HIGH-Q MEASUREMENTS OF FUSED-SILICA MICROSPHERES IN THE NEAR-INFRARED

Measurements of the quality factor Q approximate to 8 x 10(9) are repo rted for the whispering-gallery modes (WGM's) of quartz microspheres f or the wavelengths 670, 780, and 850 nm; these results correspond to f inesse F approximate to 2.2 x 10(6). The observed independence of Q fr om wavelength indicates that losses for the WGM's are dominated by a m echanism other than bulk absorption in fused silica in the near infrar ed. Data obtained by atomic force microscopy combined with a simple mo del for surface scattering suggest that Q can be limited by residual s urface inhomogeneities. Absorption by absorbed water can also explain why the material limit is not reached at longer wavelengths in the nea r infrared. (C) 1998 Optical Society of America.