Growth of Yb³⁺-doped YLiF₄ laser crystal by the Czochralski method. Attempt of Yb³⁺ energy level assignment and estimation of the laser potentiality

YLiF₄ (YLF) single crystals undoped and Yb³⁺-doped with different concentrations were grown by the Czochralski technique under CF₄ atmosphere. Detailed analysis of Yb³⁺-doped YLF spectroscopy were made to contribute to the determination of energy levels in this host. We are dealing with temperature and concentration dependences of both π and σ polarizations of the infrared (IR) absorption and emission spectra. Raman spectra were also used to give an attempt of interpretation of electronic and vibronic levels. The radiative energy transfer (self-trapping) and strong phonon-electron coupling make the assignment of Yb³⁺ energy levels difficult. Evaluation of the laser potentiality of this fluoride host is also presented.