An innovative configuration - two pieces of reflection volume phase gratings superposed is put forward, in order to
highly diffract the ultra-short laser pulse. Based on Kogelnik's coupled wave theory, and discrete Fourier transform, the
diffraction efficiency of the configuration for ultra-short laser pulse is formulated. And the diffraction efficiency for laser
pulse with a Gaussian shape in temporal domain is simulated. The results show that when the two gratings' vectors are
parallel to each other, and their parameters are selected appropriately, the diffraction spectrum of the configuration is
approximately composed of those of the two gratings. The diffraction efficiency of 70fs Gaussian laser pulse can be
improved to 0.96, which is 0.20 larger than that by only one piece of the grating. It is very useful for the application of
ultra-short laser pulse, such as beam deflector with high diffraction efficiency, spectral beam combination, and so on.