en Optimum Design of a Three Channel Demultiplexer Based on Photonic Crystal تخصصی Special پژوهشي Research We propose an ultra-compact structure to realize demultiplexing operation for Wavelengh Division Multiplexing(WDM) communication systems using resonant cavity in Photonic Crystal (PC) structure . This design improves the channel spacing which is reduced up to 2nm. The proposed demultiplexer has an area equal to (16.5 m × 6.5 m) and thus it is verified that this structure is very small and can be integrated easily into optical integrated circuits with nanophotonic technologies. The output wavelengths of designed structure can be tuned for communication applications, around 1550 nm. We propose an ultra-compact structure to realize demultiplexing operation for Wavelengh Division Multiplexing(WDM) communication systems using resonant cavity in Photonic Crystal (PC) structure . This design improves the channel spacing which is reduced up to 2nm. The proposed demultiplexer has an area equal to (16.5 m × 6.5 m) and thus it is verified that this structure is very small and can be integrated easily into optical integrated circuits with nanophotonic technologies. The output wavelengths of designed structure can be tuned for communication applications, around 1550 nm. Resonant cavity,Photonic crystal, Integrated optics, Defect Resonant cavity,Photonic crystal, Integrated optics, Defect 1653 1656 http://opsi.ir/browse.php?a_code=A-10-1-225&slc_lang=en&sid=1 soghra hayati soghra hayati soghra.hayati@gmail.com 10031947532846002642 10031947532846002642 Yes Islamic Azad University of Bushehr Islamic Azad University of Bushehr Zoheir Kordrostami Zoheir Kordrostami kordrostami@sutech.ac.ir 10031947532846002643 10031947532846002643 No Shiraz university of Technology Shiraz university of Technology