Cr4+在MgCaBa-铝酸盐玻璃中的发射及光学增益

研究了四价铬离子掺杂的MgCaBa-铝酸盐玻璃在近红外区的发射光谱,既有源于¹E—³A₂跃迁,位于1.18μm处的窄带,又有源于³T₂—³A₂范围在1.1～1.4 μm内的宽带,利用ASE(Amplified Spontaneous Emission)方法研究了其增益特性,测量了在 632.8nm激发下不同激发长度下的发射光谱,得到其光学增益系数在1.18μm和1.24 μm处分别为B_E=(0.7±0.04)mm^-1和B_T=(0.05±0.005)mm^-1,并根据这种材料的光谱性质,对其作为近红外可调谐激光介质的可能作出评估。

Luminescence and Opitical Gain of Cr4+ in MgCaBa Aluminate Glass

The fluorescence properties of Cr⁴⁺ doped inorganic glasses are of current interest, besides its potential use as a lumophore in tunable near-infrared media, Cr⁴⁺ is also useful as a spectroscopic probe to infer information about the local environment in amorphous solids. In glass hosts,Cr⁴⁺ ions are very likely surrounded by an oxygen tetrahedren. The Cr⁴⁺ emission is determined by the strength of the crystal field, for low crystal field, ³T₂ is the lowest excited state, the emission is a broadband, while for high crystal field, ¹E is the lowest excited state, the emission is a sharp line. Cr⁴⁺ ions in MgCaBa-aluminate glass were found to be the case of intermediate crystal field, where the state mixing approach should be applied to analyze the emission lineshape. The room temperature fluorescence spectrum includes a sharp line at 1.18μm and a broadband in the region 1.1～1.4μm, which assigned to ¹E→³A₂ and ³T₂→³A₂ transition respectively. In this paper, the ASE(Amplified Spontaneous Emission) method is presented to study the optical gain, this technique could be described as below:A cylindrical lens is used to focuses laser to an equally line,then make the beam get through a length adjustable slit,detected the fluorescence from the vertical side of the sample,the emission intensity for varied excited length is:I(l)=I_sA/gexp (gl)-1] Where I_s is the spontaneous emission rate per unit volume, A is the cross sectional area of the excited volume, g is the optical gain coefficient.Fitting the experiment result to the above equation, the optical gain coefficient of Cr⁴⁺:MgCaBa aluminate glass are B_E=(0.7±0.04)mm^-1 and B_T=(0.05±0.005)mm^-1 at 1.18μm and 1.24μm respectively.