Final Report Summary - LASPULSE (Multi-section semiconductor lasers for all-optical signal processing and short pulse generation) The generation of short optical pulses with low jitter is very important to extend the capacity of fibre optical communication systems. High-power short pulses are also of strong interest in telemetry, and free-space-optical (FSO) communications. On the other hand, all-optical signal processing will play a major role in the future photonic networks to fully utilise ultra-wide bandwidth of the optical carrier. Within the Seventh Framework Programme (FP7) People Marie Curie Programme (Intra- European Fellowship), at the Universidad Politécnica de Madrid, Pawel Adamiec has investigated, both from a theoretical and an experimental point of view, high-power multi-section semiconductor lasers focusing on its applications in short-pulse generation, high-speed modulation, and all-optical signal processing for optical communication systems. The main goal was to achieve a better understanding of the dynamics of these devices to assess their possible use in previous applications. The investigated devices lasers were two-section tapered lasers (TL) and monolithic master oscillator power amplifiers (MOPA). A rate equation dynamic model for two-section TL was developed and implemented. The main idea was to convert the tapered section into a rectangle with the same area, assuming uniformity of carriers and photons in each section. The input parameters for the model were taken from the simulation results obtained with a three-dimensional (3D) steady-state model, which was also used as a validation test of the simplified rate equation model in steady-state. The model was applied to simulate the pulse generation of 1 060 nm distributed Bragg reflector (DBR) TLs, which were also experimentally characterised. To improve the agreement between the modelling results and experiments one-dimensional intensity travelling wave was implemented into the model. The model was able to predict qualitatively the behaviour of the two-section DBR TLs, i.e. the pulse power, pulse width, and rise time as a function of driving parameters. The experimental setup to measure two-section TL or MOPAs in continuous wave (CW) and dynamic operation was designed and implemented. It included equipment and software tools to measure the output power and spectra as a function of both, tapered current and ridge waveguide (or MO). The dynamic measurements included different approaches, namely gain switching, direct modulation and radio-frequency measurements. Two-section TL emitting at 1 060 nm and MOPA emitting at 1 550 nm were extensively characterised to understand the static and dynamic behaviour and to study the performance limits. In this respect some outstanding results have been obtained. In gain switching regime short 100 ps pulses with 2.7 peak power were obtained from the monolithic MOPA. These devices suffer from instabilities due to mode competition and self-pulsation processes. The instabilities were consistently explained in terms of mode hopping between the distributed feedback mode of the MO (1 550 nm) and the Fabry-Perot mode of the entire cavity (1 520 nm) allowed by the residual reflectance of the PA front facet. This mode hoping results in the ripples observed in the power-current characteristics. Nevertheless, regions of high stability were found, in which high power and stable pulses were obtained. Another state-of-the-art achievement is the direct modulation of the two section TL emitting at 1 060 nm at high frequency, controlling the high output power with a relatively small current in the RW section. The eye diagram was measured providing a Q factor of 6.5 at 2.5 Gbit / s. This result points to a potential application of these devices in FSO communications. In addition, RF measurements were performed in order to determine relative intensity noise in TLs and MOPAs and further to obtain internal parameters of the device like differential gain, which was used in the modelling. Finally, the developed model was used to study the influence of different geometries on the dynamics of two-section TLs and on the bistable behaviour to be used in all-optical signal processing. Acknowledgments We acknowledge our colleagues from Ferdinand-Braun-Institute für Höchstfrequenztechnik, Berlin, for providing the 1060 nm two-section tapered lasers investigated within this project. References - P. Adamiec, B. Bonilla, A. Consoli, J.M. Tijero, S. Aguilera, and I. Esquivias, High peak power pulse generation from a monolithic Master Oscillator Power Amplifier at 1.5 µm, Applied Optics, Vol. 51 Issue 30, pp.7160-7164 (2012); http://dx.doi.org/10.1364/AO.51.007160 - P. Adamiec, A. Consoli, J.M.G. Tijero, I. Esquivias, S. Schwertfeger, A. Klehr, H. Wenzel, G. Erbert, Short pulse generation by Q-switching two section tapered lasers, Proc. SPIE vol. 8277, article number: 82771N (2012) Powiązane dokumenty Final Report - LASPULSE (Multi-section semiconductor lasers for all-optical signal processing and short pulse generation)
