Scattering of light in optical glasses

Abstract

A comparative study has been made of the intensity and state of polarisation of the light scattered transversely by a series of seventeen glasses of optical quality with the incident light in different states of polarisation (namely, unpolarised, vertically polarised and horizontally polarised). A weak fluorescence was observed in all the glasses. Measurements of the depolarisation factors ρ _u, ρ _v and ρ _h were made with an orange filter in the path of the incident beam to eliminate fluorescence. ρ _u and ρ _v are found to be of the same order of magnitude as are usually observed in the case of gases. But on the other hand, ρ _h is found to be distinctly less than 100% showing thereby the existence of molecular aggregates of size not small compared with the wavelength of light. Since no visible inclusions are observed it is concluded that the scattering in glass is really an internal phenomenon. Measurements of the relative intensity of scattering in these glasses were also made employing the photo-electric method. The influence of composition of the glass on the formation and the size of the molecular aggregates formed is fully discussed. It is found that the tendency for the formation of molecular aggregates increases with an increasing percentage of acidic oxides especially boric oxide, whereas it diminishes when the glass gets more and more basic.