# Principle and Applications of the Coupling of Surface Plasmons and Excitons
## 4 Conclusions and Development Trends  
In summary, surface plasmons [105; 106] are currently a global research hotspot because of their broad application prospects. This paper has reviewed the research progress in this field based on the coupling effects of surface plasmons and excitons and the strong coupling between conductive surfaces, localized surfaces, metal periodic structures, and transition metal dichalcogenides. The paper has shown that strong coupling can not only achieve highly local enhancement, but also has preliminarily proved the superiority of surface plasmons in terms of their ability to reduce the size of quantum devices and enhance the interactions between light and matter.  
However, there are still many unknown problems with exciton strong coupling in the micro-nano structures of surface plasmons, which should be explored further in terms of the following aspects.  
(1) Using their strong coupling mechanism, local surface plasmons can be used to couple multiple light emitters. However, ways to reduce the volume and the losses remain urgent research targets.  
(2) Strong coupling can also lead to new series of energy conversion processes, such as the photon-thermal-electricity [107] and photon-electricity-thermal [108] processes induced by surface plasmon elements. This has opened up a new route for further exploration of the physical mechanism [109] of surface plasmon and exciton coupling and for the development of new optoelectronic devices, which will have great scientific significance.  
(3) In practical applications, the research into the nonlinear interactions between internal surface plasmons or between the surface plasmons and matter is expected to provide further exploration of the physical essence of these interactions.  
Surface plasmon optics generated using a combination of quantum optics and surface plasmon optics will therefore serve as a new development direction that will not only increase the depth of study of the basic properties of surface plasmon excitons, but also will provide directions toward solutions to some of the current problems in quantum optics research.  
[PERSON], [PERSON], and [PERSON] conceived the idea; [PERSON], [PERSON], [PERSON], and [PERSON] wrote the paper; [PERSON], [PERSON], and [PERSON] revised the paper. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (Grant No. 11204222); The Natural Science Foundation of Hubei Province, China (Grant No. 2013 CFB316, Grant No. 2014 CFB793); The Innovation Fund of School of Science, Wuhan Institute of Technology (No. CX2016106).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Different Couplings** & **Principles** & **Applications** \\ \hline Coupling Between Plasmons and Excitons on Conductive Surfaces & Polaritons exist at the intersection between quantum optics, solid state physics, and quantum chemistry & Quantum optical circuitry and quantum computation \\ \hline Coupling Between Plasmons and Excitons on Localized Surfaces & A combination of photonic microcavities and metallic nanostructures & Plasmonic lasers and organic nanophotonics \\ \hline Coupling Between Metal Periodic Structure Plasmons and Excitons & With periodic corrugations for creating attenuated diffraction, increase the propagation of the incident light & Organic light-emitting diodes and all-optical ultrafast plasmonic nanocircuits \\ \hline Coupling Between Surface Plasmons and Transition Metal Dichalcogenides(TMDCs) & A photon is emitted by a quantum system, it should also be absorbed by the same system & Nanoscale optical communication and low-energy photonic devices \\ \hline \hline \end{tabular}
\end{table}
Table 1: Different coupling principles with their applications.  
**Acknowledgments:** The authors would like to thank the support of [PERSON]'s Group in Huazhong University of Science and Technology.  
**Conflicts of Interest:** The authors declare no conflicts of interest.