Publication: Estudio teórico de la dinámica no lineal en diodos láser acoplados lateralmente
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2010-01
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2010-01-28
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Abstract
En los últimos años la dinámica no lineal en láseres de semiconductor ha sido objeto de numerosos estudios. Aunque el diodo láser de por sí no puede mostrar un comportamiento caótico ya que su dinámica viene determinada por dos variables independientes, al añadir un tercer grado de libertad se posibilita la aparición de no linealidades. Esto puede ocurrir por diferentes mecanismos, como la modulación directa de la corriente, la inyección externa de luz o el acoplo lateral de los láseres de un array. En este proyecto se estudia esta última configuración, la cual ha sido propuesta con éxito para alcanzar velocidades de transmisión por encima del límite tradicional del ancho de banda de los láseres de semiconductor: la frecuencia de relajación de oscilación. Se han observado experimentalmente en estos dispositivos comportamientos no lineales y caóticos que no han sido clarificados a nivel teórico. A nivel experimental se verifica que la dinámica no lineal tiene su origen en la interacción entre la frecuencia de batido de los modos laterales del array y la frecuencia de relajación del diodo láser. Analizamos en detalle un modelo habitual basado en ecuaciones de tasa en las que un factor de acoplo complejo representa la interacción entre las colas evanescentes de los modos laterales de los emisores. Sin embargo, este modelo no consigue explicar la dinámica no lineal observada, por lo que, para una mejor comprensión de las no linealidades, se elabora un sencillo modelo fenomenológico con el objeto de simular los efectos no lineales que pueden llevar al régimen caótico, los cuales se estudian mediante una serie de diagramas de bifurcación construidos sobre distintos parámetros. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
In recent years nonlinear dynamics in semiconductor lasers has been the subject of numerous studies. Although the diode laser can exhibit no chaotic behavior on his own because its dynamics are fully determined by two independent variables, the addition of a third degree of freedom enables the rising of nonlinearities. This can happen by means of different mechanisms, like direct current modulation, external optical injection or lateral coupling in a lasers array. In this thesis the latter configuration is studied, having been proposed successfully for reaching transmission speeds above the traditional bandwidth limitation in semiconductor lasers imposed by the relaxation oscillation frequency. Non linear and chaotic behaviors have been observed experimentally in these kind of devices, but have not been fully explained by theoretical studies. Experiments show that these non linear dynamics are related to the interaction between the lateral modes beating frequency of the array and the relaxation frequency of the diode laser. We analize in detail one usual model based on rate equations in which a complex coupling factor represents the interaction between the evanescent fields of the emitters lateral modes. However, this model fails to explain the observed nonlinear dynamics. Thus, to achieve a better understanding of these nonlinearities, a simpler phenomenological model is implemented, with the scope of simulating the nonlinear effects which can lead to chaotic regime. These are studied through a series of bifurcation diagrams where different parameters are varied.
In recent years nonlinear dynamics in semiconductor lasers has been the subject of numerous studies. Although the diode laser can exhibit no chaotic behavior on his own because its dynamics are fully determined by two independent variables, the addition of a third degree of freedom enables the rising of nonlinearities. This can happen by means of different mechanisms, like direct current modulation, external optical injection or lateral coupling in a lasers array. In this thesis the latter configuration is studied, having been proposed successfully for reaching transmission speeds above the traditional bandwidth limitation in semiconductor lasers imposed by the relaxation oscillation frequency. Non linear and chaotic behaviors have been observed experimentally in these kind of devices, but have not been fully explained by theoretical studies. Experiments show that these non linear dynamics are related to the interaction between the lateral modes beating frequency of the array and the relaxation frequency of the diode laser. We analize in detail one usual model based on rate equations in which a complex coupling factor represents the interaction between the evanescent fields of the emitters lateral modes. However, this model fails to explain the observed nonlinear dynamics. Thus, to achieve a better understanding of these nonlinearities, a simpler phenomenological model is implemented, with the scope of simulating the nonlinear effects which can lead to chaotic regime. These are studied through a series of bifurcation diagrams where different parameters are varied.
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Láser semiconductor, Arrays de láseres, Acoplo lateral, Dinámica no lineal, Caos, Semiconductor laser, Laser arrays, Lateral coupling, Nonlinear dynamics, Chaos