  Two-mode nonlinear coherent states are introduced in this paper. The pair
coherent states and the two-mode Perelomov coherent states are special cases of
the two-mode nonlinear coherent states. The exponential form of the two-mode
nonlinear coherent states is given. The photon-added or photon-subtracted
two-mode nonlinear coherent states are found to be two-mode nonlinear coherent
states with different nonlinear functions. The parity coherent states are
introduced as examples of two-mode nonlinear coherent states, and they are
superpositions of two corresponding coherent states. We also discuss how to
generate the parity coherent states in the Kerr medium.
