25 September 2014 Research on chromatic properties of high order kinoform
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Abstract
This work is dedicated to the evaluation of the chromatic properties of high order kinoforms. Typical kinoform (of the first order) is a phase only structure having the phase retardation varying in the range 0-2π. Such structures are very commonly used in many practical applications for different ranges of electromagnetic radiation like ultraviolet, visible, infrared, terahertz and millimeter waves. Besides those benefits such structures have one crucial disadvantage - they suffer from big chromatic aberration. This limits their practical application only to the narrowband work, where main wavelength must be well defined (Δλ/λ<<1). This paper presents other type of diffractive structures called high order kinoforms (HOK). They exhibit phase retardation of n2π, where n is an integer number much bigger than 1. Due to this fact they are relatively thin and therefore can be manufactured using laser lithography in thick photoresist (deeply etched). On the other hand they are thick enough to suppress chromatic aberrations. In comparison to the well-known Fresnel lens, the high order kinoform structure has precisely controlled phase retardation between different zones. In the case of the Fresnel lens (known from XVIII/XIX century), phase retardations between different zones are random (designing process is based on the geometrical optics). In the case of the high order kinoform working as the spherical lens - taking into account the real size of the detector - it can be shown that the most of the energy being focused in the focal spot will be registered by the detector for different wavelengths. The paper presents simple theoretical considerations, numerical modeling and their experimental evaluation.
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K. Węgrzyńska, K. Węgrzyńska, M. Rachoń, M. Rachoń, M. Doch, M. Doch, A. Siemion, A. Siemion, J. Suszek, J. Suszek, A. Kołodziejczyk, A. Kołodziejczyk, M. Sypek, M. Sypek, } "Research on chromatic properties of high order kinoform", Proc. SPIE 9192, Current Developments in Lens Design and Optical Engineering XV, 91921I (25 September 2014); doi: 10.1117/12.2065527; https://doi.org/10.1117/12.2065527
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