Developing 2D Materials based Nano Dots for Laser Photonic Applications
2D materials research is recently a very hot topic for research in materials science and nanotechnology. A wide range of 2D materials are developed for various applications, including laser development , photodetectors  and renewable energy generation  . The 2D layered materials properties e.g. nonlinear absorption, electronic conductivity and the bandgap energy will change when it reduces in size and layer number. It is found that the enhancement of materials properties can be achieved when it’s size and thickness reduced into nano dots due to the edge effect and quantum confinement effect. We have successfully fabricated several type of 2D materials e.g. WS2, PtS2 into nano dots. The WS2 nano dots was fabricated by ultrasonic exfoliation followed by centrifugation. The average size and layer number of the WS2 flakes by controlling the treatment time. The nonlinear optical properties of WS2 with respect to different size and layer number can be quantified by the z-scan experiments . It has been shown that the optical limiting properties, e.g. onset threshold and optical limiting threshold of WS2 can be significantly enhanced by reducing in the average size and layer number of WS2. Additionally we have produced some PtS2 nano dots by having ultrasonic exfoliation and centrifugation over a long period. Then the fabricated nano dots is integrated within polyvinyl alcohol and producing saturable absorber. Laser mode locking have been achieved in two different laser systems with operational wavelength at near 1 micron and 1.57 micron. These results confirmed that the 2D materials based 2D nano dots have great potential to be used for nonlinear optics and laser photonic applications. Acknowledgments: This work is financially supported by Shenzhen Science and Technology Innovation Commission (JCYJ20170303160136888) and the National Natural Science Foundation of China (NSFC, Nos 61575167), Research Grants Council of Hong Kong, China (GRF 152109/16E, PolyU code: B-Q52T).
Keywords - 2D materials, WS2, PtS2, Nano Dots, Non-Linear Effect, Mode Locking Laser