APERIODIC MULTILAYER STRUCTURES

摘要

Aperiodic mult ilayer structures An aperiodic multilayer structure (2, 2') comprising a plurality of alternating layers of a first (4, 4') and a second (6, 6') material and a capping layer (10, 10') covering these alternating layers, wherein the structure (2, 2') is characterized in that the thickness of the alternating layers chaotically varies in at least a portion of said structure (2, 2'). The invention further comprises design method comprising the step of define a time interval and a first plurality of periodic multilayer structures (A), then calculate a first merit function ( ? R(? )10* I(?)d? ) and define a first domain for each first structures. The method further includes the step of apply at least one rando m mutation to each first structures inside the associated first domain and calculate a second merit function ( ?R(?) 10* I(?)d? for the at least one mutation. Then, the method proceeds with a co mparison of each first merit functions with the second merit function of the associated at least one mutation and if said second merit function is enhanced with respect to the first merit function, the at least one mutation is substituted for the structure of the first plurality and a second domain is defined for thw mutation, otherwise, the structure of the first plurality is maintained inside the corresponding first domain. The method further includes the step of calculate a mean value of the merit functions o f the first plurality of structures or mutations present in each first or second domain and define a threshold value to said mean value; then, for each first plurality of structures or mutations present in each first or second domain whose merit function is enhanced of the threshold with respect to the mean value, subst itute a third domain to the first or second domain unt il the corresponding merit function is enhanced of said predetermined threshold. Then, the preceding step are repeated unt il the time interval has lapsed and the merit funct ions of the first plurality of structures or mutations present in each first domain are compared and the structure or mutation whose merit function is the more enhanced is selected.