Polarization laser direct-writing system was designed and the recording and research using the azobenzence polymer film on the system was investigated. Only single laser beam was used, and move the laser focal spot on the sample film pointto- point. By composite control of the optical power density, polarization direction and exposure time of the inscribing laser, a special phase-delay distribution graph which have different etching depth in different point can be achieved. Diffractive devices, such as grating and zone plate, have been inscribed. The anisotropy and surface topography was measured by polarizing optical microscopy (POM) and profilometer. Some qualitative analysis was made. Using the red light which is insensitivity to the azo polymer film, the diffractive devices’ focal spots were collected by CCD. Compared with the holographic interference method, the method is more flexible, undemanding for the experimental environment and any two-dimension distribution graph can be written in theory. It may get extensive application.
The 3D finite difference time domain (FDTD) method was employed to simulate the polarization characteristic of the
tapered metal-coated optical fiber probe in the near-field optical. The Scanning Near-field Optic Microscopy (SNOM)'s
applications would be extended by controlling the exit light's polarization of the optical fiber probe and analyzing the
polarized light which passes through the sample. Uniaxial Perfectly Matched Layers (UPMLs) are used for the
Absorbing Boundary Condition, and the Drude model is used to deal with the non-magnetic metal. The light intensity
distribution near the optical fiber tip was calculated with linear-polarized incident light. A general relationship between
the extinction ration and the probe varying with its relevant parameters has been found by means of making alternations
on the aperture diameter(40nm-120nm), the cone angle(20°-90°), the thickness of metal film(50nm-150nm) and
material(silver, aluminum) as well as the incident light wavelength(350nm-1000nm) and other parameters. The results
show that the above multi parameters have produced a co-effect on the polarization characteristics of the optical fiber
probe. Once the other parameters remain constant, the extinction ratio is increasing as the aperture diameter or metal film
thickness increases. And the extinction ratio could be decreasing, increasing or fluctuant as the cone angle increases in
the different conditions. Al's extinction ration usually is better than Ag's under the same conditions. The wavelength's
impact should be linked to the metal's complex permittivity. Therefore, the results have positive significance to the
design and application of the high extinction ratio fiber probe.
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