# Research Progress and Applications of 2D Antimonene
## 3 Practical Applications
### Nonlinear Optics  
[PERSON] et al. [27] applied antimonene to Erbium-doped fiber lasers with a cavity length of 9.5 m through the sandwich structure, and obtained passive Q-switched signals by adjusting the polarization state of the laser cavity. The diagram of laser cavity connection is shown in Figure 15. The antimonene nanosheet was used as the experimental material to verify the relatively stable absorbance at approximately 1.5 \(\upmu\)m. The pump with the wavelength of 976 nm and the maximum output power of 600 mW was connected to the wavelength division multiplexer at 980/1550 nm. The Erbium-doped fiber was used as the gain medium, the polarization isolator was used as the guarantee of one-way transmission of the optical path, and the PC was used to change the polarization state. The nonlinear results based on the antimonene saturation absorber (Sb SA) show that the saturation strength of the saturation absorption test is 1.52 MW/cm\({}^{2}\) and the modulation depth is 11.63%. At 1558 nm, a stable signal output is obtained, which does not change significantly for a long period of time. The signal-to-noise ratio (SNR) of the output signal is \(\sim\)48 dB, which effectively proves the feasibility of antimonene and its great application potential in fiber lasers.  
With the increase in the output power of the pump source, the repetition frequency range of the fiber laser is from 25.60 kHz to 124.1 kHz, and the duration of the Q-switched pulse is reduced from 5.10 \(\upmu\)s to 1.42 \(\upmu\)s. The minimum pulse duration after Gaussian fitting is 1.42 \(\upmu\)s. Meanwhile, the saturable absorbers formed by different materials are compared, as shown in Table 2. It can be seen from the figure that antimonene has higher output power and shorter pulse duration, which proves that antimonene has great application advantages in laser Q-switching.  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**Materials**} & **Wavelength** & **Output Power** & **Pulse Duration** & **Pulse Energy** \\  & **(nm)** & **(mW)** & **(\(\upmu\)s)** & **(n)** \\ \hline Graphene & 1539.6 & 3.38 & 3.89 & 28.7 \\ BP & 1562.87 & 1.5 & 13.2 & 94.3 \\ Silicene & 1567.1 & 0.89 & 2.32 & – \\ TiO\({}_{2}\) & 1558 & \(\sim\)0.26 & 1.84 & \(\sim\)2.3 \\ ZnO & 1550 & 1.2 & 1.68 & 46 \\ WSe\({}_{2}\) & 1560 & 1.23 & 3.976 & 17 \\ MoS\({}_{2}\) & 1068.2 & 0.46 & 2.2 & 6.9 \\ Antimonene & 1559.63 & 2.85 & 1.58 & 37.9 \\ Antimonene & 1558 & 4.73 & 1.42 & 54 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of applied power and pulse time of various materials in laser [27].  
Figure 15: Schematic diagram of laser cavity connection. Reprinted with permission from Ref. [27]. Copyright 2021, Optical Materials.  
[PERSON] et al. [69] proved that antimonene can be used as a saturable absorber in mid-infrared spectrum. They prepared multilayer antimonene by liquid phase separation method and coated it on a gold mirror, using it as a reflective saturable absorption device. At the wavelength of 2865 nm, the pulse energy is 0.72 uJ, the maximum output power is 112.3 mW, and the shortest pulse time is 1.74 um. The maximum repetition frequency is 156.2 kHz.  
Using antimonene as an all-optical modulator, [PERSON] et al. [70] designed an active Q-switched laser with all-optical modulation. Suspension droplets of antimonene prepared by liquid phase separation were put into self-made microfibers. It was found that antimonene has a wide band response and a wide spectrum response range. The all-optical modulator is applied to a Q-switched laser, and the repetition rate of the pulse train is changed from 0.96 kHz to 6.64 kHz by changing the pump pulse duty cycle.