Pseudo-topological property of Julia fractal vector optical fields.

Polarization singularities have topological properties, because they can maintain their features invariably during propagation. The topological property can be destroyed by shifting the polarization singularities away from the central axis, and this destruction originates from the space separation of spin angular momentum components. We find that paired centrosymmetric off-axis polarization singularities can recover the topological property in the Fourier plane (reciprocal space), which belongs to the pseudo-topological property. We reveal that the pseudo-topological property is related to the invisible redistribution of both spin and orbital angular momentum states. We experimentally generate a series of Julia fractal vector optical fields with the pseudo-topological property. They may have potential applications in optical encryption and quantum information.

Femtosecond polarization-structured optical field meets an anisotropic nonlinear medium.

Filamentation, as a universal femtosecond phenomenon that could occur in various nonlinear systems, has aroused extensive interest, owing to its underlying physics, complexity and applicability. It is always anticipated to realize the controllable and designable filamentation. For this aim, the crucial problem is how to actively break the symmetry of light-matter nonlinear interaction. A kind of extensively used approaches is based on the controllable spatial structure of optical fields involving phase, amplitude and polarization. Here we present an idea to control the optical field collapse by introducing optical anisotropy of matter as an additional degree of freedom, associated with polarization structure. Our theoretical prediction and experimental results reveal that the synergy of optical anisotropy and polarization structure is indeed a very effective means for controlling the optical field collapse, which has the robust feature against random noise.

High-efficiency and flexible generation of vector vortex optical fields by a reflective phase-only spatial light modulator.

The scheme for generating vector optical fields should have not only high efficiency but also flexibility for satisfying the requirements of various applications. However, in general, high efficiency and flexibility are not compatible. Here we present and experimentally demonstrate a solution to directly, flexibly, and efficiently generate vector vortex optical fields (VVOFs) with a reflective phase-only liquid crystal spatial light modulator (LC-SLM) based on optical birefringence of liquid crystal molecules. To generate the VVOFs, this approach needs in principle only a half-wave plate, an LC-SLM, and a quarter-wave plate. This approach has some advantages, including a simple experimental setup, good flexibility, and high efficiency, making the approach very promising in some applications when higher power is need. This approach has a generation efficiency of 44.0%, which is much higher than the 1.1% of the common path interferometric approach.

Fractal vector optical fields.

We introduce the concept of a fractal, which provides an alternative approach for flexibly engineering the optical fields and their focal fields. We propose, design, and create a new family of optical fields-fractal vector optical fields, which build a bridge between the fractal and vector optical fields. The fractal vector optical fields have polarization states exhibiting fractal geometry, and may also involve the phase and/or amplitude simultaneously. The results reveal that the focal fields exhibit self-similarity, and the hierarchy of the fractal has the "weeding" role. The fractal can be used to engineer the focal field.

Microstructures fabricated by dynamically controlled femtosecond patterned vector optical fields.

We have presented and demonstrated a method for the fabrication of various complicated microstructures based on dynamically controlled patterned vector optical fields (PVOFs). We design and generate dynamic PVOFs by loading patterned holograms displayed on the spatial light modulator and moving traces of focuses with different patterns. We experimentally fabricate the various microstructures in z-cut lithium niobate plates. The method we present has some benefits such as no motion of the fabricated samples and high efficiency due to its parallel feature. Moreover, our approach is able to fabricate three-dimensional microstructures.

Hyperbolic-symmetry vector fields.

We present and construct a new kind of orthogonal coordinate system, hyperbolic coordinate system. We present and design a new kind of local linearly polarized vector fields, which is defined as the hyperbolic-symmetry vector fields because the points with the same polarization form a series of hyperbolae. We experimentally demonstrate the generation of such a kind of hyperbolic-symmetry vector optical fields. In particular, we also study the modified hyperbolic-symmetry vector optical fields with the twofold and fourfold symmetric states of polarization when introducing the mirror symmetry. The tight focusing behaviors of these vector fields are also investigated. In addition, we also fabricate micro-structures on the K9 glass surfaces by several tightly focused (modified) hyperbolic-symmetry vector fields patterns, which demonstrate that the simulated tightly focused fields are in good agreement with the fabricated micro-structures.