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While glass alteration in liquid water has been widely studied for decades, glass alteration in unsaturated atmosphere (relative humidity, RH < 100%) has been far less examined. However, the understanding of the mechanisms involved in the reactions between glass and water in vapor state is fundamental to several fields such as glass industry, conservation of glasses of the cultural heritage and long-term assessment of nuclear waste glasses. This paper outlines the issues raised by the atmospheric alteration of glass in these fields and attempts to summarize the scientific approaches and findings of the three communities. This short review reveals that atmospheric alteration should not be confused with liquid alteration at high S/V (S = exposed surface of glass and V = volume of solution), because the kinetics and the nature of the alteration products are distinct. Notably, alkalies and non-bridging oxygens may be significantly retained in glass hydrated in unsaturated atmosphere, depending on the glass composition. Future lines of research are drawn to progress in the understanding of the specificities of atmospheric glass alteration.

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Following an industrial process to protect manufactured glass windows against atmospheric corrosion during their storage and transport, this research is focused on the possibility that a surface deposit of a small amount of zinc salts may efficiently reduce the atmospheric alteration kinetics of ancient glasses (soda, potash, and mixed alkali silicates). To this end, the chemical action of zinc salts was investigated by means of aging experiments (with temperature and relative humidity (RH) control) on three glass models, of which compositions are representative of the cultural heritage. When the treatment was performed on pristine glass (about 1 μg/cm2 of deposited Zn2+ ions), treated glass plates developed a significantly thinner hydrated layer than the untreated ones at 80°C or at 40°C (85 RH%). The formation of alkali and Ca‐carbonates salts on the surface was also considerably reduced. The state of the glass surface undergoing the Zn treatment and the temperature of the treatment seem critical regarding the efficacy of the protection.

A plasma enhanced chemical vapor deposition process was developed to deposit SiO 2 -GeO 2 films suitable for high index contrast planar waveguides. These films were deposited in a standard parallel plate reactor from silane, germane, nitrous oxide, and a nitrogen carrier. The germania content of the film was equal to the mole fraction germane of the hydride precursors in the gas stream, and the refractive index of the film varied linearly with the mole fraction of germania. Low loss guides ranging from 1.5-4.0% ⌬ were fabricated. With standard photolithographic patterning, a 0.05 dB/cm propagation loss and minimum bend radius of 1.5 mm were measured for 2.0% ⌬. Improvements to the photolithographic patterning to reduce sidewall roughness were required to achieve low propagation loss at higher ⌬. This reduced the propagation loss for 3.5% ⌬ cores to 0.086 dB/cm. An average minimum bend radius of 570 m was measured for 3.5% ⌬, but modeling suggests the bend radius could be reduced below 500 m with offsets to reduce transition loss. Ring resonator, fabricated from 3.5% ⌬ waveguides, exhibited a free spectral range as large as 62.7 GHz and a very low round trip insertion loss of 0.06 dB.