Experimental demonstration of 10¹¹ temporal contrast in pure nanosecond optical parametric chirped pulse amplifiers

Abstract

The temporal contrast of ultrashort and ultraintense laser pulses can significantly influence the laser–plasma interactions. As the optical parametric chirped pulse amplification (OPCPA) has been widely adopted in these laser facilities, the inherent optical parametric fluorescence, exhibiting a pedestal in the time window of the pump pulse, has become a significant problem. In this paper, we investigated experimentally its influence on the contrast of the compressed pulses at 808 nm using a multistage OPCPA amplifier. Compared to the highest value of 1 0 8 ever reported in the literature for such a type of regime, by adjusting the pump energy allocation between OPCPA stages and controlling the gain of small signal regime, we for the first time, to the best of our knowledge, realized a 1 0 11 temporal contrast in a pure nanosecond OPCPA design at a gain exceeding 7 × 1 0 8 , without adopting any other noise cleaning methods, such as picosecond OPCPA, cross-polarized wave generation, etc. This indicates that the OPCPA has a very significant potential for contrast improvement and to become a candidate for the future high-energy amplifiers in ultrashort high-power laser facilities.

Demonstration of a petawatt-scale optical parametric chirped pulse amplifier based on yttrium calcium oxyborate

“…The pump for OPCPA-I was provided by the Nd:YAG laser, which delivered pulses of 450 mJ in 2.2 ns duration at 532 nm with 1 Hz repetition rate, and four BBO crystals were aligned as before [ 32 ] . In our previous work, the pump energy allocation for the prior and the lateral two BBO amplifiers was set (52 and 398 mJ) for optimizing the temporal contrast in pure nanosecond amplifiers [ 33 ] . However, in the current condition the injected chirped signal pulse energy was half that of before, so the pump energy allocation was reset (90 and 360 mJ) to ensure a delivery capacity of 150 mJ.…”

“…In our previous work, the pump energy allocation for the prior and the lateral two BBO amplifiers was set [52 mJ, 398 mJ] for optimizing the temporal contrast in pure nanosecond amplifiers [33] . But in the current condition that the injected chirped signal pulse energy was half than before, the pump energy allocation was reset [90 mJ, 360 mJ] to ensure a delivery capacity of 150 mJ.…”