Design And Fabrication Of High-quality Volume Phase Holographic Gratings Used In VIS/NIR Wavebands

Volume phase holographic grating(VPHG) recorded in dichromated gelatin(DCG) is a kind of hologram with periodic variation of refraction index. VPHGs have the characteristics of high diffraction efficiency, high signal-to- noise ratio, low scattering, with no ghosts, and good wavelength and angular selectivity. As the VPHGs recorded in DCG are more and more applied in the fields of astronomical spectroscopy, optical communications, holographic display, etc., the requirements for the diffraction properties of VPHGs are getting higher. For this reason, VPHGs with high diffraction efficiency and being prospected used in VIS/NIR wavebands are manufactured, the application of VPHG for light beams combine and the method for improving the diffraction wavefront quality of VPHGs are probed in this thesis. It is meaningful for exploring the application fields of VPHGs.Firstly, the research background and progresses of VPHGs recorded DCG is introduced. Rigorous coupled wave theory is stated briefly and applied to calculate and analyze the diffraction characteristics of VPHGs. Then, a novel kind of beam combiner composed of a reflective and a transmission VPHG is proposed, which can be used for beams combining of 532 nm, 633 nm and 808 nm wavelength. The model and design idea of the beam combiner is described in detail. Gsolver and Matlab software are used to optimize parameters of VPHGs and design results of VPHGs with high diffraction characteristics properties are obtained. It will provide theoretical guidance for the manufacture of VPHGs with high-quality and beam combiner with high efficiency.Reflective and transmission VPHGs recorded in DCG are manufactured based on theoretical calculation and design. By adjusting the process conditions of grating recording, chemical processing and packaging, a reflective VPHG with frequency of 5059 lp/mm and Bragg wavelength at 532 nm and a transmission VPHG with frequency of 1046lp/mm and Bragg wavelength at 808 nm are manufactured. Testing system is established for the measurement of the diffraction properties of VPHGs. The measurement results are compared and analyzed with theoretical values. Testing system for beam combining is also set up and the feasibility of the VPHGs applied for beams combining is verified.Finally, a method for improving the diffraction wavefront of reflective VPHGs has been explored. According to the initial diffraction wavefront measured by Zygo interferometer, it took a considerable amount of polishing on the surface of the glasssubstrate of the reflective VPHG with frequency of 4807 lp/mm and Bragg wavelength at 633 nm and the diffraction wave aberration of the grating is reduced from 9.195λ to 1.690λ(PV, λ=633nm) and from 1.630λ to 0.209λ(RMS, λ=633nm). This experiment result provides a technical support for further study of methods for reducing the wavefront aberration of VPHGs.