One of the most important properties of ultrafast-laser experiments intended for materials and physics research is high temporal contrast, as too much prepulse will destroy the target and negatively affect laser-matter interaction experiments. Consequently, contrast enhancement is of great importance for high-power ultrafast lasers.
Researchers from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (SIOM, CAS) and Hebrew University of Jerusalem have now reported a novel temporal contrast-enhancement device called a spatiotemporal plasma-lens filter (STPLF).1
STPLF combines the concept of plasma optics and a spatial filter; it uses a trigger laser to generate a spatiotemporal plasma lens to enhance the temporal contrast of high-power ultrashort laser pulse. For relatively low-intensity noise (such as in the prepulse), STPLF disperses the propagating beam with high loss by the plasma lens. When the main high intensity pulse arrives, the rising edge of the laser pulse destroys the plasma lens; thus, STPLF will act as a regular spatial filter with low loss (and will also improve the spatial beam quality).
The researchers performed demonstration experiments using the Shenguang-II 5 PW laser system in Shanghai. STPLF improved the temporal contrast by two orders of magnitude, with 80% laser transmission efficiency at a 1-Hz pulse-repettition rate, and also improved the spatial-profile quality. The results showed significant prepulse reduction and rising-edge steepening.
1. Ping Zhu et al., Optics Letters (2020); https://doi.org/10.1364/OL.388391.