Lead-indium phosphate glasses for optical applications

摘要

A new glass system based on a range of lead-indium phosphate compositions has been developed. These glasses have a relatively high index of refraction (1.8--1.9) in the visible region and exhibit moderate dispersion (typical Abbe number of 32). The ultraviolet absorption edge occurs near 300 nm and the glasses strongly absorb in the infrared at wavelengths greater than 2,800 nm. The glasses can be prepared at relatively low temperatures (900--1,000 C) and are easily poured at temperatures near 800 C due to their low melt viscosities. Lead-indium phosphate glasses exhibit good chemical durability and resistance to both weathering and intense gamma-irradiation. These materials have a glass transition temperature of 430 C, and thermal expansion coefficients in the range of 11 to 12 (times) 10(sup (minus)6)/C. The structure of these glasses consists of a distribution of chains of PO(sub 4) tetrahedra held together by bonding between the non-bridging oxygen of the tetrahedra and the metal cations. The polyphosphate chain distribution was determined using the technique of high-performance liquid chromatography. The high index of refraction of lead-indium phosphate glasses makes them attractive for several applications such as high-numerical-aperture optical fibers and specialty lenses. Optical fibers up to 60 m in length have been drawn, and several simple lenses have been designed, ground, and polished. Preliminary results on the ability to directly case optical components of lead-indium phosphate glass are also discussed as well as the suitability of these glasses as a host medium for rare-earth ion lasers and amplifiers.