Nonlinear pulse propagation in InAs/InP quantum dot optical amplifiers: Rabi oscillations in the presence of nonresonant nonlinearities

Abstract

We study the interplay between coherent light-matter interactions and non-resonant pulse propagation effects when ultra-short pulses propagate in room-temperature quantum-dot (QD) semiconductor optical amplifiers (SOAs). The signatures observed on a pulse envelope after propagating in a transparent SOA, when coherent Rabioscillations are absent, highlight the contribution of two-photon absorption (TPA), and its accompanying Kerr-like effect, as well as of linear dispersion, to the modification of the pulse complex electric field profile. These effects are incorporated into our previously developed finite-difference time-domain comprehensive model that describes the interaction between the pulses and the QD SOA. The present, generalized, model is used to investigate the combined effect of coherent and nonresonant phenomena in the gain and absorption regimes of the QD SOA. It confirms that in the QD SOA we examined, linear dispersion in the presence of the Kerr-like effect causes pulse compression, which counteracts the pulse peak suppression due to TPA, and also modifies the patterns which the coherent Rabi-oscillations imprint on the pulse envelope under both gain and absorption conditions. The inclusion of these effects leads to a better fit with experiments and to a better understanding of the interplay among the various mechanisms so as to be able to better analyze more complex future experiments of coherent light-matter interaction induced by short pulses propagating along an SOA.

Carrier dynamics in a tunneling injection quantum dot semiconductor optical amplifier

“…The theoretical investigation of ultra-short pulses propagation in a QD amplifier is based on a semiclassical description of the light-matter interaction [18], solved in the dipole moment approximation. We employ a numerical finite-difference time-domain model, developed in [16,19,20], that solves Lindblad equations for the occupation probabilities of a cascade of two-level quantum systems having different transition energies, that represent the inhomogeneously broadened ensemble of QDs. Simultaneously, it solves Maxwells equation for the electromagnetic field of the propagating pulse, where the vector polarization includes contributions from the interaction with the QDs, from two-photon absorption (TPA) and its accompanying Kerr-like effect as well as from group velocity dispersion (GVD) and the refractive index dependence on the carrier population, known as the plasma effect [20].…”

Breakthroughs in Photonics 2014: Time-Scale-Dependent Nonlinear Dynamics in InAs/InP Quantum Dot Gain Media: From High-Speed Modulation to Coherent Light–Matter Interactions

“…Also reported, was a long lasting additional gain, contributed by TPA of the pump pulse that injected carriers into the carrier reservoir of the medium, from which they slowly relaxed to the resonant QDash energy levels. In 1550 nm QDs, similar characterization revealed even more clearly this contribution, with strong gain recovery dependence on the pump energy and the probe wavelength highlighting the major role played by TPA [11], [21].…”

“…The experimental observations were confirmed by comprehensive simulations where Maxwell and Schrödinger equations are solved by the FDTD technique. A series of models with progressively higher accuracies were developed, starting from a homogeneous gain broadening model [20], followed by a model which accounts for the inhomogeneously broadened gain [18] and one which also includes non-resonant propagation effects [21], such as TPA and the corresponding Kerr-like effect it induces [14].…”

Ultra-fast charge carrier dynamics across the spectrum of an optical gain media based on InAs/AlGaInAs/InP quantum dots

“…The experimental results are validated qualitatively by simulations, which are based on a comprehensive model previously developed in order to explain dynamical effects on a sub 200 fs time scale, where quantum coherent interactions 23 take place. The model calculates, among other things, the population inversion across the QD gain spectrum during and following the pulse propagation along the SOA.…”