Interference Spectral Imaging Based on Liquid Crystal Relaxation and Its Application in Optical Component Defect Detection

In this paper, we propose a fast interference spectral imaging system based on liquid crystal (LC) relaxation. The path delay of nematic LC during falling relaxation is used for the scanning of the optical path. Hyperspectral data can be obtained by Fourier transforming the data according to the path delay. The system can obtain two-dimensional spatial images of arbitrary wavelengths in the range of 300–1100 nm with a spectral resolution of 262 cm−1. Compared with conventional Fourier transform spectroscopy, the system can easily collect and integrate all valid information within 20 s. Based on the LC, controlling the optical path difference between two orthogonally polarized beams can avoid mechanical movement. Finally, the potential for application in contactless and rapid non-destructive optical component defect inspection is demonstrated.

Mathematical Modeling of Soliton-Like Modes at Optical Rectification

We discuss the results of numerical modeling of forming optical-terahertz bullets at the process of optical rectification. Our calculations are based on a generalization of the well-known Yajima - Oikawa system, which describes the nonlinear interaction of short (optical) and long (terahertz) waves. The generalization relates to situations when the optical component is close to a few-cycle pulse. We study the influence of the number of optical pulse oscillations on the formation of an optical-terahertz bullet. We develop original nonlinear conservative pseudo-spectral difference scheme approximating the generalization of the Yajima-Oikawa system. It is realized with the help of FFT algorithm. Mathematical modeling demonstrates scheme efficiency.

Multiposition Rotation Interference Absolute Measurement Method for High-Precision Optical Component Surfaces

Modern optical engineering requires increasingly sophisticated interferometry methods capable of conducting subnanometer scale measurements of the large aperture, high-precision optical component surfaces. However, the accuracy of interferometry measurement is limited to the accuracy with which the surface of the reference mirror employed in the interferometer system is known, and the influence of gravity-induced deformation cannot be ignored. This is addressed in the present work by proposing a three-flat testing method based on multiposition rotation interference absolute surface measurement technology that combines the basic theory of N-position rotation with the separability of surface wavefront functions into sums of even and odd functions. These functions provide the rotational symmetric components of the wavefront, which then enables the absolute surface to be reconstructed based on the N-position rotation measurements. In addition, we propose a mechanical clamping combined with computational method to compensate for the gravity-induced deformations of the flats in the multiposition rotation absolute measurements. The high precision of the proposed absolute surface measurement method is demonstrated via simulations. The results of laboratory experiments indicate that the combination compensation method provides the high-precision surface reconstruction outcomes. The present work provides an important contribution for supporting the interferometry measurement of large aperture, high-precision optical component surfaces.

EXPRESS: Design Considerations for Discrete Frequency Infrared Microscopy Systems

Discrete frequency infrared (DFIR) chemical imaging is transforming the practice of microspectroscopy by enabling a diversity of instrumentation and new measurement capabilities. While a variety of hardware implementations have been realized, considerations in the design of all-IR microscopes have not yet been compiled. Here we describe the evolution of IR microscopes, provide rationales for design choices, and the major considerations for each optical component that together comprise an imaging system. We analyze design choices in illustrative examples that use these components to optimize performance, under their particular constraints. We then summarize a framework to assess the factors that determine an instrument’s performance mathematically. Finally, we summarize the design and analysis approach by enumerating performance figures of merit for spectroscopic imaging data that can be used to evaluate the capabilities of imaging systems or suitability for specific intended applications. Together, the presented concepts and examples should aid in understanding available instrument configurations, while guiding innovations in design of the next generation of IR chemical imaging spectrometers.

Metaform optics: Bridging nanophotonics and freeform optics

The demand for high-resolution optical systems with a compact form factor, such as augmented reality displays, sensors, and mobile cameras, requires creating new optical component architectures. Advances in the design and fabrication of freeform optics and metasurfaces make them potential solutions to address the previous needs. Here, we introduce the concept of a metaform—an optical surface that integrates the combined benefits of a freeform optic and a metasurface into a single optical component. We experimentally realized a miniature imager using a metaform mirror. The mirror is fabricated via an enhanced electron beam lithography process on a freeform substrate. The design degrees of freedom enabled by a metaform will support a new generation of optical systems.