We numerically demonstrate ultra slow light in a coupled optical resonator waveguide embedded in a highly dispersive medium. This combination dramatically reduces the propagation speed of light pulses in the structure to below 1% c0
On the basis of a general analysis of waveguides containing a dispersive material, we identify conditions under which slow-light propagation may enhance the gain, absorption, or phase change. The enhancement is shown to depend on the slow-light mechanism and the translational symmetry of the waveguide. A combination of material and waveguide dispersion may strongly enhance the control of light speed, e.g., using electromagnetically induced transparency in quantum dots embedded in a photonic crystal waveguide.
The optical buffer is a key component in all-optical information processing systems. Recently a number of schemes that use slow light propagation in various media and structures have been proposed as means toward implementation of all-optical buffers. We rigorously analyze the similarities and differences in approaches that use electromagnetically induced transparency (EIT) and coupled resonant structures (CRS). We introduce the figure of merit, finesse, that is common to both approaches and obtain fundamental limitations on bit rates and storage capacities of optical buffers. We show that at very low bit rates and storage capacities EIT outperforms CRS, but at rates of 10 Mbits/s and above the EIT medium becomes quite inefficient, and the situation is reversed. Two types of CRS based on high-index-contrast fiber gratings and high-index semiconductor-air photonic crystals and (or) microring resonators are found to hold promise for applications in the 1-1000-Gbits/s range, but only if the losses can be drastically reduced.
We performed optical pulse propagation experiments in a system in which two ultrahigh-Q silica microspheres of different diameters were coupled in tandem to a fiber taper to yield coupled-resonator-induced transparency. Nearly Gaussian-shaped optical pulses propagated with a large positive delay of 8.5 ns through a transparent frequency window, without significant attenuation, amplification, or pulse deformation, demonstrating classical analogy of the extremely slow light obtained with electromagnetically induced transparency.
The inverted spectral structure of coupled-resonator-induced transparency was experimentally demonstrated using an amplifying optical ring resonator, to which another dark ring resonator was coupled. A nonamplifying spectral window was induced by the dark resonator in an otherwise strongly amplifying spectral region. Within the induced window, sharp anomalous dispersion was expected. Propagation of nearly Gaussian-shaped optical pulses was observed; the pulses propagated through the amplifying medium with a negative delay of $\ensuremath{-}$20.8 ns, without significant amplification, attenuation, or pulse deformation. The inverted induced-transparency system, producing tunable fast light, is a complementary system to traditional induced-transparency systems that produce slow light and could be potentially useful in numerous applications.