Phase Manipulation Technology Of Optical-waveguide-type Integrated Metasurface

As an artificial electromagnetic material,metasurface can flexibly control the polarization,amplitude,and phase of electromagnetic waves at sub-wavelength scale.At present,a large number of literatures have reported the applications of metasurfaces in free space light.In recent years,the applications of metasurface in waveguide has gradually attracted the attention of researchers.It has been proved that metasurface has the potential to solve the problems of large volume and complex structure of traditional integrated photonic devices.Moreover,it can also realize arbitrary light response of the guided-wave.The designed optical-waveguide-type integrated metasurface devices have the functions of on-chip optical conversion,mathematical operation,and spectral manipulation,and it has a promising application in imaging,sensing,and quantum information processing.At present,there are three technical bottlenecks in the optical-waveguide-type integrated metasurfaces.Firstly,once the photonics integrated device is designed,the optical performances of the devices are fixed and cannot meet the current dynamic adjustable requirements.Secondly,most of the optical-waveguide-type integrated metadevices do not meet the large-scale integration and high information transmission capacity.Thirdly,the existing multiplexed designe methods have the problems of low scalability and high crosstalk.In order to solve these problems,the dynamic control technology and multiplexed technology of the integrated metasurfaces onto a photonic integrated circuit are studied in this thesis.At first,a design method of photonic integrated devices based on phase change materials is proposed.As a verification of the method,a tunable beam deflector is designed.Then,a design method of multiplexed devices is proposed based on the silicon waveguide,and out-of-plane focusing is realized by combining the Particle Swarm Optimization algorithm.At last,in order to expand the application scope of the existing multiplexing design methods,a design method named"Spatial Phase Multiplexing"is proposed,through which the devices with any two functions can be designed efficienctly and quickly.The main contents and innovations of this thesis are as follows:(1)In view of the problem that the optical-waveguide type integrated metadevices are difficult to realize dynamic control.A kind of ridge-waveguide structure based on phase change material is proposed,and the ability of phase control is proved.Then,the thought is extended to planar waveguide.In order to prove the phase control ability of phase change materials in the planar waveguide,a deflector is designed.When the state of the phase change material changes from amorphous to crystalline,the free space light radiated from the waveguide and deflects at different angles.Comparing to the deflector based on phase change material,the deflector designed by us has the deflection angle range of±60°and the addressable number of 12,which is 3 times and 4 times as much as previously reported.(2)To solve the problem that the optical-waveguide-type integrated metadevices are difficult to realize large-scale integration and high information transmission capacity,a multiplexed method based on waveguide is proposed and a device which can realized both polarization and orbital angular momentum(OAM)multiplexing is designed.The device can realize OAM mode with different linear polarization and different topological charges in a broadband(1450-1650 nm).Secondly,combining the above method with the Particle Swarm Optimization algorithm,one could realize more complex functional devices.As proof of the method,a focusing device with variable focal length is designed,which could achieve 3.4 times zoom ability in a footprint of35?m~2.With the increase of the footprint of the device,the zoom ability is also increased.By improving the utilization of the pixel,the above methods provided the solutions of small-scale integration and small information transmission capacity of integrated metadevices.(3)To solve the limitations of the current method which has the disadvantage of lacking of function expansibility or leading to large crosstalk,a design method named"Spatial Phase Multiplexing"is proposed.The proposed method is suitable for multiplexing of any two functions.In addition,depending on the fact that the guided-wave transmitted along the two vertical directions do not affect each other,a four-channel multiplexed device with low crosstalk can be designed.As a method verification,a four-channel multiplexed hologram generator is designed,which has very low crosstalk comparing to the previously reported four-channel multiplexed hologram generator.The method proposed in this thesis provides a new scheme for the photonic integrated devices with a large-scale integration,low crosstalk,and high information transmission capacity,and has potential application prospects in optical communication,holographic display,and augmented reality.