表面等离激元应用于红外光探测的研究

发布时间：2018-02-24 19:46

本文关键词： 光探测等离激元光学天线偏振依赖性法布里珀罗共振热电子入射光子-电流转化率　出处：《南京大学》2016年博士论文　论文类型：学位论文

【摘要】：随着微加工和化学制备水平的提高,等离激元光学在近年来得到了迅速的发展。金属纳米结构的表面等离激元的波长要远小于自由空间中的光的波长,所以电磁场能被束缚在比光波长小得多的尺度,实现了亚波长尺度的近场增强。基于这个特性,表面等离激元已被广泛用于纳米光刻,纳米光子学,生物探测器,光探测等领域。在光探测领域,能产生等离激元共振的金属纳米结构一方面可以用作增强光探测器响应的天线,另一方面也可以与半导体材料结合通过抽取金属等离激元共振产生的热电子直接进行光探测。但等离激元自身的共振波长一般都在可见光波段,难以被用于红外波段的光探测。设计可用于红外波段的等离激元天线和等离激元热电子探测器则成为了新的挑战。本文工作主要利用有限时域差分法(Finite Difference Time Domain, FDTD)和其它数值模拟方法在红外波段研究和设计了性能远高于传统牛眼结构(Bull'sEye,BE)天线的劈裂牛眼结构(Split Bull's Eye, SBE)天线和具有高响应率的等离激元Si-Au共振腔热电子探测器。所取得的创新研究成果主要包括以下几个方面：1.系统的研究了SBE天线的透射增强机制,发现该结构天线在保留了BE天线汇聚特性的同时将中心孔的传播模式从倏逝模转变为了传播模,且在特定膜层厚度下会发生法布里珀罗共振增强透射,使得其在红外波段的透射增强远大于传统的BE天线。我们进一步优化了SBE天线结构参数,将其工作波长扩展至中红外,在4μm处其透射增强值高于BE天线6个数量级。2.提出了中心孔为两个交叉狭缝的双劈裂牛眼结构(Dual Split Bull's Eye, DSBE)天线结构,其偏振依赖性能通过改变两个狭缝的夹角来被有效的调控。当两狭缝相互垂直时,DSBE天线则为完全偏振无关。而且,DSBE天线的透射增强特性类似于SBE天线,在红外波段的透射增强远大于BE天线。该新型天线结构可应用于红外波段非偏振光和任意偏振光的探测。3.建立了等离激元热电子探测器从光吸收,热电子产生到热电子收集的全过程模拟计算方法。首次在模拟过程中考虑了金属结构内具体的吸收分布,能得到更精确的光响应的模拟计算结果。4.设计了基于等离激元Si-Au复合共振腔结构的肖特基结热电子光探测器。该探测器结构不仅可对红外1550 nm的通讯波长实现98%的近乎全吸收,而且能更好的将等离激元共振产生的热电子转为光电流,提高了探测器的光响应率。
[Abstract]:With the improvement of the level of microfabrication and chemical preparation, the isobaric optics has been developed rapidly in recent years. The wavelength of the surface isophosphors of metal nanostructures is much smaller than that of the light in the free space. So the electromagnetic field can be bound to a scale much smaller than the wavelength of the light, and the near-field enhancement of the subwavelength scale is achieved. Based on this property, the surface isotherms have been widely used in nanophotography, nanophotonics, biological detectors. In the field of optical detection, metal nanostructures, which can produce isopheric resonance, on the one hand, can be used as antennas to enhance the response of photodetectors. On the other hand, it can also be combined with semiconductor materials to detect the light directly by extracting the hot electrons generated by the resonance of metal isoexcitators. But the resonance wavelengths of the isophosphors themselves are generally in the visible wavelength. It is difficult to be used in infrared band optical detection. It is a new challenge to design an isolator antenna and an isolator thermionic detector which can be used in infrared band. In this paper, finite Difference Time domain (FDTD) is mainly used in this work. And other numerical simulation methods have been used to study and design split split bullite Eyees (SBEE) antennas and Si-Au resonator thermoelectronic detectors with high responsivity in infrared band. The innovative research results mainly include the following aspects: 1.The transmission enhancement mechanism of SBE antenna is studied systematically. It is found that the structure antenna can change the propagation mode of the center hole from evanescent mode to propagating mode while retaining the convergence characteristic of the be antenna, and the Fabry-Perot resonance enhanced transmission will occur under the specific film thickness. The transmission enhancement in the infrared band is much larger than that of the traditional be antenna. We further optimize the structure parameters of the SBE antenna and extend its working wavelength to the middle infrared. The transmission enhancement value at 4 渭 m is higher than that of be antenna by 6 orders of magnitude. 2. A dual split Split Bull's eye (DSBE) antenna structure with two cross slits in the center hole is proposed. The polarization dependence can be effectively regulated by changing the angle of the two slits. When the two slits are perpendicular to each other, the DSBE antenna is completely polarization-independent. Moreover, the transmission enhancement characteristics of the DSBE antenna are similar to those of the SBE antenna. The transmission enhancement in infrared band is much greater than that in be antenna. The new antenna structure can be used to detect infrared band non-polarized light and arbitrary polarized light. The whole process simulation calculation method from hot electron generation to hot electron collection. The specific absorption distribution in the metal structure is considered for the first time in the simulation process. 4. A Schottky junction thermoelectron photodetector based on the Si-Au resonator structure is designed. The structure of the detector can not only achieve nearly full absorption of 98% for the communication wavelength of 1550nm. In addition, the hot electrons generated by Isoexciton resonance can be converted into photocurrent better, and the photoresponse rate of the detector is improved.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN215;TN820

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