Luminescence Properties Of Holmium And Erbium Doped SiO₂-PbF₂ Glass

Frequency upconversion technology becomes a popular way to obtain short- wavelength solid-state laser. Price factor is an important factor to limit the universal application of upconversion laser. High price is caused by using expensive single- crystal and longer wavelength solid-state laser as laser medium and pump source, respectively. Purposed to reduce the upconversion lasers price, we selected cheap oxyfluoride glass and 980 nm laser diode as medium and pump source, respectiverly. Studied the luminescence properties of holmium and erbium ions in SiO₂-PbF2 glass under 980 nm diode laser excited.Prepared 0.2%Ho³⁺/16%Yb³⁺codoped and 3%Er³⁺ single doped SiO₂-PbF2 glasses by rapid cooling of the melt. XRD results showed, SOPF: 0.2%Ho³⁺/16% Yb³⁺ sample was completely glass phase, and SOPF: 3%Er³⁺ sample contained someβ-PbF2 nanocrystal. It was said that the transparent oxyfluoride glass ceramic could be prepared without post-treatment. J-O theory was used to characterize the two samples optical properties. Calculated oscillator strength parametersΩλof Ho³⁺ and Er³⁺ ions in SiO₂-PbF2 glasses, and use them to calculate the spontaneous emission probability, branching ratios, theoretical radiative lifetime etc..Studied the upconversion properties of SOPF: 0.2%Ho³⁺/16%Yb³⁺ under 980 nm diode laser excited. Under low-power excited observed the phenomenon that red fluorescence is far stronger than green fluorescence. Using time-resolved curve, power dependence curve, and combining with the theoretical radiative lifetime information, to analysised the upconversion mechanism. The 5F5 level was populated by ETU process from 5I7 level, which was populated through rapid non- radiative relaxation from 5I6 level. The non-radiative rate of SOPF: 0.2%Ho³⁺/ 16%Yb³⁺ sample was very large. And the n value of red fluorescence tended to 0 under larger laser pump power. Establish the rate eauations based on simple three- level system, to analysis fluorescence intensity variation of the laser pump power. The results showed that the light-emitting core temperature were rising with the laser pump power increases, then caused non-radiative relaxation rate increases. The fluorescence intensity would go through enhanced-maximum-weaken process as the laser pump power increasing. The performance of the n value decreased. This interpretation was also supported by the experimental results. Studied the upconversion properties of SOPF: 3%Er³⁺ under 980 nm diode laser excited. Using time-resolved curves, power dependence curve, and combining with the theoretical spontaneous emission probability, branching ratios, radiative lifetime etc, analysised the upconversion mechanism. Conside that the 4F9/2 level was populated through energy transfer process: 4I11/2+4I11/2+4I11/2→4I15/2+4F9/2+4F9/2. The first demonstration of 504 nm fluorescence from Er³⁺ ions was generated by 4G11/2→4I13/2 radiative transitions. The fluorescence quantum efficiency of 4F9/2 level reached to 95.4%. Obtained the full wave at half maximum (FWHM) was 69 nm, emission cross section (σe) was 0.55×10-20 cm², fluorescence lifetime (Ï„m) was 8.93±0.03 ms, and the fluorescence quantum efficiency (η) was 100% of the 1550 nm fluorescence of Er³⁺ ions in SOPF glass ceramic. Definited the gain parameter C=FWHM×σe×τm, to characterize the material gain bandwidth of optical amplification and amplification ability. The C value was 338.9×10-6 nm3?ms for this sample and it was the biggest as we know.