Femtosecond laser excited second harmonic and multiphoton absorption induced UV luminescence generation behaviour of ZnO nanofibers

Femtosecond (fs) laser excited second harmonic (SH) and multiphoton absorption (MPA) induced UV luminescence generation behaviour of Zinc oxide (ZnO) nanofibers is reported here. The used nanofibers are grown by seed assisted chemical bath deposition technology over glass substrates and are excited by a near-infrared (NIR) Ti: Sapphire laser emitting pulses of wavelength 812 nm and duration 100 fs. The peak wavelength of SH and MPA induced UV luminescence signals are found to be 406 nm and 398 nm respectively. Due to good optical quality, no defect level related MPA induced visible luminescence is observed in nanofibers. In comparison to this, ZnO nanostructures grown over plane substrate without seed layer shows very less SH and MPA induced UV luminescence. However in this case, the defect level related MPA induced visible luminescence was found to be very high. Applications like ultrafast pulse diagnostics, NIR induced photodynamic therapy etc. require high SH and MPA induced UV luminescence and low defect level related visible luminescence. So the ZnO nanofibers can be a potential candidate for these applications.