Topic
Thin lens
About: Thin lens is a research topic. Over the lifetime, 728 publications have been published within this topic receiving 11728 citations.
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TL;DR: This work shows the design and fabrication of metasurface lenses (metalenses) with extremely large areas, up to centimeters in diameter and beyond, and experimentally implements the ideal thin lens equation, while demonstrating high-quality imaging and diffraction-limited focusing.
Abstract: Optical components, such as lenses, have traditionally been made in the bulk form by shaping glass or other transparent materials. Recent advances in metasurfaces provide a new basis for recasting optical components into thin, planar elements, having similar or better performance using arrays of subwavelength-spaced optical phase-shifters. The technology required to mass produce them dates back to the mid-1990s, when the feature sizes of semiconductor manufacturing became considerably denser than the wavelength of light, advancing in stride with Moore's law. This provides the possibility of unifying two industries: semiconductor manufacturing and lens-making, whereby the same technology used to make computer chips is used to make optical components, such as lenses, based on metasurfaces. Using a scalable metasurface layout compression algorithm that exponentially reduces design file sizes (by 3 orders of magnitude for a centimeter diameter lens) and stepper photolithography, we show the design and fabrication of metasurface lenses (metalenses) with extremely large areas, up to centimeters in diameter and beyond. Using a single two-centimeter diameter near-infrared metalens less than a micron thick fabricated in this way, we experimentally implement the ideal thin lens equation, while demonstrating high-quality imaging and diffraction-limited focusing.
107 citations
TL;DR: A thin lens experiment could provide unequivocal evidence of relativistic self-focusing and is considered the possibility of using a thin plasma slab as an optical element to both focus and compress an intense laser pulse.
Abstract: We consider the possibility of using a thin plasma slab as an optical element to both focus and compress an intense laser pulse. By thin we mean that the focal length is larger than the lens thickness. We derive analytic formulas for the spot size and pulse length evolution of a short laser pulse propagating through a thin uniform plasma lens. The formulas are compared to simulation results from two types of particle-in-cell code. The simulations give a greater final spot size and a shorter focal length than the analytic formulas. The difference arises from spherical aberrations in the lens which lead to the generation of higher-order vacuum Gaussian modes. The simulations also show that Raman side scattering can develop. A thin lens experiment could provide unequivocal evidence of relativistic self-focusing.
105 citations
TL;DR: The results presented in this study show that the proposed method is capable of reconstructing the 3-D temperature field of a Flame through the use of least square QR-factorization algorithm (LSQR).
Abstract: Compared with conventional camera, the light field camera takes the advantage of being capable of recording the direction and intensity information of each ray projected onto the CCD (charge couple device) sensor simultaneously. In this paper, a novel method is proposed for reconstructing three-dimensional (3-D) temperature field of a flame based on a single light field camera. A radiative imaging of a single light field camera is also modeled for the flame. In this model, the principal ray represents the beam projected onto the pixel of the CCD sensor. The radiation direction of the ray from the flame outside the camera is obtained according to thin lens equation based on geometrical optics. The intensities of the principal rays recorded by the pixels on the CCD sensor are mathematically modeled based on radiative transfer equation. The temperature distribution of the flame is then reconstructed by solving the mathematical model through the use of least square QR-factorization algorithm (LSQR). The numerical simulations and experiments are carried out to investigate the validity of the proposed method. The results presented in this study show that the proposed method is capable of reconstructing the 3-D temperature field of a flame.
91 citations
20 Aug 2009
TL;DR: In this paper, the authors describe a different optical system approach to solar concentrators, where a thin lens array is combined with a shared multimode waveguide, which is a uniform glass sheet held between the lens array and a corresponding array of micro-mirrors self-aligned to each lens focus during fabrication.
Abstract: Conventional CPV systems focus sunlight directly onto a PV cell, usually through a non-imaging optic to avoid hot spots. In practice, many systems use a shared tracking platform to mount multiple smaller aperture lenses, each concentrating light into an associated PV cell. Scaling this approach to the limit would result in a thin sheet-like geometry. This would be ideal in terms of minimizing the tracking system payload, especially since such thin sheets can be arranged into louvered strips to minimize wind-force loading. However, simply miniaturizing results in a large number of individual PV cells, each needed to be packaged, aligned, and electrically connected. Here we describe for the first time a different optical system approach to solar concentrators, where a thin lens array is combined with a shared multimode waveguide. The benefits of a thin optical design can therefore be achieved with an optimum spacing of the PV cells. The guiding structure is geometrically similar to luminescent solar concentrators, however, in micro-optic waveguide concentrators sunlight is coupled directly into the waveguide without absorption or wavelength conversion. This opens a new design space for high-efficiency CPV systems with the potential for cost reduction in both optics and tracking mechanics. In this paper, we provide optical design and preliminary experimental results of one implementation specifically intended to be compatible with large-scale roll processing. Here the waveguide is a uniform glass sheet, held between the lens array and a corresponding array of micro-mirrors self-aligned to each lens focus during fabrication.
90 citations
TL;DR: In this paper, a semianalytic approach is proposed to estimate the optical path length across the aperture of a VCL with a parabolic lateral index profile, and the loss reduction with different amounts of tapering that provide a better approximation to the ideal thin lens.
Abstract: In vertical-cavity lasers (VCLs) employing oxide or airgap apertures, the lasing mode typically travels unguided throughout most of the structure. For the aperture to exactly compensate for the diffraction of the mode in these regions, it would need to have a parabolic lateral index profile (i.e. that of an ideal thin lens). Although nonparabolic aperture shapes will partially compensate diffraction losses, some light will be scattered out of the mode. These scattering losses increase as the aperture size is reduced and will limit the performance of the smallest devices. We analyze these losses first using a semianalytic approach which allows us to frame the problem in terms of two parameters of the structure: the Fresnel number and the effective optical path length across the aperture. We compare the estimate with experimental results and with an iterative numerical calculation of the actual mode and losses. Lastly, we compare the loss reduction with different amounts of tapering that provide a better approximation to the ideal parabolic lens.
89 citations