Research Of Demultiplexing Device Based On Surface Plasmon Polaritons

Since the 21st century, the information technology is developed rapidly, but the microelectronic devices in the bandwidth and transmission speed are limited so that the development of all-optical integrated communication is impacted. At this time, the optical devices based on Surface plasmon polaritons (SPPs) have attracted wide attention gradually.These devices have high application value in optical communication because they can overcome the diffraction limit to restrain the light in the subwavelength structure. Because of these excellent characteristics, SPPs can be applied in data storage, light technology, biomedicine, especially in the sub-wavelength optics.Besides, optical microcavity is a hot spot, such as microring, rectangle cavity, microdisk, kinds of microcavities play a unique role in the nano-optics. Nowadays, all kinds of microcavities based on SPPs have attracted researchers' attention.Among them, the metal-dielectric-metal (MIM) structure based on SPPs is the most widely used, which constrains the light energy to the sub-wavelength-scale dielectric layer. In this way, it can realize the light localization in sub-wavelength. In this paper, we propose a structure based on metal-dielectric-metal (MIM), and the proposed system consists two waveguides and a square microcavity, which can be tuned by a square resonator and the coupling distance between the waveguide and the resonant cavity to control the reflection spectrum and the transmission spectrum. On this basis, the wavelength division multiplexing including three waveguides and two square resonators is proposed. The device can control the output wavelength by adjusting the cavity length and the coupling distance between the waveguide and the resonator. Especially, if two square resonant cavity lengths are different, the center wavelength of the reflection spectrum will be different. So this structure can distinguish multiple wavelengths from input wavelengths. In order to apply this device to optical fiber communication, the data processing of the relationship between the cavity length and the reflection of the center wavelength is carried out. As we all know, three low-loss transmission wavelengths are commonly used in optical fiber communication: 850nm, 1310nm and 1550nm. The cavity length of the square resonator has a linear relationship with the center wavelength reflected from the output port. Therefore, the wavelengths decomposed by the wavelength division multiplexing structure are 1310 nm and 1550 nm, the cavity length of the square resonator should be set as 581 nm and 702 nm. And crosstalk doesn't occur in this case. After stripping out the two different wavelengths, the optical receiver will process them and restore the original signal ultimately. It can demonstrate that the wavelength division multiplexing plays an important role of communication transmission. In addition, compared with conventional devices, the three waveguides coupled square resonator has the advantages of simplicity of manufacture, convenience of integration and high efficiency. Besides, the coupling distance of the device is larger than these similar devices and the reflectivity deficiency is higher, so this structure is easier to obtain in experiment, and its practical value is higher.