Demonstration of wavelength tuning of silica toroid microcavity via additional laser reflow

In recent years, a number of studies have reported on cavity quantum electrodynamics (cQED) [1] and electromagnetically induced transparency (EIT) based on coupled optical microcavities [2]. To demonstrate these applications requires accurate control of the resonant wavelength of the optical microcavity. However, the resonant wavelength of the fabricated cavity is usually different from the designed value as a result of imperfect fabrication. And this is a major problem in applications such as cQEDs and microcavity based EITs. Postprocessing appears to be a promising way of solving this problem and there have been several demonstrations in photonic crystal nanocavities. A toroid microcavity is another attractive platform for the above applications due to its ultra-high Q [3]. Hence in this study, we describe the wavelength tuning of a silica toroid microcavity by means of an additional laser reflow.