Electroabsorption modulators for a fiberoptic E-sensorsystem

This thesis reports on the development of waveguide electroabsorption modulators based on multiple quantum well structures. The requirements to the modulator are given by the application in a fiberoptic E-field sensor system. The theoretical calculation of a quantum well structure which is tailored to the application, of the waveguide and of the electrical structure of the device is treated first. Following the technological realization of the developed concept and the characterization of the fabricated devices is described. The achieved performance of the modulators is discussed regarding the influence on the sensorsystem. This results in a minimum detectable field of 20 mV/m, a dynamic range of 105 dB and a frequency range from 100 MHz up to 8 GHz. In a final comparison between the performance of the sensorsystem which is dominated by the modulator and that of commercially available products based on lithiumniobate modulators the advantages of the developed concept are described. In addition to a high sensitivity and a broad frequency range also the operation of the modulator in optical reflection and the low polarization dependence of the modulator which is necessary for the use of conventional non polarization maintaining fibers are worth mentioning