High harmonic generation (HHG) by two-color counter-rotating relativistic laser pulses with arbitrary frequency ratio is investigated through particle-in-cell simulations. It is shown that the dichromatic laser driver at various frequency ratios can effectively produce high-order harmonics with different spectral features. A general selection rule of this extended scheme can be obtained and the corresponding harmonic helicity can be identified through a simple analytical model based on a relativistic oscillating mirror. Thus, the results in this paper may offer new opportunities for arbitrary spectral control of generated harmonics, which is of significance for diverse potential applications in practice.

通过粒子内模拟研究了由具有任意频率比的双色反向旋转相对论激光脉冲产生的高次谐波 (HHG)。结果表明，不同频率比的双色激光驱动器可以有效地产生具有不同光谱特征的高次谐波。可以得到这个扩展方案的一般选择规则，并通过基于相对论振荡镜的简单解析模型确定相应的谐波螺旋度。因此，本文的结果可能为生成谐波的任意频谱控制提供新的机会，这对于实践中的各种潜在应用具有重要意义。