  Single photon sources to be used in quantum cryptography must show higher
order antibunching (HOA). HOA is reported by us in several many wave mixing
processes. In the present work we have investigated the possibility of
observing HOA in multiwave mixing processes in general. The generalized
Hamiltonian is solved for several particular cases in Heisenberg picture and
possibility of observing HOA is investigated with the help of criterion of
Pathak and Garcia. Several particular cases of the generalized Hamiltonian are
solved with the help of short time approximation technique and HOA is reported
for pump modes of different multiwave mixing processes. It is also found that
HOA can not be observed for the signal and stokes modes in of the cases studied
here.
