Throughout the course of her Nuffield Foundation project this summer Ewa Karczewska will be making updates of her progress on our blog. Her final instalment is below.
Ewa writes: During the 8-week project with the UCL Optical Tweezers Group I have learnt a great deal about the laboratory work as well as the current experiments run in it, which focus on the evanescent field and the micro- and nano- structures trapping. I have also gain knowledge about the evanescent wave and the different optical fibre modes.
My research was focused on the thin fibre fabrication using the “heating and pulling”method. The light (λ = 1064nm) was coupled to the tapered fibre so that the evanescent field near the taper region was created. That field was then tested with the micro-sized spheres. When the field was strong enough and the surface of the fibre was smooth enough, the spheres were observed to move along the fibre along the direction of the light propagation.
Overall, I have managed to obtain an efficient method of obtaining thin (about 1.5μm in diameter) optical fibres using the “heating and pulling” method and observe the spheres of 2μm to move along the fibre once the laser light was coupled through it. When the laser light was coupled from both sides of the fibre I could move the spheres in two directions and also balanced the two beams so that the spheres stayed in place.
I have also investigated the behaviour of the micron-sized spheres when the polarisation of the trapping light of an optical tweezers was changed from linear to circular polarisation as well as from radial to azimuthal polarisation.
That project gave me a valuable experience and a great insight into the research work, which will be very useful in my future study for PhD.
From September Ewa will be studying for the third year of her degree as a year abroad in Toronto University.