Graphene Optical Properties And Applications Under Total Internal Reflection Conditions

Graphene is a two-dimensional material made of sp2-hybridizd carbon atoms arranged in hexagonal honeycomb crystal lattice, and it is an atomic layer thickness. Because of its special lattice structure, graphene exhibits excellent properties in the field of optics and electronics, especially in the study of light-graphene interactions. Combined with the physical properties of graphene, such as electron transport characteristics, flexible and transparent, the light-graphene interaction shows tremendous value in the field of optical date storage, sensing, biomedical and photodetector.The thickness of graphene is only0.34nm and its light absorption is2.3%, thus it looks completely transparent. Under the condition of vertical incidence, light-graphene interaction is very weak. Therefore, how to enhance the light-graphene interaction and study the laws of light-graphene interaction become the most important issues. Currently, there are three main ways reported to enhance the light-graphene interaction:(1) Enhanced by surface plasmon polaritons;(2) Enhanced by increasing the optical shock cavity formed multiple transmission;(3) Enhanced by introducing the light into the Si waveguide formed multiple reflection. Use these methods the light-graphene interaction can be enhanced in different degree. However, limited by the complexity of nanometer technology, high cost, difficult spatial light operation and the specific wavelength range, these methods were restricted to be widely used.In the paper, a new method based on total internal reflection are presented, and the light-graphene interaction was successful enhanced by using graphene/prism structure, without compromising the broadband characteristics of graphene (3002500nm). Meanwhile, the polarization-dependent effects of graphene was found under the condition of total internal reflection. the polarized absorptions of graphene was able to be controlled from0to100%by adjusting the angle of incidence, by controlling the number of layers of graphene and the refractive index of medium. It is worth mentioning that these novel light-graphene interaction phenomenons do not depend on the type of graphene. They were observed on mechanical exfoliation graphene, CVD graphene and reduced graphene oxide.Next, under condition of total internal reflection, light-graphene-media interaction phenomenon was found, and the interaction between light and graphene was extraordinarily sensitive to the refractive index of media. Combined with lab-chip technology, the sensitive refractive index sensing was applied in the microfluidic experiments. Useing Maxwell’s electromagnetic theory, these phenomenons were explained well under the condition of total internal reflection.In the paper, these series of important discovery were applied in the following areas:1. Mass, flexible, multilayer films optical data storage. Different absorption of graphene caused by different polarizations. In the experiment, the light intensity signals of different polarizations were converted into the voltage signals. The part without graphene where the light intensity signal of polarizations was invariable, was denoted by "0", the part with graphene where the light intensity signal of polarizations was variable, was denoted by "1", thus "0" and "1" data storage modes were formed. Discrimination between "0" and "1" signals is very large, and signal to noise ratio is very high. Voltage difference between "0" and "1" signals is close to2V, and SNR is～100. The transparent and flexible media films with a refractive index gradient were used as the buffer layers, thereby a mass, flexible, multilayer films optical data storage was formed, and it provided a new way for massive information storage.2. Sensitive real-time monitoring of refractive indexes using a novel graphene-based optical sensor. In the paper, under conditions of total internal reflection light-graphene-media interaction phenomenon was found, and the interaction between light and graphene was extraordinarily sensitive to the refractive index of media. Combined lab-chip technology, by the formation of microfluidic channels/graphene sensing layer/prism sandwich structure, sensitive real-time monitoring of refractive indexes using a novel graphene-based optical sensor was achieved. The range of refractive index sensor is from1to1.5, and the response speed is increased to the order of microseconds. Meanwhile, the sensing system has the characteristics of real-time, label-free and non-destructive. It provides an effective means for the sensitivity measurement of fluid refractive index. And it is the foundation of microfluidic refractive index sensing in the fields of biomedical and analytical chemistry.