Dynamics of Er^sup 3+^:YAG thermal radiation spectra near solid-melt interface at single crystal fiber growth process

The evolution of the Er3+:YAG thermal radiation spectra at heating up to the melting point was investigated in the visible range when growing a crystal fiber by the Laser-Heated Pedestal Growth (LHPG) method. The Er3+:YAG melt of about 1 mm thickness radiates like a black body in several spectral bands sometimes different from the crystal absorption lines. The real melt temperature in the middle of the growth zone was estimated as 2620 ± 15 K. The spectral profile of Er3+:YAG emissivity in the visible range for a melt layer of about L ≈ 1 mm at 2620 K is shown in the Figure.