Polymer relaxations determined by use of a temporally and thermally stable interferometer

We describe a phase-controlled, highly stable interferometer that is ideal for use in long-time and high-temperature studies. We recorded output intensity variations of <0.2% for over 6 h at temperatures up to 150 degrees C. The setup was used to study in situ the temperature and frequency characteristics of a thin polymer film composed of 4-dimethylamino-4?-nitrostilbene doped into poly(methyl methacrylate). The mobility of the dopant molecules, which governed the electro-optic property of the film, was used to probe the dye-doped polymer's rheology. We demonstrate one application of the interferometer in probing both the alpha and the beta relaxations of the polymer.     

Modified laser ablation process for nanostructured thermoelectric nanomaterial fabrication

A modified pulsed laser deposition process was used to enhance the nanostructure generation inside Bi₂Te₃ nanocrystals. In this process, an additional femotosecond laser beam was used to add an energy shock on the ablated flume, which can result in rich nanostructures embedded inside Bi₂Te₃ nanocrystals. A large Si wafer was used to ‘freeze’ such nanostructures and to effectively collect such nanostructured nanocrystals for further processing. The generated nanocrystals were studied by X-ray diffraction and scanning transmission electron microscopy, and the results prove the existence of such embedded nanostructures. Such nanocrystals were also characterized electrically and thermally for the conductivity measurements.     

Cesium vapor laser with transverse pumping by multiple laser diode arrays

We have demonstrated a Cs vapor laser that utilizes fifteen laser diode arrays for transverse pumping of the gain medium. A maximum output power of 28 W was achieved with a total optical to optical efficiency of 14% and a slope efficiency of 15%. Transverse pumping allows scaling of such a laser system to a higher power level by simple increasing of the gain medium volume and the number of pump sources.