Optical impulse response of silica microspheres: Complementary approach to whispering-gallery-mode analysis

We use frequency comb interferometry to simultaneously obtain the optical impulse responses and wide-band transmission spectra of silica microspheres, as they together provide a more complete description of light dynamics inside the resonator. The grouping of periodic cavity ring-down pulses in the impulse response provides confirmation that small asphericities give rise to a precession of the orbit of the light pulse propagating along the inner surface of the microcavity. This effect also strongly depends on coupling conditions. Moreover, we notice the presence of secondary pulses associated with modes of higher radial quantum number. All these features bring valuable information on the optical properties of microspheres.