Research On The Generation Of Ultrashort Pulse Laser Based On Hybrid Locking Device

Ultra-short pulse mode-locked fiber laser has been extensively investigated due to its applications in laser physics,material science,nanotechnology and biomedicine,etc.This type of laser is simple,compact,and easy to integrate and can obtain high quality pulse.Compared with active technique,passive technique fiber lasers is more reliable with great developments in recent years.In all kinds of nonlinear optical element,different saturable absorbers(SA)can be a destructive approach to obtain ultra-short pulses.We can add some two-dimensional materials with good optical performance as SA in laser cavity.The common saturable absorber mainly include TI(Topological Insulator),Bi2Te3,Bi2Se3,Sb2Te3 and two-dimensional nonlinear materials WS2,MoS2,etc.These materials have many features such as adjustable nonlinear absorption coefficient,short relaxation time,recovery time,and low optical loss.So these compounds can be added into the laser as the SA absorption material to get high power,wide band hybrid mode locked pulse light source.Due to the good semiconductor performance and special internal electronic arrangement of the graphdiyne(GD),it is expected to be used in the field of ultra-short pulse laser as a new nonlinear optical device.Therefore,we add the graphdiyne saturable absorber(GD-SA)material into the nonlinear polarization rotation(NPR)ring cavity,getting the more stable ultra-short pulses with the combined effects of saturable absorber and Polarization dependent isolator(PD-ISO).(1)In the first chapter of this paper mainly introduces the research background and the latest research progress of fiber lasers,this paper demonstrates the applications of ultra-short pulse fiber laser in various fields,and analyses the research significance and development prospect of ultra-short pulse fiber laser for the development of the future technology.(2)The second chapter,first of all,I theoretically analyze the mechanism of ultra-short pulses formation based on nonlinear polarization rotation erbium-doped fiber laser.Secondly,by the experiment I qualitatively analyze the output spectrum,autocorrelation trace,and RF spectrum,the relationship between the width of 3 dB spectrums,the variation of the pulse width and the output power with the increase of pump power based on the NPR technology.Finally,we obtain the 3 dB spectrum width of 7.7 nm,repetition frequency rate of 14.9 MHz,signal noise ratio(SNR)of 45.4 dB,and the pulse width of 749.8 fs ultra-short pulse.(3)The third chapter firstly introduces the semiconductor saturable absorption mirrors(SESAM),graphene,carbon nanotube(CNT)and topological insulators(TI)as the saturable absorber in the application of the fiber laser and their research background.Then I add GD-SA based on the nonlinear polarization rotation(NPR)technology,and study the impact of GD-SA on the NPR cavity in the total cavity length of 14.68 m.Obtaining the center wavelength of 1530.7 nm,repetition frequency of 14.7 MHz,signal-to-noise ratio of 40 dB,3 dB spectrum width of 7.4 nm,and pulse width of 690.2 fs ultra-short pulse output.In addition,in the high power condition,the bound state soliton mode-locked pulses are obtained.Finally,we compared the experimental data of the two groups.(4)The fourth chapter mainly studies the GD-SA the preparation and characterizations,two methods are provided for the preparation of SA,GD-SA is mainly prepared by liquid phase deposition and rotary coating.One method is drop the GD solution into the fiber tail end using the liquid phase deposition;the other is made the solution into film using rotary coating method.The Raman spectrum,SEM of GD,UV-visible-infrared detection and nonlinear transmittance are also represented.(5)The fifth chapter summarizes the research contents.The main research results and the problems that need to be solved are summarized,and the future work is prospected.