Fabrication Of Ho(Yb):CaF₂ Transparent Ceramics And Research Of Its Mid-infrared Spectrum Properties

The 2-5?m mid-infrared laser has good atmospheric transmittance,overlaps with the strong absorption peak position of water and has a high absorption rate for most organic molecules.At the same time,the band also contains the characteristic radiation wavelength of some important military weapons.Therefore,mid-infrared laser has important application value and prospect in communication,remote sensing,surgical treatment,military and other fields.Rare earth elements have been widely studied and applied to doped ions of the working materials of solid lasers in recent years because of their abundant energy levels and the electron transitions between different energy levels can emit light at different wavelengths.For example,Ho³⁺ions,the energy level transition from ⁵I₇ to ⁵I₈ corresponds to the luminescence of 2.0?m,while the energy level transition from ⁵I₆ to ⁵I₇ corresponds to the luminescence of 2.8?m.In addition,Ho³⁺ion also has the advantages of large excitation area and long lifetime of the upper energy level of the laser.Ho³⁺ion is the ideal activation ion for 2-3?m medium infrared solid laser.The matrix material of a solid state laser has a very important effect on the performance of the laser,As transparent ceramics have outstanding advantages over single crystal and glass,this paper chooses transparent ceramics as the research object1.Ho:CaF2 nanopowder was prepared by chemical coprecipitation.The doping concentrations of Ho³⁺ions were 0.5 mol%,1 mol%,2 mol%,3 mol%and 5 mol%,respectively.Through hot pressing sintering calcined the series of prepared nanopowders into ceramics.The SEM of the ceramics show that with the increase of the concentration of Ho³⁺ions,the grain size of the ceramic decreases first and then increases.The fracture mode changed from intergranular fracture to transgranular fracture.In terms of fluorescence spectrum,with the increase of the Ho³⁺ions doping concentration,the fluorescence intensity first increased and then decreased which reached the maximum when the doping was 2 mol%.The number of splitting peaks decreases.The fluorescence lifetime curve shows a trend of decreasing lifetime with increasing Ho³⁺ion doping concentration.The results indicated that Ho:CaF₂transparent ceramic is a potential candidate for 2.0?m laser emission materials.2.However,due to the current Ho³⁺ion absorption band and the current common commercial laser diode pumped output wavelength(808nm,980nm)can not match,resulting in the Ho³⁺ion as the laser gain medium laser development is relatively slow.It is planned to introduce sensitized ion Yb³⁺to improve the absorption efficiency of pump light by using energy transfer.First,Yb,Ho:CaF₂ nanopowder was prepared by chemical coprecipitation.The doping concentration of Ho³⁺ions remained 1 mol%.Yb³⁺ion doping concentration were set to 1.0 at.%,3.0 at.%,5.0 at.%,7.0 at.%,9.0at.%.The Yb,Ho:CaF₂ ceramics with different Yb³⁺ion doping concentrations were sintered by vacuum hot pressing process to obtain transparent ceramics.The absorption curve showed that the doped Yb³⁺ions could improve the absorption capacity of Ho:CaF₂ ceramics to 980 nm pump light,and the absorption peak gradually increased with the increase of Yb³⁺ion doping concentration.The fluorescence spectrum shows that with the increase of Yb³⁺ion doping concentration,the luminous intensity at 2.8?m gradually increases.