International Journal of Machine Tools & Manufacture 43 (2003) 1413–1418 Loose abrasive blasting as an alternative to slurry polishing of optical fibre end faces Yousef A. Gharbia, Jayantha Katupitiya * School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052, Australia Received 23 June 2003; accepted 25 June 2003 Abstract A novel method of polishing the end face of an optical fibre by blasting it with loose dry abrasive grit travelling at high speeds is presented. The method, called loose abrasive blasting (LAB), is specifically designed to improve the surface quality of micro- lenses ground at the tips of optical fibres. Thus, the method described is suitable for polishing non-flat surfaces. Blasting is carried out by immersing the fibre tip in a stream of high kinetic energy abrasive grit. The surface finish attainable using LAB is compared with that of cleaved, ground and slurry polished fibre end faces. Optical microscopy photographs are presented as a qualitative comparison. The surface roughnesses are measured using atomic force microscopy (AFM). For cleaved fibres, the surface roughness improved by a factor of 2 and 6 for slurry polished and dry diamond blasted fibres, respectively.  2003 Elsevier Ltd. All rights reserved. Keywords: Loose abrasive blasting; Slurry polishing; Optical fibre 1. Introduction This paper presents a new method called loose abras- ive blasting (LAB) that can be used to polish optical fibre end faces. The method can be used on a mass scale to improve the surface quality of micro-lenses that are mechanically ground at the end faces of optical fibres. The surface quality attained with the LAB method was compared with that attained using slurry polishing. The fibre end faces used in these two experiments were either cleaved or mechanically ground to form flat end faces. Mirror finish of optical surfaces is needed in many applications in the optics industry. One such example is the light coupling from a laser diode to a single mode fibre. Scattering of laser light incident on the fibre end face is a major contributor in degrading the light coup- ling efficiency. Light scatter is a direct result of poor surface quality [1]. In general, mechanically ground sur- faces may have scratch marks left on them by the grind- ing surface. Although cleaved surfaces are thought to * Corresponding author. Tel.: +612-9385-4096; fax: +612-9663- 1222. E-mail address: j.katupitiya@unsw.edu.au (J. Katupitiya). 0890-6955/$ - see front matter  2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0890-6955(03)00181-0 have good surface quality, depending on the cleaver and fibre quality, the cleaved fibres can have surface quality as low as R a = 45 nm. Therefore, there is a strong need to develop a cost effective method to polish end faces of cleaved as well as ground fibres in bulk quantities. Surface qualities attainable using various methods are widely reported in the literature. Chen et al. [2] used ultra-precision grinding of optical aspherical surfaces and reported best surface roughnesses of R a = 6.5 nm. Golini et al. [3] used slurry micro-grinding of the titanium doped fused silica glass known as ULE, and Zeroder to study the effect of slurry chemistry in trans- forming brittle material removal to ductile material removal. Several slurry agents including water, meth- anol, ethanol, propanol and a series of homogeneous n- alcohols have been used in experiments. These studies found that by changing the slurry chemistry, brittle material removal can be transformed to ductile. Wet pol- ishing, in which the surface being polished was immersed in a slurry of abrasives, has produced good quality surfaces [4]. Other polishing techniques of brittle materials reported in the literature are mechanochemical polishing [5], hydroform polishing [6], chemical etching [7,8] and carbon dioxide laser polishing [9]. While slurry polishing, sometimes referred to as