The invention relates to elastic fluctuation in
engineering structures, in particular to ultrathin planar
waveguide equipment and a design method thereof.The
waveguide equipment comprises a flat plateand a
waveguide structure arranged on the flat plate, the waveguide structure is composed of two
layers of metasurfaces with sub-
wavelength thicknesses, and each metasurface is composed of periodically-arranged supercells, wherein each super
cell comprises unit cells with two gradient indexes, the transmissivity t of each unit
cell is not less than 0.9, the width of each unit
cell is H, the phasechanges of the elastic
waves passing through the two unit cells are pi and 2pi respectively, the
phase gradient of the super surface is L = 2H, L represents the width of the super cell, and
lambda / L> 2 must be met in order to make the elastic
waves incident on the super surface, wherein
lambda represents the
wavelength. By designing the waveguide equipment in any shape, the purpose that elasticwaves are propagated along an expected path can be achieved, and the waveguide equipment has the advantages of being light and thin in structure, small in size, wide in working
frequency band, high indesignability and the like.