Research On 1550 Nm Ultrashort Pulse Self-Similar Fiber Amplification System

Ultrashort pulse lasers are widely used in scientific research,industrial processing,military,biological,medical and other fields.Among many ways of generating high-power ultrashort pulse laser,the main oscillation power amplification technology has the advantages of relatively simple structure,easy integration,high stability,low cost and high energy.At the same time,self-similar pulse amplification technology has gradually been widely recognized and applied because of its own advantages.For example,it can support high pulse energy,and the output result is independent of the shape of the incident pulse.It can also amplify the pulse power and broaden the pulse spectrum at the same time.In addition,linear chirp will be generated in the process of pulse amplification,which is very convenient for subsequent pulse compression,and can obtain high-power,high-energy ultrashort pulse laser output at the same time.In this paper,self-similar pulse shaping and power amplification of soliton pulse are realized by using self-similar pulse amplification technology.The main contents of this paper are as follows:1.This paper summarizes the characteristics and development history of ultrashort pulse laser and ultrashort pulse fiber amplifier,introduces and compares several common pulse amplification technologies and pulse compression technologies,and focuses on the characteristics,advantages and development status of self-similar pulse amplification technology applied in this paper.2.Based on the nonlinear Schrodinger equation,the asymptotic solution of self-similar parabolic pulse is derived,and the formation and characteristics of self-similar parabolic pulse are analyzed.The effects of dispersion,gain,nonlinear effect and limited gain bandwidth on the transmission of ultrashort pulse laser in optical fiber are introduced.The principle of pulse compression is also described.The amplification and pulse compression process of ultrashort pulse erbium-doped fiber self-similar amplification system are simulated.The oscillation stage is an ultrashort pulse fiber laser with center wavelength of1550 nm,repetition rate of 44 MHz,output power of 0.45 m W and pulse width of 750 fs.The evolution of pulse and spectrum in the process of pre-amplification and main amplification with different length of gain fiber and different output power are simulated and analyzed.Then,the pulse compression process is simulated by ordinary single-mode fiber.The simulation results finally obtain the ultrashort pulse laser output with average output power of 58.79 m W and pulse width of 51 fs,which provides a valuable guidance for subsequent experiments.3.An ultra-short pulse erbium-doped fiber self-similar amplifier is designed and built.Firstly,an ultra-short pulse erbium-doped fiber laser based on Mode-Locked carbon nanotube saturable absorber is designed as the seed source;Then,in the pre amplification stage,the hyperbolic secant seed pulse is shaped into a self-similar parabolic pulse through a section of erbium-doped fiber with high positive dispersion;In the main amplification stage,a high gain erbium-doped fiber is used to realize power amplification and spectral broadening;Finally,the pulse compression is completed through a section of ordinary single-mode fiber.We broadened the spectral width from 3.89 nm to 61.69 nm,amplified the average output power from 0.43 m W to 60.14 m W,and the amplification gain was 21.46 d B.Finally,we obtained the ultrashort pulse laser output with peak power of 16.85 k W and pulse width of 83 fs at the central wavelength of 1563.9 nm.