School of Science Department of Physics 76 Femtosecond Laser Pulse Induced Air-Plasma Filament for Generating Thz Radiation: Experiment and Simulation Supervisor: ZHANG Jingdi / PHYS Student: LIN Yuchen / COSC Course: UROP1100, Fall Terahertz electromagnetic wave refers to electromagnetic radiation with the frequency ranging from 0.1~30 THz. Cutting-edge THz technologies, involving generation, modulation, and detection of THz frequency electromagnetic waves are considered to be one of the essential next-generation technologies and the strategic direction of research in the future. Femtosecond Laser Pulse Induced Air-Plasma Filament for Generating Thz Radiation: Experiment and Simulation Supervisor: ZHANG Jingdi / PHYS Student: LIN Yuchen / COSC Course: UROP2100, Spring Following the previous UROP 1100 research, a series of numerical simulations on the amplitude and phase modulation of high-frequency terahertz emission have been performed. Meanwhile, valid models recovering the microscopic dynamics of the amplitude and phase modulation of the terahertz radiation based on the investigation into a kind of phase anomaly have been developed. Also, in preparation for the publication of the research proceedings, illustration figures are also plotted during the project period. In the coming summer semester, we will conduct experiments to demonstrate and verify the validity of our model explaining the mechanism of the generation and modulation of terahertz radiation. Measuring Femetosecond Laser Pulse Duration with FROG Supervisor: ZHANG Jingdi / PHYS Student: YANG Yuang / DSCT Course: UROP1100, Fall Frequency-Resolved Optical Gating (FROG) is the standard method to achieve a complete characterization of ultrafast laser pulses, and the wide adoption of this technique provides convenience and accuracy to labs worldwide. After collecting data points, a retrieval algorithm must be applied to the FROG trace to retrieve the pulse intensity and phase with respect to time. This report focuses on two powerful FROG algorithms, the basic FROG algorithm and the generalized projections (G.P.), reviews some practical considerations for their application and the math and physics behind them, and showcases the pulse characterization from experiment data and data generated from theory using the FROG software by Femtosoft Technology.