Power Tunable High and Narrowband THz source for THz Pump X-ray Probe Experiments

Most time resolved studies to date have made use of readily available visible and near-visible pump sources to trigger the events and, thus were able to study only a small subset of phenomena. Recently, investigations of the dynamics stimulated by THz pulses have led to advances like the selective control of an insulator metal transition, discovery of light induced superconductivity and observation of coherent nonlinear photonic effects 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. For these experiments it is critical to obtain pump pulses in the THz frequency range from 0.3 to 10 THz that are tunable with a relative bandwidth on the order of 1% and energy per pulse of ~ 1mJ. Building on our recent successful experiment we propose a three stage THz source scheme. Two of the first stages have already been demonstrated separately. In the first stage the beam is modulated in energy by passing through a passive wakefield device. The energy modulation is then converted into a density modulation by means of a chicane. In the third stage, the bunched beam produces a narrowband high power pulse of terahertz radiation by going through a power extractor. The beam based source provides sufficient power and allows for a wide tuning range. Prior to this Phase I proposal we had separately demonstrated two key stages of the proposed three stage THz source. In Phase I we will design, fabricate and assemble a complete device including the beam modulating section followed by a power extraction unit. Additional magnet optics will be designed and manufactured to ensure proper injection of the modulated beam into the power extractor. A demonstration experiment will be performed at the Brookhaven National Laboratory if the schedule allows. Applications and benefits: A tunable, powerful, narrowband THz source will allow scientists to selectively excite and study new dynamic phenomena at light sources. Besides applications for basic science, these sources can find a variety of applications in communications, non-destructive evaluation, radar systems and medical diagnostics.