2017-18 Student of the year: Alex Sincore

2 µm Fiber Lasers: Power scaling concepts and challenges

Fiber lasers have experienced explosive growth in the past decades, with 1 µm Ytterbium- doped lasers holding >13 % of the laser market. Fiber lasers operating at longer wavelengths, specifically 2 µm Thulium-doped lasers, are experiencing a similar growth in system performance. However, the power scaling challenges faced at 1 µm are inherently different at 2 µm. The two major limitations are high thermal loads and nonlinear effects. To address the first issue, we propose in-band pumping which substantially reduces the quantum defect. We have demonstrated >90% efficient 2 µm fiber lasers with plans to scale over 100 W. As for nonlinear effects, there is a lack of data identifying which nonlinearities limit 2 µm fiber lasers. We address this by investigating nonlinear thresholds with a variable spectral bandwidth, nanosecond pulsed fiber laser. We determine that stimulated Brillouin scattering limits narrow linewidth 2 µm sources. On the other hand, modulation instability limits broader linewidth 2 µm sources, which is not found at 1 µm. Overall, with this knowledge and proper system design, Thulium-doped fibers can continue to grow and provide high power systems for emerging applications.

Alex Sincore received the B.S. degree in physics from the University of Florida, Gainesville in 2012. He went on to receive his M.S. degree in optics from CREOL, The College of Optics & Photonics at the University of Central Florida, Orlando in 2014. He is currently a Ph.D. candidate in the optics program at CREOL. Since 2012, he has been a graduate research assistant in the Laser Plasma Laboratory. His primary research interests are in designing and developing high-power and high-energy fiber lasers. Additional research interests include applications in material processing and atmospheric propagation, nonlinear effects in optical fibers, and nonlinear frequency conversion to the mid-infrared.