Arbitrary combinations of helical-conical optical beams in free space.

Helical-conical optical beams (HCOBs) have attracted considerable interest due to their peculiar optical features. Their characteristic helical light intensity distribution has exerted unprecedented advantages in many fields, but multiple combinations of HCOBs have not been reported due to the limitations of algorithms and light field modulation techniques. We propose and experimentally demonstrate arbitrary combinations of multiple HCOBs in free space to construct hybrid HCOB arrays. The similarity between the experimental results and the numerical simulation results is 94.22%. The initial orientation of the HCOBs is flexibly tuned by the rotation factor ß, and the optical pen is used to combine the HCOBs. This approach allows multiple parameters in the array to be precisely tuned, including the type, number, and position of HCOBs, adding more design flexibility. The constructed HCOB arrays have a higher degree of modulation freedom and may find applications in fields where dynamic control is in high demand, including optical tweezers, biological cell sorting, and multiparticle manipulation.

Free-space creation of a perfect vortex beam with fractional topological charge.

Perfect vortex beams can only propagate stably with integer topological charges. Thus, creating perfect fractional vortex beams capable of stable propagation in free space, as perfect integer vortex beams, is crucial. This study proposed perfect vortex beams carrying fractional topological charge of l + 0.5, which are special solutions of the wave equation, and can maintain stable propagation with physical laws same as integer topological charge. Perfect fractional vortex beams were created in free space, which can break the cognition of traditional fractional perfect vortex beams and promote the development of scientific fields such as optical communication, quantum sensing, and optical imaging.

Generation of vector elliptical perfect optical vortices with mixed modes in free space.

Vector vortex beams are widely used because of their anisotropic vortex polarization state and spiral phase. Constructing mixed mode vector vortex beams in free space still requires complex designs and calculations. We propose a method for generating mixed mode vector Elliptical perfect optical vortex (EPOV) arrays in free space by mode extraction and optical pen. It is demonstrated that the long axis and short axis of EPOVs are not limited by the topological charge (TC). Flexible modulation of parameters in the array is achieved, including number, position, ellipticity, ring size, TC, and polarization mode. This approach is simple and effective, it will provide a powerful optical tool for optical tweezers, particle manipulation, and optical communication.

Orientation of the NV centers are determined using the cylindrical vector beam array.

The determination of nitrogen-vacancy centers plays an important role in quantum information sensing. Efficiently and rapidly determining the orientation of multiple nitrogen-vacancy center s in a low-concentration diamond is challenging due to its size. Here, we solve this scientific problem by using an azimuthally polarized beam array as the incident beam. In this paper, the optical pen is used to modulate the position of beam array to excite distinctive fluorescence characterizing multiple and different orientations of nitrogen-vacancy centers. The important result is that in a low concentration diamond layer, the orientation of multiple NV centers can be judged except when they are too close within the diffraction limit. Hence, this efficient and rapid method has a good application prospect in quantum information sensing.

Free-space generation of three-dimensional tunable vector optical cages.

The generation of three-dimensional tunable vector optical cages through full polarization modulation requires complex polarization states. This paper takes the vector Airy optical cage as an example to generate a three-dimensional tunable high-quality optical cage based on the Pancharatnam-Berry phase principle. The proposed method in this paper possesses the capability of arbitrary modulation in various aspects, including the quantity of optical cages and their respective sizes as well as three-dimensional spatial positions. Moreover, the intensity of each optical cage can be modulated independently. This research will improve the capture efficiency of optical tweezers and promote further development in fields of efficient optical trapping, particle manipulation, high-resolution microscopic manipulation, and optical communication.

Generation of perfect optical vortex arrays by an optical pen.

Recently, perfect optical vortexes (POVs) have attracted substantial attention, because they have an orbital angular momentum (OAM) and the beam diameter is independent of the topological charges. There are numerous innovative results that have been found by modulating the POV optical field. However, methods for controlling the arbitrary parameters of POV are lacking. In this paper, we use the optical pen to overcome this problem. The optical pen is a high-precision optical field modulation method construction based on the relationship between the optical path difference and phase. Based on this method, we have achieved POV arrays with controllable arbitrary parameters in free space, including the spatial position, numbers, topological charges, beam diameter, and amplitude. This work can be applied not only in the fields of optical tweezers, particle manipulation, and super-resolution microscopic imaging, but also will promote the development of optical communication, quantum information coding, and so on.

