利用有限元法对领结状金纳米二聚体结构的表面等离激元共振特性进行了探究, 研究发现在几何形状保持不变的条件下, 二聚体共振波长位移与粒子间距呈e的负指数变化, 并且指数衰减系数与粒子大小无关。进一步分析了纳米结构附近电场分布, 发现共振条件下单体结构的x 轴和y 轴电场分布都遵守e的负指数衰减规律, 且场强与入射电磁波的偏振方向有关；而受二聚体间表面等离激元耦合因素的影响, 二聚体之间的距离对场强的衰减速率有着巨大的影响。最后, 对二聚体共振吸收强度进行了研究, 发现吸收强度与二聚体距离之间的关系仍为e的负指数函数规律。本研究结果对微距传感、粒子捕获等具有重要的指导意义。

In this article, we report on an experimentally generated soliton and bound-state soliton passively mode-locked erbium-doped fiber laser by incorporating a saturable absorber (SA) made of MoS2/fluorine mica (FM) that was fabricated with the Langmuir–Blodgett (LB) method. The FM substrate is 20 μm thick and easy to bend or cut, like a polymer. However, it has a higher damage threshold and a better thermal dissipation than polymers. In addition, the LB method can be used to fabricate a thin film with good uniformity. In this study, the modulation depth, saturable intensity, and unsaturated loss of the SA are measured as 5.9%, 57.69 MW/cm2, and 13.4%, respectively. Based on the SA, a soliton mode-locked laser is achieved. The pulse duration, repetition rate, and signal-to-noise ratio are 581 fs, 15.67 MHz, and 65 dB, respectively. By adjusting the polarization controller and pump power, we obtain a bound-state soliton mode-locked pulse. The temporal interval between the two solitons forming the bound-state pulse is 2.7 ps. The repetition rate of the bound-state pulses is proportional to the pump power. The maximum repetition rate is 517 MHz, corresponding to the 33rd harmonic of the fundamental repetition rate. The results indicate that the MoS2/FM LB film absorber is a promising photonic device in ultrafast fiber lasers.

We report the experimental demonstration of transform-limited sub-6 fs pulses at an optimal central wavelength by a tunable noncollinear optical parametric amplification (NOPA) source. Meanwhile, a white light continuum in the near-infrared (NIR) range from 900 to 1100 nm is also successfully generated by focusing the unconverted 800 nm beam during NOPA generation on a sapphire rod. Both visible-pump/visible-probe and visible-pump/NIR-probe experiments are realized using the same laser system. As examples, ultrafast photo-induced exciton dynamics inside two kinds of materials are investigated by the visible-pump/visible-probe and visible-pump/NIR-probe spectroscopy, respectively.