High-order harmonic signal of bond-length-variable C18 and its application in optical logic gates

Recently, a solid-state-like high-harmonic generation (HHG) mechanism has been proposed from rotationally periodic molecules. Based on the quasi-energy band model, we investigate the HHG of ring-type polyynic cyclo[18]carbon (C₁₈) by further considering its bond length difference (Rdiff) between the short and long C-C bonds. For Rdiff values ranging from 0.06 to 0.120.16em0ex with a linearly polarized laser, the seventh harmonic intensity of polyynic C₁₈ exhibits the most significant structural sensitivity compared to the third and fifth harmonics. Transition energy level distribution, paired with time-frequency analysis and transition dipole moment behavior, indicate that the seventh harmonic arises from pure interband processes. Conversely, the HHG properties driven by two consecutive circularly polarized laser pulses at each considered laser intensity combination remain unaffected by changing these Rdiff values. This characteristic allows polyynic C₁₈ to be utilized for designing a variety of logic gate operations based on its harmonic ellipticity in ultrafast strong laser fields.