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It is generally assumed that correcting chromatic aberrations in imaging requires multiple optical elements. Here, we show that by allowing the phase in the image plane to be a free parameter, it is possible to correct chromatic variation of focal length over an extremely large bandwidth, from the visible (Vis) to the longwave infrared (LWIR) wavelengths using a single diffractive surface, i.e., a flat lens. Specifically, we designed, fabricated and characterized a flat, multi-level diffractive lens (MDL) with a thickness of ≤ 10µm, diameter of ∼1mm, and focal length of 18mm, which was constant over the operating bandwidth of λ=0.45µm (blue) to 15µm (LWIR). We experimentally characterized the point-spread functions, aberrations and imaging performance of cameras comprised of this MDL and appropriate image sensors for λ=0.45μm to 11μm. We further show using simulations that such extreme achromatic MDLs can be achieved even at high numerical apertures (NA=0.81). By drastically increasing the operating bandwidth and eliminating several refractive lenses, our approach enables thinner, lighter and simpler imaging systems.
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Inverse designed achromatic flat lens operating in the ultraviolet
We demonstrate an inverse designed achromatic, flat, polarization-insensitive diffractive optic element, i.e., a multilevel diffractive lens (MDL), operating across a broadband range of UV light (250 nm – 400 nm) via numerical simulations. The simulated average on-axis focusing efficiency of the MDL is optimized to be as high as ∼86%. We also investigate the off-axis focusing characteristics at different incident angles of the incoming UV radiation such that the MDL has a full field of view of 30°. The simulated average off-axis focusing efficiency is ∼67%, which is the highest reported till date for any chromatic or achromatic UV metalens or diffractive lens to the best of our knowledge. The designed MDL is composed of silicon nitride. The work reported herein will be useful for the miniaturization and integration of lightweight and compact UV optical systems.
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- PAR ID:
- 10169158
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- OSA Continuum
- Volume:
- 3
- Issue:
- 7
- ISSN:
- 2578-7519
- Format(s):
- Medium: X Size: Article No. 1917
- Size(s):
- Article No. 1917
- Sponsoring Org:
- National Science Foundation
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