Microlens arrays can improve light transmittance in optical devices or enhance the photoelectrical conversion efficiency of photovoltaic devices. Their surface morphology (aspect ratio and packed density) is vital to photon management in solar cells. Here, we report a 100% packed density paraboloidal microlens array (PMLA), with a large aspect ratio, fabricated by direct-write UV laser photolithography coupled with soft imprint lithography. Optical characterization shows that the PMLA structure can remarkably decrease the front-side reflectance of solar cell device. The measured electrical parameters of the solar cell device clearly and consistently demonstrate that the PMLA film can considerably improve the photoelectrical conversion efficiency. In addition, the PMLA film has superhydrophobic properties, verified by measurement of a large water contact angle, and can enhance the self-cleaning capability of solar cell devices.

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A rapid method is developed for fabricating low-cost and high-numerical-aperture photosensitive-gel microlens arrays (MLAs) with well-controlled curvatures. An UV-curable photosensitive-gel film beneath the microholes of a silicon mold can be flexibly deformed by thermally manipulating the surface tension of the photosensitive gel and the pressure difference across the air-photosensitive-gel interface. The concave interface is then solidified through UV curing, forming a MLA with a concave curvature. MLAs with a focal length ranging from 51.4 to 71.9 μm and a numerical aperture (NA) of 0.49 were fabricated. The photocured MLA has high mechanical and thermal strength and is suitable as a master mold for the further production of convex MLAs. The fabricated microlenses have uniform shapes and smooth surfaces. In a demonstration of imaging and focusing performance, clear and uniform images and focused light spots were observed using concave and convex MLAs.

A compact, tunable guided-mode resonant filter (GMRF) is experimentally demonstrated whose spectral reflectance wavelength varies as a function of the illumination position on the device. The GMRF consists of a grating of gradient-varying period ranging from 402.5 to 466.6 nm, which is obtained by casting a stretched polydimethylsiloxane (PDMS) grating wedge. By spatially changing the illumination position on the GMRF over 11 mm, a spectral reflectance peak with low sidelobes varies from 596.8 to 684.1 nm. The influence on the resonance efficiency and the limitation of the wavelength tuning range are discussed in depth. The GMRF is a good candidate as a functional filtering component in wavelength selection and sensing applications.

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This paper presents an in-plane hydrodynamically reconfigurable optofluidic microlens, which is formed by the laminar flow of two streams of a low-refractive-index fluid and two streams of a high-refractive-index fluid in the two microchannels connecting to an expansion chamber where the microlens finally forms. In the expansion chamber, the stream of high-refractive-index fluid, acting as core, is sandwiched by the two streams of low-refractive-index fluid, acting as cladding. The interfaces between the streams can be flexibly manipulated by controlling the flow rate ratio between the two fluids in real time. Thus, the biconvex and biconcave microlens with different curvatures can be formed. By adjusting the microlens, the light beam can be continuously manipulated from focusing to collimation and then to divergence. In the experiment, a wide focus tuning range from 2.75 (focusing) to -1.21 mm (diverging) via collimation is achieved.

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Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing.