Adjustable repetition rate mode-locked fiber laser using a ZnO nanolaminate

•Demonstrates a mode-locked fiber laser with a repetition rate from 2 to 6 MHz.•The pulse repetition rate frequency is controlled by the polarization controller.•This control is achieved by the polarization dependence losses provided by a ZnO nanolaminate.•We show a multiwavelength pulsed laser. This paper experimentally demonstrates the use of a zinc oxide (ZnO) nanolaminate as a polarization-dependent loss element to control the frequency repetition rate in a passive mode-locked fiber laser. The ZnO nanolaminate was deposited via the atomic layer deposition technique. The system achieves repetition frequencies ranging from 2.2 to 6.6 MHz, with emission peaks occurring at wavelengths between 1569.1 nm and 1570.8 nm, exhibiting three to four peaks. The fiber exhibits a minimal pulse duration of around 9.78 ns; the maximal pulse-to-pulse separation was 452 ns. The fiber laser demonstrates excellent stability in both power and wavelength emission. The compact experimental setup leverages the properties of the thin film of zinc oxide, offering a versatile laser system capable of quickly altering pulse repetition rates by simply adjusting the polarization state.