Fluoride glass fiber: state of the art

Abstract

Fluoride glasses are the only materials that transmit light in a continuous fashion from ultraviolet up to 8 μm in the midinfrared region, and can be drawn into high quality optical fibers. In fact fluoride glass fiber technology is the second most mature, beside silica based fiber technology. Fluoride glasses have experienced extraordinary development for more than 25 years. This development was motivated in the beginning by their outstanding optical properties, especially the minimum theoretical attenuation which is 0.01 dB/km between 2 and 3 μm. High quality optical fibers are now commercially available, with attenuation ranging from 5 to 30 dB/km, and mechanical strength ranging from 50 to 100 kpsi depending on fiber diameter.. The fluoride glass transmission window is from 0.25 μm to 8 μm without any absorption peaks, while the resulting fiber transmission window can be from 0.3 μm to 4.5 μm for standard fiber and from 0.3 μm to 6 μm for the extended window fiber. In this paper we will present mechanical and optical properties of current fluoride glasses and fibers, as well as high power transmission results.

Infrared fibers

“…Another unique property of fluoride glasses is their extremely broad transmission window from the UV (∼300 nm) to the MIR (4-6 μm for ∼1-m-long fiber) [64,167,201,202]; see Fig. 10.…”

“…Fluoride glasses exhibit the lowest refractive index among IR glasses, hence, the lowest optical nonlinearity [64,167,201], which makes them particularly well suited for high-power delivery and lasing applications where nonlinear effects are undesirable. Another unique property of fluoride glasses is their extremely broad transmission window from the UV (∼300 nm) to the MIR (4-6 μm for ∼1-m-long fiber) [64,167,201,202]; see Fig.…”

“…A typical fluoride glass has less thermal and chemical stability than other IR glasses, but has a wider transmission window compared to oxide glasses (though narrower than chalcogenide glasses). While a large number of multicomponent fluoride glass compositions have been synthesized, only a few have been drawn into fibers [64] (see Section 6). To date, chloride glasses have not proven to be sufficiently stable thermally for most applications [65].…”

Reduction of scattering loss in fluoroindate glass fibers

“…They show a wide transmission range from the ultraviolet to the mid-infrared region, and have significantly lower theoretical optical loss than that of conventional silicate glass fibers [2]. Shibata et al estimated the theoretical minimum fluoride fiber loss to be <10 2 dB/km at 2-3 μm, one magnitude lower than that of silica fiber.…”

Three-octave spanning supercontinuum generation in a fluoride (ZBLAN) fiber

“…Therefore, soft glasses including tellurite [10,11], chaclogenide [12,13] and fluoride [14][15][16] glasses have been adopted for mid-IR SC generation. Tellurite and fluoride glasses exhibit high optical transparency in the long-wavelength range of up to ~5 µm [10,17], while chalcogenide glasses are transparent even above 7 µm wavelength [18]. Chalcogenide fibers are also characterized by high nonlinearity, and therefore, they are especially appropriate for the enhancement of nonlinear processes occurring in a medium.…”