Laser intensity and incidence angle dependent attosecond light pulse generation from relativistic laser-plasma surfaces

Relativistic high-order harmonics from a few-cycle laser driven plasma surface is a very promising source of an intense and isolated attosecond light pulse. The laser to harmonics conversion efficiency and the “purity” of an isolated attosecond light pulse are generally determined by a combination of interaction parameters, such as laser intensities, incidence angles, pulse durations, carrier-envelope phases and plasma scale lengths. We had already previously investigated the effect of a three-parameter combination of the laser pulse duration, the carrier-envelope phase and the plasma scale length. To complement our previous work, the parametric dependence of the other two three-parameter combinations: the carrier-envelope phase, the plasma scale length, either combined with the laser intensity or the incidence angle, were systematically investigated through one dimensional particle-in-cell simulations. We found that, although the impact of parameter combinations on attosecond pulse generations is generally complicated, there exist however an optimal plasma scale length and an optimal incidence angle to efficiently generate high-order harmonics and intense attosecond light pulses. When other parameters are fixed, a moderately intense relativistic laser is more advantageous to realize an isolated attosecond light pulse in a broad controlling parameters range. And a larger incidence angle favors a higher isolation degree as well as a broader range of controlling parameters towards the generation of intense isolated attosecond light pulses. In order to interpret these simulation results, we have modeled the corresponding relativistic electron dynamics, using which the underlying physics are discussed.