Mid/far-infrared semiconductor devices exploiting plasmonic effects

We show how metallic waveguides offer the opportunity of implementing interesting functionalities for semiconductor lasers within a simple technological approach. In the THz, we show that the active region thickness of quantum cascade lasers can be reduced by a factor of 2 without effects on the threshold current density and maximum operating temperature of the laser. Pulsed and continuous-wave operation - with a low threshold J(th)= 71 A/cm(2) - are obtained for a 5.86-mu m-thick THz QC laser. The emission is peaked at lambda approximate to 115 mu m and the waveguide resonator is based on a metal-metal geometry. In the mid-infrared, we demonstrate surface-plasmon distributed-feedback quantum cascade lasers with a first-order grating realised by the sole patterning the top metallic contact. The devices have a single mode emission with a side-mode suppression ratio greater than 20dB. The emission wavelength at 78K is centred at lambda = 7.3 mu m and has tuning rate as a function of the temperature of approximate to 0.4 nm/K.