基于周期性极化铌酸锂波导的光学频率梳研究

发布时间：2018-11-27 08:52

【摘要】：近年来,随着飞快发展的光通信技术,因在密集波分复用、光正交频分复用、光任意波形产生、短脉冲的产生等等领域中有着非常重要的应用,光学频率梳吸引了很多学者的关注。目前,人们已经提出很多产生光学频率梳的方法,由锁模激光器构成的光学频率梳,由相位、强度和偏振调制器构成的光学频率梳,由微谐振腔等非线性介质构成的光学频率梳以及由周期性极化铌酸锂(PPLN)波导构成的光学频率梳。本文结合受激布里渊散射和PPLN光波导的二阶非线性效应来实现光学频率梳,具体内容如下:首先简要介绍了基于锁模激光器、基于调制器、基于微谐振腔和基于PPLN波导的光学频率梳的相关理论基础。其次对PPLN波导中的二阶非线性效应进行相关理论的研究,并通过实验研究了泵浦光和信号光功率以及它们单次通过、两次通过PPLN波导给级联倍频差频的转换效率带来的影响。由于需要利用多波长布里渊掺铒光纤激光器(MBEFL)来作为种子光,我们在介绍完MBEFL的相关理论之后提出了基于连续光充当布里渊泵浦和瑞利散射光充当布里渊泵浦的几种多波长激光器方案,并根据实验结果选择合适的方式来抑制自激发腔模。鉴于光学频率梳时域上的要求,随后理论推导了MBEFL的相位是锁定的,时域上表现为脉冲形式。然后提出了基于PPLN波导的光学频率梳的实验原理和具体方案,分别从两个方面来对比阐述实验过程和实验结果。基于闭腔结构MBEFL的光学频率梳具有10条梳谱线,最大消光比为15 dB,光学频率梳可以随着泵浦波长的变化而在较大范围内调谐;基于开腔结构MBEFL的光学频率梳拥有8条平坦度为4.8 dB的谱线,实验过程中研究了布里渊泵浦光功率以及980 nm泵浦电流的变化给光学频率梳带来的影响。最后实验测得多波长的谱线线宽为6 MHz,线宽较窄。
[Abstract]:In recent years, with the rapid development of optical communication technology, because of the dense wavelength division multiplexing, optical orthogonal frequency division multiplexing, optical arbitrary waveform generation, short pulse generation and other fields have very important applications. Optical frequency comb has attracted the attention of many scholars. At present, many methods have been proposed to produce optical frequency comb, which consists of mode-locked laser, optical frequency comb, and optical frequency comb composed of phase, intensity and polarization modulator. Optical frequency comb is composed of nonlinear medium such as microresonator, and optical frequency comb is composed of periodically polarized lithium niobate (PPLN) waveguide. In this paper, optical frequency comb is realized by combining stimulated Brillouin scattering and second-order nonlinear effect of PPLN optical waveguide. The main contents are as follows: firstly, based on mode-locked laser, modulator and mode-locked laser are briefly introduced. The theoretical basis of optical frequency comb based on microresonator and PPLN waveguide. Secondly, the second order nonlinear effects in PPLN waveguides are studied theoretically, and the effects of pump light and signal optical power on the conversion efficiency of cascaded frequency doubling difference through PPLN waveguides are studied by experiments. Because the multi-wavelength Brillouin erbium-doped fiber laser (MBEFL) is used as seed light, After introducing the relevant theory of MBEFL, we propose several schemes of multi-wavelength lasers based on continuous light as Brillouin pump and Rayleigh scattering light as Brillouin pump. According to the experimental results, we choose a suitable way to suppress the self-excited cavity mode. In view of the requirement of optical frequency comb in time domain, it is deduced theoretically that the phase of MBEFL is locked, and that the phase of MBEFL appears as a pulse form in time domain. Then, the experimental principle and specific scheme of optical frequency comb based on PPLN waveguide are presented, and the experimental process and experimental results are compared from two aspects. The optical frequency comb based on closed cavity structure MBEFL has 10 comb lines. The maximum extinction ratio of 15 dB, optical frequency comb can be tuned in a wide range with the change of pump wavelength. The optical frequency comb based on open-cavity structure MBEFL has eight spectral lines of 4.8 dB flatness. The influence of Brillouin pump power and 980 nm pump current on the optical frequency comb has been studied in the experiment. Finally, the experimental results show that the line width of 6 MHz, is narrow.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN252

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