Ultrafast spectroscopy allows us to probe the dynamics of matter on femtosecond to picosecond timescales. The basic approach is the pump–probe technique: an intense pump pulse drives the material out of equilibrium, while a time-delayed probe monitors the resulting changes in its optical or electronic response. By varying the pump–probe delay, we track the evolution of photoexcited states and processes such as carrier relaxation, charge/energy transfer, quasiparticle interactions, and coherent collective dynamics. We employ multiple ultrafast spectroscopic schemes, including:

(1) Transient absorption spectroscopy and microscopy

(2) Terahertz (THz) time-domain spectroscopy / Optical pump - THz probe

(3) THz emission spectroscopy and theirt spatial mapping

The properties of quantum and nanoscale materials are governed by complex interactions among electrons, excitons, spins, and lattice vibrations. Many of these interactions occur on ultrafast timescales and become particularly intriguing when materials are driven far from equilibrium.

We use femtosecond pump–probe spectroscopy, terahertz spectroscopy, and nonlinear optical probes to visualize how these microscopic degrees of freedom evolve and interact in real time. These measurements enable us to explore phenomena such as quasiparticle relaxation, carrier transport, coherent lattice dynamics, spin dynamics, and light-induced transient states.

Through these studies, we aim to reveal the fundamental mechanisms governing emerging materials and establish strategies for ultrafast control of their electronic and optical functionalities.

Coherent lattice vibrations offer a unique opportunity to control quantum materials along well-defined structural coordinates. We use femtosecond laser pulses to launch coherent phonons and follow their evolution using ultrafast optical and terahertz probes. By resolving how the driven lattice couples to electronic and collective excitations, we seek to understand how atomic-scale motion can dynamically modify a material’s energy landscape and functionality.

Ultimately, we aim to use coherent phonons not only as a probe of light–matter interactions, but also as an active control knob for manipulating electronic states and emergent phenomena on ultrafast timescales. In our previous work, we investigated interlayer vibrational modes in van der Waals materials and demonstrated how these coherent lattice motions modulate their terahertz transport properties.