Research On Thermo-optic Devices And The Stability Of Polymer Planar Optical Waveguide

In optical fiber communication systems,large capacity,high speed,low loss and high reliability optical waveguide devices have been paid more and more attention and become a new research focus.The thermo-optic waveguide optical switches and variable optical attenuators based on thermo-optic effect are also from the laboratory to practical application,becoming the core components in the optical add drop multiplexer and optical cross connector,can realize wavelength division multiplexing/demultiplexing,automatic protection switching,optical power equalization,on-line monitoring and other functions in the optical fiber network.Optical waveguide thermo-optic devices attract more and more attention not only because it's small size,high ductility and good long-term stability,but also conducive to the integration of many advantages,therefore,those devices have aroused great interestes,and their parameters such as crosstalk,insertion loss,switch /response time characteristic can meet the actual application requirements.The polymer optical waveguide has the advantages of low loss,no electromagnetic interference and easy preparation,especially because the thermal conductivity of the polymer material has a lower rate,and the polymer optical fiber has good compatibility,so the polymer optical switch can be used as a signal distributor which used in visible light communication system.Through the spin-coating process,multilayer films can be fabricated to realize the integration of the three dimensional optical waveguide devices.Two types of thermo-optic devices,thermo-optic switching device and variable optical attenuation device,are designed and fabricated in this paper.The long term stability of the device is studied systematically and deeply.The main work of this thesis is as follows:1?A three-dimensional polymer thermo-optic switch vertically coupling structure of 650 nm band based on the optical coupling waveguide is proposed and studied,two vertical direction is located in the two layer of polymer material in a parallel.Through the action of the thermoelectric electrode,the light can be controlled from an upper layer waveguide or an output from the lower layer waveguide.We use finite element method and beam propagation method to optimize the structure of the device.In this thesis,two rectangular waveguides with different angles are fabricated in parallel two layer polymer structures.Through the design of precise waveguide size and relative position,the vertical structure coupler can be used as switch and optical array,and provides the basis for fabricating high integration devices on the same chip.Polymer materials is compatible with plastic optical fiber P(MMA-GMA)material,when the electrode works,the temperature gradient cause changes the effective refractive index below the electrode,thus lower waveguide light will be coupled to the upper waveguide.When the thermal power switch is 57.7 m W,the extinction ratio can reach up to 27.5 d B,in which the rise and fall time of devices are 639.8?s and 758.2?s respectively.We have measured the extinction ratio of 125 days continuously,and proved that the device has good stability.This three-dimensional waveguide structure demonstrates that multilayer optical printing devices can be applied to optical communication networks and increase the functionality of optical communication devices.2.A variable thermo-optic attenuation device based on polymer/silica material multimode interference operating at 650 nm band is designed and fabricated.Visible attenuator is an important device,which can be used in the cross connect wavelength division multiplexing(WDM)network of plastic optical fiber and adjust the energy between different optical channels and equalization.The mode transmission condition of the device,the design of the multimode interference region and the design of the cone mouth are analyzed by the finite element method.The analysis of the thermal field is based on the properties of the material,and the electrode angle is optimized after the device is optimized.The device designed and fabricated at 650 nm band has a extinction ratio of 26.5d B when the power consumption is 21 m W,in which the rise and fall times of switches are 51.99?s and 192?s respectively.Time stability measurement results show that the device has good switching stability.3.Based on PMMA materials and UV crosslinking materials(SU8),the common MZI thermo-optic switches are designed and fabricated,and more than 30 polymer planar waveguide optical switches are fabricated successfully,then the packaging processes of the chips including cutting,grinding,polishing are detailed study.After package,the fabricated devices are divided into two groups: one group were tested at room temperature for a long time,the time interval for 1-3 months,the general device testing time in more than a year,the most long time under the condition of room temperature test device for 680 days,the test results show that the maximum variation of insertion loss is 15%;the second groups are test by temperature cycling experiment,and the condition is-40? to +85?,-40?for 25 minutes,the rise time of 45 minutes,the temperature of +85? for 24 minutes,the fall time of 50 minutes,thus a cycle of 144 minutes.The performance of the electrical package thermo-optic switches are test after 24 hours and 168 hours cyclic,respectively.The test results show that the biggest change of insertion loss is the amount of 18%.The results of the three experiment sets show that the main performance indexes of the fabricated thermo-optic device have very good stability and reliability.