A high-efficiency silicon optoelectronic modulator based on a Bragg Mirror and integrated in a low-loss Silicon On Insulator waveguide

In this paper we propose a silicon optoelectronic modulator based on the Plasma Dispersion Effect used in conjunction with a Distributed Bragg Reflector which converts the phase shift induced by the free carriers injected by a P-i-N diode into variation of its reflectivity. The device is integrated in a low-loss Silicon-On-Insulator waveguide. With respect to a previous paper [A.Cutolo et al., Appl. Phys. Lett., 71 (2), 1997] we suggest an inversion of the driving scheme; we propose to tune the Bragg mirror in the ON state, when the light passes through the mirror unchanged, and then to inject the electron-hole plasma to put the mirror in the total reflection configuration and therefore to switch the light off. In this case the two plasma-induced optical effects, that is the variation of refractive index and absorption coefficient, are concurrent and both contributing to an efficient snitching of the light. This new driving scheme allows to reach better performances in terms of modulation depth efficiency; in fact we show how, in this case, a 100% modulation depth is achieved. An exhaustive description of the optical structure and its guiding properties, together with the analysis of the electrical behavior of the modulator are given. Moreover, we show how dissipated power is also reduced allowing us to design a highy optimized version of the modulator. Finally, a comparison with other interferometric structures is given and it is shown how this hind of modulator results very attractive in terms of dissipated power and reduced area occupied on chip.