عنوان مقاله
انتشار با تلفات کم در موج برهای کریستالهای فوتونی تا اندازه 60
فهرست مطالب
چکیده
مقدمه
طراحی و ساخت
نتایج
نتیجه گیری
بخشی از مقاله
طراحی و ساخت
با به حداقل رساندن دقیق نقایصی نمونه مقادیر بی نظمی حال در مرتبه1nm می باشد. محدودیت باقیمانده نویسنده پرتو الکترون ، فیلد نوشتن محدود 100 mm می باشد. موج برهایی که طول آنها بیشتر از این حد است، نیازمند استیچ فیلدهای متعدد به هم با استفاده از کنترل انترفرومتری هستند که این کار را با صحت 10-50nm می توان انجام داد.
در رژیم نور کند، به خاطر بهبود تعامل و برهم کنش بین نورو ماده، مد نور نسبت به نقایص حساسیت بیشتری نشان داده و خطاهای استیچ تاثیر بسیار قویتری اعمال می کنند. موج برها با دو هدف نیل به پراکندگی تخت باند با شاخص گروهی حدود ng≈60، مناسب برای کاربردهای غیر خطی و همچنین نیل به عملیاتی با تلفات پائین، طراحی شدند.
کلمات کلیدی:
Low loss propagation in slow light photonic crystal waveguides at group indices up to 60 Juntao Li a,b , Liam O’Faolain b , Sebastian A. Schulz b , Thomas F. Krauss b, * a State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China b SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK Received 15 February 2012; received in revised form 8 May 2012; accepted 8 May 2012 Available online 31 May 2012 Abstract We have designed slow light photonic crystal waveguides operating in a low loss and constant dispersion window of Dl = 2 nm around l = 1565 nm with a group index of ng = 60. We experimentally demonstrate a relatively low propagation loss, of 130 dB/cm, for waveguides up to 800 mm in length. This result is particularly remarkable given that the waveguides were written on an electronbeam lithography tool with a writefield of 100 mm that exhibits stitching errors of typically 10–50 nm. We reduced the impact of these stitching errors by introducing ‘‘slow–fast–slow’’ mode conversion interfaces and show that these interfaces reduce the loss from 320 dB/cm to 130 dB/cm at ng = 60. This significant improvement highlights the importance of the slow–fast–slow method and shows that high performance slow light waveguides can be realised with lengths much longer than the writing field of a given ebeam lithography tool. Crown Copyright # 2012 Published by Elsevier Ltd. All rights reserved. Keywords: Slow light; Photonic crystal waveguides; Loss; Dispersion 1. Introduction The phenomenon of slow light in photonic crystal (PhC) waveguides is rapidly turning into an essential paradigm in linear [1] and nonlinear [2–12] photonics; it enables the realisation of compact modulators [13,14] and substantially increases the efficiency of nonlinear effects [2] over a broad bandwidth range [3]. The key to thisfunctionality is the ability to engineer the dispersion and achieve the ‘‘flatband’’ condition, i.e. a dispersion band that features a section of low and constant group velocity. This type of dispersion relationship can be achieved, for example, by altering the size and/or position of the boundary holes in a line defect PhC waveguide or by a judicious alteration of the waveguide width [15–18]. In the absence of loss, the performance of such a flatband slow light waveguide is limited by its group index and bandwidth, e.g. a group index of ng = 30 and Dl = 15 nm at l = 1550 nm [18]. Within these constraints, increasing a given delay or nonlinear enhancement would simply require increasing the length of the waveguide. Unfortunately, propagation losses also increase with group index and provide the ultimate limitation to the slow light enhancement that can realistically be achieved. Opportunely, our dispersion engineering technique also provides a handle on propagation loss, giving rise to the concept of ‘‘loss engineering’’; loss engineering affords the reduction of www.elsevier.com/locate/photonics Available online at www.sciencedirect.com Photonics and Nanostructures – Fundamentals and Applications 10 (2012) 589–593
