Compact Environmentally-Stable Figure-9 Fiber Laser with Large Repetition Rate Tuning Ranges

The figure-9 fiber laser based on nonlinear amplifying loop mirror (NALM) mode-locking is susceptible to the cavity length, resulting in low repetition rates that severely limit its applicability. This paper presents a compact laser design comprising solely polarization-maintaining (PM) fiber and integrated spatial components, yielding a stable and streamlined architecture. The laser achieves a repetition rate of 246 MHz and delivers pulses with a 103 fs duration, the 3 dB spectral bandwidth of 52 nm centered at 1551 nm. By incorporating a fiber actuator within the cavity, we demonstrate a repetition rate tuning range of 16.2 kHz, highlighting the system's exceptional performance.