طراحی طبقه تطبیق‌گر برای موج‌بر بلور فوتونی نور آهسته برمبنای تزویج‌گر سمتی

نویسندگان

دانشکده مهندسی برق و کامپیوتر - دانشگاه سمنان

چکیده

در این مقاله دو موج‌بر نور آهسته بلور فوتونی برمبنای یک تزویج‌گر سمتی طراحی‌شده و به‌منظور تطبیق این موج‌برها به موج‌بر متداول W1، ساختارهایی پیشنهاد شده‌است. برای شبیه‌سازی این ساختارها از روش‌های تفاضل محدود در حوزه زمان و نیز از روش بسط موج تخت استفاده شده‌است. در ساختار نور آهسته اول، ضریب شکست گروه 18.05 و مقدار GBP برابر با 0.278 و در ساختار دوم با تغییر شبکه بلور فوتونی مثلثی به مربعی در قسمتی از ساختار، ضریب شکست گروه 11.37 و GBP برابر با 0.255 حاصل می‌گردد. برای تطبیق این موج‌برها به موج‌بر W1، طبقه‌های تطبیق‌گری برمبنای انشعاب Y طراحی و پیشنهاد شده‌است. در محل اتصال مدار تزویج و موج‌بر نور آهسته از تکنیک افزایش تدریجی حفره‌ها استفاده شده‌است تا تطبیق خوبی بین موج‌بر نور آهسته و معمولی در بازه بسامدی موج‌بر بلور فوتونی حاصل گردد. به این منظور یک پالس نوری به ساختار تابیده‌شده و میزان توان گذری، بازتابشی و پهنای باند در هر حالت محاسبه شده‌است. پهنای باند حاصل‌شده برای ساختار اول nm 28 و برای ساختار دوم برابر nm  7 می‌باشد. در ساختار اول، میزان بیشینه توان عبوری شبیه‌سازی شده به  97.3%و در ساختار دوم به 98.5%%  می‌رسد. با توجه به پهنای باندnm  28 حاصل‌شده در ساختار اول، موج‌بر نور آهسته پیشنهادی، طول موج nm 1550 استفاده‌شده در مخابرات نوری را  به‌خوبی پوشش می‌دهد.

کلیدواژه‌ها


عنوان مقاله [English]

Design of matching stage for directional coupler-based slow-light photonic crystal waveguide

نویسندگان [English]

  • F. Mazloumtehrani
  • M. Danaie
  • P. Keshavarzi
Faculty of Electrical and Computer Engineering, University of Semnan, Semnan, Iran
چکیده [English]

In this paper, two slow-light photonic crystal waveguides are designed based on a directional coupler. For the coupling of the waveguides to the conventional photonic crystal W1 waveguide, matching structures are proposed. For simulating the proposed structures, finite difference time domain and plane wave expansion methods are used. For the first structure, a group-index of 18.05 and a GBP equal to 0.278 and for the second structure, by modifying a section of photonic crystal lattice structure from hexagonal to square, a group-index of 11.37 and a GBP equal to 0.255 is obtained. For matching these waveguides to the W1 waveguide, a matching stage based on a Y-splitter is designed and proposed. Gradual change technique at the intersection of slow-light waveguide and coupling stage are used in order to maximize the waveguides coupling within the photonic crystal waveguide frequency range. For this purpose, a light pulse is inserted to the structure and the transmitted and reflected powers are calculated for each case. The bandwidth obtained for the first structure is equal to 28 nm and for the second structure it is equal to 7 nm. For the first structure, the maximum simulated transmittance is equal to 97.3% and for the second structure it is equal to 98.5%. Due to the 28 nm bandwidth obtained for the first structure, the proposed slow-light waveguide is well suited for the 1550 nm wavelength which is used in optical communications. 

کلیدواژه‌ها [English]

  • Photonic crystals
  • slow light waveguide
  • directional coupler
  • finite difference time domain
  • plane wave expansion
  • coupling circuit
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