These microspheres are fabricated by fusing the tip of a cleaved SMF fiber. The process occurs using a comercial splicer that produces a current arc causing the glass to melt. Finally, a spherical object is retrived due to surface tension, as is shown in the gif below.
I use the microspheres as a platform to investigate Backward Brillouin Scattering. Here are two illustrations: the first showing evanescent coupling of the pump wave and the second illustrating the coupling of the couterpropagating Stokes wave.