石墨烯辅助的双环并联微光纤结型谐振器可调谐宽带慢光技术研究

Tunable slow light delay has important applications in the areas of optical communications, data processing, and microwave photonics. However, it is still faced with many problems, such as narrow bandwidth, complicated systems, serious signal distortion, in the practical application. In the previous work, the applicant has obtained a slow-light group delay with a flat-top and wide band based on an analog of electromagnetically induced transparency (EIT) in the microfiber knot resonator (MKR) with a double-ring parallel structure. In this project, a single layer or multilayer of graphene will be covered on the surface of micro ring of the resonator innovatively. By using of the produced photothermal effect due to the absorption of the graphene on the strong evanescent wave located on the surface of the microfiber, the new method about producing the slow light technology with a flat top and tunable bandwidth in the resonator will be researched. The mainly researched contents conclude: 1) The optical field distribution and the photothermal effect of the graphene-covered microfiber will be researched theoretically and experimentally; 2) The characteristics on the spectrum of the graphene-covered MKR with a double-ring parallel structure will be researched; 3) The flat-top, tunable wideband slow-light technology in the graphene-covered MKR with a double-ring parallel structure will be researched. The study in this project will provide the theoretical and experimental evidence about the applications of the resonator in the fields of all optical communication data synchronization, variable optical delay, optical switching.

可调谐慢光延时在光通信、数据处理和微波光子学等领域具有重要应用。然而在实际慢光应用中仍然面临着带宽窄、系统复杂和信号失真严重等问题。申请人在前期研究工作中，基于双环并联微光纤结型谐振器（Microfiber knot resonator, MKR）中类电磁诱导透明效应获得了顶端平坦、宽带慢光群延时。本项目创新性地将单层或多层石墨烯覆盖在该类谐振器的微环上，利用石墨烯吸收微光纤表面强的倏逝场所产生的光热效应，研究实现顶端平坦、可调谐宽带慢光群延时的新方法。主要研究内容包括：1）石墨烯覆盖型微光纤中的光场分布、光热效应的理论和实验研究；2）石墨烯覆盖在双环并联MKR表面上的光谱特性研究；3）石墨烯覆盖的双环并联MKR中顶端平坦、可调谐宽带慢光技术研究。本项目研究将为该类谐振器在全光通信的数据同步、可变光学延时和光开关等方面的应用提供理论和实验依据。

微光纤谐振器以其强的表面倏世场、高的Q因子、稳定和微小的几何结构、与现有光纤通信系统兼容等特点，在慢光、光纤传感、光通信和光纤激光技术等领域具有重要的科学研究意义和应用价值。本项目理论和实验上研究了不同层数石墨烯覆盖在不同直径微光纤上产生最优光场分布和光热效应所需的物理条件；基于双环并联MKR的透射、相位和慢光延时数学表达式，理论上研究了该谐振器在不同光强耦合系数、耦合损耗系数、微环直径等情况下的光学特性，研究结果发现该谐振器在一定的参数设置下，不仅可以获得慢光延时，还可以获得快光提前。在制作的高Q值双环并联MKR中，在不同的谐振波长处获得了38 ps的慢光延时和40 ps的快光提前；把制作的高Q值MKR植入到掺饵光纤环形激光腔中，在波长1558.818 nm处获得了3 dB带宽为0.0149 nm，边摸抑制比为30 dB，最大激光功率变化为0.85 dB的稳定单波长激光输出；在研究双环并联MKR的光谱特性时，我们提出了把带Sagnac环形反射器的微光纤谐振器植入到掺饵光纤激光器的环形谐振腔中，获得了3dB带宽内不同波长激光线数目达到了42条的多波长激光，平均每条激光线的线宽约为0.05nm，边模抑制比为45dB，结果表明带Sagnac环形反射器的微光纤谐振器能被用作一个高性能的梳状滤波器来实现稳定的多波长激光。本研究工作对微光纤谐振器在可调谐慢光、光纤激光技术等方面的应用提供了理论和实验基础。