Development of a glass-based imaging phantom to model the optical properties of human tissue.

The fabrication of a stable, reproducible optical imaging phantom is critical to the assessment and optimization of optical imaging systems. We demonstrate the use of an alternative material, glass, for the development of tissue-mimicking phantoms. The glass matrix was doped with nickel ions to approximate the absorption of hemoglobin. Scattering levels representative of human tissue were induced in the glass matrix through controlled crystallization at elevated temperatures. We show that this type of glass is a viable material for creating tissue-mimicking optical phantoms by providing controlled levels of scattering and absorption with excellent optical homogeneity, long-term stability and reproducibility.

Controlled formation of gold nanoparticles with tunable plasmonic properties in tellurite glass.

Silicate glasses with metallic nanoparticles (NPs) have been of intense interest in art, science and technology as the plasmonic properties of these NPs equip glass with light modulation capability. The so-called striking technique has enabled precise control of the in situ formation of metallic NPs in silicate glasses for applications from coloured glasses to photonic devices. Since tellurite glasses exhibit the unique combination of comparably easy fabrication, low phonon energy, wide transmission window and high solubility of luminescent rare earth ions, there has been a significant amount of work over the past two decades to adapt the striking technique to form gold or silver NPs in tellurite glasses. Despite this effort, the striking technique has remained insufficient for tellurite glasses to form metal NPs suitable for photonic applications. Here, we first uncover the challenges of the traditional striking technique to create gold NPs in tellurite glass. Then, we demonstrate precise control of the size and concentration of gold NPs in tellurite glass by developing new approaches to both steps of the striking technique: a controlled gold crucible corrosion technique to incorporate gold ions in tellurite glass and a glass powder reheating technique to subsequently transform the gold ions to gold NPs. Using the Mie theory, the size, size distribution and concentration of the gold NPs formed in tellurite glass are determined from the plasmonic properties of the NPs. This fundamental research provides guidance for designing and manipulating the plasmonic properties in tellurite glass for photonics research and applications.

Large enhancements of NaYF4:Yb/Er/Gd nanorod upconversion emissions via coupling with localized surface plasmon of Au film.

Four-layered plasmonic structures of glass/Au/TiO2/NaYF4:Yb, Er, Gd nanorods were fabricated and tremendous improvement in upconversion luminescence (UCL) was observed under infrared 980 nm excitation. The TiO2 film was used as an oxide spacer. The emission intensity of the upconversion (UC) nanorods was strongly modulated by the thickness of the TiO2 layer. The extent of modulation depended on the separation distance between the Au layer and UC nanorods. A maximum UCL enhancement of 192-fold was observed for one green emission (540 nm) when a 10 nm-thick TiO2 film was used; 150-fold was observed for the other green emission (521 nm) at the same thickness of TiO2; and 105-fold was observed for the red emission (654 nm) when a 7.5 nm-thick TiO2 film was used. Alteration of the radiative decay rate was demonstrated for the first time in measurements of the decay times of UC nanorods positioned at various distances from the Au layer. The light interaction and coupling between metal Au and UC nanorods is numerically studied. The UCL mechanisms of multilayer plasmonic structures are discussed. Experimental results are explained and correspond well with those of theoretical calculations.

Sb3+/Mn2+ co-doped tunable white emitting borosilicate glasses for LEDs.

Luminescent properties of Sb(3+)/Mn(2+) co-doped borosilicate glasses containing no rare earth ions were systematically investigated through absorption, excitation, emission spectra, and decay curves. Upon 250-340 nm light excitation, the glasses exhibit broad blue emission at 400 nm (Sb(3+)) and red emission at 615 nm (Mn(2+)). The varied emitted color from blue through white and eventually to red can be obtained by properly tuning the content of Mn(2+) ions due to energy transfer from Sb(3+) to Mn(2+). Our investigation shows that Sb(3+)/Mn(2+) co-doped glasses may provide a new platform to design and fabricate luminescent materials for UV LED chips in the future.

Tunable white luminescence and energy transfer in novel Cu⁺, Sm³âº co-doped borosilicate glasses for W-LEDs.

The luminescent properties of novel Cu⁺, Sm³âº single- and co-doped borosilicate glasses were systematically investigated by absorption, excitation, emission spectra and decay curves. Cu⁺ single-doped glasses emit broad luminescence band covering all the visible range. And their peaks shift to blue with decreasing excitation wavelength from 330 to 280 nm. Cu⁺, Sm³âº co-doped samples generate the varied hues from blue white to pure white and eventually to yellow white due to an efficient energy transfer from Cu⁺ to Sm³âº. Our research indicates the potential application of Cu⁺, Sm³âº co-doped borosilicate glasses as converting phosphors for white LEDs pumped by UV LED chips.