Abstract
To improve pulse contrast in chirped pulse amplification petawatt laser systems, the regenerative amplifier is substituted with a multipass amplifier at the Shanghai Superintense Ultrafast Laser Facility (SULF). To reduce the consequent angular dispersion of the broadband spectrum, a double-grating stretcher is established in the SULF front end. A grating compressor is set up for the 10-PW front end to obtain 20-TW output. An accurate adjustment method of grating attitude (angular position) is presented, which references the direction of gravity, improving dispersion management and focusing ability of the beam. After a pulse passes the front end compressor, its duration and phase in the frequency domain are measured, and the duration can be continuously compressed to <24 fs.
Highlights
Based on the chirped pulse amplification (CPA) [1] technique and its analogs, optical parametric chirped pulse amplification (OPCPA) [2] and non collinear optical parametric chirped pulse amplification (NOPCPA) [3,4,5], petawatt-class (PW) femtosecond laser systems have made notable progress over several decades [6]
We present a 20-TW front end pre-compression system, emphasizing dispersion management
The angular dispersion is determined by the three rotation angles α, β, and γ of the grating as Gravity is a stable vector in the laboratory, whose offset is negligible in an experimental station shown in Figure 4b, where, α regulates the grating ruling direction, β maintains the grating plane of hundreds or thousands of square meters, as is the pointing direction of the laser beam
Summary
Based on the chirped pulse amplification (CPA) [1] technique and its analogs, optical parametric chirped pulse amplification (OPCPA) [2] and non collinear optical parametric chirped pulse amplification (NOPCPA) [3,4,5], petawatt-class (PW) femtosecond laser systems have made notable progress over several decades [6]. To avoid the elongation of output pulse duration due to material dispersion in broadband CPA systems, high-order dispersion management is an essential part of the petawatt-class laser facility. Since residual fourth-order dispersion compensation was proposed, it has been quite a difficult problem in large-scale laser facilities Optical elements, such as the acousto-optic programmable dispersive filter (AOPDF) [11], grism pairs [12], and deformable mirrors [13], are widely used in CPA systems for high-order dispersion management. For a double-grating Offner stretcher, with multiple degrees of freedom of optical elements, such as gratings, the roof mirror, and prism, it cannot be determined whether the position of each element is correct by the focal spot alone; it is not possible to eliminate high-order dispersion and residual angular dispersion. Focusing ability can be increased predictably, and verification of this will be the subject of current research
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