2.2. Optical resonator fabrication
The toroidal cavities were fabricated using the standard three
step method which is detailed elsewhere (Armani et al., 2003).
Briefly, 160μm diameter 2μm thick circular oxide pads on a silicon wafer are patterned using a combination of photolithography
and buffered oxide etching. They are subsequently undercut using
XeF2, an isotropic silicon etchant. Finally, the oxide is reflowed
using a CO2laser, forming the toroidal resonant cavity (Fig. 2).
A tapered opticalfiber waveguide is fabricated using theflame
pulling method. In this approach, the cladding layer of single mode
opticalfiber is removed using wire strippers, and thefiber is
mounted on a pair of motorized stages, which pull in opposite
directions. While heating thefiber with an oxyhydrideflame, the
fiber is pulled until the waist region of the taper is approximately
600 nm in diameter, or smaller than the wavelength of light.