Baojie Chen

Superbroadband near-infrared emission in Tm-Bi codoped sodium-germanium-gallate glasses.

Superbroadband emission from 1.0 to 1.7 μm wavelength was observed in thulium-bismuth (Tm-Bi) codoped sodium-germanium-gallate (NGG) glasses under 793 nm excitation. Efficient energy transfer process from Bi to Tm ions, with value as high as 67.7%, was achieved which is beneficial in achieving flat broadband lineshape. The large stimulated emission cross-section and measured lifetime confirm the potentials of Tm-Bi codopants as luminescence sources for superbroadband near-infrared (NIR) optical amplifiers and tunable lasers. Planar optical waveguides were fabricated successfully in the codoped NGG glasses using K(+)-Na(+) ion-exchange process.

Dynamic colour and utilizable white fluorescence from Eu/Tb ions codoped lithium-yttrium-aluminium-silicate glasses

A group of dynamic-colour white fluorescences with various colour temperatures that can be applied to circadian lighting are achieved in Eu/Tb-codoped lithium-yttrium-aluminium-silicate (LYAS) glasses, which can be attributed to the simultaneous generation of three primary colours emitting from Eu3+ (red), Eu2+ (blue) and Tb3+ (green) by varying the ultraviolet (UV) radiation wavelength. Fluorescence colour coordinates pass through the whole white region of the CIE x, y chromaticity diagram when the UV excitation wavelength is increased from 300 to 370 nm. A favourable white light with colour coordinates (0.338, 0.298) close to the equal energy white is obtained under 360 nm excitation. These results indicate that the Eu/Tb-codoped LYAS glasses are a promising candidate to develop white lighting devices under the excitation of commercial UV light-emitting diodes, and a smart lighting system based on rare-earth doped glasses will be a potential illumination source offering controllability of the colour temperature that can adjust to specific environments and requirements, and benefit human health, well-being and productivity.

Visible photon multiplication in Ce3+–Tb3+ doped borate glasses for enhanced solar cells

Visible photon multiplication is exposed in the Ce3+–Tb3+ doped alkaline-earth borate (LKZBSB) glass system. Efficient green and blue fluorescences originate from Tb3+ and Ce3+ emitting centres, respectively. Evaluation of absolute spectral parameters reveals that the quantum yield of Tb3+ single doped LKZBSB glasses is ~8% under UVA radiation. Furthermore, with the introduction of Ce3+ into the Tb3+ doping system, the effective excitation wavelength range and the emission intensity of Tb3+ in LKZBSB glasses are remarkably expanded and improved by a maximum sensitization factor of ~52 in the UVB spectral region. These results demonstrate that the Ce3+–Tb3+ doped LKZBSB glass system has promising potential as an efficient UV → Visible radiation conversion layer for the enhancement of solar cell efficiency, including cells employed in outer space.

Bent channel design in buried Er3+/Yb3+ codoped phosphate glass waveguide fabricated by field-assisted annealing

Bent waveguide structures (S-, U-, and F-bend) based on buried Er 3 + /Yb 3 + codoped phosphate glass waveguide channel fabricated by field-assisted annealing have been designed to achieve high-gain C-band integrated amplification. Using a simulated-bend method, the optimal radius for the curved structure is derived to be 0.90 cm with loss coefficient of 0.02 dB/cm, as the substrate size is schemed to be 4×3 cm 2 . In the wavelength range of 1520 to 1575 nm, obvious gain enhancement for the bent structure waveguides is anticipated, and for the F-bend waveguide, the internal gain at 1534-nm wavelength is derived to be 41.61 dB, which is much higher than the value of 26.22 and 13.81 dB in the U- and S-bend waveguides, respectively, and over three times higher than that of the straight one. The simulation results indicate that the bent structure design is beneficial in obtaining high signal gain in buried Er 3 + /Yb 3 + codoped phosphate glass waveguides, which lays the foundation for further design and fabrication of integrated devices.

