y form only given. A phenomenological model of frequency blueshift during laser breakdown of dielectrics by ultra-fast pulses is developed. The time scale is too short for heat conduction and diffusion consequently interaction is spatially localized. Laser causes electron-hole pair production via tunneling of valence electrons to conduction band, Joule heating and avalanche production of electron-hole pairs, via collisions. As the free carrier density rises, refractive index decreases, modulating the phase of the laser and causing frequency blueshift.