Switchable Dual-Wavelength Q-Switched Erbium-Doped Fibre Laser using Spider Silk as a Biocompatible and Eco-Friendly Saturable Absorber

This work aims to study the dual-wavelength Q-switched fibre laser performances with erbium-doped fibre as the gain medium and the fibre Bragg gratings to allow stable switchable dual-wavelength states. Spider silk was used as an alternative biological material for saturable absorber. The spider silk as a saturable absorber was prepared by directly sandwiched between the surface of fibre ferrules. A dual-wavelength system operating at 1550 nm and 1560 nm was generated by modulating the polarisation controller to regulate the mode competition in the ring cavity. This allows for a flexible switch between individual wavelengths of 1550 nm or 1560 nm. The device operates at a wavelength of 1550 nm, with 26.63 kHz repetition rate and 9.45 μs pulse width. At a wavelength of 1560 nm, it produces a repetition rate of 24 kHz and a pulse width of 10.47 μs. The output demonstrated consistent stability throughout time, with no changes recorded. This indicates a stable signal-to-noise ratio of 41.12 dB and 34 dB for wavelengths 1550 nm and 1560 nm, respectively. This study presents the latest approach using spider silk as a saturable absorber to create a dual-wavelength Q-switched fibre laser. The laser is based on a fibre Bragg gratings device and has potential uses in terahertz signal and laser radar.