Generation of Dark Pulses in Mode‐Locked Erbium‐Doped Fiber Ring Laser Operating in L‐Band Region Using Sc<sub>2</sub>O<sub>3</sub> Absorber

ABSTRACTBy incorporating scandium oxide (Sc2O3) powder into a PVA film, a Sc2O3 saturable absorber (SA) was successfully developed, boasting a modulation depth of 25%. When integrated into a ring erbium‐doped fiber laser, the Sc2O3‐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 Sc2O3 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 Sc2O3 thin film absorber and an 8‐meter‐long active fiber. These findings underscore the promising potential of Sc2O3 to be used in pulsed laser systems, particularly due to its exceptional nonlinear optical properties.

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