Optical interferometry technology is one of the most accurate and effective detection methods. For the refractive index distribution measurement of G-Lens, we propose a method to calculate the order of circular interference fringes produced by a Mach-Zehnder interference optical system. This method is not only limited to the refractive index measurement, but also suitable for applications which is measured via interference method. For example, the surface error measurement of optical components. Several specific works had been performed such as effective area masking, image preprocessing, fringe center relocation, central-radiation fringe fractional-level calculation and fitting of circular optical interference fringe images. Furthermore, the two-dimensional distribution of cross-sections and three-dimensional of fringe orders are also obtained. In addition, we propose a new primary and secondary location method for the gray value peaks and valleys of noisy interference fringes, and on the basis of this location, the relative gray fringe fractional-level calculation is performed, which effectively avoids uneven illumination, noise, and the influence of unfavorable factors such as poor circularity and over-density of large-order fringes on the fringe calculation. For the work content of G-Lens refractive index distribution measurement, the algorithm has good repeatability accuracy, and the specific value is about 0.3‰.
A fused-silica polarization grating at a wavelength of 1053 nm was designed. To achieve a high extinction ratio and
efficiency, the grating profile was optimized by using rigorous coupled-wave analysis. The results showed: when the
grating period, the duty cycle and the groove depth of polarization grating were at 650nm, 0.39 and 1340nm respectively,
the extinction ratio could reach the maximum 34700; the efficiencies of the TE-polarized wave in the -1st order and the
TM-polarized wave in the 0th order were 92.2% and 99.5% respectively. We also analyzed the effects of the deviations
of the period and depth from optimized parameters on the extinction ratio and efficiency. The holographic lithography
and the ion beam etching will be applied to fabricate a prototype polarization grating in late 2010.
Polarization imaging is a powerful tool to observe hidden information from an observed object, for instance, degree of
polarization, polarization azimuth and polarization ellipticity. According to the request of the visible light polarization
imaging, a metal sub-wavelength polarization gratings array was designed based on FDTD method. And its principle was
analyzed by effective medium theory. The effects of metal thickness and duty ratio on the TM and TE polarization
transmission efficiency as well as the extinction ratio was analyzed by FDTD method when the grating's period is 200nm
and 250nm, and the metal is Al. When the metal sub-wavelength polarization gratings array works in normal incidence,
its TM transmission efficiency are more than 45%, and the extinction ratios are more than 3.5×103 in all visible light
spectrum. Numerical results and theoretical analysis show that the designed metal sub-wavelength polarization gratings
array is a polarizer with high TM polarization transmission efficiency and high extinction ratios.
The convex grating is one of the key elements in hyperspectral imaging spectrometers. In this paper the diffraction
characteristics of the convex blazed grating is investigated by using rigorous coupled-wave theory, which indicates that
within the wavelength from 0.4μm to 0.8μm, the plus first-order diffraction efficiency can be over 35% through
controlling the blaze angle of blazed grating. The convex blazed grating with the period of 5μm in the center, the blaze
angle about 4.3 degree, and the ruled area - a convex substrate with its radius 72mm and aperture 35mm has been
fabricated by holographic- scan ion beam etching. Experimental measurements show that the plus first-order diffraction
efficiency is more than 35%, within the wavelength from 0.4μm to 0.8μm.
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