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External cavity beam combining of 21 semiconductor lasers using SPGD
Juan Montoya1, Steven J Augst, Kevin Creedon
1MIT Lincoln Laboratory, Lexington, Massachusetts 01810, USA. juan.montoya@ll.mit.edu
Applied Optics
|April 17, 2012
Summary
Active coherent beam combining achieved 81% efficiency using 21 semiconductor lasers and a stochastic parallel gradient descent algorithm. This method overcomes scaling limits of passive systems for high-power, diffraction-limited beams.
Area of Science:
- Optics and Photonics
- Laser Physics
Background:
- High output power from lasers is crucial for various applications.
- Achieving a diffraction-limited beam is essential for beam quality.
- Coherent beam combining offers a path to high power, but faces challenges.
Purpose of the Study:
- To demonstrate an active coherent beam combining system for semiconductor laser elements.
- To evaluate the efficiency and scalability of the active beam combining approach.
- To compare the active system with passive-phasing limitations.
Main Methods:
- Utilized an active beam combining system with an external cavity configuration.
- Employed 21 semiconductor laser elements for coherent combination.
- Implemented a stochastic parallel gradient descent (SPGD) algorithm for active phase control.
Main Results:
- Achieved 81% beam combining efficiency.
- Demonstrated active beam combining in an external cavity setup.
- Showcased that active beam combining is not subject to scaling limits of passive systems.
Conclusions:
- Active coherent beam combining is a viable method for achieving high output power.
- The SPGD algorithm effectively manages phase control for laser elements.
- This approach offers advantages over passive-phasing systems for scalability.
