| Solid-state lasers have a wide range of uses in military,medical,scientific research,and industrial processing.Nd3+ ion laser crystal has always been one of the most important working materials for solid-state lasers.Over the past few decades,various Nd3+-doped laser materials have been gradually developed.The traditional Nd3+ ion laser materials are mainly single-crystal materials,such as Nd:YAG/YLF/GGG and so on.In recent years,various mixed crystals have gradually attracted the interest of researchers due to their unique advantages in the spectrum.Such mixed crystals are a mixture of a plurality of crystals having a similar lattice position or a plurality of ions having the same valence occupying the same lattice position and having a disordered structure like vitrification.For example,in the process of growing YAG single crystals,two ions,Gd3+ and Lu3+,are added to compete for crystal lattice positions with Y3+ ions.The mixed crystal laser crystals formed include GdYAG,LuYAG,and GdLuAG.Mixed crystals not only have the advantages of single crystals in optics,but also have a broad spectrum of absorption and emission due to their highly asymmetric chaotic structure.They have certain advantages in the selection of excitation sources and the tuning range of tuning lasers.This dissertation mainly studies the laser performance of Nd:GdYAG mixed crystals.Firstly,the theoretical model of rate equation was established.The characteristics of two kinds of saturable absorbers Cr:YAG and Co:LMA were combined,and the laser operation characteristics of multi-wavelength competition and Q-switched modes were simulated with matlab software.Second,the absorption and emission spectra of Nd:GdYAG mixed crystals were measured and analyzed.Finally,the continuous wave and Q-switched laser characteristics of Nd:GdYAG mixed crystals at 1.06 ?m and 1.3 p,m were experimentally studied.For the continuous wave laser,in the free running condition,a 1064 in single-wavelength laser was firstly obtained,with a maximum output power of 4.01 W and an oblique efficiency of 39.7%.By inserting an etalon in the cavity,the high gain 1064 nm emission peak is suppressed,and the laser output is also obtained at other low gain emission peaks.Among them,the single-wavelength lasers have 1052 nm,1061 nm,and 1073 nm,and the corresponding maximum output powers are 2.16 W,2.88 W,and 2.66 W respectively.The corresponding oblique effects are 23.9%,28.1%,and 26.6%;two-wavelength lasers have(1052 nm,1064 nm),(1052 nm,1073 nm),(1061 nm,1064 nm),(1064 nm,1073 nm),and the corresponding maximum output power and slope efficiency are(1.34 W,14.9%),(1.80 W,18.7%),(1.91 W,18.5%),(1.92 W,18.6%).These two-wavelength lasers have been validated by the extra-cavity sum frequency method.A Cr:YAG saturable absorber was inserted into the cavity to achieve a 1.06 ?m Q-switched laser.Among them,in the case of initial transmission TO ?95.55%,the maximum output power is 1.51W,the slope efficiency is 15.8%,and the repetition frequency,pulse width,pulse energy,and peak power are 56 kHz,14.7 ns,27.0 ?J,and 1.84 kW,respectively..With an initial transmission rate of T0=74.11%,the maximum output power is 1.02 W,the slope efficiency is 14.4%,and the repetition frequency,pulse width,pulse energy,and peak power are 7.6 kHz,6.78 ns,134.2 ?J,and 19.8 kW,respectively.The 1.3 ?m continuous wave laser first obtained a maximum output power of 3.12W,an oblique efficiency of 29.3%,and an output wavelength of 1338 nm.Secondly,the same laser tuning experiment was performed.The obtained single-wavelength lasers were 1318 nm,1334 nm,and 1356 nm.The corresponding maximum power and slope efficiency were(2.33 W,22.6%),(1.63 W,16.9%),and(1.83 W,18.3).%);multi-wavelength lasers have(1318 nm,1338 nm),(1318 nm,1356 nm),(1338 nm,1356 nm)and(1318 nm,1338 nm,1356 nm),and the corresponding maximum power and slope efficiency are(2.04 W,20.4%),respectively.(1.63 W,16.7%),(1.81 W,18.8%)and(1.44 W,15.5%).A Co:LMA saturable absorber was inserted into the cavity to achieve a 1.34 ?m Q-switched laser.The maximum output power is 0.329 W,and the repetition frequency,pulse width,pulse energy,and peak power are 99 kHz,366 ns,3.32 ?J,and 9.07 W,respectively. |
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