Two photon induced lasing in 1550 nm quantum dash optical gain media

We report on a unique lasing mechanism observed in quantum dash Gain media. While the gain media is electrically pumped below lasing threshold, a strong optical pulse excites carriers by two photon absorption into high energy states of the quantum dashes and wetting layer. Fast inter band carrier relaxation and capture processes into the ground states of the quantum dashes result in increased gain followed by lasing at the gain peak irrespective of the stimulating pulse wavelength. The temporal response of the lasing line is examined on a 40 GHz scope and full characterization of the pulse by the XFROG scheme is performed. We show the lasing mechanism to be governed mainly by the wetting layer dynamics and extract a direct measurement of the carrier-carrier scattering time constant.