Zhaoyi Yin

Enhancement of the up-conversion luminescence of Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles by photonic crystals

A new method for enhancing the upconversion (UC) emission of rare-earth doped nanoparticles is reported, in which Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles are deposited on to the surface of photonic crystal (PC) films. The UC emission of the Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles on the PC surface was notably enhanced when the UC emission bands of the Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles were within the range of the photonic band gap of the PCs, indicating that the PCs were efficient and selective reflection mirrors. The results show that PCs may have potential applications in UC optoelectronics and lighting devices.

Energy transfer and photoluminescence modification in Yb–Er–Tm triply doped Y2Ti2O7 upconversion inverse opal

In this article, we fabricated Y2Ti2O7: Yb, Er, Tm upconversion inverse opal photonic crystals with energy transfer between Er3+ and Tm3+, and investigated the influence of the photonic band gap on the energy transfer between Tm3+ and Er3+. It is interesting that strong modification of the steady state upconversion emission spectra is observed, and the green or red upconversion emission from Er3+ was suppressed in the inverse opal. More significantly, the energy transfer between Tm3+ and Er3+ is enhanced by suppression of the red upconversion emission of Er3+, thus the blue upconversion emission from Tm3+ is considerably improved in the inverse opals. Additionally, the mechanisms for upconversion emission of the Y2Ti2O7: Yb, Er, Tm inverse opal are discussed. We believe that the present work will be valuable for the foundational study of upconversion emission modification and the application of upconversion displays and short wavelength upconversion lasers.

High multi-photon visible upconversion emissions of Er3+ singly doped BiOCl microcrystals: A photon avalanche of Er3+ induced by 980 nm excitation

Under 980 nm excitation, high multi-photon upconversion (UC) emission from the 2H11/2/4S3/2 (green) and 4F9/2 (red) levels of Er3+ ions were observed from Er3+ singly doped BiOCl microcrystals. These high-energy excited states were populated by a three to ten photon UC process conditionally, which depended on the pump power density and the Er3+ ion doping concentration, characterizing as a hetero-looping enhanced energy transfer avalanche UC process. UC emission lifetime and Raman analysis suggest that the unusual UC phenomena are initiated by the new and intense phonon vibration modes of BiOCl lattices due to Er3+ ions doping.

Effect of photonic bandgap on upconversion emission in YbPO 4 :Er inverse opal photonic crystals

We obtained upconversion (UC) light-emitting photonic materials (YbPO(4):Er) with an inverse opal structure by the self-assembly technique in combination with a solgel method. The effect of the photonic stopband on the UC luminescence of the (2)H(11/2), (4)S(3/2)→(4)I(15/2), and (4)F(9/2)→(4)I(15/2) transitions of Er(3+) has been observed in the inverse opals of the Er(3+)-doped YbPO(4). Significant suppression of the UC emission was detected if the photonic bandgap overlapped with the Er(3+) ions emission band, while enhancement of the UC emission occurs if the emission band appears at the edge of the bandgap.

Multi-band photon avalanche controlling performance of BiOCl:Er3+ crystals through facile Yb3+ doping

Photon avalanche (PA) is a seldom discovered phenomenon in upconversion (UC) materials on account of the requirement for high pumping intensities and strict construction conditions. Herein, we present the controllable PA emission behavior of violet, green, red and near infrared emission from the Er3+ ion in Er3+–Yb3+ co-doped BiOCl crystals. We show that the generation of “looping” and the cycle numbers of PA processes could be precisely controlled through the control of doped Yb3+ concentrations. Fluorescent probe effects from doping Eu3+ ions indicates that the manipulation of PA behaviors may arise from a strong dependence on the magnitude of the internal polarizable chemical environment of BiOCl crystals that are weakened on doping with Yb3+ ions rather than other rare-earth dopants. Our results may offer a new insight into the mechanism for constructing PA process and promote the potential applications of PA UC phosphors in solid state lasers and optical switches.

