The apodized transmitting volume Bragg grating (TVBG) with the amplitude of the refractive index modulation (RIM) dropped to zero at both the surfaces is discussed. The proposed method for apodization is based on the recording of two identical uniform TVBGs with slightly different directions of their Bragg wave vectors in a single wafer. As a result, slow sinusoidal moiré modulation occurs in the direction perpendicular to the averaged direction of the two wave vectors of Bragg modulation. The cutting of a specimen at the planes of the two closest zeros of the moiré envelope produces the apodized TVBG. The longitudinal sinusoidal semi-period profile of RIM requires its specific maximum value to achieve 100% diffraction efficiency at the exact Bragg condition. Such an apodized TVBG demonstrates a significant suppression of the sidelobes in the diffraction efficiency depending on the angular or the wavelength detuning, in comparison to the diffraction operation of a uniform TVBG.
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