Research On Polymer Optical Waveguide Devices With Loss Compensation Based On NaYF₄:Yb³⁺,Er³⁺nanocrystals

With the rapid development and update of the Internet and mobile terminal devices,the demand for the transmission rate of the communication network and the broadband capacity of the communication network is also increasing.The ultimate goal of the future fiber-optic communication network transmission system is to establish an all-optical network,that is,to achieve"fiber transmission instead of copper transmission"in the access network,metropolitan area network and backbone network.In recent years,related research on on-chip integrated optics has been rapidly developed,and it has broad application prospects in the fields of communication and sensing,and has attracted great attention from scholars and enterprises at home and abroad.The advantage of on-chip integrated optics is that its fabrication process is consistent with microelectronic complementary metal oxide semiconductor?CMOS?processes,helping to achieve optical path and circuit integration.Based on the conventional CMOS process and the characteristics of organic polymer materials,polymer waveguide devices such as thermo-optic switches,optical add/drop multiplexers,and arrayed waveguide gratings have been developed.The on-chip integration of these devices,due to absorption,loss and dispersion of light transmitted in the waveguide,the phenomenon of optical signal amplitude attenuation,system error rate increase,etc.,seriously affecting the quality of on-chip communication.Therefore,it is important to develop an optical waveguide device with on-chip integration with loss compensation.In this paper,systematic research on rare earth doped polymer optical waveguide amplifiers and thermo-optical switching devices has been carried out.The researches on material synthesis,device structure design and theoretical analysis,device process preparation and performance testing have been carried out.The research contents are as follows:NaYF₄:18%Yb³⁺,2%Er³⁺nanoparticles were synthesized,and the morphology of the nanoparticles was characterized.Then the nanoparticles were doped into UV photoresist SU-8 to obtain the core material needed for the experiment.The surface flatness of the core material film was characterized by atomic force microscopy,and the refractive index of the core material was tested and fitted by an ellipsometer.The results show that the nanoparticles are uniform in size,about 12 nm in diameter,After surface modification,it can be fully dissolved into SU-8 photoresist,and the spin-coated core film has good surface flatness.At 1550 nm,the unexposed SU-8 has a refractive index of 1.577.The exposure SU-8 refractive index was 1.562.Then the theoretical analysis of the gain performance of the device is carried out with the matlab software.According to the refractive index of the core material,the SiO₂ is used as the lower cladding layer.The nanocrystals doped SU-8 photoresist is used as the waveguide core layer,and the PMMA is the upper layer.The rectangular waveguide structure of the cladding is prepared by photobleaching and wet etching.The gain performance of the device was tested by end-face coupling.The results show that the waveguide amplifier prepared by the wet etching process obtained a relative gain of 2.7dB;the waveguide amplifier prepared by photobleaching process was obtained a relative gain of 4.5dB.Based on the research of the above optical waveguide amplifier,the paper proposes the application of optical amplifying materials to the preparation of thermo-optic switching devices.The polymer waveguide thermo-optic switches with loss compensation function based on NaYF₄:18%Yb³⁺,2%Er³⁺nanoparticles are designed and fabricated.The device uses SiO₂ as the under cladding layer,the nanocrystals doped SU-8 polymer as the waveguide core layer,and the PMMA polymer as the upper cladding layer.The test results show that the prepared device has excellent thermo-optic modulation characteristics and realizes the loss compensation function for the thermal optical waveguide switch.Using a 304 Hz square wave applied voltage measurement,the rise and fall times of the device were240?s and 380?s,respectively.At a drive power of 7 mW,the extinction ratio of the device is approximately 14 dB.When there is no pump light input,the insertion loss of the switching device is about 15dB.When the pump light power is 230 mW and the input signal optical power is 0.1 mW,the loss compensation of the device at 1530 nm is 3.8 dB.