Single-mode surface plasmon laser

The requirement of prohibitively thick dielectric waveguides has so far hindered the development of long wavelength infrared semiconductor lasers. However, optical confinement can take place also at the interface between two materials with dielectric constants of opposite sign. These surface plasmon waves are the basis for a high performance 17 μm wavelength laser where light is guided at the interface between the top metal contact and the underlying semiconductor, dramatically reducing the required thicknesses. The concept of distributed feedback (DFB) for surface plasmon propagation is introduced by developing a periodic modulation of the penetration depth in a two-metal grating. Lasing is achieved on a single longitudinal mode with high purity and temperature tuning rates of ~1 nm/K. We employ a quantum cascade (QC) active material with variable period superlattices