Last month, I accompanied recent graduate Michael Wolff ’17 to Okinawa, Japan, where Michael presented his senior independent study work as part of an international workshop-style conference for specialists in the field of optical nanofibers.
Optical nanofibers are essentially very thin cylindrical glass tubes– so thin, in fact, that their diameters are comparable in size to the wavelength of the light designed to propagate though them! Glass cylinders can “trap” light inside them due to the phenomenon of total internal reflection. However, the photons that make up light are relativistic particles, and are therefore difficult to localize, so that when the fiber becomes comparable in size to the wavelength of the light, the light “fights back” by leaking out of the fiber in the form of an evanescent field. The net effect is that the light is still guided by the fiber while much or its energy exists outside the cylindrical confines of the glass, like an abacus bead sliding along an abacus. The complex vector field structures of light guided by optical nanofibers, coupled with the relatively high light intensity just outside the fiber surface, make optical nanofibers a very interesting platform for experimentally probing various aspects of light matter interaction. An example of this is an optical “tractor beam”, in which micron-scale transparent objects near the nanofiber surface may be pushed, pulled, rotated, and otherwise spatially manipulated by the energy, momentum, and angular momentum present in the nanofiber light field. In his senior thesis work, Michael theoretically explored the forces on a submicron-sized glass beads due to realistic nanofiber fields which are currently being used in experiments performed by the light-matter interactions group in at the Okinawa Institute of Science and Technology.
Above is a photo of Michael discussing his work with Professor Fam Le Kien, an expert on optical nanofibers who was first author on the Physical Review A paper that inspired Michael’s thesis work. It was a great moment for me to catch them speaking together!