Coordination engineering in Nd3+-doped silica glass for improving repetition rate of 920-nm ultrashort-pulse fiber laser
Yafei Wang, Yinggang Chen, Shikai Wang, Meng Wang, Lei Zhang, Suya Feng, Fei Yu, Guoping Dong, Lei Wen, Danping Chen, Chunlei Yu, Lili Hu
Abstract
Ultrashort pulses at 920 nm are a highly desired light source in two-photon microscopy for the efficient excitation of green fluorescence protein. Although Nd3 + -doped fibers have been utilized for 920-nm ultrashort pulse generation, the competitive amplified spontaneous emission (ASE) at 1.06 μm remains a significant challenge in improving their performance. Here, we demonstrate a coordination engineering strategy to tailor the properties of Nd3 + -doped silica glass and fiber. By elevating the covalency between Nd3 + and bonded anions via sulfur incorporation, the fiber gain performance at 920 nm is enhanced, and 1.06-μm ASE intensity is suppressed simultaneously. As a result, the continuous-wave laser efficiencies and signal-to-noise ratio at 920 nm by this fiber are significantly enhanced. Importantly, the stable picosecond pulses at 920 nm are produced by a passive mode-locking technique with a fundamental repetition rate up to 207 MHz, which, to the best of our knowledge, is the highest reported repetition rate realized by Nd3 + -doped silica fibers. The presented strategy enriches the capacity of Nd3 + -doped silica fiber in generating 920-nm ultrashort pulses for application in biophotonics, and it also provides a promising way to tune the properties of rare-earth ion-doped silica glasses and fibers toward ultrafast lasers.