Research On Lithium Niobate Based Photonic Quantum Devices

Quantum information science is a new interdisciplinary subject integrating quantum mechanics and information science,which has very important research significance,but the physical realization of quantum information function on photonic quantum devices is still a major difficulty,and the research on related photonic quantum devices is particularly important.Thin-film lithium niobate can be used to develop new type photonic quantum devices because of its great optical properties and excellent compatibility of semiconductor processing technology.Aiming at the development of thin-film lithium niobate photonic quantum devices,this thesis studies lithium niobate based entangled light source and heterogeneous Hong-Ou-Mandel(HOM)interference devices from three aspects: theoretical design,process preparation and performance test,the specific work contents are as follows:(1)Based on the finite element analysis method,the key parameters such as structure size,effective refractive index and mode field size of ridge lithium niobate waveguide were modeled and analyzed.On this basis,combined with the frequency doubling and parametric down conversion theory of second-order nonlinear optics,the polarization period of ridge periodically poled lithium niobate waveguide was designed and optimized for the generation and heralded single photon purity optimization of correlated photon pairs based on spontaneous parametric down conversion.(2)Based on semiconductor processing processes such as lithography,lift off and inductively coupled plasma(ICP)etching,on a 600 nm thin-film lithium niobate wafer,ridge lithium niobate waveguide with the width of about 4 ?m,etching depth of about410 nm,edge roughness of no more than 80 nm and propagation loss of 2.9 d B/cm was realized.For the preparation of periodically poled lithium niobate waveguide,on the surface of lithium niobate film material,the Cr/Au electrode with the thickness of 135 nm,the period of 5 ?m and interval of 10 ?m is prepared by lithography,magnetron sputtering coating and lift off,and the periodic polarization of lithium niobite was realized.Aiming at the research on periodically poled lithium niobate waveguide quantum source,the quantum entanglement generation and test platform based on commercial waveguide devices was built,and the experimental measurements of parameters such as unilateral counting and coincidence counting of correlated photon pairs were completed.(3)Based on the finite element analysis method,the key parameters such as structural parameters and coupling length of metal/dielectric coupled heterogeneous waveguide devices were analyzed,and the heterogeneous coupled HOM interference device for testing the nature of surface plasmon polariton was designed.Based on lithography,plasma enhanced chemical vapor deposition(PECVD),ICP etching,alignment lithography,magnetron sputtering coating and lift off,the preparation of Si N/Au hetero-coupling HOM interference chip was completed,and the coupling between hetero-waveguides was preliminarily tested,which provides a reference for the development of electrically controllable lithium niobate based hetero-coupling quantum interference devices.