Quantum cascade photonic-crystal microlasers

We describe the realization of Quantum Cascade photonic-crystal microlasers. Photonic and electronic band-structure engineering are combined to create a novel Quantum Cascade microcavity laser source. A high-index contrast two-dimensional photonic crystal forms a micro-resonator that provides feedback for laser action and diffracts light vertically from the surface of the semiconductor chip. A top metallic contact is used to form both a conductive path for current injection as well as to provide vertical optical confinement to the active region through a bound surface plasmon state at the metal-semiconductor interface. The device is miniaturized compared to standard Quantum Cascade technology, and the emission properties can in principle be engineered by design of the photonic crystal lattice. The combination of size reduction, vertical emission, and lithographic tailorability of the emission properties enabled by the use of a high-index contrast photonic crystal resonant cavity makes possible a number of active sensing applications in the mid- and far-infrared. In addition, the use of electrical pumping in these devices opens up another dimension of control for fundamental studies of photonic crystal and surface plasmon structures in linear, non-linear, and near-field optics.