Abstract
With the rapid development of integrated optics, bulky and curved traditional lenses cannot meet the requirements of on-chip optical systems. Alternatively, the metalenses based on the artificial subwavelength structure possess ultra-thin and lightweight characteristics, providing a potential candidate for on-chip optical systems. Nonetheless, most metalenses have a limited field-of-view (FOV) due to the prevalence of severe off-axis aberrations. In this work, we propose and design an on-chip metalens with wide FOV based on the quadratic phase. The metalens modulates the phase of the incident light with different lengths of gold nano-bands placed on the silicon-on-insulator substrate; thus, the quadratic distribution of the phase of the output light can be achieved by shifting the lengths of gold nano-bands and the output light is focused. The metalens can be focused on a large angle (∼120°, ranging from −60° to +60°). Furthermore, the metallic strips in the metalens are very thin with a thickness of 50 nm, which can be easily integrated into a chip. The monolithic metalens of broad FOV and ultrathin thickness will have great potential for applications in areas of sensing, imaging, and on-chip information processing.
Highlights
Most of the traditional optical lenses are realized by constructing curved surfaces, so the volume and weight of the lens are relatively bulky.1,2 These significantly limit the application of traditional optical devices in integrated on-chip systems
The focusing efficiency of the on-chip metalens is kept higher than 20% in the large angle, with a peak of 68% approximately when the incidence angle along the positive (+) x-direction is titled by 0○
We designed and simulated a wide FOV on-chip metalens based on the principle of the quadratic phase
Summary
Most of the traditional optical lenses are realized by constructing curved surfaces, so the volume and weight of the lens are relatively bulky. These significantly limit the application of traditional optical devices in integrated on-chip systems. The subwavelength structured electromagnetic regulation technology has stood out among other techniques because of its flexible design, precise electromagnetic modulation capability, and multiparameter control including phase, amplitude, and polarization. Owing to this technology, many novel fields have appeared such as subwavelength electromagnetics, surface plasmon optics, and metamaterials.. As the design of HCTA reduces the effective refractive index of the metalens, the ability of structures to bind light becomes weak. This metalens cannot focus the beam on the chip with a large FOV. The wide-angle FOV and ultrathin onchip metalens holds great potential for achieving on-chip sensing, imaging, and information processing
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