Optical strength of thermally stable athermal neodymium calcium-alkali ultraphosphate glasses

The optical strength thresholds were determined for the bulk and surface layers of commercial neodymium-activated metaphosphate and alkali-silicate glasses (GLS22P, FLS1, and GLS6) and newly developed glasses with alkali-metaphosphate and ultraphosphate bases (OPS3106, OPS1111, and OPS117-1242). They were irradiated with focused single-mode single-frequency radiation (λ ≈ 1.05 μm, Δλ ≈ 3 X 10^–4 nm) pulses of 150 ns duration forming a spot d ≈ 2 mm in diameter, and also with multimode radiation pulses of 40 ns duration when the spot diameter was d ≈ 15 mm. Out of all the investigated glasses those with the highest optical strength were the newly developed neodymium Ca–alkali–ultraphosphate-based glasses of the OPS117-1242 type. This high optical strength together with a low value of n₂, a large stimulated transition cross section, a high thermal stability, and athermal properties made them very interesting from the point of view of applications. These advantages apply also to a glass made in accordance with the conventional two-stage industrial technology involving cullet digestion in platinum containers.