  We demonstrate the double electromagnetically induced transparency
(double-EIT) and double four-wave mixing (double-FWM) based on a new scheme of
non-degenerate four-wave mixing (FWM) involving five levels of a cold 85Rb
atomic ensemble, in which the double-EIT windows are used to transmit the probe
field and enhance the third-order nonlinear susceptibility. The phase-matching
conditions for both four-wave mixings could be satisfied simultaneously. The
frequency of one component of the generated bichromatic field is less than the
other by the ground-state hyperfine splitting (3GHz). This specially designed
experimental scheme for simultaneously generating different nonlinear
wave-mixing processes is expected to find applications in quantum information
processing and cross phase modulation. Our results agree well with the
theoretical simulation.
