Laser-Induced Microexplosion Confined in the Bulk of a Sapphire Crystal: Evidence of Multimegabar Pressures

Extremely high pressures ($\sim 10\mathrm{TPa}$) and temperatures ($5\times {10}^5\mathrm{K}$) have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside a sapphire crystal. The laser pulse creates an intensity over ${10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ converting material within the absorbing volume of $\sim 0.2\mu {\mathrm{m}}^3$ into plasma in a few fs. A pressure of $\sim 10\mathrm{TPa}$, far exceeding the strength of any material, is created generating strong shock and rarefaction waves. This results in the formation of a nanovoid surrounded by a shell of shock-affected material inside undamaged crystal. Analysis of the size of the void and the shock-affected zone versus the deposited energy shows that the experimental results can be understood on the basis of conservation laws and be modeled by plasma hydrodynamics. Matter subjected to record heating and cooling rates of ${10}^{18}\mathrm{K}/\mathrm{s}$ can, thus, be studied in a well-controlled laboratory environment.