Techniques
Our group employs the state-of-the-art tools of spectroscopy to address some of the most challenging issues in chemistry. The following shows a brief summary of the techniques we use. These experimental capabilities in our group provide students with the training they need to flourish in the modern world of advanced-technology settings.
Ultrafast X-ray/Infrared Lasers
Our attosecond beamline is pumped by an intense, multi-mJ femtosecond tatinium-sapphire laser system, which allows us to have versatile spectroscopic capabilities. The beamline is constructed on vibration isolation tables in a climate controlled room. The optics used in our lab are specifically designed for the ultrafast light sources such that spectral dispersion is carefully handled. As a materials research lab, we also employ optical cryostat and high-vacuum systems to study temperature/air sensitive materials.
Extreme Nonlinear Optics
Nonlinear optics play an important role in our research allowing us to tune the spectral shape and color of the ultrafast lasers. The key processes include second-harmonic generation, difference-frequency generation, self-phase modulation, and high-harmonic generation. Those processes allow us to manipulate our spectrum from extreme ultraviolet to far infrared. The wide spectral coverage is integral to access materials electronic and structural dynamics, as well as internal resonance of quasi-particle states.
Spectroscopy on Quantum Materials
We combine multiple spectroscopic tools to perform experiments on quantum materials. Ultrafast pulses are characterized by dispersion scan, SD-FROG, and transient-absorption cross correlation. The samples are characterized by photoluminescence, Raman scattering, and atomic-force microscopy. The materials dynamics are measured by attosecond transient absorption as well as solid-state high-harmonic generation. The group strives to develop new spectroscopic tools for chemical and materials applications.
Optomechanical Control and Programming
Computing and simulations are critical part of our research. We custom-build our high-vacuum chambers that are uniquely designed for our attosecond XUV beamline. The data acquisition and motion control are done by custom-written programming codes thus to carry our our measurements in a fast and efficient way. We also perform quantum-mechanical calculations for materials properties as well as simulations on electronic dynamics, which provide the basis to for the design of our experiments.