Design and experimental demonstration of a high conversion efficiency OPCPA pre-amplifier for petawatt laser facility

Abstract

We present the design and experiment of a broadband optical parametric chirped-pulse amplifier (OPCPA) which provides high conversion efficiency and good beam quality at 808 nm wavelength. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good beam quality and good output stability are discussed. To improve the conversion efficiency and broaden the amplified signal bandwidth simultaneously, the nonlinear crystal length and OPCPA parameters are analyzed and optimized with the concept of dissipating amplified idler between optical parametric amplification (OPA) of two crystals configuration. In the experiment, an amplifier consisting of two OPCPA stages of ‘L’ type configuration was demonstrated by using the optimized parameters. An amplified signal energy of 160 mJ was achieved with a total pump-to-signal efficiency of 35% (43% efficiency for the OPCPA stage 2). The output bandwidth of signal pulse reached 80 nm and the signal pulse was compressed to 24 fs. The energy stability reached 1.67% RMS at 3% pump energy variation. The optimized OPCPA amplifier operates at a repetition rate of 1 Hz and is used as a front-end injection for the main amplifier of SG-II 5PW laser facility.

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

“…The grating pairs in the pre-compressor also provided negative linear component dispersion (group velocity dispersion, GVD), and the chirped ratio of seed pulses injected into OPCPA-I at present was deduced to be 21.3 ps/nm, while the energy per pulse was reduced to approximately 0.1 nJ. 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 ] .…”

Polarization-Based Idler Elimination: Enhancing the Efficiency of Optical Parametric Amplification

“…Another approach is to suppress the back-conversion completely, which can be achieved by eliminating the idler wave from the interaction just before the pump wave is fully depleted. Besides some theoretical suggestions [17][18][19][20], this was previously achieved by employing idler second-harmonic generation (SHG) [21], non-collinear pump recycling schemes [22][23][24] and samarium (Sm +3 ) doped yttrium calcium oxyborate (Sm:YCOB) nonlinear crystals that strongly absorb the idler wave at infrared wavelengths [25,26], which led to 56% pump-to-signal conversion efficiency and pump depletion of 85%. Nevertheless, when compared to solutions employed in typical OPA devices, these approaches tend to either consume a lot of space, demand exotic materials or lack tunability.…”

Optomechanical Coupling Active Control for Improving Beam Pointing Accuracy of the Spatial Filter in PW Laser Facility

“…PW laser facility has a small focal spot and high energy. High energy requires the size of the focal spot, while the size of the focal spot has requirements for pointing stability, and the PW facility has requirements for pointing stability [11,12]. LLNL in literature [13] proposed an interference adaptive optical system for high power laser beam correction in ARC.…”