Tuning Dynamics of the Acousto-Optical Tunable SOA Fiber Laser

Acoustically-induced fiber gratings (AIFGs) can be employed as the main device to achieve wide-range, time-linear, and fast wavelength tunability of various lasers, due to their fast spectral response during the high-speed tuning process. Herein, we propose a wideband fast-tunable fiber laser that consists of a semiconductor optical amplifier (SOA) and an AIFG that induces the acousto-optical polarization conversion effect. Its laser dynamics during the tuning process are revealed. The rate equation of the inversion population is used to theoretically predict the laser intensity evolution during the dynamical tuning process. The simulation results show that the relaxation oscillation and huge laser pulse during the tuning process can be suppressed by shortening the upper energy-level lifetime of the gain medium. In order to experimentally reveal the tuning dynamics, the output intensity evolution of the tunable laser is monitored. The lasing tuning response time reaches ∼200 μs, whose value has approached that of the AIFG. Due to the short energy-level lifetime of the SOA, the laser relaxation oscillation during the dynamical tuning process can be successfully suppressed, which coincides well with the simulation prediction. This work creates an avenue to understand the acousto-optical tuning dynamics profoundly. It also provides guides to maximize the speed advantage of this tuning mechanism in various tunable laser cavities.