Photon-phonon coupling

The Laboratory of Quantum Measurement (lead by Prof. Tobias J. Kippenberg) demonstrated jointly with the CNRS-LPN laboratory in Paris (lead by Dr. Isabelle Robert) the coupling of optical and localized mechanical modes in photonic crystal defect cavities as reported in Phys. Rev. Lett. Photonic crystal defect cavities are well studied nanostructures that are capable of storing light in sub-wavelength volumes are used in a variety of photonic applications, such as ultra-compact laser sources. Using these nanostructures, Emanuel Gavartin, PhD student at EPFL showed that in addition to the well known optical modes, localized mechanical modes exist that couple to the light field via radiation pressure. The light forces in nanostructures are significantly elevated allowing efficient coupling to take place. These discovered localized vibrational modes exhibit frequencies in the GHz regime and provide novel opportunities to control light propagation. For instance the mutual coupling of mechanical vibrations to optical light field may be used for conversion of photons to phonons in applications such as narrow band filtering or optical buffers.