| Because 2μm is in the human safe band and wake atmospheric absorption band,2μm laser has unique advantages in medical treatment,material processing,laser ranging,free space optical communication and other fields.Greenhouse gases have a strong absorption peak for 2μm,such as carbon dioxide,water molecules and carbon monoxide,so it is of great significance to study the 2μm laser for the monitoring of greenhouse gases.In order to satisfy the application needs of various fields,it is very necessary to research the high power 2μm laser.In this paper,doped holmium yttrium lithium fluoride(Ho:YLF)crystal are studied for high power Ho:YLF slab continuous-wave laser and high energy Ho:YLF laser amplifier.Firstly,the research background of 2μm solid laser is presented and the research progress is introduced;the physical and spectral properties of the Ho:YLF crystals are analyzed;the quasi-two-level rate equation model of Ho:YLF slab laser is established to analyze the influence of different factors on the laser output performance;the thermal effects of Ho:YLF slab crystals are analyzed under different conditions,including temperature distribution,stress distribution and thermal lens effect.Secondly,an experimental study is performed on the high power Ho:YLF slab laser,the design method of the coupled system is introduced,the effects of different doping concentration on the laser output power and absorbed pump power are compared.The emission spectra、the maximum power stability and the beam quality factors are also studied.The experimental results show that the Ho:YLF continuous-wave slab laser of 1at.%concentration has higher output power and better absorption efficiency of the pump power.The maximum output power of 125 W is obtained with the incident pump power of245 W.The slope efficiency with respect to the incident pump power is 62.5%,and the optical-to-optical conversion efficiency is 51%.The central wavelength of laser is 2064nm.The RMS instability of the maximum output power is measured to be 0.24%in 30min.The beam quality factors M~2are 475 and 1.59 in the x and y directions,respectively.As far as we know,this is the first report for Ho:YLF laser oscillator to reach hundred-watts-level output power.Finally,the principle of plate amplifier is introduced and the design method of multi-pass amplification is introduced,and then the experimental study of 2,4 and 6 range Ho:YLF slab amplifier is conducted.The experimental results show that properly improving the seed optical energy density can effectively improve the extraction efficiency of the amplifier. |
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