Interferometric study of electronic changes in the refractive index of a Nd: YAG laser crystal caused by intense pump

摘要

Changes in the refractive index of a Nd:YAG laser crystal caused by intense pumping are measured using a polarisation interferometer. A significant electronic component in the refractive-index changes associated with the excitation of the 4~F_(3/2) electronic level of Nd~(3+) ions is revealed in the crystal pumped by 808-nm radiation of a pulsed diode array. An appreciable increase in the electronic component of the refractive index, which is caused by the population of the 2~F(2)_(5/2) high-energy level, is observed in a Nd:YAG crystal additionally pumped by a 266-nm laser beam. Analytic calculations show that the short-wavelength 4f—5d transitions provide a predominant contribution to the polarisability of excited Nd~(3+) ions at the 1064.2-nm lasing transition.