Structural resonances in absorption spectrum of quartz microsphere

The quartz microspheres with different diameters are fabricated by melting the taper fibers with corresponding diameters using CO₂ laser. The spherical microcavity coupling system is constructed with taper fiber and the quartz microsphere. In the experiment, a coupling system is made of fiber taper with the diameter of 3.1 μm and a quartz microsphere with 143.1 μm diameter. The spectrum of this system is scanned using the tunable diode laser with the resolution of 1 pm, and the discrete structural resonance in the absorption spectra of the quartz microsphere is observed. According to the spherical microcavity theory, the above structural resonance is analyzed, and the Mie scattering theory is used to calculate the position of the first order TE modes and their spacing distance. The calculated result is in accordance with the observed resonance, with an error of only 0.03%.