Marina Zajnulina
Technische Universität Berlin
Marina Zajnulina was born in Kazakhstan in 1983. She obtained her diploma in Physics at the Technical University Berlin (Germany) in 2012. After that, she received her doctoral degree in Photonics at the University of Potsdam (Germany) in 2016. Her research interests include studies on optical soliton formation in optical fibres, semiconductor waveguides, and lasers as well as investigations of four-wave mixing processes and the optical frequency comb generation in optical amplifiers.
To effectively deploy Quantum-Dot Semiconductor Optical Amplifiers (QD-SOAs) for the wavelength conversion for applications within Telecommunication, four-wave mixing (FWM), a nonlinear process driven by such third-order susceptibility effects as the charge-carrier-density pulsation, spectral hole-burning, and charge-carrier heating, needs to be thoroughly understood.
So far, the theoretical treatment of FWM in QD-SOAs has mainly occurred by modelling the optical field by means of nonlinear Schrödinger-like equations or by analytic evaluation of the optical field at the amplifier facets. [1,2] These methods usually involve only a spatially averaged gain and a constant linewidth-enhancement factor and neglect the inhomogeneous spectral line broadening due to the inhomogeneous energy distribution of the active quantum dots in a QD-SOA device. Moreover, they allow only for a limited discussion of the hierarchy and significance of spectral hole-burning, carrier-density pulsation, and carrier heating in the FWM process in QD-SOAs.
We propose a model featuring the evolution of the optical gain along the amplifying medium, including a dynamic linewidth-enhancement factor and allowing separate consideration of the nonlinear effects responsible for FWM in the quantum dots and the surrounding quantum well reservoir. It is based on a travelling-wave equation implemented as a delayed differential equation for the spatially resolved optical field. The charge-carrier dynamics in the quantum dots and the surrounding quantum well are modelled by means of balance equations using microscopically calculated Auger scattering rates. The inhomogeneous spectral line broadening is taken into account by inclusion of the light-matter interaction of all active quantum dots within the ensemble. [3]
Using this model, we numerically study the FWM wavelength conversion efficiency as a function of the device pump current and injected-field amplitude using the characteristics of a 3mm-long InAs/InGaAs QD-SOA device. The results (cf. Fig.) show a very good agreement with the experimental data in terms of efficiency curves range and shapes. [cf. 4] We found out that spectral hole-burning is the most important effect for FWM in QD-SOAs, whereas the charge-carrier heating is negligible. The carrier-density pulsation being decisive for the efficiency curves shapes constitutes the second most important effect in the hierarchy of the effects responsible for FWM processes in QD-SOA devices.
Fig. FWM wavelength conversion efficiency for different device pump currents (top) and injected-field amplitudes (bottom)
[1] A. Uskov, J. Mork, J. Mark, M. C. Tatham, G. Sherlock. Appl. Phys. Lett., Vol. 65, No. 6 (1994)
[2] D. Nielsen, S. L. Chuang. Phys. Rev. B 81, 035305 (2010)
[3] B. Lingnau: Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices. Springer (2015)
[4] B. Lingnau. W. W. Chow, E. Schöll, K. Lüdge. New. J. Physics 15 (2013) 093031
[5] C. Meuer, H. Schmeckebier, G. Fiol, D. Arsenijevic, J. Kim, G. Eisenstein, D. Biemberg. IEEE Photonics J., Vol. 2, No. 2 (2010)
