Strength of synthetic diamonds under tensile stresses produced by picosecond laser action

Results of an experimental-theoretical study of spallation in synthetic diamonds are presented. In this study, data were first obtained on dynamic tensile strength of poly- and single-crystal diamond samples at mechanical loads of up to $0.34$ TPa and strain rates of $10$–$100$ $\mu$s$^{-1}$. Shock-wave loading was performed by $70$ ps laser pulses on a Kamerton-T facility using a Nd:glass laser (second harmonics $\lambda=527$ nm, pulse energy of up to $\approx3$ J) at intensities of $\approx8$ TW/cm$^2$. The obtained maximal value of the spall strength $\approx16.4$ GPa is $24\%$ of the theoretical ultimate strength of diamond. Raman scattering experiments showed that a small amount of diamond was graphitized in the spall area on the backside of the sample.