School of Science Department of Physics 66 Mechanics of Soft Composite Materials Supervisor: XU Qin / PHYS Student: YANG Chun Hin / IRE Course: UROP1100, Summer Soft composite has shown a variety of properties by adding different liquid inclusion. The elastic response of the soft composite is also changed by the liquid inclusion. The classical Eshelby’s theory describes how does the modulus of the composite changes with different volume fraction. Recently, stiffening effect is found to occurred to a soft composite with liquid inclusion. The counterintuitive phenomenon cannot be explained by the Eshelby’s theory. In this paper, sample with different volume fraction are fabricated to investigate the elastic response of soft composite. The result shows that Eshelby’s theory can be used to explain the response for low volume fraction but fail in high volume fraction. Quantum Computing Based on NV Center in Diamond Supervisor: YANG Sen / PHYS Student: FEI Zijian / SSCI Course: UROP1100, Summer In this project, we are supposed to use a room temperature experimental setup to detect the charge state of the NV color center. The NV center is a kind of crystal defect in diamond formed by two lattice defects, a nitrogen atom and a vacancy. The NV color center can be in NV0 or NV - states, and NV - is used for quantum calculation. Therefore, in order to improve the quantum fidelity, we need to make a measurement and selection, and select the one only in NV - state. This is done by illuminating it with a 593nm laser and detecting the fluorescence intensity. We need to tune the 593nm laser, use AOM (acousto-optic modulator) to switch the laser on and off, and record the fluorescence count. We also need to optimize the parameters in our work. Femtosecond Laser Pulse Induced Air-plasma Filament for Generating THz Radiation: Experiment and Simulation Supervisor: ZHANG Jingdi / PHYS Student: HO Ka Ying / MAE Course: UROP1100, Fall The generation of T-rays is of much research interest because of its numerous applications in biomedical imaging, sensing and plasma diagnostics. The far-infrared radiation can penetrate non-polar materials such as paper, clothing, ceramics etc., and shows great potential in historical research. Current high-energy THz generation relies on large accelerators, synchrotrons and free electron lasers, which are costly and difficult to access. With growing demand for THz generation, using tabletop ultrafast lasers for THz generation is of much research interest. One of the methods is femtosecond terawatt laser system, and T-rays can be generated via two-color laser mixing in gases. This report will briefly summarize the two proposed models explaining the phenomenon of two-color laser mixing, and typical experimental setups of THz generation.