All-Optical Switching and Logic-Gates Design Using Mode (Polarization)-Conversion in Micro-Ring Resonator

Introduction

Human life is enhanced to a large extent due to computers and its application break through into all areas of human civilization. The speed of computer systems is limited by the bandwidth of electronic circuits. Therefore, a remarkable way out to increase the speed and bandwidth is needed, and unless researchers’ find out different mechanism towards different technology, it will not possible to further develop the computer performance. Signal processing circuits are also essential for optical communication and networking systems along with bio-sensing, space technology etc. Switching is basic building block in all form of signal processing units and networks. Though special types of optical switches are projected and designed, their uses are still in preliminary phase (Chattopadhyay et al, 2013).

To avoid bottleneck of optoelectronic conversions in quickly growing ultra-high speed optical system, switching, routing and signal processing desires to carry out in optical domain (Zoiros et al, 2004). All-optical switching is one of the most important technology into cutting-edge research, and might ultimately show the new path way for computing applications with faster processing speed and huge bandwidth as well as enhanced connectivity without electrical-optical-electrical conversions. Research in all optical domain can also be investigated new ideas.

All-optical switches (AOSs) attract researchers in the recent years due to its high compactness, fast response and low threshold. Due to huge potentials of optical computing, different all-optical circuits which include optical logic gates, different combinational and sequential logic circuits digital converter have been anticipated and designed by different researchers using various techniques such as semiconductor optical amplifier (SOA), Mach–Zehnder interferometer (MZI), non-linear material (NLM) and ring resonator etc (Nayar et al, 1991; Jinno et al, 1992). Some kinds of AOSs are based on intensity modulation which generally requires higher switching power. Polarization-dependent AOS can be realized by arranging waveguide in interferometric style. The fiber with Mach-Zehnder interferometer can be utilized to design polarization-dependent switch (Li et al, 2006). Some usual bulky polarization components such as wave-plates, beam splitter are used in the designing of interferometric based optical switch. These AOSs are not potential candidate in practice due to the bulky nature in structure, the large insertion losses, the strong instability caused by surroundings and so on. However, almost all of these designs are not compact and simple. Polarization rotation due to bend waveguides is shown in literature (Soref et al, 2006). In the recent years, silicon photonics has reached massive development in optical communication, information processing and designing of all-optical logic gates due to huge bandwidth and ultra-high speed of light (Soref et al, 2006). Silicon micro-ring resonators (MRRs) is suitable component for photonic integrated circuits due to ultra-compact size of MRRs and low power consumption. The MRRs are found application in signal processing, optical switches, logic gates, (Melloni et al, 2002; Rakshit et al, 2014). due to its all-optical behavior. MRRs are also used in designing adder/subtractor circuits, converters, multiplexer and demultiplexer circuits, etc (Khorasanindejdad et al, 2009) Therefore, study of the polarization-dependent AOS especially in MRR based architecture is very important.