Engineering and excitation of solitons in two-period QPM

Steffen Kjr Johansen* and Lluis Torner

Universitat Politechnica de Catalunya
Department of Signal Theory and Communications
Gran Capitan UPC-D3, Barcelona, ES 08034, Spain

Ole Bang

Department of Informatics and Mathematical Modelling
Technical University of Denmark, building 321
DK-2800 Kongens Lyngby, Denmark.

We report on a scheme which might make it practically possible to engineer the effective competing nonlinearities that on average govern the light propagation in quasi-phase-matching (QPM) gratings.

In standard one-period QPM, the grating period normally must be very short in order to compensate the large intrinsic phase-mismatch. Superimposing a second period, two-period QPM, introduces an extra degree of freedom in the system. The second period can be chosen without regard to the intrinsic phase-mismatch. Thus the engineering of spatial solitons based on competing nonlinearities is made practically possible.

For the induced averaged nonlinearities addressed here to be of potential practical importance, they have to impact the observable soliton properties, including their excitation conditions. We found that the QPM engineered averaged cubic nonlinearities, induced in feasible two-period samples, enhances the peak-efficiency and mismatch-bandwidth of the soliton excitation process with non-soliton single frequency pump light.

* Permanent address: Department of Informatics and Mathematical Modelling, Technical University of Denmark, building 321, DK-2800 Kongens Lyngby, Denmark