Study on measuring refractive index modulation of volume phase holographic gratings |
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Authors: | Yi Xie Quanxin Ding Mingwu Kang Wenqiang Li Zhuo Li Baoping Wang |
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Institution: | 1. School of Electronic Science and Engineering, Southeast University, Nanjing 210096, Jiangsu, China;2. Science and Technology on Electro-Optic Control Laboratory, Luoyang 471009, Henan, China;3. Luoyang Institute of Electro-Optical Equipment, Luoyang 471009, Henan, China |
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Abstract: | In this paper, we present an approach to measure the refractive index modulation of volume phase holographic gratings (VPHG) by use of its angular selectivity, with the advantage of avoiding the diffraction efficiency errors induced by noise. Based on Kogelnik's coupled wave theory for volume holographic gratings, the wave vectors matching relationship for reflective VPHG at different readout wavelengths is deduced and the diffraction efficiency as a function of readout angle is also obtained. Then an all-fiber experimental system is designed to measure corresponding diffraction efficiency with different readout angles for VPHG recorded in dichromate gelatin. By seeking the Bragg angle where diffraction efficiency is maximum and the blank angle where diffraction efficiency drops to the minimum value, the refractive index modulation can be calculated. The experiment results proves the feasibility of the method. |
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Keywords: | Refractive index modulation Holographic volume grating Diffraction efficiency |
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