Resonant and Nonresonant Tunneling Injection Processes in Quantum Dot Optical Gain Media

Abstract

Resonant and non-resonant tunneling injection of charge carriers in a quantum dot optical gain medium in the form of an optical amplifier operating in the telecom wavelength range were identified using multi wavelength pump probe measurements. Since the inhomogeneously broadened ensemble of quantum dots exhibits a very wide spectrum of transition energies, both tunneling injection processes take place simultaneously at different spectral locations and thus can be identified. These findings highlight the fact that at least one of the tunneling processes must occur at a wavelength at or near the gain peak, where laser oscillations take place. An energetic misalignment leads to reduced laser performance since in that case, the tunneling process becomes a carrier loss mechanism.