Local phase control for a planar array of fiber laser amplifiers

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Proceedings of SPIE - The International Society for Optical Engineering, ISSN: 1996-756X, Vol: 9616, Page: 1-12

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http://digitalcommons.calpoly.edu/stat_fac/46; https://digitalcommons.calpoly.edu/stat_fac/62; https://digitalcommons.calpoly.edu/stat_fac/47
Edward W. Taylor; David A. Cardimona; Patrick Steffanic; Benjamin T. Johannes; Claudia A. Sison; Gary B. Hughes; Philip Lubin; Peter Meinhold; Jonathan Suen; Hugh O'Neill; Miikka Kangas; Travis Brashears; Qicheng Zhang; Janelle Griswold; Jordan Riley; Caio Motta Show More Hide
SPIE-Intl Soc Optical Eng
Materials Science; Physics and Astronomy; Computer Science; Mathematics; Engineering; Amplifiers; Beam splitters; Beam steering; Connectors; Dichroic prisms; Directed energy weapons; Feedback; Fiber lasers; Lasers; Lenses; DE-STAR; Directed Energy; Laser Phased Array; Planetary Defense; Statistics and Probability
conference paper description
Arrays of phase-locked lasers have been developed for numerous directed-energy applications. Phased-Array designs are capable of producing higher beam intensity than similar sized multi-beam emitters, and also allow beam steering and beam profile manipulation. In phased-Array designs, individual emitter phases must be controllable, based on suitable feedback. Most current control schemes sample individual emitter phases, such as with an array-wide beam splitter, and compare to a master phase reference. Reliance on a global beam splitter limits scalability to larger array sizes due to lack of design modularity. This paper describes a conceptual design and control scheme that relies only on feedback from the array structure itself. A modular and scalable geometry is based on individual hexagonal frames for each emitter; each frame cell consists of a conventional lens mounted in front of the fiber tip. A rigid phase tap structure physically connects two adjacent emitter frame cells. A target sensor is mounted on top of the phase tap, representing the local alignment datum. Optical sensors measure the relative position of the phase tap and target sensor. The tap senses the exit phase of both emitters relative to the target normal plane, providing information to the phase controller for each emitter. As elements are added to the array, relative local position data between adjacent phase taps allows accurate prediction of the relative global position of emitters across the array, providing additional constraints to the phase controllers. The approach is scalable for target distance and number of emitters without loss of control.