We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15？ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50？mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8？J with pulse duration of about 10？femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments. The attosecond pulse has been of interest in recent years and proved to be a powerful tool in studying the ultrafast phenomena, such as the chemical/biological transformations occurring on the femtosecond timescale and the evolution of the dynamics of the electrons in atoms or molecules irradiated by intense lasers. There are two ways to generate an attosecond pulse/pulse train. One is through the non-linear processes of the superposition of high order harmonics generated in the laser-gas atom interactions in which the laser intensity should be low so as to avoid the ionization of atoms. Up to now, the laser intensity is no more than 1016？W？cm？2 and the efficiency of harmonic emission from the atoms is low. The other way is to generate the high order harmonics from the dense surface of a plasma created by the high-intensity femtosecond laser, which is promising for the intense attosecond pulse generation. Recent experiments and simulations have shown that attosecond pulses with high conversion efficiency, high photon energy, and excellent divergence can be generated [1–4]. The efficiency of harmonic generation from the laser-plasma surface relies on the laser intensity. In the experiments for the brilliant harmonic generation from the surface, the laser has energy of 0.1？J to less than 10？J with a pulse duration of 30–50？fs [5]. In this paper, we report a novel ultrabroadband ultrashort high-energy laser system based on optical parametric chirped pulse amplification (OPCPA). After completion, the laser can deliver 8.0？J with pulse width of about 10？fs, which is much shorter than those used in the previous intense attosecond pulse generation experiments. The laser should be beneficial to the attosecond pulse generation and other ultrafast experiments. OPCPA has been applied and becomes promising for constructing
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