Nanocrystalline Ceramic Phosphors for High-Power Lasers Operating at 2μm

Rare-earth (RE) doped silica glass optical fibers became a hearth of modern fiber-lasers. Such lasers are fully competitive with conventional solid-state lasers because of their high brightness, high quality beam, high conversion efficiency, good thermal management, tunability, compactness, size and even flexibility. However, a low solubility of RE inside a silica matrix and a high phonon energy of silica glass strongly reduce the luminescence efficiency of incorporated RE elements. Nanoparticle doping represents a powerful method that can eliminate these disadvantages.In this contribution we present an effect of the processing temperature on the luminescence properties of nanocrystalline (Eu<inf>0.05</inf>Y<inf>0.95</inf>)<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> and (Ho<inf>0.05</inf>Y<inf>0.95</inf>)<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> phosphors. The luminescence properties of (Ho<inf>0.05</inf>Y<inf>0.95</inf>)<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> improved with increasing nanocrystal size. The nanocrystals of (Ho<inf>0.05</inf>Y<inf>0.95</inf>)<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> were successfully incorporated into optical fiber with the outer diameter 125 μm and the core diameter 8 μm. The fiber’s numerical aperture was 0.13 and the background losses at 850 nm were 0.38 dB•m⁻¹.The lifetime of the ⁵I<inf>7</inf> →⁵I<inf>8</inf> transition at 1.92 μm was 0.72 ± 0.01 ms. The results bring the fundamental information about the effect of the nanocrystal size their luminescence properties of (RE<inf>0.05</inf>Y<inf>0.95</inf>)<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> and their possible application as phosphors in active optical fibers.