Storing light in active optical waveguides with single-negative materials

We show that a nonresonant planar waveguide consisting of conventional dielectric cladded with single-negative materials supports degenerate propagating modes for which the group velocity and total energy flow can be zero if the media are lossless. Absorptive losses will destroy the zero-group velocity condition for real frequency/complex wave vector modes. We show that by incorporating gain G into the core dielectric, there exists a critical gain value Gc at which we can recover the condition of zero group velocity, so that light pulses can be stopped and stored. This structure is simpler to achieve than double-negative metamaterials, has small footprint, and can be incorporated into ultracompact on-chip optoelectronics.