Nb₂CT_x Niobium-Based MXenes as a Saturable Absorber for Passively Generating Q-Switched Fiber Laser at 2 μm

In this paper, a passively generated Q-switched fiber laser at wavelength of 2 μm utilizing Niobium-Based MXene is demonstrated. The polyvinyl alcohol (PVA) is used as the host polymer and mixed with Niobium MXene to create the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Nb}_{2}\text{CT}_{\mathrm{x}^{-}}$</tex> PVA thin film SA. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Nb}_{2}\text{CT}_{\mathrm{x}}$</tex>-PVA thin film is then integrated into a Thulium-doped fiber laser (TDFL) ring cavity for pulsed laser generation. The experiment results show that the Q-switched fiber laser with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Nb}_{2}\text{CT}_{\mathrm{x}}$</tex>-PVA thin film SA possessed an operating wavelength of 1964.121 nm with pump power varying from 611.09 mW to 776.53 mW. By rising the pump power, the repetition rate increases from 31.64 kHz to 68.41 kHz while the pulse width decreases from 2.415 μs to 1.956 μs. The Q-switched laser also generates pulse energy and peak power at maximum of 121.997 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex>J and 54.732 mW, respectively. The signal-to-noise (SNR) of 52.2 dB of the Q-switched laser shows the stability of the laser system.