Silicon Photonics: Fundamentals and Devices

7.10 Performance of EO Modulators

The earlier two sections attempted to describe the representative optical and electrical structures employed for the fabrication of modulator structures. The change in RI is accomplished via the EO effect: in most situations by free-carrier plasma dispersion effect, in which an electric field injects, extracts, or induces carriers of single or both the polarities.

In this section, a summary of the performance of various types of modulators theoretically studied or experimentally reported has been presented. Table 7.1 gives most of the performance characteristics. This kind of summary is also presented by Lipson 36. The present table includes all the data reported in that work and in addition collects recent data appearing in the literature. The entries are by no means exhaustive; rather, they are representative values.

Problems

7.1 Consider a bulk effect modulator using KDP as in Section 2.2. Show that the ratio of output intensity (I_o) and input intensity (I_i) is

where r is the linear EO coefficient.

7.2 Calculate V_π for a KDP crystal, given λ = 1 µm, n₀ = 1.51, and r = 10.6 × 10⁻¹² m/V.

7.3 Draw a diagram illustrating the principle of intensity modulation of light using an EO crystal as described in Section 2.2. Indicate the state of polarization at each stage. Draw the transmission curve I_o/I_i as a function of applied voltage V. Illustrate how ...