| Popis: |
Silicon photonics is a technology of choice for the integration of complex photonic circuits on chips of a few mm² that can be mass-produced at low cost. One of the main challenges of this platform is the realization of miniature optical transceivers for high-speed telecommunications between different servers in datacenters. Numerous other applications have recently emerged: spectroscopy, radio over fiber and LIDAR. For most of these new applications, a tool is particularly useful: optical frequency combs. Shortly after the invention of the laser, these spectral structures, consisting of a set of regularly spaced and mutually coherent laser lines, aroused great interest, making it possible to improve the precision and simplicity of optical frequency measurements considerably. Several strategies have been developed for their generation, one of which exploits electro-optical modulation. The objective of my thesis was to investigate numerically and experimentally the suitability and performance of silicon modulators for both short-range high-speed digital communications and electro-optical frequency comb generation. Silicon modulators rely on the free carrier plasma dispersion effect, which involves a non-linear response of the refractive index variation to the application of a voltage, as well as a variation in the optical absorption of the material. On the other hand, several electronic and optoelectronic effects impact the modulators speed. Therefore, first part of my work was devoted to the numerical modelling of a silicon phase modulator taking into account these static and dynamic effects. This realistic model is based on experimental measurements of real modulators and has been used in the following work to simulate or analyze the performance of the modulating structures. A second part consisted in the study of a Mach-Zehnder modulator for the generation of the PAM-4 format. An important aspect of this type of application is to be able to generate a four-level signal without using power-hungry electronic components. On the other hand, it is preferable to provide these fiber transmissions in a spectral region where the optical dispersion is minimal. I have thus carried out an experimental demonstration of a PAM-4 signal generation at 20 Gb/s without using a digital/analog converter and in O-band where the dispersion is close to 0 ps/nm/km. Finally, a third part is dedicated to the generation of optical frequency combs by silicon modulators. The requirements for the combs properties depend on the applications, but two characteristics are generally desired: a large number of lines, and a power equally distributed among the lines (i.e. a flat comb). Through a numerical study, I was able to show that both structures based on silicon modulators allow to generate 9 equalized lines ( |
