ABSTRACT
As referring to the extents of SC spectra thereinafter, we mean the spectrum with intensity above 10"4. When a0 =1.6 and n0 =\.2nc, the unstable region gets broaden, as shown in Fig. 5(a). Compared with the SC extent from w/œ0 = 0 to colco{) = 18 in Fig. 4(a), the SC extent in Fig. 5(b) is extended to o)/co0 = 22. It appears that more energy near the fundamental frequency has been transferred to the high-frequency components. When a0 =3.0 and nQ - 12nc, the unstable region can also get broaden, as shown in Fig. 5(c), and the corresponding SC extent can reach up to w/œQ = 50, as displayed in Fig. 5(d). However, at higher plasma densities, high harmonics generation can significantly reduce the extent of SC generation, even though the unstable regions are quite broad.
