We have tuned the whispering-gallery modes of a fused-silica microresonator over nearly 1 nm at 800 nm, i.e., over half a free spectral range, or 10<sup>6</sup> linewidths of the resonator. This result has been achieved by use of a new method based on the stretching of a two-stem microsphere. We describe devices that will permit new cavity QED experiments with this high- Q optical resonator when it is desirable to optimize its coupling to emitters with given transition frequencies. The demonstrated tuning capability is compatible with both UHV and low-temperature operation, which should be useful for future experiments with laser-cooled atoms or single quantum dots.
© 2001 Optical Society of America
Wolf von Klitzing, Romain Long, Vladimir S. Ilchenko, Jean Hare, and Valérie Lefèvre-Seguin, "Frequency tuning of the whispering-gallery modes of silica microspheres for cavity quantum electrodynamics and spectroscopy," Opt. Lett. 26, 166-168 (2001)