【摘要】：光子晶體光纖的出現(xiàn)為非線性光學(xué)領(lǐng)域、高功率光纖激光器以及光纖通信等領(lǐng)域的發(fā)展提供了嶄新的的平臺(tái)。在非線性光學(xué)領(lǐng)域中,多芯光子晶體光纖可以克服單芯光子晶體光纖模場(chǎng)直徑以及熱效應(yīng)等問(wèn)題,為超連續(xù)譜的產(chǎn)生提供了新的思路。本論文以七芯光子晶體光纖為例,一方面針對(duì)七芯光子晶體光纖的耦合特性、色散特性以及非線性特性進(jìn)行理論研究;另一方面,基于設(shè)計(jì)得到的一種新型的七芯光子晶體光纖,通過(guò)數(shù)值模擬對(duì)超連續(xù)譜的產(chǎn)生進(jìn)行研究,取得的成果主要包括以下幾個(gè)方面:1.基于多芯耦合模理論推導(dǎo)得到七芯光子晶體光纖的耦合長(zhǎng)度,通過(guò)全矢量有限元法分析光子晶體光纖結(jié)構(gòu)參數(shù)對(duì)耦合特性的影響規(guī)律;并采用光束傳播法動(dòng)態(tài)模擬纖芯之間的能量耦合過(guò)程。比較全矢量有限元法和光束傳播法得到的耦合長(zhǎng)度,結(jié)果具有很好的一致性,為合理設(shè)計(jì)基于七芯光子晶體光纖的結(jié)構(gòu)設(shè)計(jì)和特性分析提供理論基礎(chǔ)。2.提出一種新型的七芯光子晶體光纖結(jié)構(gòu)。利用全矢量有限元方法對(duì)七芯光子晶體光纖的色散特性和非線性系數(shù)進(jìn)行了詳細(xì)的分析,結(jié)果表明,通過(guò)改變光子晶體光纖包層空氣孔間距和空氣孔直徑,可以有效地調(diào)節(jié)光纖非線性的大小以及光纖色散曲線的變化;并進(jìn)一步針對(duì)光纖中的同相超模進(jìn)行模式整形,得到在1.55μm波長(zhǎng)處,光纖的非線性系數(shù)為68W-1Km-1,損耗為4.576×10-6dB/m,且在計(jì)算波段范圍內(nèi)都處于正常色散下的光纖結(jié)構(gòu)。3.利用分布傅里葉方法數(shù)值模擬了超短脈沖的展寬過(guò)程,進(jìn)而研究了光纖長(zhǎng)度、泵浦波長(zhǎng),脈沖功率和脈寬對(duì)光譜展寬的影響。數(shù)值仿真結(jié)果表明,通過(guò)選擇合適的脈沖參數(shù)可以有效的調(diào)節(jié)產(chǎn)生的超連續(xù)譜的特性�；诒疚乃O(shè)計(jì)的七芯光子晶體光纖,當(dāng)光纖長(zhǎng)度L=5cm,初始脈寬T0=50fs,中心波長(zhǎng)為1.55μm,脈沖峰值功率為40kw-80kw時(shí),得到展寬約為1101-1331nm的超連續(xù)譜,充分顯示了具有正常色散的七芯光子晶體光纖在產(chǎn)生高平坦、寬帶寬的超連續(xù)譜方面的應(yīng)用潛力。
[Abstract]:The appearance of photonic crystal fiber provides a new platform for the development of nonlinear optics, high power fiber lasers and optical fiber communication. In the field of nonlinear optics, multi-core photonic crystal fiber can overcome the problems of mode diameter and thermal effect of single-core photonic crystal fiber, which provides a new idea for the generation of supercontinuum spectrum. In this paper, we take the seven-core photonic crystal fiber as an example. On the one hand, the coupling characteristics, dispersion characteristics and nonlinear characteristics of the seven-core photonic crystal fiber are studied theoretically. On the other hand, based on the design of a new seven-core photonic crystal fiber, the generation of supercontinuum spectrum is studied by numerical simulation. The main achievements are as follows: 1. Based on the multi-core coupling mode theory, the coupling length of the seven-core photonic crystal fiber is derived, and the influence of the structure parameters of the photonic crystal fiber on the coupling characteristics is analyzed by the full-vector finite element method. The beam propagation method is used to simulate the energy coupling process between the fiber cores. Compared with the coupling length obtained by the full vector finite element method and the beam propagation method, the results are in good agreement, which provides a theoretical basis for the reasonable design of the structure and characteristic analysis of the seven-core photonic crystal fiber. A novel seven-core photonic crystal fiber structure is proposed. The dispersion characteristics and nonlinear coefficient of seven core photonic crystal fiber are analyzed in detail by using full vector finite element method. The results show that by changing the air hole spacing and air hole diameter of photonic crystal fiber cladding, The nonlinearity of fiber and the variation of fiber dispersion curve can be adjusted effectively. Furthermore, the mode shaping of the in-phase supermode in the fiber is carried out. The nonlinear coefficient of the fiber is 68W-1Km-1 at the wavelength of 1.55 渭 m and the loss is 4.576 脳 10 ~ (-6) dB / m. And the fiber structure with normal dispersion in the calculated band range. 3. 3. The effects of fiber length, pump wavelength, pulse power and pulse width on the broadening of ultrashort pulses are numerically simulated by using the distributed Fourier method. The numerical simulation results show that the characteristics of the supercontinuum spectrum can be adjusted effectively by selecting appropriate pulse parameters. Based on the seven core photonic crystal fiber designed in this paper, when the length of the fiber is 5 cm, the initial pulse width is T 0N 50 fs, the center wavelength is 1.55 渭 m, and the peak power of the pulse is 40kw-80kw, the supercontinuum spectrum about 1101-1331nm is obtained. The application potential of the seven-core photonic crystal fiber with normal dispersion in producing high flat and wide broadband supercontinuum spectrum is fully demonstrated.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN253

【參考文獻(xiàn)】

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本文編號(hào)：2429502