Polymer-based Integrated Optical Waveguide Devices

In recent years,integrated optics have played important role in the optical communication and optical sensing areas.Among different optical materials,polymer has a variety of advantages such as low cost,easy processing,good film uniformity and controllable properties.Polymer-based integrated optical devices have a variety of simple and high yield preparation processes such as direct lithography,laser direct writing and nanoimprinting.Among them,nanoimprinting has attracted much attention,since it can achieve high accuracy with simple preparation process.UV based soft nanoimprint technique is an improved version of nanoimprinting.As soft mold is introduced to replace hard mold and the UV curing is used to replace thermal curing,high temperature and pressure can be avoid which simplify the preparation process.In this paper,several polymer-based optical waveguide devices have been studied.The measurement results have been analyzed and discussed.The optical devices include optical splitters for the communication and microring resonators and multimode waveguide interferometers for the sensing.The main contents can be summarized as follows:1.Two kinds of optical splitters including Y-junction and MMI splitters have been designed,prepared and measured.The optical polymer material,LFR is adopted as it has a low material absorption loss at the communication wavelengths.Firstly,the structures of the splitters are simulated and optimized.The simulations mainly focus on the waveguide structure,bend loss and the multimode waveguide of the MMI optical splitter.Then the splitters are fabricated using Soft UV NIL.Finally they are characterized and measured.The insertion losses of Y-junction and MMI splitters at the wavelength of 1550 nm are 11.28 dB and 12.98 dB,respectively.2.The polymer-based mirroring resonator has been designed,fabricated and measured.The wavelength of 890 nm is adopted as the working wavelength.Optical polymer material Ormocore is used as it has low material absorption loss at short wavelengths.The structure of the microring resonator is simulated and optimized in order to improve several important parameters including Q factor,extinction ratio and free spectral range.Then the microring resonator is fabricated and measured.Based on the single microring resonator,polymer-based microring array is designed and fabricated in order to realize the comprehensive detection of multiple parameters.In order to improve the free spectral range of polymer-based microring resonators,we designed and fabricated a double cascaded microrings which can not only effectively improve the free spectral range but also improve the sensing sensitivity.3.The bimodal waveguide interferometer refractive index sensor has been designed,fabricated and measured.Firstly,the structure of the interferometer is simulated and optimized.The location of the single mode waveguide is optimized in order to give the equal power to the both modes.Then the interferometer is fabricated and measured.The extinction ratio of the interference spectrum can reach 15 dB and the sensitivity of the refractive index sensor reaches 316 π rad/RIU.In order to further improve the sensing sensitivity,we designed a trimodal interferometric refractive index sensor.A long period grating structure was designed to balance the power of the two modes.The sensitivity of the trimodal waveguide interferometer refractive index sensor can reach 4100 π rad/RIU.