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We present experimental results on the emission characteristics of a 1.5-μm distributed feedback (DFB) tapered master oscillator power amplifier (MOPA) in a wide range of steady-state injection conditions, showing different dynamical behaviors. A detailed analysis of the optical and radio-frequency spectra has allowed the identification of three different emission regimes: i) stable amplified DFB emission, but with wavelength jumps when sweeping the injection currents; ii) multimode Fabry-Perot (FP) operation of the complete MOPA cavity; and iii) self-pulsed operation at frequencies between 5 and 8 GHz. The quasi-periodic occurrence of these emission regimes as a function of the injected currents is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes. The physical origin of the wavelength jumps and of the alternation between regimes is discussed.

We present the characterization of the optical response of a commercially available 1310 nm VCSEL under gain-switching operation. We demonstrate short pulse generation with pulse widths of 45 ps at 2 GHz repetition rate. The experimental results are compared with simulations based on a rate equation model for single-mode semiconductor lasers. A good agreement is found after a sensible estimation of the simulation parameters.

Space-borne lidar systems require laser transmitters with very good performance in terms of output power, beam quality, conversion efficiency, long term reliability and environmental compatibility. Atmospheric gas sensing additionally requires spectral purity and stability. Solid state lasers are considered the most mature technology for space lidar applications, at expenses of a relatively large size and low conversion efficiency [1]- [3]. Fiber lasers present very high power levels and very good beam quality, but they require specific attention due to their sensitivity to radiation. In this sense, progresses have been made to develop high power fiber amplifiers for different space applications [4]-[6]. Recently, a new generation of high brightness semiconductor lasers based on tapered geometry has demonstrated relatively high average power levels together with a good beam quality [7]-[10]. These devices are emerging candidates for its direct use in space lidar systems.

We analyze the large (>10 nm) and abrupt jumps in emission wavelength, together with the multimode instabilities associated with them, which are observed in monolithically integrated master oscillator power amplifiers emitting at 1.5 μm. The physical origin of such phenomena is investigated in the framework of a travelling-wave model which phenomenologically incorporates thermal effects via self and cross-heating of the different sections of the device. The occurrence of the wavelength jumps and the instabilities as a function of the injected currents in the two sections is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes.

A theoretical analysis of the error probability and the precision of Random Modulation-Continuous Wave LIDAR systems is presented. Both the signal to noise ratio prior and after the correlation process are calculated taking into account the main noise sourc es. Analytical expressions for the estimation of the probability of catastrophic errors in the determination of the distances due to random noise peaks are derived. The effect of the signal to noise ratio on the precision is also theoretically evaluated. As illustrative examples, plots for the signal to noise ratio, the error probability and the precision corresponding to a LIDAR system currently developed in our laboratory are presented.

We analyze the large (>10 nm) and abrupt jumps in emission wavelength, together with the multimode instabilities associated with them, which are observed in monolithically integrated master oscillator power amplifiers emitting at 1.5 \mum. The physical origin of such phenomena is investigated in the framework of a travelling-wave model which phenomenologically incorporates thermal effects via self and cross-heating of the different sections of the device. The occurrence of the wavelength jumps and the instabilities as a function of the injected currents in the two sections is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes.

The performance of new three-section master oscillator power amplifiers emitting at around 1.5 ?m has been analyzed in regard with their application as laser sources for a differential absorption lidar. The devices incorporate a modulation section that can be separately driven thus allowing the required random modulation of the laser emission. The bent design of this section together with the tilting of the output facet ensures a stable single-mode emission in the entire range of driving conditions. At the required modulation frequency (12.5 MHz) a square wave emission profile with high optical modulation amplitude and 22 dB extinction ratio is obtained.

Direct optical modulation of a 1.55 ?m three-section Master Oscillator Power Amplifier has been demonstrated. The temporal response, the optical spectra and the optical modulation amplitude have been analyzed as a function of the frequency and the modulating amplitude. For low modulation amplitude, no spectral broadening was observed up to 1.5 GHz. However, at 12.5 MHz an optical broadening of ~ 4 pm was observed for high modulation amplitudes. At this frequency an extinction ratio of 42 dB has been achieved. The modulation amplitude degrades for frequency values higher than 30 MHz. The device performance under modulation at 12.5 MHz is interesting for its application as laser source for CO2 detection by differential absorption LIDAR operating in the Continuous Wave Random Modulation mode.

