M.Sc Thesis

M.Sc StudentHadass Din
SubjectGain and Index Dynamics of Quantum Dash Amplifiers and
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Gad Eisenstein


The thesis deals with Quantum Dash (QDash) devices. QDashes are quantum wire like but they share many of the characteristics associated with quantum dots. In addition, they operate efficiently in the important wavelength region of 1550 nm.

We present a theoretical model for QDash amplifiers. We calculate and measure the static gain and noise in the linear and saturated regimes. We demonstrate a large gain bandwidth and an asymmetry in gain, noise and saturation spectra.

We also show an incoherent spectral hole corresponding to the homogeneous linewidth and calculate a coherent hole which results from the four-wave-mixing like interaction between the signal and noise.

In addition, we experimentally quantify the cross‑saturation in QDash amplifiers. We measure the cross‑saturation dependence on spectral detuning, relative spectral positioning and modulation bit rate.

We demonstrate the low cross‑saturation in QDash amplifiers in a multi wavelength amplification experiment over a bandwidth of 100 nm. The fast response of the amplifier is utilized to amplify 40 Gbit/s signals.

Next, we present QDash amplifier frequency chirp measurements. We measure time resolved chirp for several saturation levels. In addition, we measure the chirp related alpha parameter in two different ways and demonstrate the low chirp in a fiber transmission experiment.

We conclude with the investigation of inhomogeneous gain in QDash lasers. We show that different spectral regions can lase simultaneously and respond at different rates to a step in the injected bias current. We verify this behavior experimentally, and our results correspond to the theoretical calculations.