Influences of Fluorescence Lifetime and Round-Trip Time on Temporal Dynamics of Laser Based on Er:YAG Crystal-Derived Silica Fiber

A homemade Er: YAG crystal-derived silica fiber (ECDSF) was used to construct a distributed Bragg reflector (DBR) fiber laser using 980 nm pumping (τ = 7.38 ms). Self-pulsing phenomena were observed. By heat treatment of the ECDSF at different temperatures, we found that as the heat treatment temperature was increased from 25 °C to 300 °C, the temporal state changed from a sinusoidal state to a pulsed trend. At the same time, the fluorescence lifetime of the ECDSF changed from 7.38- ms to 9.19 ms. On the other hand, as the cavity length increased from 3.5 cm to 100 m, the temporal characteristics of the lasing underwent a transition from pulsed state to a sinusoidal state and eventually to a continuous state. We further noticed that the period of the sinusoidal envelope is roughly equal to the round-trip time of the cavity. the mechanism of temporal dynamics of the laser may be related to the fluorescence lifetime and the round-trip time of the cavity. Furthermore, the theoretical analysis was carried out using the mechanism of passive Q-modulation, and the simulated phenomena were in agreement with the experiments. Finally, a continuous-wave lasing using a 1480 nm pumping source (τ = 6.29 ms) has been obtained at single longitudinal mode operation. It's believed that our experimental endeavors offer valuable insights for regulating the temporal state of the lasing and single-frequency lasers we have implemented can be utilized in laser communication, laser radars, and other potential applications.