Creation of luminescent defects in crystals by coherent pairs of femtosecond laser pulses

Highlights: • Laser filaments create luminescence centers in the crystal. • Luminescent method for monitoring the concentrations of color centers in crystals. • Efficiency of laser defects formation for various states of polarization. • Multiphoton tunneling ionization and laser defect formation in crystals. The processes of creation of luminescence centers by laser radiation in transparent anisotropic crystals are investigated using MgF₂ as an example. To monitor the concentration of the created centers, a luminescent method was developed, which ensured a direct proportionality between the luminescence intensity and the concentration of centers. By the joint action of coherent pairs of femtosecond laser pulses, the longitudinal positioning of the action of light on the medium was performed during the creation of spatially modulated structures. Laser filaments resulting from self-focusing contained both ordinary and extraordinary components. A simple method is substantiated for studying the efficiency of the formation of quantum systems depending on the polarization state of the acting radiation in one experiment. It is shown that the experiments implemented an intermediate mechanism of multiphoton-tunneling ionization of a crystal during laser defects formation.