以時域擬光譜法模擬光在隨機介質中擴散的性質

PSTD Simulation of Light Beam Expansion with the Presence of a Scattering Medium

楊士玄(Shi-Xuan Yang)

指導教授 ： 曾雪峰

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802726

摘要

為了模擬光經過隨機分布的介質中散射的擴散情形，本研究建造了隨機分布的介質模型並且利用時域擬譜法(Pseudospectral time-domain technique, PSTD)來模擬分析他們的光學特性，其中，擬譜時域分析法是源自於馬克斯威方程式(Maxwell’s equation)的數值解，利用此方法可以應用在模擬大範圍空間中的電磁波問題。本論文中，分析各種因素，包含入射光的波長、介質數量與分佈，將模擬結果量化分析，模擬結果中可以明顯地看出光經過隨機介質有擴散的情形，其中分別討論在固定頻率下，不同散射介質數目對光擴散程度的影響，以及在固定散射介質數目下，不同光源頻率對光擴散程度的影響。本研究中利用二維時域擬譜法模擬光在散射介質中的傳播，在本論文中採用的散射介質以圓柱狀的散射介質並且以隨機分布的形式作排列，模擬光在隨機散射介質中的傳播，並且計算散射後的Radar Cross-Section (RCS)再加以分析，研究光經過隨機分布的散射介質後光束擴散的情形，而實驗結果也表明光會受到哪些因素而有光束寬度上的影響。

關鍵字

時域擬譜分析法 ； 隨機散射介質 ； 光束寬度擴散

並列摘要

Here we model a light propagating through a scattering medium. We employ the pseudospectral time-domain (PSTD) simulation technique to model light propagation through the scattering media. To analyze the scattering characteristics of light, various factors are analyzed, including the wavelength of incident light, the number of the scattering medium, position of the scattering medium and size distribution of the scattering medium. Simulation results show that the direction of propagation is affected by the scattering medium. Specifically, different angular span of out-coming light are affected by randomly-positioned scattering medium.

並列關鍵字

pseudospectral time-domain (PSTD) ； randomly-positioned scattering medium ； Beamwidth Expansion

參考文獻

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