Study On Pulsed Laser Of Dissipative Soliton With Extreme Spike Generation Method Based On Algaas Waveguide Array

Space exploration missions such as satellite-based time reference synchronization and gravitational wave detection have put forward higher technical requirements for the pulse energy and volume of the pulse laser.In the conventional technique,it is necessary to amplify the seed source at one or more stages,which undoubtedly increases the complexity of the light source device and occupies more space and power resources.In order to improve the output pulse energy from seed source directly,relevant scholars employed the Ginzburg-Landau equation as the foundation and predicted the existence of Dispassive Soliton with Extreme Spike,which is a new kind of optical pulse with high energy.Al Ga As waveguide array based fast saturable absorption method has the advantages of optimizable structure parameters and high damage threshold,making it possible to generate Dispassive Soliton with Extreme Spike in the experiment.But there is no clear saturable absorption model quantitatively describing the energy coupling process in waveguide array.It is difficult to design and optimize the structure and material parameters of waveguide array.Aiming the problems above,this subject proposes a fast saturable absorption model based on the energy coupling of Al Ga As waveguide array.Based on this model,an optimization method for saturable absorption characteristics is proposed.A pulse laser generation system is established to verify the above method,and the equivalent modulation depth of the Al Ga As waveguide array is improved,and Dispassive Soliton with Extreme Spike is observed for the first time.The main research works are as follows:In order to solve the problem that the quantitative model of equivalent saturable absorption process of Al Ga As waveguide array is missing and it is difficult to design the material&structure parameters of the waveguide array,a fast saturable absorption model based on the energy coupling of Al Ga As waveguide array is proposed.The model based on mode coupling theory is to deduce the function relationship among the coupling coefficient of Al Ga As waveguide array,the refractive index of waveguide array materials and geometric structure parameters.By solving the nonlinear Schr?dinger equation,the influence of coupling coefficien t,nonlinear coefficient and multiphoton absorption coefficient on the coupling process of electromagnetic energy in the waveguide array is analyzed.The energy transmittance curve of the central waveguide is equivalent to the saturable absorption transmittance curve under different incident light power,and a complete theoretical model between the basic physical parameters and the equivalent saturable absorption parameters of the waveguide array is established.The model can be used to model and analyze the equivalent saturable absorption process of energy in Al Ga As waveguide array with different structure and material properties,which provides theoretical support for the systematic design of basic physical parameters of waveguide array.In order to solve the problem that the saturable absorption characteristics of Al Ga As waveguide array is difficult to be optimized due to the difficulty of multiple parameters in the saturable absorption model due to their interrelation and decoupling,an optimization method of saturable absorption characteristics based on parameter mapping and sensitivity analysis is proposed.The method based on parameter mapping theory establishes a three-level mapping model of the basic physical parameters,the energy coupling parameters and saturable absorption parameters.Quantitative calculation of the sensitivity of each map path and actual preparation process of the Al Ga As waveguide array are also taken into consideration.Key physical parameters with high efficiency and low operation difficulty are selected to find out a local optimal solution.According to the saturable absorption model of Al Ga As waveguide array,an optimization strategy is developed to reduce the multi-photon absorption effect from the aluminum concentration of the core layer,enhance the nonlinear effect from the etching depth of waveguide,and adjust the coupling coefficient from the spacing of waveguide to improve the modulation depth.Experimental results show that the modulation depth of Al Ga As waveguide array is increased from 17% to 35% after the optimization process of this method.In view of the fact that the pulse energy of Dispassive Soliton with Extreme Spike is expected to break through the limitation of the traditional soliton area theorem,but there are no experimental results,the pulsed fiber laser satisfying the condition of Dispassive Soliton with Extreme Spike is analyzed.Based on the analysis from the pulsed laser rate equations and the inequality condition of Q-switched mode-locked pulse,the key factors to restrict the pulse energy are the modulation depth of the saturable absorption effect and cavity pump power.Considering that the nature of Dispassive Soliton with Extreme Spike is Q-switched mode-locked pulses with special spike envelope,a large modulation depth and a high pump power are the basic condition of generating Dispassive Soliton with Extreme Spike.Then by analyzing the influence of the coefficients of the Ginzburg-Landau equation on the solution results,the parameters of the lase r cavity meeting the requirements of generating Dispassive Soliton with Extreme Spike are obtained.Finally,according to the content above,the material and structural parameters of the waveguide array are optimized,and a pulsed fiber laser generation system based on the waveguide array is built.When the waveguide array with modulation depth of 17 % is used as the saturable absorption device,and the single pulse energy of the traditional Q-switched mode-locked pulse is 0.45 n J.When the waveguide array with modulation depth of 35 % is used as the saturable absorption device,the generation of Dispassive Soliton with Extreme Spike is observed for the first time in the experiment.The single pulse energy of Dispassive Soliton with Extreme Spike is2.38 n J.The geometric size of the Al Ga As waveguide array is 8 mm×10 mm×0.35 mm,which is favorable for integration with other micro-nano optical devices.