Optically Tunable Ultrafast Fiber Laser Based on a Ti₃C₂T_<i>x</i> MXene Coated Bandpass Filter

A stable and rapidly wavelength-tunable ultrafast fiber laser was demonstrated using an all-optical tunable bandpass filter based on Ti<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>T<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_x</i> MXene-coated fiber Sagnac loop, which serves as an efficient and fast optical-induced thermal modulator. Utilizing the optical-photothermal conversion properties of MXene, localized heating of the polarization-maintaining fiber in the Sagnac interferometer induces phase modulation of the interferometer, enabling precise control of the operating wavelengths of the filter. By embedding the fiber into an ultrafast laser, the soliton laser achieved a wavelength tuning range of 21.2 nm while maintaining soliton stability and excellent repeatability throughout the optical tuning process. This tuning method offers great potential for the rapid reconfiguration of bandpass filters, as light interacting with materials-coated fiber can induce complex and dynamic phase modulations in the filter. Optically tunable capability contributes to realizing highly flexible and rapidly tunable ultrafast lasers.