Proc. SPIE. 5966, Seventh International Symposium on Optical Storage (ISOS 2005)
KEYWORDS: Microscopes, Light sources, Ferroelectric materials, Optical microscopy, Optical testing, Near field scanning optical microscopy, Near field, Objectives, Spatial resolution, Near field optics
We report a method for testing small light spot produced by an optical system with high numerical-aperture (NA). A high NA objective was used to converge the incident linear polarized light, and a tapered optical fiber probe with an opening of 50-80 nm mounted in the near-field optical microscopy (SNOM) apparatus was used to measure light intensity. The small light spot can be measured with high spatial resolution. The results show that a resolution of 50~100 nm can be obtained.
Measurement technology plays an important role in the research of optical storage. Aiming at constructing research platform for blue-ray optical data storage, we designed and built a modularized static testing system, in which laser wavelength is 406.7nm. Modulation/demodulation technique is employed to weaken the test noise. The focus move mode decreases the requirement in size of samples. And Piezoeletronic nano-positioner is used to facilitate the relocation of recording marks and improve test repeatability. Experimental results are also given to verify the performance of the static testing system.
The axial intensity distribution and focal depth of an apodized focusing optical system are theoretically investigated with two kinds of incident light fields: a uniform-intensity-distribution beam and a Gaussian beam. Both a low-numerical-aperture and a high-numerical-aperture optical system are considered. Numerical results show that the depth of focus can be adjusted by changing the geometrical parameters and transmissivity of the apodizer in the focusing optical system. When a Gaussian beam is employed as the incident beam, the waist width also affects the depth of focus. The tunable range of the focal depth is very considerable.