极化子荧光及其断层扫描对Ti:LiNbO3光波导表征研究

小极化子(Nb⁴⁺_Li)荧光处于700—950 nm谱段，对不同化学还原程度同组分的纯铌酸锂晶体的研究表明荧光的强度反映了化学还原程度的强弱.从小极化子浅层能级出发，提出以“1中心3级态跃迁”来描述小极化子的受激荧光过程.钛扩散铌酸锂光波导(Ti：LiNbO₃)表面还原程度的均匀性可能在波导制造的热扩散过程中被破坏.在对铌酸锂波导表面、深部的扫描结果中，荧光的强度呈现出表面与深部、波导内与外的差异，表面的强度是深部的6—8倍.研究表明，利用非损伤性的极化子荧光谱，对加工过程热处理进行检控是非常有效的.同时，波导内与外的荧光强度差异间接反映了波导的横切面的外形.

Polaron fluorescence and tomograpy of Ti:LiNbO3 waveguide

The small polaron Nb⁴⁺_Li fluorescence spectrum is in the range of 700—950 nm. Researches of the pure lithium niobate samples with the same composition and different reduction degrees show that the intensity of the fluorescence spectrum reflects the chemical reduction degree of the material. From the shallow level of small polaron, we propose a model of “one center and three energy level” to explain the process of polaron fluorescence. For titanium-diffused lithium niobate (Ti：LiNbO₃), homogeneity of the chemical reduction level would be destroyed during fabrication. From the scans of Ti：LiNbO₃ waveguide sample, the intensities of fluorescence spectrum on the surface and in the bulk, as well as inside the waveguide and outside the waveguide, are evidently different (intensity on the surface is 6—8 times of that in the bulk). Our researches indicate, using the non-destructive technology of polaron fluorescence spectrum is effective to control the necessary heat treatment in the waveguide fabrication processes. At the same time, the difference in intensity reflects indirectly the profile of the waveguide.