Throughout the course of her Nuffield Foundation project this summer Ewa Karczewska will be making updates of her progress on our blog. Her first instalment is below.
Ewa writes: For the past two weeks, I have been investigating and making improvements to the flame brushing method, which then allowed me to obtain the fibres of less than 2µm in diameter. Therefore, after the study on how to make a good coupling between two optical fibres using the splices, the laser beam was coupled into the fibre and the nearby spheres of 2µm in diameter have been observed to move along the fibre in the direction of the light propagation. The spheres were observed to accelerate in the thinnest part of the fibre. When the laser beam was split into two and coupled to each end of the fibre, it was possible to move the spheres in both directions by changing the intensity of the light coupled to each end. Also it has been observed that if the fibre breaks in the thin part and the laser beam is coupled into it, the spheres accelerate and shoot off from the broken end.
Above you can see a movie of 2µm diameter polystyreen microspheres propelled along a tapered optical fibre in the evanescent field of the guided laser beam. More movie can be found on our YouTube Channel.