Many elementary processes in matter, such as interactions between electrons, spins, and phonons, involve low energies (on the order of a few meV) as well as dynamics on a (sub)-picosecond timescale. Unlike visible light, whose photon energy is high, terahertz (THz) radiation can directly probe and excite these low-energy processes, since THz photon energies fall in the same range (1 THz corresponds to 4 meV). Moreover, the vibrational and rotational modes of many molecules have resonance frequencies that lie within the THz spectral range. As a result, THz spectroscopy and optical pump–THz probe experiments are powerful techniques for exploring a wide range of low-energy physical phenomena and their ultrafast dynamics. The internship aims to explore many-body interactions in 2D perovskites using optical pump-THz probe experiment. The candidate will study exciton and free carrier dynamics to assess their respective contributions to the photoexcited population, a crucial information for advancing 2D perovskite optoelectronics. The project will also involve studying gain dynamics in ammonia molecules using a MIR pump-THz probe experiment to provide key insights for the development of a THz pulsed gas laser. Long term developments include studying topological insulators, 3D Dirac materials and quantum dots, studying the dynamics of elementary processes when these materials are integrated into THz cavities. Different light–matter coupling regimes will be explored.