Compact dark-field confocal microscopy based on an annular beam with orbital angular momentum

Color image information transmission based on elliptic optical vortex array encoding/decoding

A multichannel high-dimensional data encoding/decoding scheme based on composite elliptic optical vortex (EOV) arrays is proposed. By exploiting the rotation angle of the EOV, a 4 × 4 composite EOV array is used for high-dimensional data encoding. The conjugate symmetric extension Fourier computer-generated holography algorithm with controllable reconstruction focus is used to assign different reconstruction focus to the data of the three channels (R, G, and B) of the color image. Then, the data of the three channels is transmitted simultaneously by a single hologram to further improve the transmission efficiency. At the receiver, the initial information sequence is decoded by directly identifying the captured intensity patterns with a deep learning-based convolutional neural network. In the experiment, a 128 × 128-pixel color image is successfully transmitted, which confirms the feasibility of our proposed encoding/decoding scheme. This method has great potential for future high-capacity optical communications.

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.

3D microscopy in industrial measurements

Quality control is essential to ensure the performance and yield of microdevices in industrial processing and manufacturing. In particular, 3D microscopy can be considered as a separate branch of microscopic instruments and plays a pivotal role in monitoring processing quality. For industrial measurements, 3D microscopy is mainly used for both the inspection of critical dimensions to ensure the design performance and detection of defects for improving the yield of microdevices. However, with the progress of advanced manufacturing technology and the increasing demand for high-performance microdevices, 3D microscopy has ushered in new challenges and development opportunities, such as breakthroughs in diffraction limit, 3D characterisation and calibrations of critical dimensions, high-precision detection and physical property determination of defects, and application of artificial intelligence. In this review, we provide a comprehensive survey about the state of the art and challenges in 3D microscopy for industrial measurements, and provide development ideas for future research. By describing techniques and methods with their advantages and limitations, we provide guidance to researchers and developers about the most suitable technique available for their intended industrial measurements.

High-resolution dark-field confocal microscopy based on radially polarized illumination

Dark-field confocal microscopy (DFCM) facilitates the 3D detection and localization of surface and subsurface defects in high-precision optical components. The spatial resolution of conventional DFCM is commonly undermined owing to complementary aperture detection. We employed a radially polarized (RP) beam for illumination in DFCM. The RP beam creates a sub-diffraction-sized longitudinal optical component after being focused and effectively enhances the lateral resolution by 30.33% from 610 nm to 425 nm. The resolution improvement was verified by imaging a 2D sample containing sparsely distributed gold nanorods along with a 3D neodymium glass containing surface and subsurface defects.