Injection of midinfrared surface plasmon polaritons with an integrated device

We demonstrate a compact, integrated device in which surface plasmon polaritons (SPPs) are injected into a passive metal waveguide. We directly excite a SPP mode at a metal-air interface using a room-temperature midinfrared quantum cascade laser which is integrated onto the microchip. The SPP generation relies on end-fire coupling and is demonstrated via both far-field and near-field imaging techniques in the midinfrared. On one hand, a metallic diffraction grating is used to scatter in the far-field a portion of the propagating SPPs, thus allowing their detection with a microbolometer camera. On the other hand, direct images of the generated SPPs in the near-field were collected with a scanning optical microscope.