Confined terahertz waves for dynamical modulation of material properties

Control of material properties (e.g. critical temperatures, magnetization, conductivity tensor), are regularly achieved with methods such as pressure, strain and electromagnetic fields. It is desirable to extend this degree of control to high frequencies. In an ongoing research effort, solids are excited in the terahertz (10¹² Hz) with new intense terahertz photon sources, exploiting this interesting band which lies at the edge of quasistatic approximations, intermediating between static control of matter and resonant interaction with low-energy modes. In an alternative approach, rather than using intense sources, I will use the idea of spatial confinement to enhance the coupling of terahertz drives (photons or phonons) to solid properties. Tailored cavities for photons and phonons will serve to amplify and tune their fields, with the aim of modulating macroscopic properties at faster timescales and larger amplitudes than conventionally possible.