Abstract: We have fabricated a large aperture random phase plate (RPP) in Chinese K9 glass substrate for target-plane laser beam smoothing at 1.06 micrometer wavelength, by using large aperture photolithography and dilute HF etching processes. The RPP's clear aperture is $phi@250 mm. The measured average step height is 1.060 micrometer, which has a relative standard deviation of 1.24% at 5 locations on the RPP to the theoretical value. A focal spot with very sharp edges and nearly flat-top overall envelope intensity distribution is obtained at the focal-plane of a focusing lens. These results show that our fabrication techniques for RPP is effective, and is easily scaleable to even larger apertures. !7
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