Metalenses promise potential for a paradigm shift of conventional optical devices. However, the aperture sizes of metalenses are usually bound within hundreds of micrometers by the commonly used fabrication methods, limiting their usage on practical optical devices like telescopes. Here, for the first time, we demonstrate a high-efficiency, single-lens, refractive metalens telescope. We developed a mass production-friendly workflow for fabricating wafer-scale (80 mm aperture) metalenses using deep-ultraviolet (DUV) photolithography. Our metalens works in the near-infrared region with nearly diffraction-limited focal spot sizes and a high peak focusing efficiency of 80.84% at 1450 nm experimentally. Based on the metalens, we built a single-lens telescope and acquired images of the lunar surface, revealing its geographical structures. We believe our demonstration of the metalens telescope proves the exciting potential lying in the metasurfaces and could bring new possibilities for areas involving large optical systems, including geosciences, planetary observation, and astrophysical science.

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A photonic crystal fiber based highly sensitive sensing mechanism is proposed, in the terahertz frequency band, able to detect a wide range of analytes, such as toxic or non-toxic chemicals and illicit drugs. The proper optimization of the PCF structure increases the light-matter interaction in the core, which results in a high relative sensitivity of about 94.0% with negligible confinement loss at the optimum frequency. Few liquids, chemicals, and drugs are considered to justify the sensing mechanism: a relative sensitivity of 99.60% can be achieved for the maximum porosity of core while ketamine was the analyte. Other fiber properties are also analyzed to check the feasibility of the proposed fiber with standard fiber and have obtained good performance. Therefore, the sensor may find applications to sense a wide range of analytes, non-toxic and toxic chemicals, as well as illicit drugs for example, in the THz region.

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