采用提拉法从近化学计量比的熔体中生长出尺寸为φ20mm×60mm的优质LiNbO3:Cr (CLN)晶体,其光学均匀度为7.05E-005.进行了吸收和荧光光谱的测定研究.吸收谱测试表明:Cr3+离子在晶体中有两个宽且强的吸收带及两个微弱的吸收线,两宽带中心波长分别为481和657nm,对应于4A2→4T1和4A2→4T2两个具有相同的总自旋能级之间的跃迁,在4A2→4T2吸收宽带的长波边缘处有个很小的吸收峰,其波长为727nm,对应于4A2→2E(R 线)的跃迁.荧光测试表明:当激发波长为660nm时,CLN晶体荧光宽带和一个较弱的荧光线峰并存,宽带范围为800—982nm,峰值波长为870nm,对应于4T2→2E,4A2的联合能级跃迁,荧光线峰波长约为752nm,其强度较弱,相应于2E→4A2(零声子线)能级跃迁.计算了晶场强度和Racah参数,其Dq,B,C大小分别为1522.1、542.5和3218.7cm-1,Dq/B=2.81, 晶体属于强场介质.研究表明,CLN晶体具备可调谐激光晶体的基本光谱要求,且有良好的物化性能,可以实现宽频带可调谐激光输出.又具有较大的倍频系数,有望实现410nm附近紫外
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 657nm, 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 ^4T_2→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.
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