915 nm single-frequency all-PM all-fiber ring laser with kHz-level linewidth

Single-frequency fiber laser is of principal role either in frontier interdisciplinary science or advanced practical applications. Here, we present a 1-kHz-level linewidth 915 nm all-polarization-maintaining Nd³⁺-doped single-frequency all-fiber laser featuring a ring cavity configuration. Particularly, a piece of commercial unpumped Nd³⁺-doped single-cladding silica fiber is employed to achieve a single longitudinal mode operation by forming a dynamic grating. By introducing a fiber amplifier, a 915.24 nm single-frequency all-fiber laser with a linewidth of 1.58 kHz is obtained. To the best of our knowledge, this is the narrowest linewidth, as well as the first ring cavity scheme reported in a Nd³⁺-doped single-frequency all-fiber laser at the 900 nm band. This work provides significant potential for the future development of high-performance lasers utilizing the ⁴F_3/2-⁴I_9/2 transition of neodymium ions.