Zhiqiang Zheng

The dynamics of frequency upconversion in Er3+/Yb3+-codoped PLZT transparent ceramics

The upconversion fluorescence spectrum and the luminescence decay curves from transitions of 4I13/2→4I15/2 and 4I11/2→4I15/2 in the Er3+-doped PLZT transparent ceramic were measured experimentally. A model for the dynamics of frequency upconversion in Er3+-doped PLZT transparent ceramic based on the rate equations was proposed. The dynamics of the upconverted emissions were studied to evaluate energy transfer (ET) rates by solving the rate equations of the model and fitting the experimental curves. The upconversion coefficient C22 for the cross relaxation 4I13/2+4I13/2→4I9/2+4I15/2 and the upconversion coefficient C33 for the cross relaxation 4I11/2+4I11/2→4I15/2+4F7/2 were 0.91×10-18 cm3/s and 18.23×10-18 cm3/s, respectively. The model provides a good basis for explaining the experiment data because it shows a high sensitivity to the input fitting parameters. The analysis reveals that Er3+-doped PLZT transparent ceramic have a great prospect to be applied for monolithic multifunction compact devices and upconversion devices.

Analysis of clustering in Eu(DBM)3 phen-doped polymer optical fiber by effective-medium approximation

The Eu(DBM)3phen-doped polymer optical fiber slice was prepared, and the population of Eu3+ ion was up to 1.0 wt.-%. The chromatic dispersion and absorption characteristics of fractal clusters of Eu3+ ions in Eu(DBM)3phen-doped POF slice were explored. The dielectric components homogeneously and inhomogeneously doped circumstances of this kind of POF slices were studied and their transmissions were analyzed and compared theoretically. Using near-field scanning optical microscopy (NSOM), the near-field light intensities of this kind of POF slice were measured, and agreement was obtain between experiment and theory. The result indicates that the clustering in this kind of POF is not obvious.

Analysis of the dynamics of frequency upconversion in Er 3+ /Yb 3+ co-doped KY(WO 4 ) 2 crystal

The absorption spectrum, upconversion spectrum and the fluorescence decay curve of Er³⁺/Yb³⁺ co-doped KY(WO<inf>4</inf>)<inf>2</inf> crystal were measured. The radiative transition rates were calculated by Judd-Ofelt theory. A model for the dynamics of frequency upconversion process in Er³⁺/Yb³⁺ co-doped KY(WO<inf>4</inf>)<inf>2</inf> crystal was proposed. The Yb-to-Er energy transfer rate and the upconversion coefficients were estimated by numerically solving the rate equations and fitting simulated curve to the experimental data.

Design and analysis of two-dimensional photonic crystals resonant cavity

A novel three-port resonant cavity in two-dimensional photonic crystals (2D PCs) with two wavelength-selective reflection micro-cavities is proposed. In the structure, three micro-cavities are used. One is used for a resonant tunneling-based input waveguide and the others are used to realize wavelength-selective reflection feedback. According to coupled mode theory in time, the conditions to achieve ultra-high quality in the system are derived thoroughly. The performance of the designed resonant cavity has been numerically calculated by using the finite-difference time domain (FDTD) method and the results imply that the design is feasible.

Study of clusters in Sm-doped polymer optical fibers

Sm(DBM)3phen-doped polymer optical fibers were prepared by thermal polymerization. The cross relaxation model of clustering Sm3+ ions was described, and the cluster in this kind of fibers was studied based on the above model. The percentages of clustering ions in different fibers were obtained by the rate equation combining with fiber transmission experiment. While rare-earth-doped concentrations in these fibers are 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm and 10000 ppm, the percentages of clustering ions are 0.05, 0.05, 0.05, 0.05, 0.06, and 0.07, respectively. The result shows that this kind of fibers has low percentage of clustering ions. With the increasing of Sm3+ concentration, the percentage of clustering ions hardly increases, the clustering of Sm3+ ions is not obvious.

Study of rhodamine B-doped polymer optical waveguides by using scanning near-field optical microscopy

The rhodamine B-doped polymer optical planar waveguide with low propagation loss of 0.44 dB/cm has been fabricated and measured by using scanning near-field optical microscopy and m-line method. The mode structure, near-field topography and near-field fluorescence are obtained, respectively. This may have potential applications in the study of polymer waveguide laser and amplifier.