With the development of petawatt (PW) even 100-PW laser facilities, ultra-intense laser pulses with focal intensity higher than 10^22 W/cm2 become available. Among lots of laser matter interaction experiments, the temporal contrast is the most important parameter except for focal intensity. However, precise single-shot characterization of the temporal contrast is the first key step with only few limited methods.
Among all these typical methods previously developed, it is hard to achieve high dynamic range, precise time resolution, nice pulse contrast fidelity, and wide time window in single-shot at the same time while those are most important parameters for temporal contrast characterization
A research team from State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made two successive important contributions to the single-shot temporal contrast measurement with high dynamic range and precise time resolution simultaneously. The results were published in Optics Express.
Firstly, they demonstrated a compact single-shot cross-correlator with a dynamic range of 10^10, in which the intense signal of the cascaded four wave mixing process was used as the sampling pulse. The temporal resolution was improved to 160 fs, which was even better than a commercial delay-scanning third-order correlator. Moreover, the single-shot cross-correlator would avoid the ghost prepulse introduced by the postpulse benefiting from the better temporal contrast enhancement of the sampling pulse.
Fig 1 Characterizations of the temporal contrast of a laser pulse
Secondly, they developed a new idea or direction of temporal contrast reduction techniques for high dynamic-range single-shot temporal contrast measurement, where the temporal contrast will be reduced and measured by using current common techniques. The pulse stretching, anti-saturated absorption and the optical Kerr effect were simultaneously proposed and the temporal contrast reduction of about one-order of magnitude was realized.
The proposed method has the potential to break the dynamic-range barrier of temporal contrast measurements, and make it possible for higher dynamic-range single-shot temporal contrast measurement.
Fig 2 Principle of high dynamic temporal contrast characterization.(Image by SIOM)
The work was supported by National Natural Science Foundation of China (NSFC); the Instrument Developing Project and the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS); Shanghai Municipal Science and Technology Major Project.
Mr. Cao Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS