通过数值求解含时Schr(o)dinger方程,研究了氦离子在不同双色场下的高次谐波.结果显示,尽管倍频光强度仅为基频光的1/10,高次谐波辐射却发生了极大变化.虽然谐波级次推进不多,但效率大大提高了,平台区平均提高10³倍,高倍频光对应的高次谐波产生效率提高10⁴～10⁵倍.氦离子在添加倍频光的双色场作用下高次谐波产生效率极大提高的原因是:倍频光极大地加快了电子电离到连续态及返回基态这一过程,使辐射出的高次谐波光子数大大增加,该初步阐释可为高次谐波真正应用到实际中提供一些理论启示.

The high-order harmonic generation spectrums of He⁺ irradiated by the two-color coherent laser field are researched by numerically solving the 1-D time-dependent Schr(o)dinger equation using symplectic algorithm.The computational results show that great changes have already taken place at the emission of the high-order harmonics and the efficiency of the harmonic generation increases greatly and it averagely increases 10³ times in the plateau,despite the fact that the intensity of the higher frequency laser is only 10% of the initial field in the two-color coherent field.The efficiency of the high-order harmonics is enhanced by nearly four orders of magnitude relative to the monomer field;moreover,the corresponding order of the higher frequency field is enhanced by about five orders,even ten orders though the harmonic plateau isn't extended to a higher frequency.The reason is that the population of the ground state descends and the population of the first-excited state increases in the two-color coherent lase relative that in the monochromic laser and the transition channel of the electron to the even-parity continuum becomes easy and smoothes.In particular,the high-frequency laser quickens the process that the electron ionizates and rebounds to the ground state.