Determination of small angular displacement by moiré fringes of matched radial-parallel gratings

Quasi-seamless stitching for large-area micropatterned surfaces enabled by Fourier spectral analysis of moiré patterns

The main challenge in preparing a flexible mold stamp using roll-to-roll nanoimprint lithography is to simultaneously increase the imprintable area with a minimized perceptible seam. However, the current methods for stitching multiple small molds to fabricate large-area molds and functional surfaces typically rely on the alignment mark, which inevitably produces a clear alignment mark and stitched seam. In this study, we propose a mark-less alignment by the pattern itself method inspired by moiré technique, which uses the Fourier spectral analysis of moiré patterns formed by superposed identical patterns for alignment. This method is capable of fabricating scalable functional surfaces and imprint molds with quasi-seamless and alignment mark-free patterning. By harnessing the rotational invariance property in the Fourier transform, our approach is confirmed to be a simple and efficient method for extracting the rotational and translational offsets in overlapped periodic or nonperiodic patterns with a minimized stitched region, thereby allowing for the large-area and quasi-seamless fabrication of imprinting molds and functional surfaces, such as liquid-repellent film and micro-optical sheets, that surpass the conventional alignment and stitching limits and potentially expand their application in producing large-area metasurfaces.

Investigation of the moiré patterns of defected radial and circular gratings using the reciprocal vectors approach

In this work, for the first time to the best of our knowledge, an investigation on the moiré patterns of superimpositions of two radial or two circular gratings consisting of topological defects and their mutual superimpositions with each other, or with linear forked gratings or defected zone plates, is presented. For characterization of the resulting moiré patterns, we use the reciprocal vectors approach. In this approach, by considering local spatial frequencies for the superimposed structures, their reciprocal vectors are determined from the transmission function of the structures. The local reciprocal vector of the resulting moiré pattern at a given point is determined in terms of the local reciprocal vectors of the superimposed structures defined at the same point. In this approach, the topological singularities of the superimposed structures are described by the azimuthal component of the reciprocal vectors. This formulation is very simple, uniform, and comprehensive. In this work, we offer a detailed discussion on the different resulting moiré patterns for the above-mentioned superimpositions and some potential applications of the proposed superimpositions are introduced. In addition, different resulting moiré patterns are simulated.

Precision alignment of integrated optics in hybrid microsystems

We achieve submicrometer precision in the integration of micro-optics with surface electrode ion traps. The high-precision alignment is accomplished using off-axis linear Fresnel zone plates (FZPs). Four pairs of FZPs are fabricated on the optics chip that contains the high numerical aperture microlens, a diffractive optical element (DOE). The four pairs of FZPs enable alignment in six translational and rotational degrees of freedom. Four corresponding alignment rulers are etched in the top metal layer of the ion trap, enabling quantification of misalignment. The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions are key to achieving scalability in quantum information processing. An accurate and precise approach to the integration of DOEs advances the scalability of surface electrode ion traps and many other hybrid microsystems.