Biography
Prof. Wiesław Strek
Prof. Wiesław Strek
Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw, Poland
Title: Laser stimulated lighting of graphene materials
Abstract: 
The investigations of continuum broad band white light emission under interaction with focused beam of CW laser diode  were reported by us for graphene-based materials such as ceramic [1]  or foam [2]. The measurements were performed in vacuum by using high power density irradiation with CW 975 nm laser diode. The laser stimulated white lighting of graphene has demonstrated the specific features as: 
- white lighting is a point emission arising only from the excitation spot;
- emitting light is propagated in opposite direction to incident laser beam;
- the threshold dependence on excitation wavelength and excitation power density;
- sharp exponential increase of emission intensity with excitation power density;
- saturation of emission intensity at high excitation power density;
- white emission is assisted by efficient photocurrent and electron emission;
- fast rise and decay times of white emission;
- coherence features.
  
The mechanism of laser stimulated lighting of graphene is discussed in terms of multiphoton ionization. Recently we have reported  the laser induced broad band emission of graphene foam in  infrared range centred around 2100 nm. Moreover it was observed that laser induced white emission is characterized by relatively high spatial coherence degree. The coherence allows to apply the graphene  lighting in a wide range of applications for optical communication in visible and infrared, sharp display for medical images and sensing.
[1] W. Strek, B. Cichy, L. Radosinski, P. Gluchowski, L. Marciniak, M. Lukaszewicz, D. Hreniak, Laser-induced white-light emission from graphene ceramics–opening a band gap in graphene, Light Sci. Appl. 4 (2015) e237. doi:10.1038/lsa.2015.10. 
[2] W. Strek, R. Tomala, M. Lukaszewicz, B. Cichy, Y. Gerasymchuk, P. Gluchowski, L. Marciniak, A. Bednarkiewicz, D. Hreniak, Laser induced white lighting of graphene foam, Sci. Rep. 7 (2017). doi:10.1038/srep41281.
Biography: 
Research activity: luminescence properties of rare earth and transition metal ions in crystal, glasses and nanostructures, laser spectroscopy, optical sensors, laser induced white emission in rare earth systems and graphene.