Department of Applied Physics, The Hong Kong Polytechnic University , Hong Kong, China.
Department of Physics and Materials Science, City University of Hong Kong , Hong Kong, China.
ACS Nano. 2017 Jan 24;11(1):843-849. doi: 10.1021/acsnano.6b07322. Epub 2017 Jan 4.
We discover that emission efficiency of Tm-doped upconversion nanoparticles can be enhanced through the use of a laser cavity. With suitable control of the lasing conditions, the population of the intermediate excited states of the Tm can be clamped at a required value above the excitation threshold. As a result, upconversion efficiency for the 300-620 nm emission band of the Tm-doped nanoparticles under 976 nm excitation can be enhanced by an order of magnitude over the case without a laser cavity. This is because the intrinsic recombination process of the intermediate excited states is suppressed and the surplus of excitation power directly contributes to the enhancement of multiphoton upconversion. Furthermore, our theoretical investigation has shown that the improvement of upconversion emission efficiency is mainly dependent on the cavity loss, so that this strategy can also be extended to other lanthanide-doped systems.
我们发现，通过使用激光腔，Tm 掺杂上转换纳米粒子的发射效率可以得到增强。通过适当控制激光条件，可以将 Tm 的中间激发态的粒子数固定在激发阈值以上的所需值。结果，在 976nm 激发下，Tm 掺杂纳米粒子的 300-620nm 发射带的上转换效率比没有激光腔的情况下提高了一个数量级。这是因为抑制了中间激发态的本征复合过程，并且过剩的激发功率直接有助于多光子上转换的增强。此外，我们的理论研究表明，上转换发射效率的提高主要取决于腔损耗，因此该策略也可以扩展到其他镧系掺杂系统。
