Abstract

We report recent research which shows that the basic feedback and mutual injection experienced by N individual component lasers which are combined coherently is essentially the same for the spatial filter phaselocking technique as it is for intracavity beam splitter or hologram coupled lasers. First a component laser that is unlocked faces an intracavity round trip optical power attenuation of 1/N² which prevents individual lasing with the common output mirror. Second, the return power from the common output mirror is divided among the N component lasers resulting in uniform injection by the collective amplitude and phase. Third, a single component laser which is 90° out of phase (only marginally better than being completely dead) produces an internal round trip power loss of ~(2/N) which is equivalent to losing two lasers. In addition, the versatile spatial filter can act as a multiport beam splitter having adjustable coupling which ranges from a simple nearest-neighbor overlap to the complete mutual injection of the entire array as obtained by an archetypical beam splitter or a holographic coupler. The variable coupling also affects the round trip losses for the incoherent components which are unnecessarily high in the present unadjustable laboratory systems.

© 1986 Optical Society of America