Most time resolved studies to date have made use of readily available visible and near-visible pump sources to trigger theevents and, thus, were bound to study of only a small subset of phenomenon accessible to photon with an eV energies. In contrast, a few recent experiments have emerged in which the dynamics stimulated by THz and mid-infrared pulses led to a selective control of an insulator metal transition, discovery of the light induced superconductivity in a stripe-ordered cuprate and observation of coherent nonlinear phononics that can be used for ultrafast control of materials. Many low frequency excitations of complex condensed matter driven by THz pulses are likely to exhibit interesting dynamics that can also be used in a new generation of electronics. Furthermore, one may wish to study the response of the system in a controlled fashion using a variety of pump pulses.
It is therefore necessary to have light sources over broad range of frequencies. Particularly important is obtaining pump pulses in the frequency range from 1 to 20 THz that are 1) narrow band and tunable with the relative bandwidth of the order of 1% and the peak electric field of the order 100 kV/cm; 2) broad band and near-half-cycle with the peak electric field larger than 1MV/cm.
We propose a workshop to discuss various ideas that could help to build tunable THz sources satisfying above stated requirements. It is presumed that these sources should work in tandem with a free-electron laser or a storage ring based synchrotron light source producing x-ray probe pulse. Thus, synchronization between THz pulse and the x-ray pulse with a picosecond level accuracy is essential. It is also desirable to match the repetition rate of THz pulse with a repetition rate of x-ray pulses that in the case of a storage ring base light source is of the order of few MHz