Transparent electromagnetic wave focusing device
A transparent electromagnetic wave focusing device is provided, which includes a plurality of metamaterial unit cells arranged to form a metamaterial array plate, and each metamaterial unit cell includes a plurality of metal layers and a plurality of transparent substrates stacked alternately. Each of the metal layers has a comb-tooth pattern, and the plurality of metamaterial unit cells correspond to a plurality of comb-tooth pattern combinations, respectively. The metamaterial array plate has an incident surface and an exit surface opposite to each other, and for an incident electromagnetic wave with a predetermined operating frequency band incident from the incident surface, the metamaterial unit cells correspond to a plurality of compensation phase differences, such that the incident electromagnetic wave that passes through the exit surface are focused on a reference point. The comb-tooth pattern combinations vary with the corresponding compensation phase differences.
1. A transparent electromagnetic wave focusing device, comprising:
a plurality of metamaterial unit cells arranged to form a metamaterial array plate, each metamaterial unit cell including a plurality of metal layers and a plurality of transparent substrates stacked alternately, and wherein each of the metal layers has a comb-tooth pattern, and the plurality of metamaterial unit cells correspond to a plurality of comb-tooth pattern combinations, respectively;
wherein the metamaterial array plate has an incident surface and an exit surface opposite to each other, and for an incident electromagnetic wave with a predetermined operating frequency band incident upon the incident surface, the metamaterial unit cells correspond to a plurality of compensation phase differences, such that the incident electromagnetic wave that passes through the exit surface is focused on a reference point; and
wherein the comb-tooth pattern combinations vary with the corresponding compensation phase differences.
2. The transparent electromagnetic wave focusing device according to claim 1 , wherein the compensation phase differences are periodically changed in a phase difference range of 0 to 360 degrees from an edge region of the incident surface to a central region of the incident surface, such that phase differences of a plurality of portions of the incident electromagnetic wave that pass through different regions of the incident surface are reduced or eliminated at the reference point.
3. The transparent electromagnetic wave focusing device according to claim 2 , wherein each of the plurality of metamaterial unit cells includes:
a first metal layer;
a first transparent substrate disposed above the first metal layer;
a second metal layer disposed above the first transparent substrate;
a second transparent substrate disposed above the second metal layer; and
a third metal layer disposed above the second transparent substrate,
wherein each of the metamaterial unit cells has one of the comb-tooth pattern combinations, and in the corresponding comb-tooth pattern combination, the first metal layer has a first comb-tooth pattern, the second metal layer has a second comb-tooth pattern, the third metal layer has a third comb-tooth pattern, and the first comb-tooth pattern and the third comb-tooth pattern have a first quantity of teeth and a third quantity of teeth that are greater than or equal to 2, and the second comb-tooth pattern has a second quantity of teeth that is greater than or equal to zero.
4. The transparent electromagnetic wave focusing device according to claim 3 , wherein a portion of the metamaterial unit cells further includes a spacer disposed between the second transparent substrate and the second metal layer, or disposed between the first transparent substrate and the second metal layer.
5. The transparent electromagnetic wave focusing device according to claim 4 , wherein in each of the plurality of metamaterial unit cells, when the spacer is disposed between the second transparent substrate and the second metal layer, the second metal layer contacts the first transparent substrate without contacting the second transparent substrate, and when the spacer is disposed between the first transparent substrate and the second metal layer, the second metal layer contacts the second transparent substrate without contacting the first transparent substrate.
6. The transparent electromagnetic wave focusing device according to claim 4 , wherein the metamaterial unit cells with the spacers are arranged in the metamaterial array plate in an equidistant distribution.
7. The transparent electromagnetic wave focusing device according to claim 3 , wherein each of the first comb-tooth patterns, the second comb-tooth patterns and the third comb-tooth patterns is formed by a plurality of metal meshes, and the plurality of metal meshes each have dimensions that are smaller than tooth lengths, tooth widths and tooth intervals of teeth in the first comb-tooth pattern, the second comb-tooth pattern and the third comb-tooth pattern.
8. The transparent electromagnetic wave focusing device according to claim 7 , wherein the first comb-tooth pattern, the second comb-tooth pattern and the third comb-tooth pattern each include:
an outer frame; and
a plurality of teeth protruding from opposite inner sides of the outer frame toward a center portion of the outer frame, and the teeth are symmetrical,
wherein the teeth of the first comb-tooth pattern, the second comb-tooth pattern and the third comb-tooth pattern correspond to the first quantity of teeth, the second quantity of teeth and the third quantity of teeth, respectively, and when the second quantity of teeth is zero, the second comb-tooth pattern only has the outer frame.
9. The transparent electromagnetic wave focusing device according to claim 7 , wherein a quantity of the compensation phase differences is 8, and the compensation phase differences each differ by 45 degrees.
10. The transparent electromagnetic wave focusing device according to claim 8 , wherein the comb-tooth pattern combinations include a first to a fifth comb-tooth pattern combinations, the first to the fifth comb-tooth pattern combinations correspond to a plurality of teeth quantity combinations, and the plurality of teeth quantity combinations have a first teeth quantity, a second teeth quantity and a third teeth quantity of (3, 3, 3), (3, 1, 3), (3, 0, 3), (2, 0, 2) and (2, 3, 2), respectively for each of the teeth quantity combinations.
11. The transparent electromagnetic wave focusing device according to claim 9 , wherein the second comb-tooth pattern combination further includes a first sub-pattern combination, a second sub-pattern combination and a third sub-pattern combination, and the tooth lengths of the first sub-pattern combination are larger than those of the second sub-pattern combination, and the tooth lengths of the second sub-pattern combination are larger than those of the third sub-pattern combination, the fourth comb-tooth pattern combination further includes a fourth sub-pattern combination and a fifth sub-pattern combination, and the tooth lengths of the fourth sub-pattern combination are larger than those of the fifth sub-pattern combination.
12. The transparent electromagnetic wave focusing device according to claim 10 , wherein the tooth width of the fifth comb-tooth pattern combination is different from the tooth width of the first to the fourth comb-tooth pattern combinations.
13. The transparent electromagnetic wave focusing device according to claim 10 , wherein the plurality of metamaterial unit cells has an arrangement formed by periodically arranging, from the edge region toward the central region, the first comb-tooth pattern combination, the fifth comb-tooth pattern combination, the third sub-pattern combination, the second sub-pattern combination, the fifth sub-pattern combination, the third comb-tooth pattern combination, the fourth sub-pattern combination, and the first sub-pattern combination.