Laser field strength dependence of solid high-harmonic generation from doped systems

We have theoretically studied the field-strength dependent high-harmonic generation (HHG) in doped systems like nano-size or bulk materials. Our results show when the amplitude of the vector potential A_peak of the driving laser reaches the half-width of the Brillouin zone ({\pi}/a0), the harmonic yield of the undoped systems is larger than the doped systems. The band-climbing process enhances the interband transition of HHG for higher conduction bands. When A_peak is below {\pi}/a0 , the harmonic yield of the doped systems is stronger than the undoped systems. The atomic doping density also influences the field-strength dependent spectra.