Perfect optical vortices (POVs) provide a solution to address the challenge induced by strong dependence of classical optical vortices on their carried topological charges. However, traditional POVs are all shaped into bright rings with a single main lobe along the radial direction. Here we propose a method for enhanced control on the ring profile (the radial intensity profile of circular rings) of POVs based on modulated circular sine/cosine radial functions, which is realized by a circular Dammann grating embedded with a spiral phase. Specifically, a type of “absolute” dark POVs surrounded by two bright lobe rings in each side is presented, which provides a perfect annular potential well along those dark impulse rings for trapping low-index particles, cells, or quantum gases. In addition, several POVs with different ring profiles, including conventional POVs with bright rings, the dark POVs mentioned above, and also POVs with tunable ring profiles, are demonstrated. This work opens up new possibilities to controllably tune the ring profile of perfect vortices, and this type of generalized POVs will enrich the content of singular optics and expand the application scope of perfect vortices in a range of areas including optical manipulation, both quantum and classical optical communications, enhanced optical imaging, and also novel structured pumping lasers.

Recently, optical computing has emerged as a potential solution to computationally heavy convolution, aiming at accelerating various large science and engineering tasks. Based on optical multi-imaging–casting architecture, we propose a paradigm for a universal optical convolutional accelerator with truly massive parallelism and high precision. A two-dimensional Dammann grating is the key element for generating multiple displaced images of the kernel, which is the core process for kernel sliding on the convolved matrix in optical convolutional architecture. Our experimental results indicate that the computing accuracy is typically about 8 bits, and this accuracy could be improved further if high-contrast modulators are used. Moreover, a hybrid analog–digital coding method is demonstrated to improve computing accuracy. Additionally, a convolutional neural network for the standard MNIST dataset is demonstrated, with recognition accuracy for inference reaching 97.3%. Since this architecture could function under incoherent light illumination, this scheme will provide opportunities for handling white-light images directly from lenses without photoelectric conversion, in addition to convolutional accelerators.

We propose a new paradigm for generating the perfect optical vortex (POV) with a controlled structure and orbital angular momentum (OAM) distribution in the focal region of a tightly focused system. The superiority of the proposed technique is demonstrated with an experiment involving the dynamic manipulation of small particles. This technique for creating the POV could open new routes to optical manipulation based on OAM.

It is well known that higher diffraction order suggests a stronger dispersion for gratings with the same period. Here, a broadband high-efficiency three-layer all-dielectric rectangular-groove transmission grating operating at the -2nd order is designed under second Bragg incidence. An initial solution of the grating parameters is obtained quickly by using the simplified modal method (SMM). Moreover, a clear explanation for the physical mechanism behind the high efficiency and wide bandwidth is also given through this method. After that, a more accurate solution of the grating structure is optimized in further based on rigorous coupled wave analysis and simulated annealing algorithm. The simulation results indicated that the wavelength bandwidth from 1.454 μm to 1.531 μm and an angle bandwidth from 37.32° to 43.3° could be achieved for the efficiency over 95% under second Bragg incidence at the wavelength of 1.5 μm for TE polarization. It is the first time using SMM to predict the broadband characteristic of multilayer-gratings under second Bragg incidence.

The accuracy of optical three-dimensional (3D) shape measurement is always influenced by the defocusing of a projection or imaging system. In this paper, a novel optical element made by picometer-differential twice-exposed holography, called a picometer comb, is proposed to generate the projection pattern for 3D shape measurement. Two interference fields with picometer-scale period difference are recorded on a substrate to fabricate the picometer comb by twice-exposed laser holography; this element reconstructs the diffraction field, which is essentially the interference between the holograms of two object waves with a slight angle. This picometer comb has the advantage of the generation of a stable light field distribution with extremely long depth of field and small divergence angle. We demonstrate that this diffraction field provides a solution for non-defocusing 3D shape measurement.

A two-dimensional (2D) picometer comb, a novel optical element made by picometer-differential four times exposed in two perpendicular directions, is proposed to generate the dot array projection pattern for three-dimensional (3D) shape reconstruction and other applications. Not only does a 2D picometer comb generate a stable light field distribution with extremely long depth of field and small divergence angle as a one-dimensional picometer comb, it also has new properties, such as periodicity of diffraction field in two perpendicular directions and high concentration of energy of points, which is particularly suitable for providing dot array structured light. We demonstrate that the diffraction field of a 2D picometer comb provides a solution for non-defocusing 3D reconstruction with a dot array. In fabrication of a 2D picometer comb, we can modulate the holography by changing the angle of two beams slightly, so its period can be measured at picometer accuracy. A 2D picometer comb can be made to any scale, then it can be integrated to mobile devices, such as a mobile phone, for 3D shape reconstruction. Furthermore, the concept of a 2D picometer comb would be applied to generate a picometer light field for opening the door of pico-optics in the future.