Design and development of high speed optical modulator on silicon on insulator platform

Abstract

Optical communication has transformed information technology and enabled the present-day data explosion. The new era of data centric society is primarily driven by the ability to communicate data at high-speed. Migration from copper cables to optical fibres has created basic infrastructure for the revolution of optical interconnect. One of the important functionalities in an optical communication network is light modulation that imprints electrical signal information on to an optical carrier. Optical modulators are the devices that do the conversion. Optical modulator changes either the phase or intensity of the carrier light in accordance with the electrical signal. Broadly, modulators are classi fied as electro-refractive; where the phase of light is changed and electro-absorptive; where the intensity is changed based on the electrical signal. Both types of modulators rely on the refractive index of the optical material. The research work in this thesis is primarily focused on the design, fabrication and characterization of an electro-optic (EO) modulator in Silicon and electro-optic materials on Silicon-on-Insulator (SOI) platform for the implementation of high-performance electro-optic functionalities. The dominance of silicon in commercial CMOS for electronic applications led to the investigation of silicon photonic integrated circuits and enabled the implementation of photonic integrated circuit in silicon for many applications, including, high-speed communication and on-chip sensing. In addition, high-index contrast of silicon-silicon dioxide structures enabled the fabrication of complex and compact integrated circuits. Since silicon has a very-poor linear electro-optic coefficient, modulation is achieved through plasma dispersion effect, where the concentration of free carriers alters the real and imaginary part of the refractive index. The modulation speed of silicon optical modulators is limited by carrier mobility. In this research work, we demonstrated for the fi rst time carrier-injection based...