Fluorine-doped SiO_2 glasses for F_2 excimer laser optics:?fluorine content and color-center formation

Abstract

Color-center formation in F-doped, OH-free synthetic SiO(2) glasses by irradiation with F(2) excimer lasers (157 nm) was examined as a function of the F content. The concentration of photoinduced E(') centers was reduced to approximately 1/20 by 1 mol.% F(2) doping and remained almost constant on further doping to 7.3 mol. %. The absorption edge was considerably shifted to a lower wavelength (157.4 nm -->153 nm for a 5-mm-thick sample) by 1-mol. % doping and decreased only slightly on further doping. The intensities of the Raman bands that are due to three- and four-membered ring structures were significantly reduced by 1-mol. % F doping. These results strongly suggest that elimination of strained Si-O-Si bonds by F doping plays a central role in the improvement of radiation resistance of SiO(2) glasses to F(2) laser light.

Structural role of fluorine in amorphous silica

“…The addition of 1 mol% (approximately 0.33 wt%) fluorine to pure silica results in a relatively large blueshift of the absorption edge [12]. Further additions of fluorine, ranging from 1.5 to 7.3 mol%, do little to improve the UV transmission of these glasses, especially at 157 nm.…”

“…Further additions of fluorine, ranging from 1.5 to 7.3 mol%, do little to improve the UV transmission of these glasses, especially at 157 nm. Moreover, the resistance of these glasses against formation of color centers on laser exposure also increases on initial addition of fluorine to up to 1 mol% and the effect saturates at higher fluorine concentrations [12]. It was hypothesized in these studies that the role of initial addition of fluorine is to widen the optical band-gap by removal of the strained bonds in the structure of amorphous silica that may have high-energy electronic states associated with them.…”

“…Another potential technological use of fluorine-doped silica is in the field of photolithography, especially as a photomask material for next-generation systems based on 157 nm technology [10,11]. Fluorine blueshifts the absorption edge of pure silica and appears to reduce color-center formation in glasses exposed to deep UV radiation [12,13]. Finally, these materials have been studied for their role in catalysis, as fluorination can often increase the surface area of silicas [14,15].…”

Function Cultivation of Transparent Oxides Utilizing Built-In Nanostructure

“…1). As for optical materials, Hosono et al 5 reported novel photosensitive or photorefractive glasses, SiO 2 glasses, 6 and CaF 2 crystal 7 for excimer laser applications. These materials were found through accumulated fundamental research on defects in glass and dielectric crystals.…”

Fabrication of strong long-period gratings in hydrogen-free fibers with 157-nm F_2-laser radiation

“…7 In low-GeO 2 (i.e., 5%) glasses, the 157-nm photons directly bridge the ϳ7.1-eV bandgap, 8 which allows access to strong single-photon photosensitivity mechanisms without the need for traditional enhancement techniques. 3 -5 In this Letter we describe, for what is to our knowledge the first time, the formation of strong and good-quality LPFGs in standard single-mode f ibers (Corning SMF-28) without fiber pretreatment.…”