Time scale dependent dynamics in InAs/InP quantum dot gain media

Dr. Gadi Eisenstein, Technion

Nov. 1st (Tue), 10:30AM ,#1323(E6-2 1st fl.)

Recent advances in the density and uniformity of InAs / InP QDs, emitting near 1550 nm, have led to vast improvements in QD laser performance in terms of the dynamical properties and the temperature stability. Record modulation bandwidths and operation up to 150 0C have been demonstrated in the past few months. The superb dynamic performance can be traced to the carrier and gain dynamics of devices made of this material. These dynamics are dictated by physical processes in three time scales. A few to ten ps represents the direct photon density variations during modulation. Gain nonlinearity is determined by carrier capture and escape to and from the QDs; processes that last a fraction of 1 ps to about 3 ps. The sub 200 fs time scale brings the system into the coherent quantum regime as this time is shorter than the room temperature coherence time at room temperature.
Modulation characteristics are characterized using standard high speed telecom techniques and are modeled by a spatially resolved complex simulation. The time scale around 1 ps is extracted from multi wavelength pump probe measurements and the ultrashort coherent phenomena are measured using X-FROG. The two fast time scales are modeled using the same comprehensive numerical model that solves the Maxwell-Schrödinger equations by an FDTD code.

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