Optical features of a PtO<sub>2</sub> mask layer in a superresolution near-field structure are investigated in detail by use of the Z-scan technique. The high photothermal stability of the PtO<sub>2</sub> mask is revealed, and a phenomenon in which laser-irradiated PtO><sub>2</sub> decomposes to yield Pt particles is confirmed. We also find a physical change in the mask layer that accompanies the chemical decomposition. Microscopic observations and atomic force microscope studies support the theory that the physical deformation is induced by the decomposition of PtO<sub>2</sub> . It is clear that the optical nonlinear responses of the PtO<sub>2</sub> mask layer result from two mechanisms.
© 2003 Optical Society of America
(190.4350) Nonlinear optics : Nonlinear optics at surfaces
(190.4400) Nonlinear optics : Nonlinear optics, materials
(210.4590) Optical data storage : Optical disks
(210.4810) Optical data storage : Optical storage-recording materials
(310.6860) Thin films : Thin films, optical properties
Qian Liu, Toshio Fukaya, Junji Tominaga, Masashi Kuwahara, Takayuki Shima, and Jooho Kim, "Nonlinear features and response mechanisms of a PtO2 mask layer for optical data storage with a superresolution near-field structure," Opt. Lett. 28, 1805-1807 (2003)