基于石墨烯的慢光波導研究
發(fā)布時間：2018-12-13 01:19
【摘要】：慢光波導是一種能有效減慢光信號傳播速度而不改變光自身有效信息的新型光波導,由于其光緩存功能,已逐漸成為了光通信中的核心器件之一。近年來,寬帶慢光已由光子晶體慢光波導、金屬等離子體慢光波導等實現(xiàn)。然而,這些波導普遍存在帶寬小的缺點,繼而容易引發(fā)光信號在傳輸時的群速度色散,最終導致信號傳輸失真。此外,現(xiàn)有的慢光波導的性能動態(tài)不可調(diào)。為了解決這些問題,在本研究中我們設(shè)計了兩種寬帶、低色散、高品質(zhì)因子(延遲帶寬積)且性能動態(tài)可調(diào)的石墨烯寬帶慢光波導。主要研究成果如下： 1.通過調(diào)研近十余年來的慢光波導文獻,總結(jié)對比了不同結(jié)構(gòu)慢光波導的性能后,我們發(fā)現(xiàn)目前的慢光波導帶寬較小且波導性能動態(tài)不可調(diào)。為了獲得更優(yōu)越的波導性能,同時使波導動態(tài)可調(diào),我們將研究重點集中在了石墨烯上,因為石墨烯同時具備高群折射率傳播SPP波和可調(diào)性兩大優(yōu)勢。我們根據(jù)近期石墨烯波導文獻中提供的色散公式,繪制了單張石墨烯的色散曲線和群折射率圖。分析后發(fā)現(xiàn),石墨烯上傳播SPP波的群折射率確實非常高,繼而確認了石墨烯上可以傳播慢光,為下一步的工作奠定了基礎(chǔ)。 2.論證了石墨烯可傳播慢光后,我們通過在石墨烯上構(gòu)造周期性的空氣孔來得到寬帶慢光,并利用時域有限差分法來仿真模擬波導性能。首先,我們提出了光柵石墨烯慢光波導結(jié)構(gòu)。在特定的波導結(jié)構(gòu)參數(shù)下,當入射波導的諧振頻率f從87THz至89THz范圍變化時,波導慢光因子ng維持在(130+4)左右。在此區(qū)間內(nèi)ng可認為是一個不變的常數(shù)值,即在此諧振頻率范圍內(nèi),波導呈現(xiàn)出寬帶慢光的傳輸性質(zhì)。此外,改變波導中石墨烯的化學勢,即可動態(tài)調(diào)節(jié)慢光波導的各項性能指標,如其慢光因子ng、諧振頻率f、帶寬w等。 3.為了進一步簡化波導結(jié)構(gòu),同時保持波導的優(yōu)異慢光性能,我們又設(shè)計了三角孔石墨烯慢光波導。同樣,在特定的波導結(jié)構(gòu)參數(shù)下,當入射波導諧振頻率f從90.15THz至90.75THz變化時,ng維持在107+5左右的數(shù)值,同時具備動態(tài)可調(diào)性。為了獲得更大的延遲帶寬積NDBP、慢光因子ng、帶寬w等,我們仿真記錄了每組波導三角孔參數(shù)Wg、Ws變化下的波導性能數(shù)據(jù)。分析對比后,最終可得的最大波導延遲帶寬積NDBP達0.96,極大地提高了現(xiàn)有波導的慢光性能。
[Abstract]:Slow optical waveguide is a new type of optical waveguide which can effectively slow down the propagation speed of optical signal without changing the effective information of light itself. Because of its optical buffer function, slow optical waveguide has become one of the core devices in optical communication. In recent years, broadband slow light has been realized by photonic crystal slow optical waveguide and metal plasma slow optical waveguide. However, these waveguides generally have the disadvantage of small bandwidth, which can easily lead to the group velocity dispersion of the optical signal during transmission, and eventually lead to the distortion of the signal transmission. In addition, the performance of the existing slow optical waveguides is unadjustable. In order to solve these problems, we have designed two kinds of graphene broadband slow optical waveguides with low dispersion, high quality factor (delay bandwidth product) and dynamic tunable performance. The main research results are as follows: 1. By investigating the literature of slow optical waveguides in recent ten years and comparing the performances of slow optical waveguides with different structures, we find that the bandwidth of slow optical waveguides is small and the dynamic performance of waveguides is not adjustable. In order to obtain better waveguide performance and make waveguide dynamic adjustable, we focus on graphene, because graphene has the advantages of both high group refractive index propagating SPP wave and tunability. Based on the dispersion formula provided in recent graphene waveguides, the dispersion curves and group refractive index diagrams of single graphene are plotted. It is found that the group refractive index of SPP wave propagating on graphene is very high, and it is confirmed that slow light can be propagated on graphene, which lays a foundation for further work. 2. It is proved that graphene can propagate slow light, we obtain broadband slow light by constructing periodic air holes in graphene, and simulate the performance of waveguide by using finite-difference time-domain (FDTD) method. Firstly, we propose a grating graphene slow optical waveguide structure. When the resonant frequency f of the incident waveguide varies from 87THz to 89THz, the waveguide slow light factor (ng) is maintained at (1304) under certain waveguide structure parameters. In this region, ng can be regarded as a constant value, that is, in the range of resonance frequency, the waveguide exhibits the propagation property of broadband slow light. In addition, by changing the chemical potential of graphene in the waveguide, we can dynamically adjust the performance of the slow optical waveguide, such as the slow light factor ng, resonance frequency f, bandwidth w and so on. 3. In order to further simplify the structure of the waveguide and maintain the excellent slow optical properties of the waveguide, we have also designed the triangular hole graphene slow optical waveguide. Similarly, when the resonant frequency f of the incident waveguide varies from 90.15THz to 90.75THz, the value of ng is about 107.5, and it has dynamic tunability under certain waveguide structure parameters. In order to obtain larger delay bandwidth product (NDBP,) slow light factor (ng,) bandwidth w and so on, we simulated and recorded the waveguide performance data of each set of waveguide triangulation hole parameters Wg,Ws. After analysis and comparison, the final maximum waveguide delay bandwidth product (NDBP) is 0.96, which greatly improves the slow optical performance of the existing waveguides.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN252
