The typical temporal contrast of the femtosecond front end a few ns before the actual pulse is shown in Figure 1. In addition, the contrast can be tailored to the special requirements of different experiments with controlled pre-pulses.
For this purpose, the option of generating a double pulse with adjustable delay and energy ratio from a single pulse can be used downstream of the femtosecond front end. Alternatively, a femtosecond pulse can be overlaid with a nanosecond pulse at the input of the preamplifier. The nanosecond front end can generate almost any pulse shape. The pre-pulses generated in this way can be up to 10 ns before the main pulse with energy ratios of up to 1:1.
Figure 1: Measurement of the temporal contrast at the femtosecond front end with ultrafast parametric amplifier (blue). The prepulses marked with arrows are artefacts of the measurement system. [1]
Reference:
[1] Y. Zobus, et al., High Power Laser Science and Engineering Vol. 11, e48 (2023), doi:10.1017/hpl.2023.30
