Preparation And Study Of Organic/inorganic Composite Gain Medium For S-band Optical Waveguide Amplifier

The emergence of optical communication technology not only improves the efficiency of information transmission and changes the way of life of human beings,but also greatly promotes the development and progress of the world.In this field,the all-optical amplification technology represented by erbium-doped fiber amplifier?EDFA?which was born in 1980 s solves the problem of speed and distance limitation in optical communication network transmission due to optical signal attenuation loss in long-distance transmission.With the exponential growth of network communication demand,the demand for data transmission is also increasing.It has become the focus of attention that how to achieve larger capacity information transmission and faster real-time information processing to meet the growing demand in network communication.At present,the research of optical amplification technology in C+L?1530-1625 nm?band has made great progress,but the optical amplification technology in S band?1460-1530 nm?is still in the exploration stage.Because the 1.4?m near-infrared radiation of Tm³⁺ion ³H₄-³F₄ energy level is located in the S-band of optical communication,the development of Tm³⁺doped optical amplifier is of great significance to the amplification of S-band optical signal.Optical amplifiers used in all-optical amplification communication system mainly include optical fiber amplifiers and optical waveguide amplifiers.At present,great progress has been made in the development of Tm³⁺doped fiber amplifier TDFA.However,because fiber-optic amplifier takes fiber as the carrier,it needs a long fiber to realize the effective amplification of signal light.Therefore,there are some limitations in short distance communication systems,such as integrated devices,fiber to home,vehicle,airborne and so on.Compared with the fiber amplifier,the waveguide amplifier can achieve higher gain per unit length by increasing the doping concentration of rare earth ions.In short distance and integrated communication system,the miniature optical waveguide amplifier which can be integrated with other electronic devices can effectively reduce its insertion loss and coupling loss,so it has a more integrated development prospect.According to different gain media,optical waveguide amplifiers can be divided into inorganic and organic optical waveguide amplifiers.Compared with inorganic crystals and other materials,organic polymers have the advantages of simple processing technology,low price,easier preparation and compatibility with silicon matrix.Therefore,the organic optical waveguide amplifier has become one of the most promising optical waveguide devices.In order to effectively doping rare earth ions into optical waveguide devices,the researchers modified the oil soluble groups on the surface of rare earth nanoparticles and doped them into polymers to prepare organic optical waveguide amplifiers.At present,the preparation and luminescent properties of thulium doped nanocomposites for S-band organic waveguide amplifiers are still in the initial stage.There are many key scientific problems to be solved in this study.First of all,the influence factors include the morphology and size of rare earth nanoparticles,the doping concentration of thulium ion and sensitizer ion,and the luminescent properties of thulium ion at 1.4?m,how do these parameters affect the gain per unit length of an optical waveguide device?Secondly,how the size,surface properties,the specific gravity of the nanoparticles in the polymer and the doping method affect their dispersion in the polymer matrix,and then influence the scattering loss of optical waveguide devices?The exploration of these scientific problems will provide a theoretical basis for the preparation of S-band organic waveguide amplifiers.In view of the above problems,we have carried out the following experimental work in this paper:?1?NaYF₄:20%Yb,x%Tm nanoparticles with good dispersion and uniform sizes were prepared by high temperature pyrolysis.We explored the doping ratio of Tm³⁺ions which increased from 0.2%,0.4%,0.6%to 2.0%in nanoparticles.The morphology,size and crystal structure of the nanoparticles were characterized by high resolution TEM and XRD.The surface properties of the materials were characterized by FTIR.The luminescent properties and excited state lifetime of nanomaterials were measured by SPEX 1000M fluorescence spectrometer and oscilloscope.The experimental results show that the nanoparticles doped with different concentrations of Tm³⁺have the same size of about 11 nm,good dispersion and hexagonal crystal structure.The down conversion luminescent intensity of nanoparticles at 1.4?m was obtained by spectroscopic method.With the increase of Tm³⁺doping concentration,it first increased and then decreased.The Tm³⁺doping concentration of NaYF₄:20%Yb,x%Tm nanoparticles with the strongest luminescence at 1480 nm was found,and it was verified that the main reason for the decrease of the luminescence intensity of nanoparticles was the quenching of Tm³⁺concentration by the change of excitation energy level life of nanoparticles.The infrared absorption spectrum data show that the surface of nanoparticles is successfully modified with C=C unsaturated functional group,which is ready for the next step of copolymerization of nanoparticles and polymer monomers and the chemical doping of nanoparticles in polymer.?2?The nanoparticle NaYF₄:Yb,Tm and PMMA are linked together by covalent bond inlay by copolymerization,and the nanoparticle is uniformly and stably doped in the polymer.The colorless and transparent NaYF₄:Yb,Tm PMMA organic-inorganic composite polymer is obtained.Using the organic-inorganic composite polymer as the gain medium,an organic optical waveguide amplifier capable of optical amplification in the S-band is obtained.Firstly,the viscosity of the composite polymer is changed by adjusting the reaction temperature and time.Then,when the composite polymer has the appropriate viscosity,the composite polymer is spin coated in the PMMA groove etched by ICP,and then the inverted ridge structure optical waveguide device is prepared by drying.The relative gain of 1.4 dB is measured in the 13 mm length waveguide device with 1480 nm light as the signal light.This is the first time to obtain the S-band signal gain in the organic-inorganic composite waveguide device doped with rare earth NaYF₄:Yb,Tm nanocrystals.The experimental results show that the preparation of organic-inorganic composite polymer by linking rare earth nanoparticles in polymer matrix by chemical method is conducive to the dispersion of rare earth nanoparticles and reduce agglomeration.The polymer optical waveguide device made of the NaYF₄:Yb,Tm PMMA organic-inorganic composite polymer has good optical amplification performance.The S-band signal gain is obtained in the organic-inorganic composite waveguide device doped with rare earth NaYF₄:Yb,Tm nanocrystals.In the future,it is of great significance to use the organic-inorganic composite polymer as the gain medium to prepare the optical waveguide amplifier for all-optical amplification and short-distance communication band broadening.