Coherent THz radiation from laser-wakefield-accelerated electron bunches

In recent years the concept of the Laser Wakefield Accelerator (LWFA) has demonstrated to deliver electron bunches that are dense, short, and ultra-relativistic. While originally producing electrons at beam energies of a few MeV with large energy spread, recently electron energies of 1 GeV were realized, with percent level energy spread. In addition to the reduced size of the accelerator (and price), a major advantage of the LWFA is its ability to deliver femtosecond synchronized radiation pulses, ranging from electrons, VUV pulses, laser light, THz radiation, X-rays, protons, and others. I will talk about the experimental efforts of the LOASIS program (Lawrence Berkeley National Laboratory, Berkeley, California) concerning the measurement of the electron bunch duration. This was realized by analyzing the coherent radiation (at THz frequencies) that these bunches emit. A series of techniques will be discussed, with a single-shot time-domain electro-optic scheme being its most valuable. The THz pulses themselves also prove to be unique (single field cycle) and intense, which opens possibilities for strong-field applications in the THz domain.