Third-harmonic generation modulation achieved through ground-state depletion.

Without real-state transition, third-harmonic generation (THG) cannot be modulated simply by fluorescence-based methods. However, utilizing the absorption-enhancement property of THG, the modulation of THG intensity has been demonstrated through ground-state depletion (GSD) in this Letter. By suppressing the absorption of materials with GSD, the THG intensity can be reduced due to a decreasing of absorption enhancement. The ability to modulate THG intensity can benefit from applying super-resolution techniques to THG microscopy.