Generation of Dark Pulses in Mode‐Locked Erbium‐Doped Fiber Ring Laser Operating in L‐Band Region Using Sc₂O₃ Absorber

ABSTRACT By incorporating scandium oxide (Sc 2 O 3 ) powder into a PVA film, a Sc 2 O 3 saturable absorber (SA) was successfully developed, boasting a modulation depth of 25%. When integrated into a ring erbium‐doped fiber laser, the Sc 2 O 3 ‐SA facilitated the production of mode‐locked dark pulses featuring multi‐wavelength emission, leveraging its saturable absorbing ability along with the nonlinear properties inherent in the Sc 2 O 3 thin film and the long erbium‐doped fiber. Mode‐locking operation was achieved within a pumping range of 209.3–239.8 mW, resulting in a peak pulse energy of 0.71 nJ. Operating at 1597.8 nm, the mode‐locked laser demonstrated a repetition rate of 10.42 MHz and a pulse width of 23 ns. Domain‐wall dark pulse operation was demonstrated in the L‐band region, achieving a relative stability with a signal‐to‐noise ratio of 55.6 dB, utilizing a Sc 2 O 3 thin film absorber and an 8‐meter‐long active fiber. These findings underscore the promising potential of Sc 2 O 3 to be used in pulsed laser systems, particularly due to its exceptional nonlinear optical properties.