We investigated the Talbot effect in an anti-parity-time (PT) symmetric synthetic photonic lattice composed of two coupled fiber loops. We calculated the band structures and found that with an increase in the gain-loss parameter, the band transitions from a real spectrum to a complex spectrum. We study the influence of phase in the Hermitian operator on the Talbot effect, and the Talbot effect disappears when the period of the input field is N > 8. Further study shows that the variation of Talbot distance can also be modulated by non-Hermitian coefficients of gain and loss. This work may find significant applications in pulse repetition-rate multiplication, temporal invisibility, and tunable intensity amplifiers.

Self-healing in optics generally refers to the ability to reconstruct itself and restore the original state after encountering obstacles in the propagation of the light field. In this research, we observe the processes of the wave fields from perfect to defect in front of the focal plane of the 4f system, finally returning to an intact situation after the plane. According to simulations and experimental results, there is a minimum self-healing distance for the moiré lattice field that positively associates with the radius of the defect (obstacle) in the nondiffracting transmission range. Furthermore, it is observed that the defect self-healing is a process of “repairing the center and then repairing the edges.” These findings can be applied in areas such as optical imaging, capture, and information processing.

报道了LiNbO₃：Fe晶体内光致散射过程中偏振态的变化。将圆偏振光聚焦成极细的光片，并将其照射在c轴沿竖直方向放置的晶体上，研究了不同入射角时的光散射现象。在散射光从产生到达到稳态的数十分钟内，散射光主要在平行于c轴的方向上产生，同时在平行于光片的方向上存在分量，散射光产生速度随入射角的增大而减小。进一步观察表明，圆偏振光通过晶体后变成普通椭圆偏振光，不同入射角下出射光椭圆度也不同。结合晶体内部形成的噪声光栅，建立了圆偏振光的散射模型，并计算分析了偏振态变化的原因和机理。这一发现提出了一种利用光折变晶体的光致散射特性产生椭圆偏振光的方法，在基于光折变材料的光存储、光子晶格等方面有应用价值。

We reported a wavelength-flexible all-polarization-maintaining self-sweeping fiber laser based on the intracavity loss tuning brought by the bent optical fiber. The bidirectional cavity structure achieved the self-sweeping effect due to the appearance of the dynamic grating in the active fiber with the spatial hole burning effect. Under this, a section of fiber was bent into a circle for adjusting the loss of the cavity. With a descending diameter of bent fiber circle, the sweeping range moves to the shorter wavelength and covers a wide range from 1055.6 to 1034.6 nm eventually. Both the initial wavelength of self-sweeping regime and the threshold of the fiber laser show exponential correlation with the diameter of the circular fiber. Our work provides a compact and low-cost way to achieve the broad wavelength-flexible self-sweeping operation.