Abstract
High-power, ultrafast laser has been used in research because the strong electromagnetic field associated with an ultrafast laser can strongly interact with materials to generate a new phenomenon that differs from that under a weak electromagnetic field. This thesis is divided into two parts; the first part is related to the study of a Ti:sapphire laser amplifier and the second part is related to the use of a Ti:sapphire laser amplifier to excite an electric pulse in a helical wire to generate quasi-relativistic radiation. For the first part, we attempted to build a femtosecond laser amplifier based on the chirped pulse amplification technique. The laser pulse width of the seed laser was first stretched to 300 ps from a Ti:sapphire oscillator. The energy of the stretched pulse was about 1 nJ. We used a Pockels Cell to select precisely the laser pulse from the oscillator for amplification. We expected that the amplification gain of the stretched pulse laser is on the order of 106 times in a regenerative amplifier. We completed the design of the regenerative amplifier and waited for a high-voltage switch to test the amplifier. For the second part, we discovered that the radiation mechanism for a laser excited helical wire antenna is similar to that from a helical undulator. We carried out the measurements of radiation from ultrafast laser-excited helical wires in air and wrapped on a PVC tube. The measured radiation frequencies from both sets of data fit well to the theoretical model of undulator radiation. In the future, we will continue to investigate the physics of such radiation, including radiation power and stimulated emission. The major contribution of this thesis includes the complete design of a Ti:sapphire amplifier and the demonstration of quasi-relativistic radiation from an ultrafast laser-excited helical wire.