Contrast Measurement Of Ultra-short Laser Pulse With Single Shot

Remarkable progress in chirped-pulse amplification （CPA） technology has recentlyallowed for laser intensity as high as10²²W/cm². Along with the increasing of theintensity is the improving of the temporal contrast which has reached10¹⁰or higher.However, it is still a challenge to measure such high contrast, especially for asingle-shot laser pulse.To measure the temporal contrast of a single-shot pulse, based on the third-orderintensity correlation principle, using optical pulse replicators, a measurement method isproposed. The input pulse is first divided into two beams. One of them passes throughthe nonlinear crystal, generating the second-harmonic pulse signal. Then thesecond-harmonic pulse signal along with the other beam pass through the pulsereplicators, generating two pulse sequences with different periods, named the probesequence and the signal sequence respectively. After that, the two sequences passthrough the sum-frequency crystal, generating third-harmonic pulses. Thus the temporalinformation of the pulse is converted into the transversely spatial information. Detailedtheory analysis and computational simulation have been done for the measurementmethod proving that the method is validated. The measuring method based on opticalpulse replication can achieve high resolution and large time window at the same time.What’s more, this method is less sensitive to stray light and has a larger measuringdynamic range.A detailed theory analysis has been done in this paper including second-harmonicgeneration, sum-frequency generation, third-order intensity correlation. Besides, anumerical analysis has been done to the second-harmonic generation. Throughanalyzing the stray light in the crystal, the limiting factors of the dynamic range isfound.