Narrow-band line-emitter phosphors offer improved lm/W for white LEDs, while maintaining high CRI. Especially Eu3+-doped phosphors are ideal from an emitter perspective. However, using Eu3+ for practical LEDs is hampered by the lack of absorption in the blue spectral region. To solve this problem, we have developed nano-engineered phosphors harvesting interparticle energy transfer (IFRET), an innovative approach to sensitize Eu3+, and other ions, in the blue spectral range. In this presentation, we will share our progress on our IFRET materials, as well as demonstrate high-quality (high QY and small-size) nano-YAG phosphors.
The recent miniaturization of semiconductor light emitting devices (LEDs), such as mini- and micro-LEDs demands stable and efficient down-converting materials with nano-to-submicron dimensions. YAG:Ce, because of its many beneficial properties, is an interesting candidate for these applications when available at the nanoscale. This talk gives an overview of our technologies on achieving stable, well-defined nano-YAG:Ce phosphors with high energy conversion efficiencies. We discuss different synthesis approaches, after treatments and encapsulation technologies, and how these influence the structural and optical properties, and offers nano-YAG:Ce from sub-micron particles down to sizes in the order of ten to 20 nm.
Narrow band (i.e. line) emitters have an enormous potential for use in LEDs, as they will allow both improvement of color rendering while maintaining high lm/W, and open up new spectral engineering possibilities for specific applications. The major bottle neck for implementation of line emitters in LEDs, is the lack of absorption in the blue spectral region of conventional trivalent lanthanide doped phosphors. In this talk, I will present a new nanoscale approach to engineer phosphor materials, which allows tuning of absorption and emission wavelengths over a wide range of the spectrum. The underlaying mechanism of these engineered phosphors is interparticle energy transfer, which will be discussed in more detail.
Enantiomer separation is a critical step in many chemical syntheses, particularly for pharmaceuticals, but prevailing chemical methods remain inefficient. Here, we introduce an optical technique to sort chiral specimens using coaxial plasmonic apertures. These apertures are composed of a deeply subwavelength dielectric channel embedded in silver (or gold) and can stably trap sub-20-nm dielectric specimens. Using both full-field simulations and analytic calculations, we first show that selective trapping of enantiomers can be achieved with circularly polarized illumination and proper index-matching of the immersed liquid with the particles being trapped. Opposite enantiomers experience distinct trapping forces in both sign and magnitude: one is trapped in a deep potential well while the other is repelled with a potential barrier. These potentials maintain opposite signs across a range of chiral polarizabilities and enantiomer-aperture separations. We also demonstrate how atomic force microscopy can be used to directly probe the near field optical forces from our coaxial nano-aperture. Our measurement reveals the spatial distribution of the optical near-field forces on a nanometer-sized dielectric specimen. To directly visualize the enantio-selective optical forces, we pattern silicon AFM-probes with chiral patterns. Our near-field force mapping indicates a differentiable force in the piconewton range on the chiral probes, exerted by our coaxial aperture with circularly polarized illumination. Our theoretical and experimental demonstrations indicate that the interaction of chiral light and chiral specimens can be mediated by achiral plasmonic apertures, providing a possible route toward all-optical enantiopure syntheses.
Conference Committee Involvement (7)
Light-Emitting Devices, Materials, and Applications XXIX
27 January 2025 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications XXVIII
29 January 2024 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications XXVII
30 January 2023 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications XXVI
24 January 2022 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications XXV
6 March 2021 | Online Only, California, United States
Light-Emitting Devices, Materials, and Applications XXIV
3 February 2020 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications
4 February 2019 | San Francisco, California, United States
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