Photonic lantern based real-time modal instability diagnostic tool for high power fiber lasers

Matthew A. Cooper; Stephanos Yerolastsitis; Alejandro Lopez-Zelaya; Daniel Cruz-Delgado; Joseph Wahlen; Daniel Parra; Jose E. Antonio-Lopez; Axel Schülzgen; Rodrigo Amezcua Correa

doi:10.1117/12.2650999

8 March 2023 Photonic lantern based real-time modal instability diagnostic tool for high power fiber lasers

Matthew A. Cooper, Stephanos Yerolastsitis, Alejandro Lopez-Zelaya, Daniel Cruz-Delgado, Joseph Wahlen, Daniel Parra, Jose E. Antonio-Lopez, Axel Schülzgen, Rodrigo Amezcua Correa

Author Affiliations +

Proceedings Volume 12400, Fiber Lasers XX: Technology and Systems; 124000V (2023) https://doi.org/10.1117/12.2650999
Event: SPIE LASE, 2023, San Francisco, California, United States

Abstract

We demonstrate a fast and versatile approach to analyze the modal content of a high power fiber amplifier using a low-loss photonic lantern. By monitoring the first three modes of the photonic lantern on a photodetector we can directly determine the modal content of a laser beam, enabling real time diagnostics of the output and its corresponding beam quality factor, M². We first investigate the beam quality and modal content of the output of a passive LMA double clad fiber commonly used as a delivery fiber in high power fiber laser amplifiers. The output of the fiber is analyzed by both a 6-mode mode-selective photonic lantern and a conventional M² setup utilizing a translation stage and beam profiler. The modal content and beam quality measurements produced in real-time by the photonic lantern are compared to the M² measurements resulting in an RMS error less than 0.098 across M² values between 1.020 to 2.260. We then conduct a follow on experiment using the same photonic lantern to monitor modal instability in a large mode area fiber laser amplifier. In this case, we compare our photonic lantern mode analysis approach versus the commonly used RIN/pinhole method evaluating modal instabilities. Not only does the photonic lantern estimate the modal content and beam quality in real-time but the modal content trends with the RIN metric as the fiber laser amplifier progresses from stable regime below 300W through the chaotic transverse modal instability regime above 400W.

Conference Presentation

Citation Download Citation

Matthew A. Cooper, Stephanos Yerolastsitis, Alejandro Lopez-Zelaya, Daniel Cruz-Delgado, Joseph Wahlen, Daniel Parra, Jose E. Antonio-Lopez, Axel Schülzgen, and Rodrigo Amezcua Correa "Photonic lantern based real-time modal instability diagnostic tool for high power fiber lasers", Proc. SPIE 12400, Fiber Lasers XX: Technology and Systems, 124000V (8 March 2023); https://doi.org/10.1117/12.2650999

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