Bismuthene quantum dots (Bi-QDs) were synthesized via the liquid phase exfoliation (LPE) method for the passive Q-switching operation in near-infrared (NIR) region. The nonlinear optical properties of the prepared Bi-QDs were investigated by the open-aperture Z-scan technology. The modulation depths were 18.1% and 5.1% at 1.06 and 1.34 µm, respectively. Based on the Bi-QDs saturable absorber, passively Q-switched Nd:GdVO₄ lasers operating at ⁴F_3/2 → ²I_11/2 and ⁴F_3/2 → ²I_13/2 transitions were demonstrated, showing the wideband optical modulation in NIR regime. For the ⁴F_3/2 → ²I_13/2 transition lasing at 1.34 µm, the shortest pulse duration of 155 ns was obtained with a repetition rate of 457 kHz. With respect to the ⁴F_3/2 → ²I_11/2 transition at 1.06 µm, the minimum pulse duration was 150 ns with a repetition rate of 424 kHz, leading to a single pulse energy of 261 nJ and a peak power of 1.68 W. In addition, the ground state absorption cross section and the excited state absorption cross section of Bi-QDs were also investigated for the first time. The impact of the excited state lifetime on the output parameters was numerically stimulated by the coupled rate equations. Our work confirmed that the trap state in Bi-QDs played an important role in the pulse generation mechanism.

通过液相剥落（LPE）方法合成了铋量子点（Bi-QDs），用于近红外（NIR）区域的被动Q切换操作。通过开孔Z扫描技术研究了制备的Bi-QD的非线性光学性质。在1.06和1.34 µm处的调制深度分别为18.1％和5.1％。基于Bi-QDs饱和吸收体，演示了在⁴ F _3/2  →  ² I _11/2和⁴ F _3/2  →  ² I _13/2跃迁下工作的无源Q开关Nd：GdVO ₄激光器，显示了宽带近红外光调制。对于⁴ F在1.34 µm的_3/2  →  ² I _13/2过渡激光中，以457 kHz的重复频率获得了最短的155 ns脉冲持续时间。关于⁴ F _3/2  →  ² I _11/2在1.06 µm处跃迁时，最小脉冲持续时间为150 ns，重复频率为424 kHz，导致单脉冲能量为261 nJ，峰值功率为1.68W。此外，基态吸收截面和激发态还首次研究了Bi-QD的吸收截面。耦合速率方程在数值上激发了激发态寿命对输出参数的影响。我们的工作证实了Bi-QDs中的陷阱状态在脉冲生成机制中起着重要作用。