A maskless lithography method to realize the rapid and cost-effective fabrication of micro-optics elements with arbitrary surface profiles is reported. A digital micro-mirror device (DMD) is applied to flexibly modulate that the exposure dose according to the surface profile of the structure to be fabricated. Due to the fact that not only the relationship between the grayscale levels of the DMD and the exposure dose on the surface of the photoresist, but also the dependence of the exposure depth on the exposure dose, deviate from a linear relationship arising from the DMD and photoresist, respectively, and cannot be systemically eliminated, complicated fabrication art and large fabrication error will results. A method of compensating the two nonlinear effects is proposed that can be used to accurately design the digital grayscale mask and ensure a precise control of the surface profile of the structure to be fabricated. To testify to the reliability of this approach, several typical array elements with a spherical surface, aspherical surface, and conic surface have been fabricated and tested. The root-mean-square (RMS) between the test and design value of the surface height is about 0.1 μm. The proposed method of compensating the nonlinear effect in maskless lithography can be directly used to control the grayscale levels of the DMD for fabricating the structure with an arbitrary surface profile.

As is well known, there is a contradiction between the high resolution (HR) and wide field of view (FOV) in conventional microscopy, due to limited physical space-bandwidth-product (SBP). Therefore, it is difficult to get HR with wide FOV in the conventional microscope. To solve this problem, a computational super-resolution imaging method known as Fourier ptychography microscopy (FPM) has been proposed.^{1 – 3} In FPM, a programmable LED array is used to provide illumination with varying angles. When the LEDs are turned on sequentially, the low-resolution (LR) images of the sample with the corresponding illumination angle are collected from a wide FOV objective lens.^4,5 After that, the corresponding spectra of the LR image sequence are stitched through an iterative phase recovery process.⁶ In this way, FPM can obtain the HR and wide FOV complex amplitude of the sample.

The application of moth-eye nanostructured polymer film on the flexible polyethylene terephthalate (PET) substrate is an effective way to improve its antireflection (AR) performance. However, many factors affect the AR properties of the moth-eye structure in the actual manufacturing process. Moreover, the antireflection research based on PET substrate has been relatively lacking compared with the silicon substrate. In this paper, we simulate and analyze the AR performance of the moth-eye nanostructured polymer film on PET substrate by using the finite-difference time-domain method within the wavelength range of 400–1100 nm. Simulation results show that the parabola-shaped moth-eye structure (PSMS) can suppress the Fresnel reflection significantly. Moreover, the height and filling ratios are the dominant factors that affect the AR performance of PSMS. Additionally, the base diameter, residual layer thickness, and the refractive index of PSMS polymer film also affect the reflectivity of PET slightly. As a result, an optimal PSMS with base diameter of 400 nm, height of 300 nm, and the hexagonal close-packed arrangement is appropriate, and the solar-weighted reflectivity of PET can be suppressed to 0.21%, which shows a prominent advantage over the bare PET (≈6%). Therefore, this research has promising potential for improving the optical performance of optoelectronic devices by using nanostructured polymer materials.

The wafer pre-aligner is a crucial component in the lithography process to correct the wafer center and notch orientation. To improve the precision and the efficiency of pre-alignment, a new method to calibrate the center and the orientation of a wafer based on the weighted Fourier series fitting of circles (WFC) method and the least squares fitting of circles (LSC) method, respectively, is proposed. The WFC method effectively suppressed the influence of the outliers and had high stability compared with the LSC method when fitted to the center of the circle. While the weight matrix degenerated to the identity matrix, the WFC method degenerated into the Fourier series fitting of circles (FC) method. The fitting efficiency of the FC method is 28% higher than that of the LSC method, and the fitting accuracy of the center of the FC method is the same as that of the LSC method. In addition, the WFC method and the FC method perform better than the LSC method in radius fitting. The pre-alignment simulation results showed that the absolute position accuracy of the wafer was ±2 µm, the absolute direction accuracy was 0.01°, and the total calculation time was less than 3.3 s in our platform.

Due to their excellent photoelectric performance, nanostructures have attracted considerable attention in research to improve the power conversion efficiency of thin-film solar cells (TFSCs). Furthermore, cylindrical silicon nanowires (Cy-SiNWs) are regarded as promising candidates for a new generation of TFSCs. On this basis, many new nanostructures derived from conventional Cy-SiNWs have been studied extensively, but most of these structures require high manufacturing accuracy because of their complex morphology. In this paper, an ingenious design of clustered silicon nanowires (Cl-SiNWs) is introduced, whose cross section is similar to the flower shape and consists of four arcs with the same radius. Hence, it requires lower manufacturing difficulty compared with nanostructures with curvature variation of the cross-section profile (i.e., elliptic shape, crescent shape, etc.). In this study, the optical and electrical characterizations are numerically investigated using the finite-difference time-domain method. The numerical simulation shows that the optimized Cl-SiNWs achieve an optical ultimate efficiency ( η u l ) and circuit current density ( J sc ) of 33.66% and 27.54 m A / c m 2 , respectively, with an enhancement of 7.3% over conventional Cy-SiNWs. Further, the η u l and J sc improve to 42.20% and 34.53 m A / c m 2 by adding the silicon substrate and silver backreflector. More importantly, the η u l of Cl-SiNWs always obtained a higher value than Cy-SiNWs at a recommended diameter range of 360–560 nm. Therefore, the suggested Cl-SiNWs have exhibited tremendous potential for the future development of low-cost and highly efficient solar cells.

Scanning broadband light interferometry (SBLI) has been widely utilized in surface metrology due to its non-contact and high-accuracy method. In SBLI, phase evaluation through Fourier Transform (FT) is a prevalent and efficient technique, where the topography measurement can often be achieved through one interferogram. Nevertheless, the accuracy of the FT method would be significantly influenced by intensity modulation depth: “the lower the modulation of the pixel, the higher the error probability of its phase assignment”. If the structure has a large enough range along the z-axis, several areas in an individual interferogram would be weakly modulated due to the limited depth of focus (DOF). In this paper, we propose an advanced FT-based method when it comes to large-height structures. Spatial modulation depth is first calculated for each interferogram independently. After that, a binary control mask is reasonably constructed to identify the pixels that are valid for phase unwrapping. Then, a phase stitching method along the z-axis is carried out to conduct the large-height topography measurement within a giving field of view. The theoretical principle, simulation, and experimental validation are elaborated to demonstrate that the method can achieve an improved robustness for the reconstruction of large-range microstructures, the advantages of which include the elimination of stepping errors, the suppression of light fluctuations, and the freedom of a limited DOF.