Titanium diselenide (${\mathrm{TiSe}}_2$) is a transition-metal dichalcogenide material that undergoes a charge-density-wave (CDW) transition at $T_c\approx 200\mathrm{K}$. In a recent experiment [I. Tyulnev et al., Commun. Mater. 6, 152 (2025)], the high harmonic generation (HHG) spectra of this material has been studied, which exhibits asymmetric behavior with respect to the polarization angle of the incident light and provides a different perspective to the CDW phase transition. In this work, we work out a theoretical explanation for the experimentally observed behavior of HHG spectra. We propose a simplified phenomenological mean-field model for this material, based on which the HHG spectra is calculated through the time-dependent Schrödinger equation. This model correctly describes the measured intensity distribution of the third-, fifth-, and seventh-order harmonic generation as a function of polarization direction and reveals a strong asymmetry due to the anisotropic CDW order in the low temperature phase. Our work provides a basis for applying high harmonic spectroscopy to reveal a different perspective on the nature of CDW orders.

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• Charge density waves
• High-order harmonic generation
• Transition metal dichalcogenides
• Mean field theory