Polymer Optical Waveguide Amplifiers At 1.53 ?m And 0.53 ?m Wavelengths Based On Erbium-ytterbium Co-doped Fluoride Nanocrystals

Optical waveguide amplifier is one of the important devices in planar photonic integration,which is used to compensate the attenuation of optical signal during transmission.In order to match the low loss window of optical fiber communication,the study of optical waveguide amplifiers are mainly carried out in C band.At the same time,plastic optical fiber communication and visible light communication are developing rapidly,and the visible light waveguide amplifiers corresponding to their low loss window are also in urgent need of research and development.Optical waveguide amplifiers working in C band and visible band are gradually becoming important core components in quartz fiber communication system and plastic optical fiber communication system.The development of high performance optical waveguide amplifier with easy integration is a hot topic in this field.The photoluminescence of rare earth ions provides an effective way for the development of optical waveguide amplifiers.Compared with rare earth doped inorganic optical waveguide amplifiers,polymer optical waveguide amplifiers have many advantages,such as simple process,easy adjustment of refractive index difference,low cost and easy to silicon-based integration.If high performance polymer optical waveguide amplifiers can be developed and commercialized,the development of planar photonic integration technology will be greatly promoted.However,rare earth doped polymer optical waveguide amplifiers still have the problems of large losses and difficulty in achieving net gain.One of the main reasons is that inorganic rare earth ions are difficult to realize high concentration doping in polymer.Second,physical doping is a commonly used method to disperse rare earth nanocrystals in polymer medium.This method will lead to agglomeration of nanocrystals,which will cause luminescence quenching of rare earth ions and greatly reduce the luminescence intensity,so it will increase the transmission loss of devices.In view of these problems in rare earth doped polymer optical waveguide amplifier,self-synthesized Na YF₄:Er³⁺,Yb³⁺nanocrystals were used in this thesis.Based on the luminescence properties of nanocrystals at 1.53?m and 0.53?m under the excitation of 976 nm pump light,polymer optical waveguide amplifiers with two operating wavelengths were systematically studied from the aspects of material design and synthesis,device structure optimization,waveguide process preparation and optimization of pump scheme.The main innovative work is as follows:1.Na YF₄:Er³⁺,Yb³⁺nanocrystals with uniform particle size and high luminescence intensity were synthesized by high-temperature thermal decomposition method.The synthesis conditions of nanocrystals were optimized,and a 1.53?m polymer optical waveguide amplifier was designed and fabricated by selecting the optimum nanocrystals doped SU8 polymer as gain medium.A seven-level model of the erbium-ytterbium co-doped system was established,and the structure size of the waveguide was designed and optimized based on the finite difference method.The gain and noise characteristics of the amplifier were simulated and analyzed.The gain characteristics of forward pump scheme,backward pump scheme,and bidirectional pump scheme were analyzed and compared.According to the simulation results,a waveguide amplifier was designed and fabricated.The transmission loss of the device was about 3.8 d B/cm,of which the absorption loss was 0.6 d B/cm,and the device coupling loss was about 7.7 d B/side.Excitated by a 976 nm pump laser,the gain characteristics for forward pump,backward pump,and bidirectional pump schemes are 12.3 d B,12.6 d B and 13.8 d B,respectively.2.Based on Na YF₄:Er³⁺,Yb³⁺nanocrystals,a 0.53?m polymer waveguide amplifier under 976 nm pump excitation was realized.In this thesis,the nine-level model of erbium and ytterbium ions is analyzed and determined.Combined with atomic rate equation and optical power transmission equation,the gain characteristics of 0.53?m visible optical waveguide amplifier were simulated and optimized.An embedded optical waveguide amplifier was designed and fabricated.The transmission loss of device was about 2.6 d B/cm,and the coupling loss was about 8.4 d B/side.When the signal optical power was 0.1 m W,the relative gain of 4.4 d B was obtained in the 0.8 cm waveguide under the excitation of 976 nm bidirectional pump,which made a breakthrough in the field of green light waveguide amplifier.3.In order to improve the dispersibility of nanocrystals in polymers and reduce the agglomeration of nanocrystals,the Na YF₄:Er³⁺,Yb³⁺NCs-PMMA composites were prepared by co-polymerizing the synthesized Na YF₄:Er³⁺,Yb³⁺nanocrystals with organic monomer MMA.Based on this composite polymer,a polymer waveguide amplifier structure with low loss SU8 polymer as the waveguide core layer,silica as the bottom cladding,and Na YF₄:Er³⁺,Yb³⁺NCs-PMMA composite as the upper cladding was proposed.The gain medium material in the upper cladding was used to realize the amplification of the signal light,which can effectively reduce the transmission loss of signal light.The gain performance of the device was analyzed and optimized.The device was designed and fabricated.The transmission loss of the device was about 2.8 d B/cm,of which the absorption loss was 0.5 d B/cm,and the device coupling loss was about 5.4 d B/side.When excited by 976 nm bidirectional pump,the relative gain of the 2.4 cm device were greater than 10 d B in the range of1520 nm to 1570 nm,and the maximum gain of 17.2 d B was achieved at a wavelength of 1530 nm.Na YF₄:Er³⁺,Yb³⁺NCs-PMMA composite polymer prepared in this thesis can effectively improve the doping concentration of nanocrystals in the polymer,and solve the problems of easy agglomeration and poor stability of nanoparticles in the polymer.Combined with the waveguide structure proposed in this thesis,the gain of the device was effectively improved and the loss of waveguide was reduced,which provided a new research idea for further improving the performance of polymer optical waveguide amplifier.