KiLoS LASER · Challenging the state-of-the-art of low intensity noise, single frequency fiber lasers

The focus of this project is the development of state-of-the-art kW-class, low noise, single frequency (SF) fiber laser. SF lasers operate with a single longitudinal mode, emitting quasi-monochromatic light with kHz-class linewidth and low intensity noise. This class of lasers are in great demand for precision time/frequency metrology, atom cooling, coherent LIDAR, and laser spectroscopy. However, power scaling SF fiber lasers, while maintaining its low noise properties and high beam quality has been a challenge due to the onset of stimulated Brillouin scattering (SBS) and transverse modal instability (TMI) that disrupt the stable system operation beyond a certain power level (known as threshold). But high-power (> 500 W) low-intensity noise, SF lasers with high beam quality are quintessential for building next generation interferometric gravitational wave detectors (GWDs) and efficient neutral beam injector systems for fusion reactors. The current state-of-the-art for these systems is limited to ~ 400 W in an all-fiber architecture. We intend to challenge it by developing kW-class, low-noise SF fiber laser by using optimized laser design, novel ytterbium-doped fibers (commercial and customized) and efficient techniques to suppress the undesirable nonlinear and thermal effects. Such a system would also be valuable in understanding the dynamics and interplay between SBS and TMI and developing an accurate system model for optimized laser parameters and threshold levels. For this, we seek to combine the expertise of the applicant (Roopa Prakash), in building kW-class, narrow linewidth (~10 GHz), polarization-maintaining fiber lasers with the expertise of Giorgio Santarellis group in developing state-of-the-art low-intensity noise, SF lasers using specialty fibers. The interdisciplinary nature of this project will generate advances beyond the state-of-the-art not only in the fields involved in its development, but also in those where this laser can be applied.