Investigation Of Laser Diode Pumped Ultrafast Laser Performance Based On Fluoride Disordered Crystal At 1?m Band

Ultrafast laser technology with artificial crystals as the core is developing toward ultrafast and ultra-intensive.Ultrafast lasers with narrow pulse width,high peak power and high repetition rate could stimulate medical,optical communication,micro machining,and promote the developments of many natural basic sciences such as physics,materials,chemistry,biology,and so on.It has crucial practical value to realize compact,efficient and low cost all solid-state lasers with diode laser pumped?LD?light source,which has become a hot spot of researches.The high thermal conductivity crystal materials with wide spectrum characteristics and suitable for LD pumped are the core and motive force to promote the developments of miniature all solid-state ultrafast laser technology.The fluoride crystals doped with rare-earth ion have gradually become the mainstream of the research of all solid state passively mode-locked lasers domain.The multiple local coordination structure provides the potential of wide spectral properties for the rare-earthion doped fluoride crystals,which makes it have the same physical properties as ordered crystals and a larger emission cross section at the macro level,but a disordered structure at the micro level.Therefore,this kind of crystals is a very interesting type of ultrafast crystals.Since 2003,it has been found that co-doped charge compensating ions in Yb:CaF₂ crystals can effectively regulate their quantum efficiency and spectral properties.Increasingly researchers have focused their researches on the structure design of laser crystals by adding buffer ions M⁺?Na⁺,K⁺,etc.?or Me³⁺(Y³⁺,Lu³⁺,La³⁺,etc.)to meet the requirements of continuous-wave laser,tunable laser,short pulse laser and ultra short pulse laser performances.In this dissertation,we investigated the spectral characteristics,continuous-wave laser characteristics and tunable laser characteristics of Nd³⁺-doped calcium fluoride crystals and Yb³⁺-doped strontium fluoride crystals with Gd³⁺as buffer ions.Combined with the new saturable absorbers and SESAM,the LD pumped nanosecond short pulse and the sub-picosecond ultra short pulse laser operations are implemented.The main contents include the following parts:1.The background and significance of researches on the ultrafast lasers were expounded.Many progresses of ultrafast laser technology in the 1?m band were summarized.The principle of mode-locked laser,the design concept of mode-locked laser resonant cavity and the dispersion calculation were elaborated.The performances and research progresses of fluoride laser crystals doped by Nd³⁺and Yb³⁺were investigated and studied.The parameters of ultrafast laser crystals suitable for mode-locked laser operation were obtained by testing the continuous-wave laser properties.The characteristics of different types of saturable absorbers were summarized,and the advantages of the silver nanorods materials as a saturable absorber in the field of all solid state laser were analyzed.2.LD pumped tunable and ultrafast laser performances based on Nd,Gd:CaF₂ crystals.The spectral characteristics and wavelength tunability of Nd,Gd:CaF₂(0.5%Nd³⁺,5%Gd³⁺:CaF₂;0.5%Nd³⁺,8%Gd³⁺:CaF₂)crystals were comprehensively characterized based on different concentrations.Thedualwavelengthmode-locked?ML?laseroutputof0.5%Nd³⁺,8%Gd³⁺:CaF₂ crystal was achieved,and the center wavelengths were 1065.45 nm and 1066.48 nm,respectively.Compared with 0.5%Nd³⁺,5%Gd³⁺:CaF₂ crystal,the performance of mode-locked laser was optimized,and the average output power was increased to 394 mW.3.Investigation of LD pumped tunable and ultrashort pulsed lasers performances based on Yb,Gd:SrF₂ crystal.[Yb³⁺-Yb³⁺]_n cluster structures and non-activated Yb²⁺ion pairs are easily broke by introducing buffer ions,which can significantly improve the conversion and emission efficiency and broaden the emission spectrum.LD end-pumped Yb,Gd:SrF₂continuous-wave laser output was achieved.Maximum average output power of 3.92 W was obtained,delivering slope efficiency of 58.7%.The tunable laser characteristic of Yb,Gd:SrF₂crystal was studied for the first time using a birefringent filter with a thickness of 1 mm.An about 61.08 nm continuously tuning range from 1020.23 nm to 1081.31 nm was obtained.Using a semiconductor saturable absorber mirror,the LD pumped passively mode-locked pulse laser with pulse width of 951 fs was realized.The highest average output power recorded was 296 mW.And the laser wavelength peaked at 1046.04 nm with a full width at half maximum?FWHM?of 4.13 nm4.Investigation of passively Q-switched pulsed laser based on silver nanorods saturable absorbers.The silver nanorods?SNRs?with a longitudinal surface plasmon resonance?SPR?absorption peak at 1.06?m band was synthesized through a seed-mediated growth method,and the nonlinear optical properties such as modulation depth,saturation loss and saturation intensity were also characterized.The performance was investigated in a passively Q-switched?PQS?Nd:Y₃Al₅O₁₂?YAG?ceramic laser for the first time.Stable pulse trains with a pulse width of 197 ns were obtained.For the case of passively Q-switched operation,the single pulse energy and peak power of 0.51?J and 2.59 W were generated with a repetition rate of 223.7 kHz.Combined with the novel Nd³⁺-doped calcium fluoride crystals,we obtained a LD pumped passively Q-switched Nd,Gd:CaF₂ crystal laser output for the first time.And its pulse laser performances have been studied comprehensively and systematically.The highest average output power and shortest pulse width recorded were 116 mW and 1.046?s,respectively.Repetition rate and single pulse energy were calculated to 53.92 kHz and2.15?J,respectively.