عنوان مقاله
افزایش تاثیر نور کند در موجبر نقص خطی کریستال فوتونی
فهرست مطالب
چکیده
مقدمه
شبیه سازی
نتایج و بحث
نتیجه گیری
بخشی از مقاله
نتایج و بحث
برای اثر نور کند، ساختارPCW که در آن کلیه سوراخ های هوایی جای خودرا به پراکنده سازهای چشمی شکل داده اند، بهتر از ساختاری است که ردیف های اول و دوم سوراخ های هوایی جای خود را به پراکنده سازهای چشمی شکل داده اند، به شکل 1 رجوع کنید.
مکانیسم اثر نور کند درPCW معمولاً به دو جنبه متفاوت تقسیم می شود، توزیع و پراکندگی معکوس و انعکاس همه سویی. برای پراکنده سازهای استوانه ای، پراکندگی و انتشار معکوس، دلیل اصلی پراکندگی محسوب می شود، که با کاهش عرض موجبر با استفاده از موجبرهای کریستال فوتونی شکافدار، تعدیل قطرهای سوراخ ها یا جابجایی ردیف های اول و دوم سوراخ های هوایی با پراکنده سازهای چشمی شکل، می توان آن را بهبود بخشید.
کلمات کلیدی:
low light effect in photonic crystal line defect waveguide by using eye-shaped scatterers Yong Wan a,b,n , Kai Fu a , Changhong Li c , Maojin Yun a a College of Physics Science, Qingdao University, Qingdao 266071, PR China b Institute of Multifunctional Materials (IMM), Qingdao University, Qingdao 266071, PR China c College of Automation, Qingdao University, Qingdao 266071, PR China article info Article history: Received 31 July 2012 Received in revised form 5 September 2012 Accepted 8 September 2012 Available online 24 September 2012 Keywords: Scatterers Photonic crystal Waveguide Slow light Group index abstract Eye-shaped scatterers are adopted into a photonic crystal waveguide (PCW) in two ways: (1) slow light with wide bands and group index ng from 14.1 to 32.8 can be generated by simply replacing the first and second rows of air holes adjacent to the linear defect with eye-shaped scatterer and (2) slow light with wide bands of ng from 36.5 to 287.5 are achieved by substituting all air holes with eye-shaped scatterers. More simulation results show that the latter method can achieve slow light with low dispersion at large ng, and near zero dispersion structures by adjusting the lattice parameter a and parameter e (e is inversely related to the ratio of the radius of the minor axis c to that of the major axis b). & 2012 Elsevier B.V. All rights reserved. 1. Introduction Slow light with a small group velocity vg is found useful in compact optical delay lines and optical buffers. It can be observed close to the Brillouin zone edge in a photonic crystal waveguide (PCW) by using the photonic bandgap of photonic crystal [1–3]. Photonic nanostructures can also generate on-chip slow light at room temperature and achieve any slow light operating wavelength by correctly, scaling the structural parameters of the photonic crystal with less loss [4–6]. There are two basic kinds of PCWs for slow light: line defects waveguide and coupled resonator waveguide. Unfortunately, both of them encounter the same problem: a low group velocity may accompany a high group velocity dispersion (GVD), which may offset most of the advantages of operation in the slow light region and severely limit the width of flat band [7]. Aimed to achieve wide band and low GVD slow light with high group index ng, many successful researches have been conducted. For line defect waveguides, the improvements include reducing the waveguide width [8], changing the PCW parameters by shifting anticrossing points [9],using slotted photonic crystal waveguides [10,11], adjusting the diameters of the holes [12–14], introducing a hetero-group velocity waveguide [15,16], shifting the first and second rows of air holes or shifting lattice along the waveguide defects [17–19], infiltrating microfluid into the air holes [20,21] or using a technique based on selective liquid infiltrations to precisely and reversibly change the structures [22], etc. For coupled resonator waveguide, the improvements include chirping airhole diameters only or both radius of holes in the center row and radius of those besides the waveguide [23,24], shifting the shear along the defect interface over a distance of one crystal period [25], using a chain of weakly coupled cavities [26], changing the radius of defect rods and the position of the rods nearby the missing rods simultaneously [27], integrating side-coupled cavities in photonic crystal waveguide [28], etc. Some existing researches also combined two kinds of PCWs to achieve low group velocity and low dispersion, such as adding high-Q multicavities or single quantum nanocavity side-coupled to a line defect photonic crystal waveguide [29,30]. Among the above papers, experimental ones are minority [4,6,10,12,19,22,29], while most of them are theoretical research and they neglected the acceptable tolerance of fabrication. Another phenomenon is that most of these methods focus on the variation of periodic arrays of scatterers, and the scatterers are usually cylindrical. Only a few research changed the shapes of scatterers [31]. In our previous study, we at first introduced eye-shaped scatterers into PCWs instead of cylinder holes on silicon wafer. It is found that the widths of bandgaps and their positions can be effectively adjusted by changing parameters of eye-shaped scatterers [32]. In this paper, according to the PCW1 waveguide, we adopted eye-shaped scatterers into PCWs in two ways: (1) wide Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optcom Optics Communications 0030-4018/$ - see front matter & 2012 Elsevier B.V
