All-Optical Nano-Positioner (No. 0126)

Technology

The technology is based on whispering-gallery modes (WGM), which are a type of wave that can travel around a concave surface, such as in a glass sphere. Originally discovered for sound waves in the whispering gallery of St Paul’s Cathedral, they can exist for light and for other waves, with important applications in nondestructive testing, lasing, cooling and sensing, as well as in astronomy. Using the WGM principle, there is provided a means of achieving nanometer scale tunable coupling by taking advantage of thermal-mechanical effects arising from a unique microsphere stem fabrication, external laser heating and thermal expansion in a single mode optical fiber. Silica microspheres were made using a focused laser directed onto a piece of silica fiber. A small weight attached to the bottom of the fiber ensured the formation, upon heating, of a unique tapered part which acts as the stem of the microsphere. With this system, the coupling gap between a micro resonator and a waveguide can be controlled optically with nanometer resolution (4-17 nm/mW) thus stepping towards an integrated all opto-mechanical system. This fiber-based nano-positioner could be used to move not only a microsphere but any structure fabricated on the taper fiber tip such as plasmonic devices or AFM (Atomic Force Microscopy) tips.

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