Fabrication method of large-area polarization grating based on tunable shearing holography
In conventional dual-beam polarization holography system,the desired polarization profiles of LCPG are accomplished with complicated optics and careful precision alignment,and wherein the relative distances for redirecting beams limit the upper range of periods that can be fabricated.In this paper,we propose a new tunable shearing holography to fabricate large-area LCPGs using small aperture LCPGs as masks.We discuss the grating period dependence on azimuthal rotating angle and position along the optical axis of the grating masks.Using this exposure setup,we demonstrate two long-period PGs where the diameters of the active area are 200 mm.The 200 mm polarization grating exhibits nearly ideal diffraction properties showing over 99％first-order diffraction efficiency.The average grating period is about 59.86 μm and the variation is only 0.07％over the entire aperture.The experimental results show that the tunable shearing holography method enables easy fabrication of large-area and arbitrarily long-period polarization grating with good uniformity.Moreover,the new approach is very compact,much easier to tune the period,more robust to vibration compared with prior polarization holography.
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