Photonic crystal ring resonator based optical MUX/DEMUX design structures: a survey and comparison study

For the past few decades, the design of photonic crystal (PC)-based optical devices and components are mainly focused by several researchers as miniaturisation becomes a crucial need in many integrated applications. In optical communication system, the PC-based wavelength division multiplexer and demultiplexer is considered as one of the most essential component as it offers high transmission rate in single optical fibre by performing multiplexing operation. Due to its major role, numerous optical MUX/DEMUX structures based on different design mechanisms like resonant cavity, super prism effect, cascading multiple channel drop filters, coupling and cascading the PC waveguide, defect waveguides and photonic crystal ring resonator (PCRR), etc., have been reported and analysed so far. However, despite the various mechanisms, the design structure based on PCRR mechanism has attracted the attention of many researchers in recent years due to its design flexibility, high quality factor and low loss which satisfies the requirements of major applications. Hence, the main aim of this paper is to discuss about the various existing design structures of optical MUX/DEMUX based on PCRR mechanism along with its respective pros and cons. Further, the comparison of their corresponding structural and performance parameters is also tabulated in detail. From the literature review and comparison study, the future design considerations are suggested for the researchers which would be helpful for them in designing better structure with improved performance.