Microexplosions in bulk sapphire driven by simultaneously spatially and temporally focused femtosecond laser beams

Confined microexplosions driven by tightly focused femtosecond laser pulses inside the bulk of transparent dielectrics [1] had been argued to produce extreme pressure and temperature conditions on the tabletop. Early estimates suggested that transient pressures exceeding 10 TPa can be attainable [2]. Our numerical analysis [3] based on the non-paraxial Maxwell propagator for the optical field, initiated by the non-paraxial boundary conditions and coupled with the rate equations for the material response, shows rigid clamping of both the free-electron density and temperature in the interaction volume (Figure 1). The clamped values correspond [4] to the peak attainable pressures of ~250 GPa, which is about two orders of magnitude lower than the earlier estimates [2]. Our numerical results are robust against very large variations of the ionization and electron-heating parameters of up to one order of magnitude up or down from their nominal accepted values.