The Study Of High Speed Silicon-based Optical Logic Gate

With the explosive growth of information requirements,construction of all optical communication networks is extremely urgent in order to avoid electronic bottlenecks.Since it is one of the key devices in the all-optical network,optical logic gate has an extremely important role.However,the emerged optical logic gate devices usually have some defects.For example,the devices based on SOA(semiconductor optical amplifier)or nonlinear fiber usually have the defect of high power consumption,long response time or low integration etc.In future,the development direction of optical fiber communication is high speed,high bandwidth,low power consumption,and miniaturization.As an integral part of optical communication system,optical logic gate also has to meet requirement of high extinction ratio,high modulator speed,wide modulation bandwidth,low insertion loss,low energy loss,small size,ease of integration,and more.Therefore,the purpose of this paper is to design a high-speed silicon-based optical logic gate device and its innovation and contribution lies in:(1)In this paper,a thermo-optical NOR logic gate based on polymer is designed,according to the theory of dielectric slab waveguide,thermo-optic effect and the working principle of the modulator.The simulation results show that the thermo-optical switching power consumption is 6 vW,the total footprint is 300 mm2.Then,a thermo-optical logic gate chip based on polymer is successfully fabricated by spin coating,vacuum coating,contact exposure,reactive ion etching(RIE),cutting and polishing.The test results demonstrate that the measured power consumption is 28.2 mW,the insertion loss is 20.8 dB,and the rising response and the falling response time are 400 ?s and 550 ?s,respectively.From the response characteristics,the test results initially verify the design considerations.(2)To further improve the characteristics of power consumption,integration and response time,we put forward an electro-optical logic gates device based on SOI.For the strong confinement,footprint of the device is just about 90 ?m2.As the simulation results show that the driving voltage of the device is 1.8V and the power consumption is 6.66mW.A high coupling efficiency of more than 99%is obtained at the wavelength of 1550 nm and it could obtain an extinction ratio(ER)of 21.8dB.The response time of rising edge and falling edge are 3 ns and 1.5 ns,respectively.Thus,it has great potential to achieve high speed response,low power consumption and small footprint,which fulfill the demands of next generation on-chip computer multiplex processors.(3)In order to further improve the response characteristics,we attempt to combine graphene film material with SOI materials,according to the strong electric absorption of graphene,we put forward to a monolayer-graphene based dual gate logic gates device with the same structure.The device has inherited the advantages of low loss,high integration,what's more,it also owns the strong electrical absorption characteristic of graphene.In the case of incident light at 1550 nm,an extinction ratio of 43.67 dB can be achieved.Although the footprint increase to 200 ?m2,its extinction ratio and response characteristics have been significantly improved.According to simulation results,the response time of "open" and"close" of logic gate based on monolayer graphene is 0.5 ns and 1.2 ns,respectively,and the response time of "open" is up to sub-nanosecond magnitude,which shows great potential in the future optical network system.