We theoretically investigate a dynamical regime, experimentally observed in monolithically integrated master oscillator power amplifiers emitting at 1.5 7 μm, consisting in large emission wavelength jumps of the device from the Bragg wavelength to that of the gain peak. Our analysis is based on numerical simulations by means of a travelling wave model that incorporates spatial effects such as spatial hole burning and coupled-cavity effects. Thermal effects are included by considering the optical response of the quantum well active medium within the quasi-equilibrium approximation at finite temperature, with a phenomenological description of the redshift of the gain peak and the changes in the background material refractive index by means of self- and cross-heating coefficients for both sections. We find that whereas the thermally-induced index changes are the responsible of the modal jumps between consecutive modes, the carrier-induced refractive index changes are the responsible of the jumps occurring between the Bragg wavelength and the gain peak.

High power (> 0.5 W) single-mode frequency laser at 1.55 μm are nowadays key components for a large number of applications such as lidar systems, telemetry or free-space communications. For this level of power, the most suitable and available sources are solid-state lasers and fiber lasers. Semiconductor devices, which are more compact and more efficient, have still to demonstrate very high power operation to be a credible competitor. In order to obtain these levels of power with semiconductor devices, the more suitable device seems to be the Master Oscillator Power Amplifier (MOPA). Single-mode emission is generated by a Distributed Feedback laser (DFB) and the signal is then amplified with a Power Amplifier (PA). To avoid complex optical coupling and to simplify the packaging, it is possible to integrate on the same chip the laser and the amplifier. The main challenges are the fabrication of the multi-section device (at least 2 sections: one for the laser and one for the amplifier) and the reduction of the reflections. Indeed the facet and the internal reflections can create multiple cavities behavior and disturb the laser single-mode emission. In this contribution, we report the realization of a 3-section monolithic MOPA on InP.

We present a high power semiconductor Master Oscillator Power Amplifier monolithically integrated on InP, which includes a modulation section. This device can be used for random-modulation-continuous wave lidar systems or free-space communications.

High brightness semiconductor lasers are potential transmitters for future space lidar systems. In the framework of the European Project BRITESPACE, we propose an all-semiconductor laser source for an Integrated Path Differential Absorption lidar system for column-averaged measurements of atmospheric CO2 in future satellite missions. The complete system architecture has to be adapted to the particular emission properties of these devices using a Random Modulated Continuous Wave approach. We present the initial experimental results of the InGaAsP/InP monolithic Master Oscillator Power Amplifiers, providing the ON and OFF wavelengths close to the selected absorption line around 1572 nm.

Póster presentado en: VI Jornadas de Innovación Docente de la UBU, Burgos, 23 y 24 de febrero de 2012, organizadas por el Instituto de Formación e Innovación Educativa-IFIE de la Universidad de Burgos

Tesis leída en la Universidad de las Islas Baleares, Palma de Mallorca en septiembre de 2011, La presente tesis trata sobre el modelado de l aseres de anillo de semiconductor centr andose en la din amica no lineal, la propiedades modales y la estabilidad din amica que muestran estos dispositivos. Para este n se usan distintos modelos basados en una descripci on semicl asica. En esta aproximaci on, la radiaci on electromagn etica se describe mediante las ecuaciones de Maxwell, mientras que la interacci on radiaci on- materia se describe por medio de las ecuaciones de Bloch, provenientes de la f sica cu antica. Estos modelos se pueden dividir en dos bloques: (1) Ecuaciones de bal- ance (rate equations), basados en ecuaciones diferenciales ordinarias que no tienen en cuenta los efectos espaciales y que hist oricamente han tenido mucho exito al ofrecer buenos resultados al ser comparados con los experimentos; y (2) los modelos basados en ecuaciones diferenciales con derivadas parciales que tienen en cuentan los efectos espaciales. En el caso tratado en esta tesis, donde se tiene en cuenta la dimensi on espacial longitudinal, estos modelos de ondas viajeras (traveling waves) presentan m as complicaciones desde el punto de vista del an alisis matem atico y el tratamiento num erico que las ecuaciones de balance, no obstante presentan ventajas como la des- cripci on de forma natural del comportamiento multimodo y el poder ser aplicados a diferentes tipos de l aseres tras m nimas modi caciones. De hecho, este segundo bloque de modelos incluye el primero bajo aproximaciones o l mites donde la dependencia espacial puede ser simpli cada. Sin embargo, ultimamente con el uso de nuevos mate- riales y nuevas cavidades opticas, estos l mites y aproximaciones dejan de ser v alidos y se requiere una descripci on f sica m as detallada. Este es el caso de los l aseres de anillo de semiconductor.

