Research On Low Half-Wave Voltage Mach-Zehnder Electro-Optic Modulato

As a key component of photonic integrated chip,Mach Zehnder（M-Z）electro-optic modulator plays an important role in signal transmission.The study of nonlinear optical electro-optic modulator with low half-wave voltage,low insertion loss and high integration can effectively improve the signal transmission quality of photonic integrated chip,It has an important impact on the development of optoelectronic integration technology.The main work of this thesis is carried out in combination with the research contents and objectives of the National Natural Science Foundation of China and the key R&D plan of Tianjin.Based on silicon and polymer materials,three types of M-Z electro-optic modulators are studied.Combined with the optical characteristics of different kinds of nonlinear optical polymer electro-optic materials and inorganic materials,the structure design and process development of different types of M-Z electro-optic modulators are carried out,and the process preparation and optical test of the designed devices are carried out.The main research contents of this thesis are as follows:（1）The silicon-based electro-optic modulator based on M-Z is studied.Combining BPM and FDTD,three types of silicon-based M-Z electro-optic modulators are designed:traditional electro-optic modulator,asymmetric electro-optic modulator,and slow-light electro-optic modulator,the design of a silicon-based electro-optic modulator is described in 1×2 beam splitter,branch waveguide,modulation arm waveguide and 2×1 beam combiner.The results show that the half-wave voltages of traditional electro-optic modulator,asymmetric electro-optic modulator,and slow-light electro-optic modulator are 2.4 V,2.2 V and 2.1 V respectively,the optical losses of the devices are-2.46 d B,-1.61 d B and-3.84 DB respectively,and the core size of the devices are 450μm×2800μm,160μm×700μm,160μm×420μm.Based on IMECAS silicon photonic platform,three types of silicon-based M-Z electro-optic modulators are designed.（2）The polymer electro-optic modulator based on M-Z is studied,A flexible polymer electro-optic modulator based on polydimethylsiloxane（PDMS）was designed.Epoxy resin-based photoresist（SU-8）was selected as the main material and dispersed red 1（DR1）.The results show that the half-wave voltage of SU-8 polymer M-Z electro-optic modulator is 1.8 V,the loss of the device is-1.2 d B and the core size of the device is 4000μm×22000μm.The layout of the proposed polymer electro-optic modulator is designed based on the SINANO micromachining platform of the Suzhou Institute of Nano-Tech and Nano-Bionics,CAS.（3）The polarization process of cross-linked nonlinear polymer material DR1/SU-8 is studied.The polarization equipment with two mechanical structures of upper and lower bipolar plate electrodes and probe electrodes are designed and built.The process tests of corona polarization and contact polarization are compared.When the polarization voltage is 7000 V,the three-stage temperature rise method（step temperature of 60℃,95℃and glass transition temperature of 130℃）is used to corona polarize the device,and the polarization efficiency is 73.2%.The results show that the electro-optic coefficient of the DR1/SU-8 nonlinear polymer film with a thickness of 2μm can reach 18.3 pm/V.（4）The preparation process of nonlinear polymer electro-optic modulator based on M-Z is studied.In order to reduce the non-polar silane groups on the surface of PDMS and overcome its hydrophobicity,Oxygen plasma（O₂ plasma）was used for cleaning（the power was 400 W and the time was 5 min）in combination with silylation reagent（3-glycidoxypropyltrimethoxysilane with volume fraction of 2%）（mixed solution of GPTMS and absolute ethanol）immersion treatment for surface modification,which significantly improves the adhesion of DR1/SU-8 photoresist on the surface of PDMS.A device process from spin coating,modification,lithography,development to metal graphics is developed.The test results show that the half-wave voltage of SU-8polymer M-Z electro-optic modulator is 2.0 V,and the loss of the device is only-2.01d B.The bright near-field output spot can be obtained by the test of optical waveguide coupling alignment platform.