Second harmonic generation and cascaded second order processes using quasi-phase-matched counter propagating waves

Nonlinear counterpropagating quasi-phase-matching (c-QPM) process is rigorously investigated using various analytical and numerical techniques. First, the numerical solutions to the nonlinear coupled wave equations for a basic mirrored c-QPM device are analyzed for both second harmonic generation (SHG) and cascaded processes. SHG conversion efficiency is derived as a function of normalized input intensity. The nonlinear phase shifts acquired in this device by cascaded second order processes are shown to be promising for all-optical-switching (AOS) applications. The effects of non-ideal (e.g., metallic) mirrors are also presented. Additionally, power balance is investigated, and Manley-Rowe type expressions for c-QPM are found.; Numerical solutions to the set of coupled nonlinear wave equations for a mirrorless c-QPM device are also investigated. Mirrorless c-QPM is studied in stand-alone and in two interferometric configurations for all-optical switching applications. The switching intensity is found to be very low using existing materials (e.g., 500 mW in a 1 cm long KTP waveguide with a 10 {dollar}mu{dollar}m{dollar}sp2{dollar} effective area). Additionally, parameter sets are found that minimize pulse breakup and improve the possibility of a practical implementation. SHG is also investigated in the stand-alone device, and the conversion efficiency is shown to be eight times less efficient than the mirrored configuration.; In order to study c-QPM independent of the boundary conditions, the nonlinear system of equations is transformed into a Hamiltonian form. Using the conservation of the Hamiltonian and the conservation relations derived in this work, projections of the four dimensional phase space are presented. These plots provide insight into system behavior under an arbitrary set of boundary conditions. The Hamiltonian form also provides the nonlinear eigenmodes, which govern the cross-sections of the Hamiltonian level sets.; Finally, the basic mirrored c-QPM device is studied with a pulsed input fundamental plane wave. Several examples are given under varying spatial pulse length to device length ratios. An approximate upper bound on the device length is established from this study for practical pulsed applications; the largest usable length is approximately the same as the spatial length of the pulse.