Research On Silicon-based Reconfigurable All-optical Computing Chip

Computing is the backbone of modern society.Faced with increasingly complex problems in science and engineering,as well as the rise of big data,higher performance computing has always been required in the singal processing domain.In the past decades,there is no doubt that electrical computing has played the most crucial role.From supercomputers to smartphones,a series of innovations in the transistor technology has driven its developments.However,as the demise of Dennard scaling and slowing down of Moore’s law,the limits of electrical computing are already in sight.Especially the speed limitation and energy dissipation brought by the shrink of metallic wire,and the low computing efficiency caused by the traditional Von Neumann model in some complex issues such as recognition and optimization,have prompted people to find some new computing ways as effective supplements.All-optical computing is just one of the most important directions.Although it has a checkered past,the developments of optical interconnects and photonic integration technology in recent yaers has brought some new possibilities.On one hand,the on-line optical computing combined with optical interconnects can avoid the speed limitation and energy dissipation caused by O/E and E/O conversions.On the other hand,by fully combining the parallelism and high bandwidth of light with the small footprint and low power consumption of integrated components,optical computing is able to realize high performance in some special applications.As a result,optical computing has regained many attentions since 2010.In the thesis,aiming at several problems in optical logic computing,optical metaphoric computing such as optical differentiation and optical solving of ordinary differential equations,the correspoding solutions are proposed.Based on the silicon chip,some reconfigurable optical computing functions are achieved theoretically or practically.The detailed research contents are as follows:(1)Typical devices and basic theories in silicon-based devices are analyzed by combining with all-optical computing.Nonlinear devices and effects fit for optical logic gates are summarized.Transfer functions of some linear devices used for differentiation and related computing are deduced.(2)A method that can perform high-speed reconfigurable logic gates based on four-wave-mixing in silicon waveguide is proposed.Simultaneously generation of a full set of the two-input logic minterms is demonstrated for the first time,and arbitrary two-input logic functions are realized by properly combining these minterms.The operating speed is 40 Gb/s.(3)A light-controlled directed logic circuit is proposed,which can avoid the problem that signals are still loaded on electricity in the current directed logic gates.Two microrings with different radius are cascaded,which are controlled by pump light through free-carrier effect.The generation of all the two-input minterms based on this structure is explored through nonlinear coupled mode theory,which are realized successfully at the working speed of 10 Gb/s and 40 Gb/s.(4)An ordinary differential equations(ODE)solver based on microdonut is proposed.Two different modes in one microdonut are designed to be used simultaneously to realize a second-order ODE,without cascading different devices.Transfer matrix method and temporal coupled mode theory are used to demonstrate the feasibility of our proposal,and the solving of ODEs are realized based on a silicon chip.(5)Based on the optical ODE solvers,silicon-based optical systems of ODEs(SODEs)solver are proposed for the first time.By properly introducing feedback waveguides among different output ports of microrings,the solving of three kinds of SODEs at a working bandwidth of 10 GHz is experimentally demonstrated,and the coefficients can be adjusted through micro-heaters.In addition,a general SODE solver with tunable styles,dimensions and coefficients is proposed at last.(6)Aiming at the application of optical differentiator,a silicon chip for reconfigurable pulse shaping based on cascaded optical differentiators is designed and fabricated.Flat-top pulses,parabolic pulses and triangular pulses with tunable pulse widths can be generated accurately from a Gaussian pulse based on this system.