Imaging of optical disc using reflection-mode scattering-type scanning near-field optical microscopy

Area of Science:

• Optical microscopy
• Materials science
• Nanotechnology

Background:

• Phase-change optical discs store data using materials that change phase upon laser irradiation.
• Observing these nanoscale recording marks is crucial for understanding data storage mechanisms and improving disc performance.
• Conventional optical microscopy often lacks the resolution to clearly image these sub-wavelength features.

Purpose of the Study:

• To investigate the capability of reflection-mode scattering-type scanning near-field optical microscopy (RS-SNOM) for imaging phase-change optical disc recording marks.
• To compare the performance of a.c.-mode and d.c.-mode RS-SNOM for resolving nanoscale data.
• To validate experimental findings with numerical simulations.

Main Methods:

• Utilized a reflection-mode scattering-type scanning near-field optical microscope (RS-SNOM) to observe a phase-change optical disc.
• Acquired images in both a.c.-mode and d.c.-mode SNOM operation.
• Performed numerical simulations using the finite difference time domain (FDTD) method for comparison.

Main Results:

• Successfully resolved 1.2 microm x 0.6 microm recording marks on the groove of the phase-change optical disc using a.c.-mode RS-SNOM.
• No recording marks were resolvable in d.c.-mode SNOM imaging.
• Achieved a resolution better than 100 nm with a.c.-mode RS-SNOM operation, consistent with FDTD simulations.

Conclusions:

• a.c.-mode RS-SNOM offers superior resolution for directly observing nanoscale recording marks on phase-change optical media compared to d.c.-mode.
• RS-SNOM is a viable technique for high-resolution imaging of data storage features on optical discs.
• The findings provide direct evidence of the capability of RS-SNOM in nanoscopic data visualization.