摘要 |
A method for designing an aperiodic grating structure for mode conversion and control which is based upon an inverse scattering optimization procedure. In accordance with this method, no predetermined shape or material variation of the grating structure is assumed. A constrained domain of all surfaces and material variations is searched to find an optimum aperiodic conversion surface profile for maximum conversion efficiency into the required output mode(s) or optimum control. Accordingly, the present method results in the design of rough surfaces or non-homogeneous structures for mode conversion and control. Because this method relies on scattering produced by short, forceful field perturbations, it is possible to achieve very small conversion lengths which are much less than one grating period. For microwave frequencies this method can be used to design mode converters, mode filters, frequency filters, phase shifters, mode launchers, waveguide transitions and adapters, power splitters, phase shifters, couplers, etc. Optical applications of this method include and are not limited to the design of waveguide transitions and couplers, mode converters, aperiodic gratings, aperiodic Bragg reflectors, narrowband filters, holographic elements, etc. In all these cases the propagation medium may be a waveguide of any shape, material and size, or it could be free space. Efficiencies close to the theoretical maximums are obtainable with this method.
|