. In contrast to active phasing where a master oscillator feeds an array of fiber amplifiers and the phase error for each amplifier is measured and corrected by an electro-optic phase modulator; passive phasing corrects phase errors automatically. In a typical passive phasing system, a feedback signal closes the loop and an appropriate filtering mechanism in the feedback loop forces the system to operate at a wavelength that has the highest feedback and consequently minimum phase error. Minimum phase error leads to maximum system Strehl.