Mach-Zehnder waveguide modulator

Figure 4.15 Illustration of the constructive and destructive interference pattern in a Mach-Zehnder waveguide modulator. Only if the outgoing waveguide is single mode, the resulting antisymmetric mode will be completely radiated into the substrate. A multimode waveguide cannot be used for an efficient Mach-Zehnder modulator...

Recently, Enami and co-workers [118] presented a hybrid cross-linked EO polymer/sol-gel Mach-Zehnder waveguide modulator with of 0.65 V at 1,550 nm. Such a low value of half wave voltage, which is one of the best results obtained in literature, is related to the combination of a very high electro-optic effect and to the device design that combines physical vertical tapers in the sol-gel core, index tapers in the EO polymer, a suitable electrode structure and a top buffer layer designed for cross-linked EO polymer systems. In such a device also the optical losses result to be reduced with respect to a more traditional configurations. 

Also all-optical Mach-Zehnder waveguide interferometer devices working as switches have been presented in the last years [142]. In this case the change of the refractive index in the arms of the modulator is produced by the light inducing a local optical nonlinearity. Recently, Wu et al. [143] reported on an all optical switch by using the position shift of the spatial solitons controlled by phase modulation... 

Figure 4.14 Three different electrooptic waveguide devices [1] (a) Mach-Zehnder modulator with push-pull arrangement of the electrodes, (b) electrically controlled directional coupler, (c) coupler with phase-reversal electrodes.

For waveguide phase modulators and especially the Mach-Zehnder modulator, there are two main electrode configurations, which are explained in Figure 4.18. 

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. 

Thapliya, R., Okano, Y., Nakamura, S. (2003). Electrooptic characteristics of thin-film PLZT waveguide using lidge-type mach-zehnder modulator. f.Lightwave Technol, Vol. 21, No. 8, pp. 1820. 

In this chapter we will shortly summarize the nonlinear optical properties of macromolecular systems and some of the main experimental techniques for their optical characterization. Some basic optoelectronic patterns will be reported in order to give a brief account of the advances in the realization of active waveguide systems and telecommunication devices based on organic materials. The main optoelectronic devices based on nonlinear optical properties of chromophores in polymeric and hybrid matrices will be illustrated. In particular Mach-Zehnder modulators, microring resonators, switches and wavelength filters will be reviewed. 

Recently poling and modulation of a polymeric Mach-Zehnder modulator with conductivity dependency free, overcoming the latter poling issues, has been accomplished by using an in-plane coplanar waveguide (CPW) stmcture.[48] Furthermore, the use of buried electrode can improve overlap factor to enhance poling efficiency. A MZ modulators using the buried CPW showed the Vn s of 6.7 V [53]. 

Fig. 4.26 Waveguide electro-optic modulators and their response characteristics (a) phase modulator (b) Mach-Zehnder interferometer (c) directional coupler.

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