Introduction
Ultra-fast optic fiber networks have led the communication systems on long distance network and communication systems on data network for the past forty-year [1] and [2]. Nowadays, silicon photonics has been widely used in next generation communications systems and data interconnects where high levels of integration can be archived using conventional silicon integrated circuit infrastructure that has low manufacturing costs. This is mainly due to high data densities and transmission over long distances in a platform [3]–[5] and [6]. For the development of silicon photonics devices, researchers had carried out the study of propagation loss in single-mode Silicon-On-Insulator (SOI) based waveguides with the fabrication of rib waveguide [7]. In most optical telecommunication systems, silicon normally operates in the region of infrared light above 1.1 micrometers [8 and 9]. The refractive index of silicon is very high at a value of about 3.5. The beneficial of silicon photonics is such that existing semiconductor fabrication techniques are used to make silicon photonic devices. Furthermore, it is possible for the creation hybrid devices in which integration of optical and electronic components are on a single microchip as in most integrated circuits, silicon is already used as the substrate [8]. In addition to that, silicon is a material that have high thermal conductivity and thus well insulating oxide (SiO2) can be formed easily. As a result, the fabrication of silicon waveguide is retrieved with the waveguide core in the intrinsic region of a laterally formed PIN diode [10]. This will eventually result in the charge carrier concentration to be modulate at a higher speed. In order to increase the refractive index of the silicon, there must be an increase in the number of free charge carriers. Thus, it is deduced that the refractive index of the silicon is directly proportional to the number of free charge carriers. A higher refractive index is required for the modulation of light at a higher speed in a silicon waveguide with low power consumption [11]. One of the challenges is the realization of optical modulator based on silicon. The most frequent approach used in optical modulator based on silicon is the plasma dispersion effect. The real and imaginary parts of the refractive index vary with the free carriers concentration [12]. Free carrier-based modulation in Silicon can be achieved by three modulation schemes namely, (i) carrier-injection (ii) carrier-depletion (iii) carrier-accumulation [1] and [12].