Copper Aluminum Oxide for enabling Q-switching and mode-locking in erbium-doped fiber lasers

This study experimentally demonstrates Copper Aluminum Oxide (CuAlO₂) as a saturable absorber (SA) for both Q-switched and ultrafast mode-locked pulse generation in an erbium-doped fiber laser (EDFL) cavity. The SA was fabricated by embedding the conductive oxide in a polymer matrix to form a composite film, which was then integrated into two distinct pulse-generation setups. In the Q-switched configuration, stable operation was achieved by modulating the cavity's loss and gain, with pump powers ranging from 132.15 mW to 210.62 mW. The repetition rate increased from 66.09 kHz to 84.96 kHz, while the pulse width decreased from 6.31 μs to 5.03 μs. The laser operated at a central wavelength of 1563.3 nm, delivering a maximum pulse energy of 43.55 nJ and a slope efficiency of 1.95 %. For mode-locking, the inclusion of a 100 m fiber spool in the cavity enabled self-starting mode-locked operation, sustained over a pump power range of 141.38 mW to 233.7 mW. At 141.38 mW, the mode-locked EDFL produced pulses centered at 1560 nm, with a repetition rate of 1.792 MHz and a pulse duration of 3.17 ps. These findings validate the suitability of CuAlO₂ for use as a pulse transducer in fiber laser applications.