  In a recent experiment [1], it was observed that a sequence of two standing
wave square pulses can split a BEC at rest into +/- 2 h_bar k diffraction
orders with almost 100% efficiency. By truncating the Raman-Nath equations to a
2-state model, we provide an intuitive picture that explains this double square
pulse beamsplitter scheme. We further show it is possible to optimize a
standingwave multi square pulse sequence to efficiently diffract an atom at
rest to symmetric superposition of +/- 2n h_bar k diffraction order with n>1.
The approach is considered to be qualitatively different from the traditional
light pulse schemes in the Bragg or the Raman-Nath region, and can be extended
to more complex atomic optical elements that produce various tailored output
momentum states from a cold atom source.
