Wave-front conversion between a Gaussian beam with a cylindrical phase and a plane wave for on-axis off-Bragg incidence

The theoretical model for an off-Bragg on-axis conversion between a Gaussian beam with cylindrical phase function and a plane wave by a volume aperiodic nonplanar inhomogeneous holographic grating is presented. A two-wave first-order coupled-wave theoretical framework is adopted. Analytical solutions for the amplitudes of two space harmonics of the field inside the grating zone are derived. Both the chromatic and the geometric deviations from the exact Bragg condition are studied. Numerical evaluations show that some anomalous phenomena (Pendellosung fringes, angle amplification effect, achromatism) can arise. High diffraction efficiency (approximate to 1) is predicted even for relatively large off-Bragg deviations. The deterioration of the reconstruction fidelity due to the Pendellosung effect is discussed. (C) 1996 Optical Society of America