Experimental Design and Construction for Critical Velocity Measurement in Spin-Orbit Coupled Bose-Einstein Condensates

Quantum simulation using ultra-cold atoms, such as Bose-Einstein Condensates (BECs), offers a very flexible and well controlled environment to simulate physics in different systems. For example, to simulate the effects of spin orbit coupling (SOC) on electrons in solid state systems, we can make a SOC BEC which mimics the behavior of SOC electrons. The goal of this project is to see how the superfluid property of BECs change in the presence of SOC. In particular, we plan to measure the critical velocity of an 87Rb BEC with and without SOC by stirring it with a laser. This laser needs to be blue-detuned for generating a repulsive potential as an obstacle. For this purpose, we build an external cavity diode laser (ECDL) at 776.47nm, which is blue-detuned to the D1 and D2 transition of 87Rb. To drive the ECDL, temperature and current controllers are designed and built. Since we need to focus the laser beam to the center of a BEC (about 20 by 55 micron), we set up a telescope to shrink the beam size to less than 10 micron. The optical design is accomplished by OSLO (optical system simulation software) with simulation results consistent with the Ray Transfer Matrix. To examine the superfluidity under different relative velocities, an acoustic-optic modulator will be used to move the beam against the BEC. At this point, the optical system is mostly finished. Our next step is to perform the critical velocity measurement of a BEC with and without SOC

Highly sensitive transient absorption imaging of graphene and graphene oxide in living cells and circulating blood

We report a transient absorption (TA) imaging method for fast visualization and quantitative layer analysis of graphene and GO. Forward and backward imaging of graphene on various substrates under ambient condition was imaged with a speed of 2 μs per pixel. The TA intensity linearly increased with the layer number of graphene. Real-time TA imaging of GO in vitro with capability of quantitative analysis of intracellular concentration and ex vivo in circulating blood were demonstrated. These results suggest that TA microscopy is a valid tool for the study of graphene based materials

Synthetic Graphene Grown by Chemical Vapor Deposition on Copper Foils

The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interests. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapour deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality comparable to exfoliated graphene. In this chapter, we review the synthesis and characterizations of graphene grown on copper foil substrates by atmospheric pressure chemical vapour deposition. We also discuss potential applications of such large scale synthetic graphene.Comment: 23 pages, 4 figure