Kumar Kaushal, Rai S B, Rai D K
Laser and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2007 Apr;66(4-5):1052-7. doi: 10.1016/j.saa.2006.04.039. Epub 2006 Jun 2.
An enhancement of luminescence properties in Er3+ doped ternary glasses is observed on the addition of PbO/PbF2. The infrared to visible upconversion emission bands are observed at 410, 525, 550 and 658 nm, due to the 2H9/2-->4I15/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 transitions respectively, on excitation with 797 nm laser line. A detailed study reveals that the 2H9/2-->4I15/2 transition arises due to three step upconversion process while other transitions arise due to two step absorption. On excitation with 532 nm radiation, ultraviolet and violet upconversion bands centered at 380, 404, 410 and 475 nm wavelengths are observed along with one photon luminescence bands at 525, 550, 658 and 843 nm wavelengths. These bands are found due to the 4G11/2-->4I15/2, 2P3/2-->4I13/2, 2H9/2-->4I15/2, 2P3/2-->4I11/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 and 4S3/2-->4I13/2 transitions, respectively. Though incorporation of PbO and PbF2 both enhances fluorescence intensities however, PbF2 content has an important influence on upconversion luminescence emission. The incorporation of PbF2 enhances the red emission (658 nm) intensity by 1.5 times and the violet emission (410 nm) intensity by 2.0 times. A concentration dependence study of fluorescence reveals the rapid increase in the red (4F9/2-->4I15/2) emission intensity relative to the green (4S3/2-->4I15/2) emission with increase in the Er3+ ion concentration. This behaviour has been explained in terms of an energy transfer by relaxation between excited ions.
在添加PbO/PbF₂后，观察到掺Er³⁺三元玻璃的发光特性有所增强。在797 nm激光线激发下，红外到可见光的上转换发射带在410、525、550和658 nm处被观察到，分别归因于²H₉/₂→⁴I₁₅/₂、²H₁₁/₂→⁴I₁₅/₂、⁴S₃/₂→⁴I₁₅/₂、⁴F₉/₂→⁴I₁₅/₂跃迁。详细研究表明，²H₉/₂→⁴I₁₅/₂跃迁是由于三步上转换过程产生的，而其他跃迁是由于两步吸收产生的。在用532 nm辐射激发时，观察到以380、404、410和475 nm波长为中心的紫外和紫光上转换带，以及在525、550、658和843 nm波长处的单光子发光带。这些带分别归因于⁴G₁₁/₂→⁴I₁₅/₂、²P₃/₂→⁴I₁₃/₂、²H₉/₂→⁴I₁₅/₂、²P₃/₂→⁴I₁₁/₂、²H₁₁/₂→⁴I₁₅/₂、⁴S₃/₂→⁴I₁₅/₂、⁴F₉/₂→⁴I₁₅/₂和⁴S₃/₂→⁴I₁₃/₂跃迁。虽然掺入PbO和PbF₂都增强了荧光强度，但是PbF₂含量对上转换发光发射有重要影响。掺入PbF₂使红色发射（658 nm）强度提高了1.5倍，紫色发射（410 nm）强度提高了2.0倍。荧光的浓度依赖性研究表明，随着Er³⁺离子浓度的增加，红色（⁴F₉/₂→⁴I₁₅/₂）发射强度相对于绿色（⁴S₃/₂→⁴I₁₅/₂）发射强度迅速增加。这种行为已根据激发离子之间通过弛豫进行的能量转移来解释。
