Liu Shimei, Tie Shaolong, Chen Jingdong, Li Guangcan, Yang Jiaxin, Lan Sheng
Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China.
School of Chemistry, South China Normal University, Guangzhou 510006, China.
Nanophotonics. 2022 Oct 21;11(21):4715-4725. doi: 10.1515/nanoph-2022-0380. eCollection 2022 Dec.
Polystyrene (PS) is generally considered as a passive optical material that is transparent to light with wavelengths longer than 300 nm. In practice, PS micro- and nanospheres with uniform sizes are usually used to build photonic crystals based on self-assembly mechanism. Here, we demonstrate experimentally that PS microspheres supporting whispery gallery modes can be transformed into multimode light sources by laser irradiation. We show that a PS microsphere placed on a silica substrate can be lighted up when it is consecutively irradiated by using a 488-nm continuous wave laser beam with a pumping power above a threshold. Broadband luminescence emitted from the PS microsphere increases rapidly to a maximum value and decreases gradually with increasing irradiation time, implying the generation and degradation of a certain luminescent material upon laser irradiation. However, the PS microsphere is found to be damaged by high temperature based on morphology examination. By replacing the silica substrate with a thin silver film, the threshold laser power for lighting up a PS microsphere is dramatically reduced. More importantly, we can see enhanced luminescence intensities from the whispery gallery modes supported by the PS microsphere, which becomes an efficient multimode light source. Interestingly, the threshold laser power can be further lowered by inserting a molybdenum disulfide monolayer in between the PS microsphere and the silver film. As a result, the PS microsphere remains nearly unchanged except the formation of the luminescence material. Our findings open a new horizon for the interaction of polymer with laser light by exploiting the optical resonances supported by micro- and nanoparticles and pave the way for constructing photonic devices based on laser-induced luminescent materials in polymers.
聚苯乙烯（PS）通常被视为一种对波长大于300 nm的光透明的无源光学材料。实际上，尺寸均匀的PS微球和纳米球通常用于基于自组装机制构建光子晶体。在此，我们通过实验证明，支持回音壁模式的PS微球可以通过激光照射转化为多模光源。我们表明，当使用泵浦功率高于阈值的488 nm连续波激光束连续照射放置在二氧化硅衬底上的PS微球时，它可以被点亮。PS微球发出的宽带发光随着照射时间的增加迅速增加到最大值，然后逐渐降低，这意味着在激光照射下某种发光材料的产生和降解。然而，基于形态学检查发现PS微球会被高温损坏。通过用薄银膜代替二氧化硅衬底，点亮PS微球的阈值激光功率显著降低。更重要的是，我们可以看到PS微球支持的回音壁模式的发光强度增强，它成为了一种高效的多模光源。有趣的是，通过在PS微球和银膜之间插入单层二硫化钼，可以进一步降低阈值激光功率。结果，除了发光材料的形成外，PS微球几乎保持不变。我们的发现通过利用微米和纳米颗粒支持的光学共振，为聚合物与激光的相互作用开辟了新的视野，并为基于聚合物中激光诱导发光材料构建光子器件铺平了道路。
