Growth and Spectrum Characteristics of LiNbO_3:Cr Crystal

The LiNbO3:Cr crystals with the sizes up to φ20mm × 60mm were grown by the Czochralski technique. The absorption spectrum shows that there are two strong absorption wideband peaks and one weak absorption peak belonging to Cr3+ ion in the crystal. The peak values of two strong absorption wideband peaks are 481nm and G57nm, which correspond to 4A2 → 4T1 and 4A2 → 4T2 transitions, respectively. The weak absorption peak at 727nm corresponds to 4A2 → 2E (R line) transition; The fluorescence spectrum shows that one emission wideband peak ranging from 800nm to 982nm coexists with one weak emission peak at 750nm corresponding to 4T2 → 2E transition. The peak value of emission wideband is 870nm, which corresponds to 4T2 →4A2 transition. The crystal field and Racah parameters were calculated, the values of Dq, B and C are 1522.1, 542.5 and 3218.7cm-1, Dq/B=2.81 indicates that it has an stronger crystal field. The result shows that the wideband tunable laser can be gotten from this crystal because it not only has the necessary spectra characteristics required for tunable laser crystal but also has the good physics chemical properties. Furthermore, the UV laser at about 410nm can also be gotten from the crystal by its self-frequency doubling because it has a higher frequency-doubling coefficient.