Cr^(4+)在MgCaBa-铝酸盐玻璃中的发射及光学增益

Luminescence and Optical Gain of Cr^(4+) in MgCaBa-Aluminate Glass

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—3 A2 跃迁 ,位于1 1 8μm处的窄带 ,又有源于3 T2 —3 A2 范围在 1 1～ 1 4 μm内的宽带 ,利用ASE(AmplifiedSpontaneousEmis sion)方法研究了其增益特性 ,测量了在 63 2 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 1 8μm和 1 2 4 μm处分别为BE=( 0 7± 0 0 4 )mm-1和BT=( 0 0 5± 0 0 0 5)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。

The fluorescence properties of Cr 4+ doped inorganic glasses are of current interest, besides its potential use as a lumophore in tunable near infrared media, Cr 4+ is also useful as a spectroscopic probe to infer information about the local environment in amorphous solids. In glass hosts,Cr 4+ ions are very likely surrounded by an oxygen tetrahedren. The Cr 4+ emission is determined by the strength of the crystal field, for low crystal field, 3T 2 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. Cr 4+ 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 → 3A 2 and 3T 2 → 3A 2 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 s A/g[ exp (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 Cr 4+ ∶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.