本文選題：環(huán)光纖 + 扭轉(zhuǎn)光纖　； 參考：《哈爾濱工業(yè)大學(xué)》2017年碩士論文

【摘要】：軌道角動(dòng)量(Orbital angular momentum,OAM)是經(jīng)典力學(xué)和量子力學(xué)的基本物理量,近來(lái)已經(jīng)證明,光子也具有軌道角動(dòng)量。光學(xué)上,它與射線束的空間相位分布有關(guān),是具有螺旋相位的射線束的自然特性,這樣的射線束又稱為渦旋光。研究結(jié)果表明,OAM與光子的波長(zhǎng)、極化等特性一樣,是信息復(fù)用技術(shù)的一個(gè)新自由度。因而OAM光通信技術(shù)的研究近年來(lái)引起了世界各國(guó)科研工作者的廣泛興趣,取得了迅猛的發(fā)展。OAM光通信系統(tǒng)的組建包括OAM光束的產(chǎn)生、OAM信號(hào)的傳輸媒介和OAM的復(fù)用與解復(fù)用這三部分。本文的研究涉及前兩部分,即OAM模轉(zhuǎn)換器和OAM模在環(huán)光纖中的穩(wěn)定傳輸。提出能穩(wěn)定傳輸OAM模的光纖—扭轉(zhuǎn)環(huán)光纖,該光纖所支持的正負(fù)渦旋之間有效折射率去簡(jiǎn)并,從而可用于穩(wěn)定傳輸OAM�！，F(xiàn)有渦旋光纖都是環(huán)光纖,OAM模本質(zhì)上為矢量模(HEmn或EHmn)的奇偶型的疊加態(tài),因此環(huán)光纖中OAM模正負(fù)渦旋簡(jiǎn)并是固有的問(wèn)題。這使得渦旋光在傳輸中會(huì)因?yàn)槲⑿〉耐獠繑_動(dòng)而發(fā)生渦旋反轉(zhuǎn),造成OAM模傳輸不穩(wěn)定。正負(fù)渦旋傳輸中功率交換的主要原因是它們之間相對(duì)小的有效折射率差。將環(huán)光纖施加扭轉(zhuǎn)的方法可增大正負(fù)OAM模之間的有效折射率差,從而提高OAM模傳輸?shù)姆�(wěn)定性。本文從理論和數(shù)值模擬上對(duì)弱導(dǎo)環(huán)光纖和高折射率對(duì)比度的環(huán)光纖進(jìn)行了施加扭轉(zhuǎn)的研究,在環(huán)光纖可承受的扭率極限內(nèi)得到了理想的結(jié)果,所設(shè)計(jì)的扭轉(zhuǎn)空氣芯光纖可支持?jǐn)?shù)個(gè)OAM模穩(wěn)定傳輸上千米的距離。提出一種寬帶寬的光纖OAM模轉(zhuǎn)換器,應(yīng)用于單模光纖通信網(wǎng)絡(luò)與環(huán)光纖通信網(wǎng)絡(luò)的連接。在光纖通信中,OAM模的傳輸介質(zhì)是環(huán)光纖,而現(xiàn)有的通信網(wǎng)絡(luò)使用的大多是單模光纖。針對(duì)環(huán)光纖與現(xiàn)有網(wǎng)絡(luò)的連接問(wèn)題,提出OAM模轉(zhuǎn)換器的設(shè)想,即用單模光纖中基模來(lái)激發(fā)產(chǎn)生環(huán)光纖中OAM模�，F(xiàn)有的光纖OAM模轉(zhuǎn)換器,就我們目前所知,帶寬都很窄,這實(shí)際上限制了頻譜效率及通信容量的提高。但超材料實(shí)現(xiàn)的渦旋光生成具有帶寬較寬的優(yōu)點(diǎn)。因此,本文提出一種光纖端面超材料q-板,用來(lái)實(shí)現(xiàn)光纖中OAM模轉(zhuǎn)換,并就工作帶寬和生成效率,分別對(duì)金屬等離子體超材料和電介質(zhì)納米鰭超材料OAM模轉(zhuǎn)換器進(jìn)行了理論和數(shù)值模擬上的研究。研究結(jié)果顯示,金屬超材料OAM模轉(zhuǎn)換器的帶寬可達(dá)800nm;電介質(zhì)超材料OAM模轉(zhuǎn)換器的帶寬可達(dá)180nm,且轉(zhuǎn)換效率和OAM模生成純度都較高,分別63%和93%。
[Abstract]:Orbital angular momentum (Orbital angular momentum) is the basic physical quantity of classical mechanics and quantum mechanics. Recently, it has been proved that photons also have orbital angular momentum. Optically, it is related to the spatial phase distribution of a ray beam, which is the natural characteristic of a ray beam with helical phase, which is also called vortex light. The results show that OAM is a new degree of freedom in information reuse technology, which is similar to the wavelength and polarization of photons. Therefore, the research of OAM optical communication technology has attracted the extensive interest of researchers all over the world in recent years. The construction of OAM optical communication system includes the transmission medium of OAM beam and the multiplexing and demultiplexing of OAM. The first two parts, OAM mode converter and OAM mode, are studied in this paper. A torsional loop fiber which can stably transmit the OAM mode is proposed. The effective refractive index between the positive and negative vortices supported by the fiber is dedegenerate and can be used for stable transmission of the OAM mode. The existing vortex fiber is essentially an odd and even superposition state of vector mode HEmn or EHmnn, so the degeneracy of positive and negative vortices of OAM mode in annular fiber is an inherent problem. This results in vortex inversion in the propagation of vortex light due to small external disturbances, resulting in instability of OAM mode transmission. The main reason for power exchange in positive and negative vortex propagation is the relatively small effective refractive index difference between them. The effective refractive index difference between positive and negative OAM modes can be increased by torsion of ring fiber, thus the stability of OAM mode propagation can be improved. In this paper, torsion of weak guide ring fiber and high refractive index contrast ring fiber is studied theoretically and numerically. The ideal results are obtained within the limit of torsional rate of ring fiber. The torsional air core fiber can support several OAM modes to transmit thousands of meters. A wide band fiber OAM mode converter is proposed, which is applied to the connection between single mode optical fiber communication network and annular optical fiber communication network. In optical fiber communication, the transmission medium of OAM mode is ring fiber, while most of the existing communication networks use single mode fiber. Aiming at the connection between ring fiber and existing network, the idea of OAM mode converter is put forward, that is, the fundamental mode in single mode fiber is used to excite and generate OAM mode in ring fiber. As far as we know, the bandwidth of existing optical fiber OAM mode converters is very narrow, which actually limits the increase of spectrum efficiency and communication capacity. But the vortex light generated by metamaterials has the advantage of wide bandwidth. Therefore, this paper presents a kind of optical fiber end surface supermaterial q-board, which is used to realize OAM mode conversion in optical fiber, and in terms of working bandwidth and generation efficiency, The theoretical and numerical simulation of metal plasma supermaterial and dielectric nano-fin supermaterial OAM mode converter are presented. The results show that the bandwidth of metal supermaterial OAM mode converter can reach 800 nm, and that of dielectric supermaterial OAM mode converter can reach 180 nm, and the conversion efficiency and the purity of OAM mode generation are higher, 63% and 93%, respectively.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN929.11;TN253

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