Research On PbS Quantum Dots-doped Polymer Few-Mode Optical Waveguide Amplifier

In recent years,Erbium-doped fiber amplifiers have a great success in the field of optical communication due to their excellent gain performance in the C band.Researchers are working to develop optical amplifiers into optoelectronic devices and chips which are high-performance,multifunctional,integrated.Doped waveguide amplifiers have attracted wide attention for multi-band optical communication,they have great advantages in terms of gain,bandwidth,selectivity of core layer materials.As well as advantages of high integration and miniaturization,which have become a hot topic in today’s society.With the rapid development of integrated photonics,researchers have been using integrated optical waveguides to construct low power consumption and high stability optical amplifiers.However,owing to the limitation of substrate material and waveguide mode,the output performance of integrated optical waveguide amplifier is still to be improved compared with the developed optical fiber amplifier.To solve this problem,in this paper,the high-gain,multi-mode amplification and compact PbSdoped quantum dot polymer few-mode optical waveguide amplifier are investigated in detail both theoretically and experimentally.The main work and innovations carried out in this paper are as follows.:1.Based on the working principle and theoretical model of PbS quantum dots,the gain calculation method is combined with the optical transmission equation and the atomic rate equation.The modes in rectangular waveguides are analyzed and their orthogonality is proved.Combined with Runge-Kutta method and genetic algorithm,Comsol and Matlab programming are used to obtain the gain characteristics of fewmode PbS quantum dot optical waveguide amplifier are simulated and analyzed.Then the pumping structure is optimized and different pumping modes are combined to achieve the effect of reducing the gain difference among modes.2.Previous researchers have explored doped optical waveguide amplifiers with a core layer material that is generally rare earth ions,but waveguide amplifiers with rare earth ion doped polymers have low gain and limited bandwidth.To solve these problem,we choose PbS quantum dots as the core layer material,which can improve the gain.Meanwhile,compared with mature rare earth ions,PbS quantum dots also have the advantages of wider emission spectrum and larger absorption cross section.3.In terms of experiments,this paper prepared 7×7 μm few-mode optical waveguide amplifiers with silicon as substrate,silicon dioxide as lower cladding,SU-8 doped with PbS quantum dots as core layer,and poly(methylmethacrylate)as upper cladding.Through the analysis of SU-8 UV photosensitivity and PbS quantum dots soluble in water,the process is improved.Instead of using the developer for wet development,the rectangular waveguide is displayed by thermal ultraviolet photobleaching technology,which makes easier to the processing process.4.Compared to single-mode doped optical waveguide amplifiers,less-mode doped optical waveguide amplifiers have some basic indicators such as gain,noise,etc.,but also a unique indicator-Differential Modal Gain.Large differential modal gain affect the effectiveness of the amplifier.Therefore,how to minimize the differential modal gain is also very critical in few-mode PbS quantum dot optical waveguide amplifier.In order to further investigate the gain characteristics of few-mode PbS quantum dot optical waveguide amplifier,the gain characteristics of different modes of the few-mode waveguide amplifier are analyzed and the structural parameters such as pumping power and length are optimized.The pumping structure adjustment scheme is used to achieve gain equalization for different modes in the few-mode waveguide amplifier.