Laser-conditioning mechanism in KD2PO4 crystals revealed by fluorescence and Raman scattering analysis

Abstract. To analyze the mechanism of damage threshold enhancement after laser conditioning, the fluorescent and stimulated Raman scattering properties of unconditioned and laser-conditioned KD2PO4 crystals are compared in detail. It is revealed that the intensity of fluorescence decreases significantly, especially fluorescence <400  nm, after nanosecond laser conditioning, and the change of the stimulated Raman scattering peak at 921  cm  −  1 is very weak. Moreover, the intensity of fluorescence further decreases after subnanosecond laser conditioning. A sharp decrease in the fluorescence intensity <400  nm reflects a change in energy levels of the electron defects in a crystal. The Raman scattering proves very weak change of the PO4 vibrational modes. Furthermore, a laser-conditioning mechanism is discussed in combination with electronic transition and thermal processes.

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