Investigation Of Ld Pumped Short Pulse Laser Performance Based On Nd³⁺ Doped Strontium Fluoride Disordered Crystal

Ultra fast lasers with high power,wide tuning range and short pulse duration are anticipated to widely applying in the fields of precision industrial processing,controlled nuclear fusion,optical communication and biomedicine.Pursuing the compact,stable ultra high and ultra short laser source have been a urgent demand to the scientific research field.With the preparation technique of the laser diode?LD?improving,ultra short laser deviecs pumped directly by LD with sub-picosecond to tens of femtosecond have been a hot pursuit in the laser field.As a main part of a solid state laser device,laser materials decide its output performance.Until now,Ti:sapphire crystal,generating ultra fast pulse short to several femtosecond by means of self mode-locking,is still the near-infrared laser material with best comprehensive performance and application fields.However,Ti:sapphire should be pumped by the blue light,not suitable for the LD directly pumping,which result in the huge volume and difficult maintaining.This drive the researchers to explore new wide band laser materials which is suitable to be pumped by LD directly.Recently,four-level Nd³⁺ doped fluoride disordered crystals have been a new interest.Fluoride crystals have abundant lattice sites generated by diversified charge compensation,as a result,they have wide absorption and emission band,which are suitable for the LD pumping and generating the ultra short tunable laser.In this dissertation,we investigate the spectrum property of the Nd³⁺ dopd strontium fluoride.End pumped by the LD,we also investigated the ultra fast laser properties.The main contents are listed as follows:1.Review the the properties and applications of ultra fast laser.Analyze the mode locking technique for the laser generation and autocorrelation method for the measurement.Interpret the design of a solid state mode locked laser resonator.Review the wide band Nd³⁺ doped disordered crystals development and the novel nano-materials saturable absorbers.2.Passively Q-switched operation based on Nd,Y:Sr F₂ polycrystalline ceramic.A novel Nd,Y:Sr F₂ polycrystalline ceramic is obtained by using hot pressing processing technique,based on the single crystal.Continuous-wave?CW?and passively Q-switched pulse was generated on the laser ceramic for the first time.Employing a Cr4+:YAG saturable absorber,Q-switched pulse with shortest pulse duration of 169 ns,corresponding single pulse energy of 19.2?J was obtained.3.Ultra fast laser properties of a Nd,La:Sr F₂ disordered crystal.To break the Nd³⁺--Nd³⁺ clusters in Nd³⁺ doped strontium fluoride crystal,we introduce buffer ion—La³⁺.As a result,we obtain wide band disordered structure crystal Nd,La:Sr F₂.For the first time,we systematically investigate the CW,wavelength tuning,passively Q-switching and continuous-wave mode locking?CML?properties on the Nd,La:Sr F₂ disordered crystal.In the CW operation,we obtained maximum average output power of 1.234 W,corresponding slope efficiency of 50.6% laser.The total tuning range up to 24.1 nm with smooth tuning curve.Investigate the nonlinear optical absorption of the gold nanobypyramid?G-NBPs?by a home-made ps laser.Stable Q-switched pulse was generated with 1.15?s shortest duration,by employing the G-NBPs SA.Employing the SESAM mode locker,739 fs mode locked pulse was obtained from the Nd,La:Sr F₂ disordered crystal laser.4.Dual wavelength synchronously mode locked operation on novel Nd,Gd:Ca F₂/Nd,Gd:Sr F₂ crystals.The clusters quenching effect could be alleviated by introducing the buffer ion Gd³⁺ to the Nd³⁺ doped fluoride crystal.Moreover,the lattice sites become more abundant,fluorescence intensity higher and emission line inhomogeneously broadened.Nd,Gd:Ca F₂ and Nd,Gd:Sr F₂ have excellent thermal and optical properties,wide and split spectra make it beneficial to generate ultra short pulse.Pumped by the laser diode,and mode locked by SESAM,dual-wavelength synchronously mode locked operation on the crystals are investigated.As a promising candidate of THz pulse source, dual-wavelength synchronously mode lock laser worth investigating deeply.