Mach-Zehnder intensity modulator

Figure 8. The Pockels effect leads to a change in the refractive index of an electro-optic material due to the application of a static electric field. This can be used to build a Mach-Zehnder intensity modulator, for example, which will have an optical transmission dependent on the electric field applied to the Pockels material.

Other devices that can be fabricated with NLO polymers are for example sensors for electric field. A number of sensors fabricated with EO polymers to detect electric field signals and map the electric field distribution have been implemented in the last years based on Mach-Zehnder intensity and polarization modulators. Other sensors are based on asymmetric Fabry-Perot microcavities to convert phase modulation into amplitude modulation and enhance the samphng signals. Very recently Sun et al. [172] presented a novel broadband electrooptic electric field sensor fabricated with an EO polymer microring resonator coupled to the core of a side-polished optical fiber. A sensitivity of 100 mV/m has been achieved at frequencies up to 550 MHz. 

Fig. 1. Representative device configurations exploiting electrooptic second-order nonlinear optical materials are shown. Schematic representations are given for (a) a Mach-Zehnder interferometer, (b) a birefringent modulator, and (c) a directional coupler. In (b) the optical input to the birefringent modulator is polarized at 45 degrees and excites both transverse electric (TE) and transverse magnetic (TM) modes. The appHed voltage modulates the output polarization. Intensity modulation is achieved using polarizing components at the output.

Figure 12. Measurement arm of the Mach-Zehnder interferometer covered by a sensitive polymer layer, resulting in a intensity modulation by a change of the refractive index. This schematic changes are combined with the experimental data on the right side on top the curve of uptake of analyte, and its diffuseion out of the layer (right part), in the middle the experimental modulation, and at the bottom the related changes in refractive index. Bottom left shows the result of intensity signal versus the amount of substance for eight different analytes.

Figure 4.10 Free beam interferometric Mach-Zehnder setup. Two beam splitters permit the interference between phase-modulated and primary beam. This is an intensity modulator...

Fig.17a,b. TMoo single-mode pattern in channel waveguide (a) and intensity modulation response of Mach-Zehnder modulator (b)... 

FIGURE 9.54 (a) General layout of an intensity modulator based on a Mach Zehnder interferometer, (b) detail of output waveguides, (c) electrode configuration for lumped element modulators, (d) electrode configuration for traveling wave modulators. 

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