An active ultrafast formation and modulation of dual-band plasmon-induced transparency (PIT) effect is theoretically and experimentally studied in a novel metaphotonic device operating in the terahertz regime, for the first time, to the best of our knowledge. Specifically, we designed and fabricated a triatomic metamaterial hybridized with silicon islands following a newly proposed modulating mechanism. In this mechanism, a localized surface plasmon resonance is induced by the broken symmetry of a C2 structure, acting as the quasi-dark mode. Excited by exterior laser pumps, the photo-induced carriers in silicon promote the quasi-dark mode, which shields the near-field coupling between the dark mode and bright mode supported by the triatomic metamaterial, leading to the dynamical modulation of terahertz waves from individual-band into dual-band PIT effects, with a decay constant of 493 ps. Moreover, a remarkable slow light effect occurs in the modulating process, accompanied by the dual-transparent windows. The dynamical switching technique of the dual-band PIT effect introduced in this work highlights the potential usefulness of this metaphotonic device in optical information processing and communication, including multi-frequency filtering, tunable sensors, and optical storage.

为实现精密气浮转台低速精确控制，提高转台定位精度和动态响应性能，提出一种变带宽线性自抗扰控制算法。首先，根据转台及驱动电机的数学模型，建立包含扰动项的控制系统模型。接着，构造线性扩张状态观测器，分析初值误差对观测精度的影响，提出一种观测器带宽调节方法以提升观测精度。然后，根据控制器带宽设计思想，设计加入扰动补偿后的控制律。最后，在精密气浮转台实验平台中对变带宽线性自抗扰控制性能进行了实验验证。结果表明：低速工况下，跟踪误差不大于0.000 8°；位置阶跃响应中，角定位误差不大于0.000 7°，与传统线性自抗扰控制相比，超调量由0.001 7°下降到0.001 4°；在转动惯量和电机电感参数单一失配的情况下，转台仍能保持高定位精度。满足精密气浮转台定位精度高、速度平稳性好、抗扰性强的要求。

Recently reported plasmon-induced transparency (PIT) in metamaterials endows the optical structures in classical systems with quantum optical effects. In particular, the nonreconfigurable nature in metamaterials makes multifunctional applications of PIT effects in terahertz communications and optical networks remain a great challenge. Here, we present an ultrafast process-selectable modulation of the PIT effect. By incorporating silicon islands into diatomic metamaterials, the PIT effect is modulated reversely, depending on the vertical and horizontal configurations, with giant modulation depths as high as 129% and 109%. Accompanied by the enormous switching of the transparent window, remarkable slow light effect occurs.

We experimentally demonstrate for the first time an active all-optical ultrafast modulation of electromagnetically induced transparency-like effect in a hybrid device of sapphire/Si/metamaterial. From numerical simulations, it can be deducted that the tuning process is attributed to the coupling between the dark mode existing in split-ring resonators and the bright mode existing in cut wire resonators. The transmission amplitude modulation is accompanied by the slow-light effect. In addition, the ultrafast formation process is measured to be as fast as 2 ps. This work should make an important contribution to novel chip-scale photonic devices and terahertz communications.

In this work, a soliton mode-locked erbium-doped fiber laser (EDFL) with a high-quality molecular beam epitaxy (MBE)-grown topological insulator (TI) Bi₂Se₃ saturable absorber (SA) is reported. To fabricate the SA device, a 16-layer Bi₂Se₃ film was grown successfully on a 100 μm thick SiO₂ substrate and sandwiched directly between two fiber ferrules. The TI-SA had a saturable absorption of 1.12% and a saturable influence of 160 MW/cm². After inserting the TI-SA into the unidirectional ring-cavity EDFL, self-starting mode-locked soliton pulse trains were obtained at a fundamental repetition rate of 19.352 MHz. The output central wavelength, pulse energy, pulse duration, and signal to noise ratio of the radio frequency spectrum were 1530 nm,18.5 pJ, 1.08 ps, and 60 dBm, respectively. These results demonstrate that the MBE technique could provide a controllable and repeatable method for the fabrication of identical high-quality TI-SAs, which is critically important for ultra-fast pulse generation.