Toward 10-watt-level single-frequency fiber laser oscillators

High-power single-frequency laser oscillators are in great demand for some specific applications, such as quantum information and laser interferometer gravitational-wave observatories, where 10-watt or even 100-watt-level narrow-linewidth lasers with extremely low noise levels are required. In this paper, we present numerical investigations on the power scalability of single-frequency distributed Bragg reflector (DBR) ytterbium-doped phosphate fiber lasers and identify the low-quantum-defect operation approach to 10-watt single-frequency laser oscillators with the best figure of merit, defined by the ratio of the laser efficiency to the quantum defect. This research offers valuable insights for the design and development of high-power single-frequency DBR fiber laser oscillators at many other wavelengths.