| With the development of modern communication networks and the advent of the 5G era,people have increasingly higher requirements for communication speed and bandwidth,but modern communication networks are still limited by "electronic bottlenecks".Therefore,all-optical communication has become the most promising and potential future communication technology choice.The all-optical switch and all-optical logic,as the key components in the all-optical communication network,play a role in monitoring the communication path and constructing the optical switching network.The all-optical network directly controls light with light because there is no photoelectric conversion process,which can get rid of the "electronic bottleneck" constraint,thereby increasing the communication rate and expanding the bandwidth capacity.In recent years,chalcogenide phase change materials have been used in many tunable photonic devices due to their adjustable optical constants and non-volatile properties.Among them,phase change all-optical logic has received extensive attention.However,the existing phase change all-optical logic mostly focuses on the logic operation of the on-chip waveguide.It uses the principle of “evanescent wave coupling” to limit the switching contrast,and the coupling of the optical fiber system to the on-chip waveguide also introduces additional loss,which limits its use for application of optical fiber communication devices.This paper uses the phase-change all-dielectric metasurface structure to realize the special-shaped transmission spectrum,explores the change rule of the metasurface geometric parameters to its spectral resonance peak,and proposes the design of the logic operation function realized in the free space.The main research results in this paper are as follows:1.The influence of the geometric parameters of the proposed phase-change all-medium metasurface all-optical switch on the transmission spectrum is studied.The geometric parameters include the thickness of each layer,the radius of the nano-hole,and the period of the holes.Among them,according to the difference of the resonance field enhancement distribution mode,we divide the two resonance peaks near 1550 nm into two resonance modes-the film thickness sensitive resonance mode and the nano-hole geometry sensitive resonance mode.The change rule of the influence of each parameter on the transmission resonance peak of the two modes is summarized and analyzed,and the mechanism is explained.2.Based on the resonance bonding theory,the amorphization process of the phase change material excited by the femtosecond laser will lead to the recovery process of the resonance bond due to carrier migration.We proposes a reasonable mechanism explanation for the faster switching rate of the phase-change all-dielectric metasurface all-optical switch.It shows that the phase-change all-dielectric super-surface compared to the plasma super-surface can significantly improve the switching speed of the device in addition to the loss advantage.3.A phase-change all-dielectric metasurface all-optical switch is proposed as a unit in a three-dimensional space perpendicular to the optical path cascade design.In addition,four metasurface geometric parameter structural designs with different logic functions are proposed.In addition to the single-input NOT gate,by demonstrating the vertical cascade of two unit films,two-port input AND gates,OR gates,and NOR gates in free space are realized respectively.The phase-change all-dielectric meta-surface all-optical logic design proposed in this paper has the following characteristics: a meta-surface area with multiple operating wavelengths and logic functions can be integrated on a unit film;Change its working area by mechanical means or other all-optical wavefront modulation to realize the switching of functions;The optical logic operation of parallel processing can be realized in free space. |