Parallel creation of propagable integer- and fractional-order vector vortex beams using mode extraction principle.

Propagable fractional-order vector vortex beams with fractional topological charge provide new possibilities in optics. However, their complicated polarizations give rise to a big challenge in creating multiple vector vortex beam channels. Here, we solve this scientific problem by generating fractional- and integer-order vector vortex beams in parallel using the mode extraction principle along with an optical pen. Based on the principle of mode extraction, integer- and fractional-order vector vortex beams can be extracted in the focal region of an objective lens directly from a single m = 30-order vector vortex beam. Their number, position, amplitude, and phase are further controlled by the parameters of an optical pen. This work not only presents an example of how to manipulate the polarization and phase of a light beam simultaneously using the principle of mode extraction, but also may open new avenues for the applications of integer- and fractional-order vector vortex beams.

Generation of a sub-wavelength sized optical needle with arbitrary longitudinal rotation.

We show that under tight focusing conditions, arbitrarily rotating the longitudinally polarized optical needle in space is possible. Applying the Richards and Wolf vector diffraction methods, the explicit expressions underlying the simultaneous control depth of focus (DoF), intensity suppression of the sidelobes, as well as the orientation of the optical needle can be obtained, and then the strength vectors of the three-dimensional electromagnetic fields can be calculated. Calculations reveal that the sidelobe suppression ratio reaches 5.35% of the principal lobe, the optimal DoF is 5.1λ, and the maximum length is about 18.2λ. In addition, we specify the necessary conditions for rotating the sub-wavelength sized optical needle in the longitudinal field. Such an optical needle with controllable length, purity, and orientation can provide a flexible approach and additional degree of freedom for 3D precise fabrication and some other potential application areas.

Microsphere-lens coupler with 100 nm lateral resolution accuracy in visible light.

We propose a microsphere-lens coupler that can successfully constrain the beam with near-field details to achieve ∼100nm lateral resolution accuracy. In theory, we use the finite-difference time-domain method to analyze the properties of the "photonic nanojet." The optimal focusing ability scope can be obtained by adjusting the focusing parameters, such as refractive index, paraxial optical intensity attenuation ratio, sizes of microspheres, and so forth. In experiment, the "non-brush scrubbing" cleaning technology is adopted to optimize the experimental results. Aiming to self-assemble properties of dielectric spheres, we introduce the deagglomeration method to produce homogeneous liquid. Meanwhile, by tiling a 5 µm-diameter microsphere-lens on a specimen, a traditional optical microscope can realize 100 nm lateral superresolution microimaging, which lays a certain foundation for further development of superresolution microimaging.

Focal shift of an axisymmetric Bessel-Gaussian beam under Airy mixing modulation.

In this paper, the focusing characteristics of Bessel-Gaussian beams are studied by means of vector diffraction theory. The vector field distribution of the axisymmetric Bessel-Gaussian beam of a cylindrical vector is derived by calculating and adding Airy mixing modulation to the Bessel-Gaussian beam. It is found that with a series of regular focusing change characteristics, the focusing presents strong stability of the optical chain structure, and the number of optical chain links can be adjusted. At the same time, it is pointed out that in the case of a tightly focused helically polarized beam, the polarization in the focal region is not uniform, but there was a similar horizontal shift in focus. Finally, the relevant practical application scenarios are briefly introduced. The correlation focus shift conversion can be widely used in electronic acceleration, optical sampling and operation, and biological imaging.

Focusing and propagation characteristics of radially polarized helical-conical Airy beams.

This paper uses a spiral cone wavefront to modulate a radially polarized Airy beam. Based on the vector diffraction theory, the focusing and propagation characteristics of a radially polarized spiral cone Airy beam are studied. In order to conduct in-depth analysis on the unique properties of radial polarized spiral cone-shaped Airy beams, the focused light intensity, optical gradient force distribution, and propagation characteristics under different spiral cone parameters were simulated. The results show that the parameters of the helical-conical have a significant effect on the focusing characteristics of the radially polarized helical-conical Airy beam. The radial polarization of the radially polarized helical-conical Airy beam shows a lateral stretching trend. During propagation, focused light field distribution gradually becomes an optical trap. The light trap-like mode displayed after Airy beam modulation can be applied to optical tweezers operation, optical capture, and other fields.