| Coherent laser sources emitting mid-infrared(MIR)radiation around 2.7 ?m have recently attracted tremendous attention and become a hot research topic owing to the potential applications in remote sensing,laser surgery,gas monitoring and detection,precision spectroscopy measurement,material processing and countermeasure,etc.With the development of the laser techono logy and the great progress in material science,976 nm diode laser end-pumped Er3+ ions crystallines lasers have been proved to be one of the most effective way for direct 2.7 ?m laser emittion due to the advantages of compact and robust,high conversion efficiency,long working life and various modes of operation(continuous,pulse,Q-switched and mode-locked).In this thesis,we foucus on laser properties of Er,Pr:YLF,Er:LLF and Er:YAP crystals at 2.7 ?m wavelength band,exploring the influence of the co-doped Pr3+ions and the low phonon energy matrix materials on 2.7 ?m MIR spectral characteristics,realizing the continuous-wave(CW)and pulsed laser operation with the three cyrstals.The detailed research contents are as following:1.The applications of 2.7 ?m band laser in biomedicine,gas detection and other fields are summarized and analyzed.The mainly technologies for generating 2.7 ?m band laser are reviewed,especially the research progress of Er3+-doped solid-state crystalline lasers,and pointing out the exsited technical difficulties and problems.In addition,the optimal combination of rare earth activated ions and host materials in 2.7 ?m band is analyzed.Finally,we summarize the research content and significance of this paper.2.The spectral characteristics of Er,Pr:YLF and Er:LLF crystals are measured and analyzed.Results show that co-doping with Pr3+ions can effectively"deactivated" the lower energy level lifetime of Er3+:4I 13/2 laser to alleviate the"self-terminated" effect.And the lower phonon energy of LLF host material is also helpful.Besides,the emission cross sections of Er,Pr:YLF and Er:LLF crystal are calculated by J-O theory and F-L formula.The results indicate that the two crystals are promising candidates for generating 2.7 ?m MIR laser.3.The CW laser performances of LD end-pumped Er,Pr:YLF,Er:LLF and Er:YAP lasers are studied.Based on the analysis of the thermal effect,the CW laser operations of the three crystals are realized,in which the maximum output power of 849 mW is achieved based on Er:YAP crystal with the corresponding slpoe efficiency of 16.8%at 2.71 ?m.4.The study on pulsed laser properties of Er:YAP crystal at 2.7 ?m laser are carried out.Considering that the problems of poor beam quality and low efficiency in the traditional side pumping method of flash lamp,the advantages of pulsed LD end pumping are compared and analyzed.Then,high efficiency and high beam quality microsecond pulsed laser is realized by using Er:YAP crystal.Besides,in passively Q-switching regime,the semiconductor saturation absorption mirror(SESAM)is used as the modulation element to achieve the pulsed laser output with a pulse width of 774.4ns and slope efficiency of 16.8%.Finally,the pulse modulation potential of novel two-dimensional materials(graphene,MoTe2)based saturable absorber at 2.7 ?m band is investigated,where the narrowest pulse width output of 64.85 ns is achieved by using MoTe2.5.The research contents and innovations of this paper are summarized and analyzed. |
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