A general N-by-N coupling matrix that provides lossless uniform feedback to all laser array elements is demonstrated in the analysis of a passive coherent beam combining resonator. The resonator contains a spatial filter that sends rejected optical power from the combining optic back into the cavity. This recycling of otherwise unused power yields an increase in the average laser output power that scales with array size N, even in the absence of passive phase effects that depend on the gain, intensity, and wavelength of the laser mode. To achieve this improvement, tailored path lengths and mirror reflectivities are required in the feedback arms, where the phase may be fixed, whereas in the gain arms, the path lengths vary randomly.
Bibliographical noteFunding Information:
Manuscript received March 21, 2019; revised June 18, 2019; accepted June 21, 2019. Date of publication June 27, 2019; date of current version July 18, 2019. This work was supported by the U.S. Air Force Office of Scientific Research under Grant FA9550-14-1-0382 P00001. (Corresponding author: W. Minster Kunkel.) The authors are with the Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA (e-mail: email@example.com; firstname.lastname@example.org).
- Coherent beam combining
- optical arrays
- optical fiber lasers
- optical resonators