本文編號：2375596
[Abstract]:Slow optical waveguide is a new type of optical waveguide which can effectively slow down the propagation speed of optical signal without changing the effective information of light itself. Because of its optical buffer function, slow optical waveguide has become one of the core devices in optical communication. In recent years, broadband slow light has been realized by photonic crystal slow optical waveguide and metal plasma slow optical waveguide. However, these waveguides generally have the disadvantage of small bandwidth, which can easily lead to the group velocity dispersion of the optical signal during transmission, and eventually lead to the distortion of the signal transmission. In addition, the performance of the existing slow optical waveguides is unadjustable. In order to solve these problems, we have designed two kinds of graphene broadband slow optical waveguides with low dispersion, high quality factor (delay bandwidth product) and dynamic tunable performance. The main research results are as follows: 1. By investigating the literature of slow optical waveguides in recent ten years and comparing the performances of slow optical waveguides with different structures, we find that the bandwidth of slow optical waveguides is small and the dynamic performance of waveguides is not adjustable. In order to obtain better waveguide performance and make waveguide dynamic adjustable, we focus on graphene, because graphene has the advantages of both high group refractive index propagating SPP wave and tunability. Based on the dispersion formula provided in recent graphene waveguides, the dispersion curves and group refractive index diagrams of single graphene are plotted. It is found that the group refractive index of SPP wave propagating on graphene is very high, and it is confirmed that slow light can be propagated on graphene, which lays a foundation for further work. 2. It is proved that graphene can propagate slow light, we obtain broadband slow light by constructing periodic air holes in graphene, and simulate the performance of waveguide by using finite-difference time-domain (FDTD) method. Firstly, we propose a grating graphene slow optical waveguide structure. When the resonant frequency f of the incident waveguide varies from 87THz to 89THz, the waveguide slow light factor (ng) is maintained at (1304) under certain waveguide structure parameters. In this region, ng can be regarded as a constant value, that is, in the range of resonance frequency, the waveguide exhibits the propagation property of broadband slow light. In addition, by changing the chemical potential of graphene in the waveguide, we can dynamically adjust the performance of the slow optical waveguide, such as the slow light factor ng, resonance frequency f, bandwidth w and so on. 3. In order to further simplify the structure of the waveguide and maintain the excellent slow optical properties of the waveguide, we have also designed the triangular hole graphene slow optical waveguide. Similarly, when the resonant frequency f of the incident waveguide varies from 90.15THz to 90.75THz, the value of ng is about 107.5, and it has dynamic tunability under certain waveguide structure parameters. In order to obtain larger delay bandwidth product (NDBP,) slow light factor (ng,) bandwidth w and so on, we simulated and recorded the waveguide performance data of each set of waveguide triangulation hole parameters Wg,Ws. After analysis and comparison, the final maximum waveguide delay bandwidth product (NDBP) is 0.96, which greatly improves the slow optical performance of the existing waveguides.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN252
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