Repository logo
  • English
  • 中文
Log In
Have you forgotten your password?
  1. Home
  2. College of Electrical Engineering and Computer Science / 電機資訊學院
  3. Photonics and Optoelectronics / 光電工程學研究所
  4. Finite-Difference Numerical Investigation of Several Optical and Terahertz Guided-Wave Structures
 
  • Details

Finite-Difference Numerical Investigation of Several Optical and Terahertz Guided-Wave Structures

Date Issued
2010
Date
2010
Author(s)
Lai, Chih-Hsien
URI
http://ntur.lib.ntu.edu.tw//handle/246246/253743
Abstract
In this research several optical and terahertz (THz) guided-wave structures are analyzed using the Yee-mesh-based finite-difference frequency-domain (FDFD) method and beam propagation method (BPM). When solving leaky waveguide modes, the perfectly matched layer (PML) is employed as the boundary condition. Our results show that the reflection coefficient, which is one PML parameter, has a significant effect on leaky-mode analysis and its preferred magnitude is much smaller than the conventional values. We propose a simple leaky structure for THz waveguiding, i.e., the pipe waveguide, which is a simple pipe with a large air core and a thin dielectric layer with uniform but low index. Modal characteristics of the pipe waveguide are investigated in the THz region, by calculating the modal indices and attenuation constants of the core modes for various core diameters, cladding thicknesses, and cladding refractive indices. Numerical results reveal that the guiding mechanism of the core modes is that of the antiresonant reflecting guiding. Moreover, modal patterns including modal intensity distributions and electric field vector distributions are shown for the fundamental mode and the higher order modes, and these patterns resemble those of the conventional step-index fiber. Then, the effect of metallic coating on pipe waveguide is investigated. For the 1-D case, i.e., the slab-type pipe waveguide, numerical results indicate that the loss spectrum will shift half period for TE polarization, but will not for TM polarization. This is because the magnitudes of the electric field for TE waves must be continuous in both sides of the metal-dielectric interface; whereas for TM waves, the magnitudes can be different. Such spectral shift phenomenon is promising for the application of the THz polarization filter. For the 2-D case, i.e., the circular pipe waveguide, the spectrum of TE01 mode will shift half period and the spectrum of TM01 mode remains unmoved. While for the HE11 and HE21 modes, their period becomes one half owing to their hybrid nature (mixed TE and TM). We also study two types of THz couplers. One is composed of two slab-type pipe waveguides and the other is composed of two subwavelength dielectric fibers. For the first type THz coupler, the odd system mode of the coupler is unstable near the antiresonant frequencies, which makes the coupler unable to be operated like the conventional fiber-optic ones. Adding an additional layer between the two slab-type pipe waveguides can solve this problem. For the second type THz coupler, when the fiber separation is small, odd-mode cutoff occurs and only the even system mode is guided. Thus the beating phenomenon usually observed in conventional fiber-optic couplers can not take place. The x-polarized even system mode has a more confined field distribution than that of the y-polarized one when the fiber separation is small, similar to the behavior of a slot waveguide, which leads to different attributes between the two polarizations. With these characteristics, the THz couplers might be applied to THz devices such as power dividers and polarization filters. In the final part, behaviors of some optical guided-wave devices are investigated, including two different types of rib-waveguide based polarization convertors and the gain-guided and index-antiguided slab waveguide which is subject to gain saturation. The effect of gain saturation is observed from the propagation of the fundamental mode.
Subjects
Terahertz
Waveguides
Couplers
Guided-Wave Strucutre
Finite-Difference Method
Type
thesis
File(s)
Loading...
Thumbnail Image
Name

ntu-99-D93941025-1.pdf

Size

23.32 KB

Format

Adobe PDF

Checksum

(MD5):d9646c3ad44a3803772d0da2e1b74b82

臺大位居世界頂尖大學之列,為永久珍藏及向國際展現本校豐碩的研究成果及學術能量,圖書館整合機構典藏(NTUR)與學術庫(AH)不同功能平台,成為臺大學術典藏NTU scholars。期能整合研究能量、促進交流合作、保存學術產出、推廣研究成果。

To permanently archive and promote researcher profiles and scholarly works, Library integrates the services of “NTU Repository” with “Academic Hub” to form NTU Scholars.

總館學科館員 (Main Library)
醫學圖書館學科館員 (Medical Library)
社會科學院辜振甫紀念圖書館學科館員 (Social Sciences Library)

開放取用是從使用者角度提升資訊取用性的社會運動,應用在學術研究上是透過將研究著作公開供使用者自由取閱,以促進學術傳播及因應期刊訂購費用逐年攀升。同時可加速研究發展、提升研究影響力,NTU Scholars即為本校的開放取用典藏(OA Archive)平台。(點選深入了解OA)

  • 請確認所上傳的全文是原創的內容,若該文件包含部分內容的版權非匯入者所有,或由第三方贊助與合作完成,請確認該版權所有者及第三方同意提供此授權。
    Please represent that the submission is your original work, and that you have the right to grant the rights to upload.
  • 若欲上傳已出版的全文電子檔,可使用Open policy finder網站查詢,以確認出版單位之版權政策。
    Please use Open policy finder to find a summary of permissions that are normally given as part of each publisher's copyright transfer agreement.
  • 網站簡介 (Quickstart Guide)
  • 使用手冊 (Instruction Manual)
  • 線上預約服務 (Booking Service)
  • 方案一:臺灣大學計算機中心帳號登入
    (With C&INC Email Account)
  • 方案二:ORCID帳號登入 (With ORCID)
  • 方案一:定期更新ORCID者,以ID匯入 (Search for identifier (ORCID))
  • 方案二:自行建檔 (Default mode Submission)
  • 方案三:學科館員協助匯入 (Email worklist to subject librarians)

Built with DSpace-CRIS software - Extension maintained and optimized by 4Science