Effect of Zn2+ dopant on photon avalanche upconversion behavior of BiOCl:Er3+ crystals

Effect of divalent dopants, Zn2+ ion, on the high-order photon avalanche (PA) upconversion (UC) emission of Er3+ doped BiOCl microcrystals was investigated. XRD results indicated that Zn2+ ion dopants would mostly enter into the lattice space at low and moderate doping concentration, and began to substitute Bi3+ ion gradually at heavily doping level. Under exaction at 980 nm, the PA UC of violet, green and red emission of Er3+ ions could be observed, and the UC emission intensity increased with increasing the Zn2+ addition below 8 mol.%, then decreased with further addition. Power dependence study showed that the dopant concentration of Zn2+ had no obviously negative effect on the occurrence of PA emission. On the bases of results investigated herein, we considered that the lattice distortion by Zn2+ doping could not directly change the special PA emission of BiOCl:Er3+, but would improve the emission intensity when used as lattice modifier.

UPCONVERSION LUMINESCENCE ENHANCEMENT OF NaYF4:Yb3+, Er3+ NANOPARTICLES ON INVERSE OPAL SURFACE

LaPO4 inverse opal photonic crystals with different photonic band gaps were fabricated by template-assisted method. The Yb3+/Er3+ co-doped NaYF4 nanoparticles were deposited on the surfaces of the inverse opals, and their up-conversion emission properties were investigated. The upconversion emissions of Yb3+/Er3+ co-doped NaYF4 nanoparticles on the inverse opal surfaces have been enhanced when the upconversion emission bands of the nanoparticles are in the range of photonic band gaps of the inverse opals, which is attributed to an efficient and selective reflection of photonic band gaps.

Investigation of upconversion and near infrared emission properties in CeO 2 : Er 3+ , Yb 3+ inverse opals

The upconversion emission of rare earth ions can be modified in photonic crystals, however, the influence of upconversion emission modification of rare earths on near infrared emission has not been investigated yet in the photonic crystals. In the paper, CeO₂: Er³⁺, Yb³⁺ inverse opals with the photonic band gaps at 545, 680 and 450 nm were prepared by polystyrene colloidal crystal templates. The upconversion and the near infrared emission properties of Er³⁺ ions were systematically investigated in the CeO₂: Er³⁺, Yb³⁺ inverse opals. Comparing with the reference sample, significant suppression of both the green and red upconversion luminescence of Er³⁺ ions were observed in the inverse opals. It is interesting that the infrared emission located at 1,560 nm was enhanced due to inhibition of upconversion emission in the inverse opals. Additionally, mechanism of upconversion emission of the inverse opal was discussed. The photon avalanche upconversion process is observed.

Preparation and characterization of Er3+-Yb3+-Ce3+ co-doped transparent glass ceramic containing nano Ca5(PO4)3F crystals

Abstract A transparent glass ceramic tri-doped with Ce 3+ /Er 3+ /Yb 3+ was fabricated by the high-temperature melting technique and following heat-treatment. X-ray diffraction and transmission electron microscope results demonstrated that Ca 5 (PO 4 ) 3 F(FAP) nanocrystals, possessed with preferable emission performances for the 1.54 μm transition for doping Er 3+ , were homogeneously precipitated among the glass matrix with a mean size of 30 nm. Addition of Ce 3+ greatly enhanced 1.54 μm fluorescence of Er 3+ by the cross relaxation energy transfer between Er 3+ and Ce 3+ . Meanwhile, incorporation of Ce 3+ dramatically decreased the visible upconversion emission intensity of glass ceramic than that of glass, suggesting that Ce 3+ might incorporate into the FAP nanocrystals. The properties of this transparent glass ceramic showed the potential application as an efficient 980 nm pumped infrared laser medium.

Investigation on the near-infrared-emitting thermal stability of Bi activated alkaline-earth aluminoborosilicate glasses

Stability of near-infrared (NIR) emission form Bi doped 42.5SiO2-12.5B2O3-25Al2O3-20RO (SBAR, R = Ca, Sr, Ba) glasses under treatment between annealing and softening temperature were studied. Results show that the thermal stability of Bi-NIR-emitting centers in SBAR glasses generally decreases with the increase of the radius of modifier cations but is greatly higher that in similar alkali glasses. Comparative experiments indicate these phenomena can be understood by the tendency that the smaller and higher charged alkaline earth ions as higher field strength modifier cations will increase the concentration of negative charge on non-bridging oxygens and also help to stabilize the non-bridging oxygens, which can restrain the thermally activated diffusion and valence change of Bi-activated centers, respectively. The results can provide an improved understanding for the NIR-emitting thermal stability of Bi doped glasses and a scientific reference for composition design of Bi-doped optical fiber.