Enhancing nonlinear energy deposition into transparent solids with an elliptically polarized and mid-IR heating laser pulse under two-color femtosecond impact

Abstract

We report on an enhancement of deposited energy density of up to 10 kJ cm−3 inside transparent solids (fused silica and quartz) from using two-color µJ energy level tightly focused (NA = 0.5) co-propagating linearly polarized seeding (visible, 0.62 µm) and elliptically polarized heating (near-IR, 1.24 µm) femtosecond laser pulses. The rise in temperature under constant volume causes pressure of up to 12 GPa. It has been shown experimentally and theoretically that the production of seeding electrons through multiphoton ionization by visible laser pulse paves the way for controllability of the energy deposition and laser-induced micromodification via carrier heating by delayed infrared laser pulses inside the material. The developed theoretical approach predicts that the deposited energy density will be enhanced by up to 14 kJ cm−3 when using longer (up to 5 µm) wavelengths for heating laser pulses inside transparent solids.