Comunicación presentada en The European Conference on Lasers and Electro-Optics, celebrada en Munich (Alemania), del 22 al 26 de mayo de 2011. Organizada por la IEEE, In this contribution, we investigate theoretically the multistability by means of a travelling wave model (TWM) for a homogeneously broadened medium with the appropriate boundary conditions, that allow us to model RLs and FP lasers. We take into account that the presence of counter-propagating fields creates a spatial modulation or grating of the population inversion (D2). We compute the monochromatic steady state solutions of the system via a shooting method and we numerically perform their linear stability analysis by diagonalising the jacobian obtained from the evolution operator of the discretized system. Cop.IEEE 2011

We present here a brief overview of the main topics studied in the Institute for Cross Disciplinary Physics and Complex Systems (IFISC) within the context of semiconductor laser dynamics. In particular we study nonlinear effects and chaos in edge emitting lasers, feedback and delay effects, dynamics of coupled lasers and multimode dynamics in ring cavity lasers, with the perspective of possible applications in information and communication technologies., We acknowledge financial support from the European Commission Projects PICASSO Grant IST-2005-34551, PHOCUS Grant FP7-ICT-2009-C- 240763 and IOLOS Grant FP6-IST-2005-34743 and from MICINN (Spain) and FEDER (EU) through Projects TEC2006-1009/MIC (PhoDECC), TEC2009-14101 (DeCoDicA) and FIS2007-60327 (FISICOS). A.P. acknowledges financial support from the Govern Balear

Presentación en el XXXth Dynamics Days Europe, celebrado del 6 al 10 de septiembre de 2010 y organizado por la Universidad de Bristol (UK)

Memoria de Master en Física de la Universidad de las Islas Baleares, Facultad de Física y del Instituto de Física Interdisciplinar y Sistemas Complejos (IFISC-CSIC/UIB).-- Texto en inglés, prefacio en castellano.-- Fecha de lectura: 19-07-2007., We study the influence of spontaneous emission noise in a two-mode model for semiconductor ring lasers, biased in the bidirectional static emission regime. The analysis is carried out by linearizing the model close to a stable stationary solution, and considering effect of noise as stochastic perturbations expressed by Langevin forces. At a linear level, pertubations concerning the total intensity and carrier inversion dynamics decouple from the energy distribution processes between the two modes. This fact permits a full analytic analysis, well confirmed by numerical simulations of the complete non linear system. The analysis shows that semiconductor ring lasers have peculiar noise properties. On one side the total intensity and carrier density show a noise spectrum characterized by a resonance induced by the typical field-medium exchange processes (relaxation oscillations) and the global phase invariance induced by the Goldstone mode, so as far as those variables are concerned, it behaves as a standard single-mode Fabry-Perot semiconductor laser. Besides, the degree of freedom associated to the simultaneous presence of two counterpropagating modes allows for a further process of energy exchange between the two modes. Our analysis unveils that such process presents a resonance peak as well, influenced mainly by the backscattering parameters, and can be excited in the bidirectional regime as a ’noisy precursor’ of a Hopf bifurcation., The present work represents the development of reliable tools for the simulation and analytical analysis of a model for semiconductor ring lasers. Reliability is tested by a thoughout comparison between simulation and calculations. Future developments will range from quantitative evaluation of two-times correlations functions, to applications to rotation sensing, to analysis of the stochastic jumps induced by noise in the bistable regime., Este trabajo ha sido realizado bajo el marco del proyecto europeo ”IOLOS: Integrated Optical Logic and Memory Using Ultrafast Micro-ring Bistable Semiconductor Lasers”, STREP within the Information Society Technologies program of the European Commission.