Controlling interface states in 1D photonic crystals by tuning bulk geometric phases

There is no known simple rule that assures the existence of interface states in photonic crystals (PCs). We show here that one can control the existence or absence of interface states in 1D PCs through engineering the bulk geometrical phase such that interface states can be guaranteed in some or all photonic bandgaps. We verify experimentally the interface state design paradigm in 1D multilayered PCs fabricated by electron beam vapor deposition. We obtain the geometrical phases by measuring the reflection phases at the bandgaps of the PCs and achieve good agreement with the theory. Our approach could provide a platform for generating a PC interface state for various applications.

Nanofiber electrospinning in samarium complex-doped PMMA

Herein, an electrospinning process of samarium complex-doped PMMAs was carried out to fabricate ultrafine fibers with a uniform diameter of about 230 nm. Under ultraviolet excitation, luminescence comparison between bulks and nanofibers verifies the existence of spectral reshaping, which alters the emission ratio of ligands to Sm3+; moreover, the effectiveness of electrospun fibrosis in enhancing the fluorescence emission is further identified in the case of Phen-containing. In addition, color tunability is achieved with the fluorescence changing from reddish-orange in bulks to near-white light in nanofibers. The nanosizing in rare-earth phosphors by electrospun fibrosis is proven to optimize the fluorescence properties, which provides a new route to develop the effective light-converting materials.

Near-infrared fluorescence in neodymium acetylacetonate hydrate doped poly methyl methacrylate

Abstract. Neodymium acetylacetonate hydrate (NAH) doped poly methyl methacrylate (PMMA) has been prepared and near-infrared (NIR) 1069 and 1342 nm emissions possessing the full widths at half maximum of correspondingly 61 and 75 nm have been observed. Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) are respectively derived to be 16.34×10−20, 11.35×10−20, and 9.50×10−20  cm2, indicating a high asymmetrical and covalent environment of Nd3+ in NAH doped PMMA. The spontaneous emission probabilities for F3/24→I11/24 and F3/24→I13/24 transitions are severally 2542.4 and 456.9  s−1, from which the associated maximum stimulated emission cross sections have been determined to be 3.19×10−20 and 1.28×10−20  cm2, respectively. High emission probabilities and large emission cross sections of NIR fluorescence in NAH doped PMMA reveal its potential as an NIR polymer optical material in practical applications as optical thin films and fibers.

Super-broadband near-infrared photoluminescence from thulium, bismuth, and thulium-bismuth doped sodium germanium gallate glasses and waveguides

Substantial progress in the production of hydroxyl-free silica fibers (dry optical fibers) have led to transmission wavelength region from 1.2 to 1.7 µm, thus it is attractive to explore superbroadband luminescence sources for broadband near-infrared (NIR) optical amplifiers, and tunable lasers operating in this entire low loss wavelength region [1]. Rare earth ions (e.g., erbium, thulium, holmium, and praseodymium) doped material systems play a significant role in the optical amplification and laser sources at separate C-, L-, S-, E-, and O-band wavelength regions [2]. Novel gallate/tellurite oxide glasses have been investigated to further improve the bandwidth and the quantum efficiency of specific rare earth luminescence [3,4]. Also, wavelength/frequency resources located in the first window (1.45–1.65 µm) have been explored and obtained from Tm-Er codoped configuration due to their NIR emission characteristic in this region [5]. However, up to now it remains a challenge to obtain super-broadband luminescence/amplification covering the entire extended transmission window from rare earth ions doped materials due to their restricted gain bandwidth characteristics.

Near-infrared emission in Tm 3+ -Tb 3+ /Eu 3+ codoped gallo-germanate glasses

Broadband 1.20 μm emission (¹G<inf>4</inf>→³H<inf>4</inf> transition) in Tm³⁺-Tb³⁺/Eu³⁺ codoped gallo-germanate glasses was observed. The population inversion is realized by depleting the lower ³H<inf>4</inf> level, and the possible energy transfer processes involved are discussed.