  We present a geometrical representation of sum frequency generation process
in the undepleted pump approximation. The analogy of such dynamics with the
known optical Bloch equations is discussed. We use this analogy to present a
novel technique for the achievement of both high efficiency and large bandwidth
in a sum frequency conversion processes using adiabatic inversion scheme,
adapted from NMR and light-matter interaction. The adiabatic constraints are
derived in this context. Last, this adiabatic frequency conversion scheme is
realized experimentally by a proper design of adiabatic aperiodically poled KTP
device, using quasi phased matched method. In the experiments we achieved high
efficiency signal to idler conversion over a bandwidth of 140nm.
