- We have developed the up-conversion coherent light emitted devices based on Er-doped silica microsphere coated thin film metal on the surface, which has strong local surface plasmonic resonance for enhancement of green light emission. The coherent green light emission threshold is ultralow of 60 nW of pump power in the Al-coated Er-doped silica microsphere, but it gradually degraded as oxide formed, and significantly reduced for some thousand times after one month kept in air. Based on experiment result, we can make ultralow threshold of green coherent emission by Al-coated Er-doped silica microsphere operated for long time, if we could prevent the oxidation of aluminum layers. In other hand, the spectra of green light emission from degraded Al-coated Er-doped silica microsphere changed from single mode to double mode at high pump power. This effect can use for optical sensing field, when we manipulate the multilayer coating cavity and material reflective indices of coating layers.
- We have developed the carbon quantum dot coated Er-doped silica microspheres for green up-conversion emitted devices with narrow line-width. The carbon quantum dot coatings present strong enhancement of green light emission, and the emission intensities depend upon kinds of carbon quantum dots synthesized with different reaction temperatures. In addition, the intensities of green up-conversion emission from carbon quantum dot coated Er-doped silica microspheres depended upon thickness of coating layers verified via times of dipping process. We believe that obtained result calls for next experiments to explain the light enhancement effect of carbon quantum dots, and obtained results have a large potential of applications in the photonic devices and optical sensing technique using carbon quantum dots.
- The primary focus of the research task is fundamental research, with some component fabrication research falling within the framework of basic research on manufacturing technology and some component properties. Therefore, the results of the task have significance in fundamental knowledge of materials and quantum components, laying the foundation for the development of quantum technology in the future. The application of the task's results will be discussed with partners to further develop future collaborations. The research results achieved on the up-conversion emission of co-doped rare-earth ions in nano-coated materials can be developed into larger-scale topics and projects once the task is completed.
- The proposed task serves as a basis for long-term collaboration with the Stepanov Institute of Physics, the National Academy of Sciences of Belarus, and contributes to the training of young research personnel in this new research field.
- Based on the results and experience of this project, we can jointly explore and develop new aspects of quantum materials and reverse transition emission quantum components. We also propose considering the establishment of specific collaborative projects to continue promoting research and development in this field.

- Publications:
+ Thuy Chi Do, Thuy Van Nguyen, Huy Bui, Thanh Binh Pham, Dmitry Sergeevich Mogilevtsev, Tu Le Tuan & Van Hoi Pham, Light Enhancement of Green Up-Conversion Emission from Er-Doped Silica Microspheres by Carbon Quantum Dot Coatings, J Fluoresc (2023). https://doi.org/10.1007/s10895-023-03420-y.
+ Do Thuy Chi, Nguyen Thuy Van, Vu Duc Chinh, Hoang Thi Hong Cam, Vilaysak Sayyasone, Pham Thanh Binh, Bui Huy, Pham Van Hoi, Efficient and reliable detection of rhodamine B using SERS from silver-decorated photonic crystal silicon nanoscale pores, Vietnam Journal of Science and Technology 61(3), pp 620-630, 2023.
+ Nguyen Thuy Van, Pham Thanh Binh, Bui Huy and Pham Van Hoi, Upconversion Emission from Erbium doped silica microspheres, The 5th International conference on Advanced Materials and Nanotechnology – ICAMN-2022, p.111-115, 2022.