Generation of mode-locked pulses assisted by reduced graphene oxide/cerium oxide (rGO/CeO₂) embedded in arc-shaped fiber

Abstract This study demonstrates the synthesis of a reduced graphene oxide/cerium oxide (rGO/CeO 2 ) composite and its successful use as a saturable absorber (SA) in ultrafast photonics. The rGO/CeO 2 composite was synthesized using a facile hydrothermal approach, and an arc-shaped fiber was fabricated using a polishing technique. The arc-shaped fiber employed indirect evanescent field coupling, allowing interaction between the composite material and the laser, and facilitating the generation of mode-locked pulses. An arc-shaped fiber drop-casted with rGO/CeO 2 was connected to a 2.0 μm laser source, achieving a modulation depth of 50.16%. The emitted laser pulses have a duration of 1.428 ps, an operational wavelength of 1904 nm, and a spectral bandwidth of 2.76 nm. The pulse energy was 1.92 nJ with a high signal-to-noise ratio (SNR) of 50 dB. This study introduces rGO/CeO 2 embedded in an arc-shaped fiber as an effective SA, exhibiting favorable nonlinear optical absorption in the near 2.0 μm wavelength region, making it suitable for applications in ultrafast photonics.