Ultra-short Pulse Laser Based On Mxene Saturable Absorber

Due to the advantages of high peak power,short pulse duration and wide spectral range,ultrashort pulse laser has attracted a lot of attention and research.At present,ultrashort pulse laser has a wide range of application prospects in cold processing,medical treatment,national defense,precision micro processing,scientific research and other fields.The main technology to realize ultrashort pulse is passive mode locking,and the saturable absorber is its key device.At present,the device that has been commercialized is the semiconductor saturable absorption mirror（SESAM）,which is monopolized by foreign manufacturers,and has the problems of complex manufacturing process,high cost,narrow bandwidth and so on.People have been committed to the development of new saturable absorbers.As a new class of two-dimensional materials,two-dimensional transition metal carbides（mxene）are expected to be used to prepare a new generation of optical devices with ideal broadband saturable absorbers.It is of great significance to study the preparation of new saturable absorbers based on mxene and develop the ultrashort pulse laser technology.In this paper,the ultrashort pulse laser technology and mxene as a new saturable absorber are studied.In the aspect of laser,the thesis mainly studies the femtosecond laser with Ti:sapphire Kerr lens self-locking mode;in the aspect of new two-dimensional nano materials,it mainly explores the preparation of mxene new saturable absorber,and the experimental research of ultrashort pulse laser based on the saturable absorber.The main contents of this paper are as follows:1.Study on Mode-Locked second laser with Ti:sapphire Kerr lens.In this paper,the propagation circle method is used to dynamically analyze the evolution process of the beam radius in the mode-locked cavity of the Kerr lens,and the equivalent laser cavity which is easy to realize the mode-locked of the Kerr lens is determined by this method.The specific parameters of the cavity are calculated by combining the ABCD matrix.According to the calculated cavity data,a Ti:sapphire ultrashort pulse laser is built.In the cavity,a prism pair and chirped mirrors are used to compensate the dispersion.Finally,a ultrashort pulse laser with a central wavelength of～803nm,a FWHM of 4.71nm,a pulse width of 179fs and an average output power of 280m W is obtained.2.Experimental study of a novel two-dimensional material MXene saturable absorber in solid-state lasers.MXene has good hydrophilicity.Liquid MXene saturable absorber with heavy water as solvent is prepared and applied in Nd:YAG laser.Stable Q-switched pulse output is achieved.Q-switched laser with pulse width of 1.5μs,repetition frequency of 65.79k Hz and maximum output power of 100m W is obtained.In addition,two-dimensional material MXene is spun on the end mirror of Ti:sapphire laser to achieve stable Q-switched mode-locked output.The pump power of 4.5w corresponds to the average output power of 113mw.3.In view of the problems of easy absorption and low damage threshold in saturable absorption,sol-gel method is used to mix the ethyl silicate,ethanol and water in proportion to 1:4:8 to prepare sol-gel.The MXene nanosheets were doped into the sol to form a MXene saturable absorber in the gel state and an ultrashort pulsed fiber laser based on MXene sol-gel saturable absorber was studied.The pulse with repetition rate of 8.6MHz and pulse width of 819fs is obtained.The central wavelength is near 1552nm and the spectral 3d B bandwidth is 4.3nm.4.MXene films were prepared by pulse laser deposition（PLD）.The conventional method to prepare two-dimensional mxene is to etch MAX with HF,which is highly toxic and corrosive.This method has a long preparation time and a high risk factor.Pulse laser deposition technology has the advantages of fast deposition rate,simple target fabrication and safe and controllable deposition process.Under the condition of pulse energy of 400m J,450m J,target base distance of 3cm,pulse frequency of 10Hz and substrate temperature of 750℃,W₂C films with good crystal quality were obtained after one hour deposition.The reflectivity of the film is 56.5%at 800 nm and 79.6%at2000 nm.