Reaserch Of Polymeric Waveguide Thermo-optic Switch Based On Directional Coupler

In recent years,along with modern social unceasing informative process,the previous information transmission rate and capacity have gradually failed to meet people's needs.In the decades since the birth of optical fiber,the communication capacity of single-mode fiber has been improved several orders of magnitude through various technologies.However,due to the Shannon Limit,its communication limition is limited to about 100 Tbps and can't be further improved.In order to expand the communication capacity of optical fiber communication systems,more and more researchers are no longer limited to the single-mode fiber and focus their research on the few-mode fiber.Among them,the mode division multiplexing technology has attracted widely attention due to its unique advantages.The mode division multiplexing technology has greatly improved the transmission capacity of optical fibers by utilizing various spatial modes in few-mode fibers.The mode division multiplexer for combining and separating different modes is an important component in the mode division multiplexing optical transmission system.However,with the rapid development of mode division multiplexing technology and systems,passive mode division multiplexing/demultiplexers have gradually been unable to meet the needs of the system.It is necessary to develop reconfigurable active mode-controlling devices.Based on this situation,in this th,two mode optical switch devices are designed and manufactured to achieve controllable conversion of modes.This thesis mainly includes the following parts:First,the research background and significance of this thesis and the research progress of the mode division multiplexing technology are introduced.The mode theory of optical waveguides and the thermo-optical effects of polymers are analyzed.Secondly,a polymer waveguide thermo-optic mode switch based on the MZI structure is designed and prepared,and the controllable switching between the LP₀₁mode and the LP_11a1a mode is realized.We use the effective index method of the rectangular waveguide to calculate the effective refractive index of the two modes by using Matlab software.The 3D finite-difference beam propagation method?3DFD-BPM,RSoft?is used to simulate and optimize the mode field propagation in the device,and the size of the device is determined.According to this parameter,a mask is designed and fabricated,and the device is fabricated by the semiconductor microfabrication process.We test the prepared thermo-optic mode switch.The test results show that the device meets the design expectations that completing the controllable switching of the LP₀₁1 mode and the LP_11a1a mode.At 1550nm,the switching power of the device is 9.35 mW,the extinction ratio is 15.6 dB,and the rise time and fall time are 540.0?sand 440.0?s,respectively.In the whole C band,the extinction ratio of the device is higher than 11 dB.Finally,a polymer waveguide thermo-optic mode switching device based on a directional coupling structure is designed and prepared,and also achieve the controllable conversion of the two modes.At 1550nm,the switching power of the mode switch is 29.5 mW,the extinction ratio is 14.6 dB,and the rise time and fall time are 660?s and 480.0?s,respectively.When the operating wavelength is C-band,the switching function can still be realized,and the extinction ratio of the device is larger than 10 dB.We analogize this structure,and design the three modes thermo-optic switch based on directional coupling structure.In summary,this thesis studies polymer thermo-optic mode switching devices based on the MZI structure and the directional coupling structure,and the corresponding mode switches are fabricated by experiments.The designed device can be applied in the reconfigurable MDM system to play a control function of the mode transmission.