Estimate of the minimum optical losses in chalcogenide glasses

Abstract

In the vicinity of a surface which is being eroded there is a region where particles arriving at and departing from the surface can collide. The frequency of collisions and the resulting motion of spherical particles has been investigated theoretically and experimentally. An expression is derived for the flux of spheres necessary for a high frequency of collisions. The directions and velocities of particles after collision have also been calculated, assuming elastic collisions. In the low-flux limit collisions do not reduce the number of particles reaching the surface. Long-exposure (ca. 1s) and high-speed (5000 frames 5 -l ) photography confirm these findings for the case of 0.6 ? 0.1 mm diameter glass spheres travelling at 13 ? 1 m S -' . These conclusions conflict with the ideas of many authors who suggest that collisions help protect the erodedsurface. The present paper shows that collisions degrade the incident beam of particles by increasing the angular divergence of the beam and creating a spectrum of velocities. Stray particles have also been observed entering the region of interest, increasing the frequency of collisions. Stray particles and changes in the incident beam are probably the causes of the observed reduction in erosion rate at high levels of flux.

Preparation of low-loss core–clad As–Se glass fibers

“…According to estimates [4,5], the minimum optical losses in glassy arsenic selenide are 0.08-0.1 dB/km at a wavelength of 6.1 lm.…”

Low loss Ge-As-Se chalcogenide glass fiber, fabricated using extruded preform, for mid-infrared photonics

“…The world champion loss of chalcogenide glass fiber remains 12 dB/km at 3.0 μm in an As-S core/clad. fiber, reported by Snopatin et al in 2009 [2]; they referred to the theoretical minimum loss of As-S as 0.05 dB/km at 4.3 μm wavelength [19]. Compare this with another estimated theoretical minimum loss of As-S glass, of 4 dB/km at 5.0 μm wavelength, when the weak absorption tail was considered [20].…”

Recent advances in preparation of high-purity glasses based on arsenic chalcogenides for fiber optics

“…The position of minimum of optical losses has shifted to 4.8 μm, i.e. to the theoretically predicted position [16]. To attain the optical losses of 1-5 dB/km in the maximum transparency range it is necessary to lower the content of silicon impurity down to~10 ppb wt and of hydrogen impurity down to 1-5 ppb at.…”

“…The intrinsic nature of these bands and bands with maximum at 6.85 and 7.6 μm determines the position of multi-phonon absorption edge of arsenic-sulfide glass and the level of optical losses in As-S fibers between 5 and 8 μm. Estimations, made in view of this fact and of the concentration constituent of Rayleigh scattering related to the presence of homo-bonds in glass, lead to the minimum optical losses which are by 3-5 times higher than the level of 8.10 − 2 dB/km at 4.8 μm given in literature [16,17].…”