Mingjie Ding

Noncontact Ultrasonic Transport of Liquid Using a Flexural Vibration Plate

We have succeeded in the noncontact transportation of ethanol droplets inside a semi cylindrical acoustic waveguide. The waveguide was composed of a vibration bottom plate and a semi cylindrical reflector, and a propagating acoustic field was excited in the waveguide. The droplet was levitated at the nodal position of the standing wave mode in the cross section of the waveguide and transported by the traveling wave component in the horizontal direction. The transportation distance was 65 mm and the terminal velocity reached 2.3 m/s when the droplet was 1.5 mm in diameter and 1.38 g in weight.

Brillouin gain spectrum dependences on temperature and strain in erbium-doped optical fibers with different erbium concentrations

Brillouin Stokes power in erbium-doped optical fibers (EDFs) can be potentially controlled by pumping, but no report has been provided on its detailed characterization. In this study, as the first step toward this goal, the Brillouin gain spectra in EDFs with three different erbium concentrations (0.72, 1.20, and 2.28 wtppt) are measured at 1.55 μm without pumping, and the Brillouin frequency shifts (BFSs) and their dependences on strain, temperature, and erbium concentration are fully investigated. In the EDF with 0.72-wtppt concentration, the BFS was 11.42 GHz, and its temperature and strain coefficients were 0.87 MHz/K and 479 MHz/%, respectively.

Discriminative strain and temperature measurement using Brillouin scattering and fluorescence in erbium-doped optical fiber

We develop a novel discriminative sensing technique of strain and temperature using Brillouin scattering and fluorescence in an erbium-doped fiber (EDF). First, we show that the fluorescence intensity ratio (FIR), the ratio of the fluorescence intensities at two different wavelengths (1530 nm and 1565 nm in this experiment), is linearly dependent on temperature (with a coefficient of 5.6 × 10⁻⁴ /°C) but almost independent of strain. Then, by combined use of the FIR and the Brillouin frequency shift in an EDF, we experimentally demonstrate discriminative measurements of strain and temperature with four different sets of strain and temperature changes.

Thermal Effect on Attenuation and Luminescence of Bi/Er Co-Doped Fiber

We investigated thermal effect on attenuation and luminescence of Bi/Er co-doped fiber (BEDF). A strong and irreversible thermal darkening effect in both near-infrared (NIR) and visible spectral range was observed, accompanied by a luminescence quenching of bismuth active centers (BACs), in temperature range from 600 °C to 800 °C. This thermal darkening effect is believed to be linked to the precipitation of metallic bismuth nanoparticles and takes place at a relatively low temperature. We also observed that the quenching of BAC-Si in the BEDF is more prominent than other BACs. The BAC-Si related emission at 1420 nm is decreased by 80% when the temperature is increased to 600 °C - before the significant thermal darkening occurs and while the quenching of others BACs is not significant.

γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres.

We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres.

Photo-bleaching mechanism of the BAC-Si in bismuth/erbium co-doped optical fibers

Photo-bleaching of the silica-related bismuth active center (BAC-Si) in bismuth/erbium co-doped optical fibers is investigated. By analyzing dynamic spectral characteristics of BAC-Si, the photo-bleaching of the BAC-Si is found to be linked to the escape of an excited electron from the bismuth site in the BAC-Si. This mechanism of BAC-Si bleaching linked to an escaping excited electron is further confirmed with both photo-bleaching experiments by different laser pump wavelengths and a potential energy model describing the loss of an excited electron. Additionally, the temperature effect on the photo-bleaching, which is in good agreement with the above findings, is observed and discussed.

Reversible photo-bleaching effect in a bismuth/erbium co-doped optical fiber under 830 nm irradiation

We observed photo-bleaching in a bismuth/erbium co-doped optical fiber (BEDF) under 830 nm irradiation. As a result of the photo-bleaching, the absorption at 814 nm and the near-infrared luminescence at 1420 nm are decreased, indicating that the silicon-based bismuth active center (BAC-Si) in a BEDF is bleached in the process. We further found that the photo-bleaching is reversible under room temperature. This is the first time that the BAC-Si could be bleached under 830 nm irradiation, and the photo-bleaching is reversible. The underlying mechanism of the reversible photo-bleaching effect is discussed.

Enhanced Gamma Radiation Effect in Bi/Er Co-Doped Optical Fibre by Co-Doping Yb

Gamma radiation effects on bismuth/erbium co-doped fibre and bismuth/erbium/ytter-bium co-doped fibre have been investigated and compared. We found co-doping Yb enhanced the pump absorption and accelerated the formation of new BAC-Si by

Dynamic behavior of pump light radiation induced photo-bleaching effect on BAC-Si in bismuth/erbium co-doped optical fibers

\gamma

Discriminative measurement of strain and temperature using Brillouin scattering and fluorescence in erbium-doped optical fiber

radiation.