Volume Phase Holographic Grating Used For Beam Combination Of RGB Primary Colors

Volume phase holographic grating (VPHG) has the characteristics of high diffractionefficiency, high signal to noise ratio, high wavelength and angle selectivity, low scattering,low absorption and low cost. It has been widely used in high resolution spectrometer,wavelength division multiplexing and pulse compression technique.In this paper, the Bragg’s condition, Kogelink’s coupled wave theory and rigorouscoupled wave analysis (RCWA) are described briefly. a novel kind of RGB primary colorsbeam combination device which is consisted of a transmission VPHG and a reflectionVPHG as core components is proposed. As an example, three primary colors atwavelengths of632.8nm,532nm and476.5nm are taken into account. The parameters oftransmission and reflection VPHG are determined by the Bragg’s condition, the diffractionproperties of the transmission and reflection VPHG are calculated and optimized based onKogelink’s coupled wave theory and rigorous coupled wave analysis (RCWA).Based on the theoretical calculation and analysis, the transmission and reflectionVPHG are designed by the holographic recording material of Dichromated gelatin (DCG),the diffraction properties (including the diffraction of TE and TM waves, the wavelengthselectivity and the angular selectivity) are measured, analyzed and compared withtheoretical value. At last, the transmission VPHG and reflection VPHG are boned as abeam combination device. By using a He-Ne laser, an Ar iron laser and a semiconductorlaser, three beams at different wavelengths of632.8nm,532nm and476.5nm are induced tothe device and the validity of the beam combination performance is verified. The device isprospected to be used as a beam combiner in laser projector.