Improving coupling between integrated photonics chips and optical fibers is an important topic of study for many applications. For photonic integrated circuits, different coupling methods have been implemented including edge coupling, grating coupling and 3D-integration using direct laser writing. Silicon nitride is a widely proven material for non linear optical phenomena such as frequency comb, optical parametric oscillation etc. Here in this thesis, coupling mechanisms based on direct laser writing are presented for use in nonlinear integrated photonics. Simulation works show that a polymer tapered coupler printed on a single mode fiber could be a good alternative to a cleaved fiber and equivalent to a lensed fiber. It is also shown that an out-of-plane polymer coupler on a silicon nitride access waveguide could be a prospective alternative for coupling to nonlinear integrated photonic circuits while avoiding chip separation and facet polishing. Both mechanisms could be good coupling options for shorter wavelength applications.