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Dielectric mirrors based on Bragg reflection and photonic crystals have broad application in controlling light reflection with low optical losses. One key parameter in the design of these optical multilayers is the refractive index contrast, which controls the reflector performance. This work reports the demonstration of a high-reflectivity multilayer photonic reflector that consists of alternating layers of TiO2films and nanolattices with low refractive index. The use of nanolattices enables high-index contrast between the high- and low-index layers, allowing high reflectivity with fewer layers. The broadband reflectance of the nanolattice reflectors with one to three layers has been characterized with peak reflectance of 91.9% at 527 nm and agrees well with theoretical optical models. The high-index contrast induced by the nanolattice layer enables a normalize reflectance band of Δλ/λoof 43.6%, the broadest demonstrated to date. The proposed nanolattice reflectors can find applications in nanophotonics, radiative cooling, and thermal insulation.
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Ultra-thin sputter-deposited infrared rugate mirror for enhancing solar-to-thermal energy conversion
A dielectric mirror with high infrared reflection and high visible transmission, based on an easily fabricated stepped index rugate filter structure, is presented. Its fabrication involves sputtering depositions, using only two targets, to make five different material compositions. The ultra-wide reflection band is tunable in both position and width, adapting the thickness of the layers and eventually introducing chirped layers. When applied to evacuated solar thermal devices, efficiency improvements of up to 30% can be achieved, making this mirror an attractive solution for reducing radiative losses through the cold-side photon recycling mechanism.
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- Award ID(s):
- 1735282
- PAR ID:
- 10368535
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 47
- Issue:
- 2
- ISSN:
- 0146-9592; OPLEDP
- Format(s):
- Medium: X Size: Article No. 230
- Size(s):
- Article No. 230
- Sponsoring Org:
- National Science Foundation
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