Relativistic electrons generated by the interaction of petawatt-class short laser pulses with solid targets can be used to generate bright x-rays via bremsstrahlung. The efficiency of laser energy transfer into these electrons depends on multiple parameters including the focused intensity and pre-plasma level. This paper reports experimental results from the interaction of a high intensity petawatt-class glass laser pulses with solid targets at a maximum intensity of 1019 W cm−2. In-situ measurements of specularly reflected light are used to provide an upper bound of laser absorption and to characterize focused laser intensity, the pre-plasma level and the generation mechanism of second harmonic light. The measured spectrum of electrons and bremsstrahlung radiation provide information about the efficiency of laser energy transfer.

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The spatiotemporal plasma-lens filter proposed here enhances the temporal contrast of the ultrashort pulse laser by combining plasma optics and spatial filtering. Experimentally, the spatiotemporal plasma-lens filter has improved the temporal contrast by 2 orders of magnitude with 80% laser transmission efficiency under a 1 Hz repetitive laser operation. Not only were the pre-pulse and the pedestal cleaned out, but also the rising edge of the main pulse was sharpened.