  We investigate the nonclassical properties of output fields propagated
through a contradirectional asymmetric nonlinear optical coupler consisting of
a linear waveguide and a nonlinear (quadratic) waveguide operated by second
harmonic generation. In contrast to the earlier results, all the initial fields
are considered weak and a completely quantum mechanical model is used here to
describe the system. Perturbative solutions of Heisenberg's equations of motion
for various field modes are obtained using Sen-Mandal technique. Obtained
solutions are subsequently used to show the existence of single-mode and
intermodal squeezing, single-mode and intermodal antibunching, two-mode and
multi-mode entanglement in the output of contradirectional asymmetric nonlinear
optical coupler. Further, existence of higher order nonclassicality is also
established by showing the existence of higher order antibunching, higher order
squeezing and higher order entanglement. Variation of observed nonclassical
characters with different coupling constants and phase mismatch is discussed.
