| 2?m laser is widely used in precision measurement,environmental monitoring,industrial processing,laser medical treatment,lidar and other fields because its central output wavelength is in the absorption peak of water molecules and eye safety spectrum,and at the same time is in the strong absorption band of the main components of the atmosphere.In recent years,Yb,Ho co-doped 2?m solid-state laser has great development potential due to the development of different technical fields,and as a main output way of 2?m laser,it has become a new research hotspot.In view of this,the laser output characteristics of Yb,Ho:LuVO4,Yb,Ho:YVO4 and Yb,Ho:GdVO4 crystals are studied in this paper.Firstly,the absorption spectra and fluorescence spectra of the three crystals were measured,and the stimulated emission cross sections were calculated.It was clear that there was a strong absorption peak in the 2?m band,and the optimal pump wavelength range of different axial cutting crystals was predicted.The energy level transition theory and laser generation mechanism of Yb,Ho co-doped crystals are described theoretically.The rate equation model of end pumped CW Yb,Ho laser is established.On this basis,the laser output characteristics of Yb,Ho:LuVO4 crystal are numerically simulated.The numerical simulation results show that when the laser reaches the maximum conversion efficiency,the corresponding optimal output mirror transmittance is between 3%and 5%,and it is found that the product of crystal length and concentration is about 30.At the same time,in order to ensure the safety of laser crystal in the resonant cavity,the thermal effect theory of Yb,Ho co-doped laser crystal is studied,which provides the basis for the selection of cooling mode of laser crystal.Secondly,on the basis of theoretical research,a diode laser with the central output wavelength near 980nm is selected as the pump source.The crystal parameters,focusing coupling parameters and resonator parameters of Yb,Ho laser are determined,and the reasonable resonator structure is designed.The continuous wave mode laser output performance of Yb,Ho co-doped vanadate crystal is deeply studied.The results show that the output power of the Yb,Ho:LuVO4 laser is 709mw when the output mirror transmittance is 5%and the cavity length is 65mm,which is the maximum reported in the current literature.The corresponding optical to optical conversion efficiency is 12.94%,and the central output wavelength is 2059.76nm.For the first time,314mw and 132mw power outputs are obtained with Yb,Ho:GdVO4 and Yb,Ho:YVO4 as the working medium when the output mirror transmittance is T=5%and the cavity length is L=55mm.The corresponding conversion efficiency is 5.73%and 3.12%,and the central output wavelengths are 2055.28nm and 2054.88nm.These CW Yb,Ho co-doped vanadate lasers can be used as new light sources in the field of special processing,environmental monitoring and laser medical treatment.Finally,based on the experimental study of Yb,Ho co-doped vanadate in CW mode,the passive Q-switched mode laser output of Yb,Ho:LuVO4 crystal was studied with SESAM as saturable absorber.The output power of Yb,Ho co-doped vanadate crystal passively Q-switched mode is obtained for the first time.The average output power is 45mW,the corresponding optical to optical conversion efficiency is 1.50%.The output wavelength of the laser is 2044.42nm,the narrowest pulse width is 100ns,the maximum single pulse energy is 12.61nJ,and the maximum peak power is 58.5mW.This passively Q-switched laser has potential applications in lidar and remote sensing.In this paper,three new 2?m CW mode laser devices and a new passive Q-switched mode operating laser device are obtained,which provide a new high-quality 2?m laser source for precision measurement,environmental monitoring,industrial processing and other fields. |
PDF Full Text Request