Microwave Induced Diffraction of Matter Waves from an Optical Lattice*

We demonstrate a novel type of Kaptiza-Dirac diffraction of matter waves from a microwave-dressed optical lattice. In our experiment, coherent momentum transfer is driven by internal-state coupling of a BEC to a single orbital of a state-dependent optical lattice. We analyze the internal and external dynamics of the diffraction process and characterize the matter-wave interference using a pump-probe scheme. Possible applications of our scheme will be discussed.