We investigate the degradation of the <i>Q</i> factor of a fundamental whispering-gallery mode of a microsphere resonator when a fiber tip is placed in the evanescent field of the mode. With a tip diameter of 80 nm it is possible to maintain a <i>Q</i> factor exceeding 10<sup>8</sup>, even when the tip is as close as 10 nm to the sphere surface. This result demonstrates the possibility of using such a tip as a “nanotool” to actively place a single nanoparticle in a single high- <i>Q</i> mode with great precision to achieve well-controlled coupling.
© 2002 Optical Society of America
S. Götzinger, O. Benson, and V. Sandoghdar, "Influence of a sharp fiber tip on high-Q modes of a microsphere resonator," Opt. Lett. 27, 80-82 (2002)