Tingshuai Li

Low threshold random lasing actions in natural biological membranes

We report random lasing actions stemming from natural biological membranes doped with Rhodamine 6G (Rh6G) laser dye which were then stimulated by a pulsed laser. The membranes have concave–convex structures and are expected to form resonators for weak light scatterings. The laser emission varies with the type of membrane and is also closely related to the dye concentration and pump energy. The threshold for the laser generation obviously rises when the concentration of doped laser dye is increased. The simulation results show lasing distributions are localized, indicating that the laser modes are very sensitive to the indicant angles of pump light.

Random laser action from a natural flexible biomembrane-based device

Abstract Incoherent random lasing action in flexible eggshell membranes infiltrated with rhodamine 6G laser dyes is demonstrated. Laser radiation is achieved by exciting samples with 1-ns pulses at 526 nm. A threshold of 58 μJ/pulse is measured for the samples. The minimum threshold decreases to 35 μJ/pulse after the sample is coated with gold nanoparticles using a magnetron sputtering technique. The peaks of emission spectra are observed to redshift from 576 to 596 nm as dye concentration rises from 0.03 to 0.6 wt%. A linewidth of approximately 5 nm is obtained for most samples. This study is expected to offer a new way to induce lasing emission using biological microfibrils, and enriches basic knowledge of biophotonics.

Solid Oxide Fuel Cell Interconnect Design Optimization considering the Thermal Stresses

The mechanical failure of solid oxide fuel cell (SOFC) components may cause cracks with consequences such as gas leakage, structure instability and reduction of cell lifetime. A comprehensive 3D model of the thermal stresses of an anode-supported planar SOFC is presented in this work. The main objective of this paper is to get an interconnect optimized design by evaluating the thermal stresses of an anode-supported SOFC for different designs, which would be a new criterion for interconnect design. The model incorporates the momentum, mass, heat, ion and electron transport, as well as steady-state mechanics. Heat from methane steam reforming and water–gas shift reaction were considered in our model. The results examine the relationship between the interconnect structures and thermal stresses in SOFC at certain mechanical properties. A wider interconnect of the anode side lowers the stress obviously. The simulation results also indicate that thermal stress of coflow design is smaller than that of counterflow, corresponding to the temperature distribution. This study shows that it is possible to design interconnects for an optimum thermal stress performance of the cell.

Random laser action from ceramic-doped polymer films

Abstract We report random lasing emission from polymer films doped with ceramic particles in a gain medium. The Al2O3 particles and Rh6G laser dye-doped PVP films were fabricated by a spin-coating technique and they were exposed to a pulsed laser at 526 nm, by which we collected intensive feedback random laser (IFRL) emission when the pump energy reached thresholds. The threshold depended on particle size, film thickness and particle contents in solution. A model with randomly distributed scatterers was established to confirm that the scattering properties could strongly effect the thresholds and lasing spatial distributions.

Measurement and Analysis of Electromagnetic Pulse from Laser-Target Interaction at ShenGuang II Laser Facility

Abstract Electromagnetic pulses (EMPs) generated from lasers interacting with solid targets at the ShenGuang II laser facility were measured and analyzed in this work. The EMP radiations were related to the target geometries, where the strongest EMP signal with a magnitude of 103u2009V and duration of several dozens of nanoseconds resulted from the monopole flat coil and Au foil targets. The EMPs detected inside the laser facility were seriously affected by the chamber wall, which could reflect EMPs and prolong the signals with several typical pulsed peaks. This study was expected not only to provide basic information to interpret physical processes caused by laser irradiating targets but also to offer a path for electromagnetic interference shielding designs and protect the diagnostics from damage in inertial confinement fusion.

Random Lasers with Coherent Feedback from Polymer Films Based on Rh6G-PVP

The observation of random laser (RL) with coherent feedback in transparent polymer films based on Rh6G-PVP by spin-coating was carried out in the present investigation. Some sharp peaks with FWHM identified to be 2 nm appeared on the fluorescent spectra of polymer films which pumped by Nd:YLF pulse laser (wavelength: 526nm, frequence: 1Hz, pulse duration: 1ns, energy power: 1.2mJ/pulse). The threshold of emission spectra is ~35 and the spectra range from 570 ~ 610 nm. Streak camera was used to record the temporal process of RLs and the pulse duration time was measured to ~400ps. Rh6G-PVP transparent films were a kind of polymer films with numerous nanogaps distributed randomly on the surface of the film. The photons will be multiple scatterred and amplified during the spreading in the polymer film owing to the refractive index difference between nanogaps and polymer films. As the Rh6G-PVP polymer films have characters of convenient fabrication processes, low threshold and low cost, it shows great potential application in photoelectron and laser imaging.

Characterization of a quasi-sinusoidal transmission grating without membrane substrate in the 200–1500 eV photon energy regions

A 1000-line/mm quasi-sinusoidal transmission grating (QSTG) without membrane substrate has been designed and fabricated, which is utilized to eliminate the higher order diffraction for soft X-ray spectrum measurement in the experiments of inertial confinement fusion. The grating was calibrated using an X-ray beam on synchrotron radiation facility. It shows that the QSTG has the desired diffraction property and the higher order diffraction components are efficiently suppressed in the photon energy ranges from 200 to 1500 eV.