Ultrahigh-Q nanocavities and their dynamic control

High-Q photonic-crystal nanocavities [1], [2] are currently the focus of much interest because they can strongly confine photons in a tiny space. Nanocavities with ultra-high quality (Q) factors exceeding 2,000,000 and modal volumes of a cubic wavelength have been successfully realized [3], [4]. If the Q factor could be dynamically controlled within the lifetime of a photon, significant advances would be expected in areas of physics and engineering such as the slowing and/or stopping of light and quantum information processing. For these applications, the transfer, storage, and exchange of photons in nanocavity systems on such a time-scale are highly desirable. In the present talk, I will at first describe the recent progress of ultra-high-Q nanocavities from the experimental [3], [4] and theoretical [5] points of views. Then, I will present the demonstration of dynamic control of the Q factor, by constructing a system composed of a nanocavity, a waveguide with nonlinear optical response, and a photonic-crystal hetero-interface mirror [6], [7]. The Q factor of the nanocavity is successfully changed from ∼3,800 to ∼22,000 within picoseconds.