First stage development of a single-shot 3rd order cross correlator for measuring PW laser contrast

Abstract

Measuring the temporal contrast of an ultrahigh power laser is important to rigorously perform laser-matter interaction experiments. The prepulse contained in the ultrahigh power laser can distort the interaction processes since it interacts with target material before an arrival of the main pulse. There already exist various types of instruments to measure the temporal profile of high-power femtosecond lasers. As multi-shot scanning diagnostic tools cannot provide the temporal structure of the laser precisely, a single-shot cross-correlator was investigated in this thesis. A single-shot cross-correlator(SSCC) characterizes a laser pulse in real-time, providing directly such information as the temporal structure of the whole laser pulse, including the pre- and post-pulses, and the sign of GDD. The third cross-correlator performs non-collinear sum frequency generation in a BBO by overlapping the fundamental at 800nm and its second harmonic at 400nm generated in another BBO. The image of the third harmonic at 266nm was obtained using a beam profiler. The contrast of the incident laser pulse could be analyzed from the detected image. For the performance of SFG, a 30 fs laser at 1 kHz with power of about 700 mW was used. For the first stage development only one channel of the whole SSCC system was tested, which covers ~5 ps temporal range. When the whole channels are constructed for a PW femtosecond laser, we expect ~100 ps temporal range and high dynamic range.