Surface-plasmon distributed-feedback quantum cascade lasers operating pulsed, room temperature

Abstract

We report distributed-feedback surface-plasmon quantum cascade lasers operating at λ≈7.6μm. The distributed feedback is obtained by the sole patterning of the top metal contact on a surface plasmon waveguide. Single mode operation with more than 30dB side mode suppression ratio is obtained in pulsed mode and at room temperature. A careful experimental study confirms that by varying the grating duty cycle, one can reduce the waveguide losses with respect to standard, unpatterned surface-plasmon devices. This allows one to reduce the laser threshold current of more than a factor of 2 in the 200–300K temperature range. This approach may lead to a fabrication technology for midinfrared distributed-feedback lasers based on a very simple processing.