Metasurface with an absorptive aperture border
A metasurface optical device can include an array of pillars 13 on a first-side 11 f of a substrate 11 aligned with an aperture 15 of, or proximate to, a blocking-layer 12 . The blocking-layer 12 can located on the first-side 11 f of the substrate 11 , on a second-side 11 s of the substrate 11 opposite of the first-side 11 f , or both. The blocking-layer 12 can prevent light from transmitting through the device in undesirable locations. The blocking-layer 12 can be opaque to incident light and can include an absorptive-layer. Thus, the blocking-layer 12 can have dual functions—blocking and absorbing light.
1. A metasurface optical device comprising:
a transparent substrate including a first-side and a second-side opposite of the first-side;
a blocking-layer on the substrate, the blocking-layer configured to block light from transmitting therethrough;
an aperture extending through the blocking-layer, the blocking-layer encircling the aperture, and the aperture configured to allow light to transmit through the device;
an array of pillars located on the first-side of the substrate and aligned with the aperture, the array of pillars including different pillars with different diameters with respect to each other; and
the blocking-layer includes an absorptive-layer configured to absorb the light and a reflective-layer configured to reflect the light, the absorptive-layer includes a first-absorptive-layer and a second-absorptive-layer, and the reflective-layer is sandwiched between the first-absorptive-layer and a second-absorptive-layer.
2. The device of claim 1 , wherein the blocking-layer is located on the first-side of the substrate.
3. The device of claim 1 , wherein the blocking-layer is located on the second-side of the substrate.
4. The device of claim 1 , wherein
the blocking-layer includes a first-blocking-layer and a second-blocking-layer, the first-blocking-layer is located on the first-side of the substrate, and the second-blocking-layer is located on the second-side of the substrate.
5. The device of claim 1 , wherein the reflective-layer adjoins the first-absorptive-layer and the second-absorptive-layer.
6. The device of claim 1 , wherein the reflective-layer is sandwiched between the absorptive-layer and the substrate.
7. The device of claim 1 , wherein k>0.1 and R≤0.6 for the absorptive-layers, where k is an extinction coefficient of the absorptive-layer, and R is a bulk reflectance of an interface between air and a uniform slab of the absorptive-layer at normal incidence, calculated by as follows:
R
=
(
n
-
1
)
2
+
k
2
(
n
+
1
)
2
+
k
2
and n is a refractive index of the absorptive-layer.
8. The device of claim 1 , wherein the absorptive-layer adjoins the substrate.
9. The device of claim 1 , wherein the first-absorptive-layer, the reflective-layer, and the second-absorptive-layer are located on the first-side of the substrate.
10. The device of claim 1 , wherein the first-absorptive-layer, the reflective-layer, and the second-absorptive-layer are located on the second-side of the substrate.
11. A method of making the metasurface optical device of claim 1 , the method comprising:
forming the array of pillars on the first-side of the transparent substrate;
applying a thin-film on the array of pillars and extending past borders of the array of pillars such that an outer-ring of the thin-film encircles the array of pillars and an inner-portion of the thin-film covers the array of pillars; and
removing the inner-portion of the thin-film, thus forming the thin-film into the blocking-layer.
12. The method of claim 1 , further comprising applying an overcoat-layer on the array of pillars before applying the thin-film, the overcoat-layer spans channels between the array of pillars without filling the channels, and the overcoat-layer is transparent in a wavelength range of use.
13. The device of claim 1 , further comprising an overcoat-layer on the array of pillars, the overcoat-layer spans channels between the array of pillars without filling the channels, and the overcoat-layer is transparent in a wavelength range of use.
14. The device of claim 1 , wherein the array of pillars have nanometer-sized dimensions and nanometer-sized spacing between each other.
15. The device of claim 1 , wherein the first-absorptive-layer and the second-absorptive-layer each include germanium, silicon, carbon, or combinations thereof.
16. The device of claim 1 , wherein the array of pillars comprises niobium oxide, titanium oxide, silicon nitride, or combinations thereof.
17. The device of claim 1 , wherein the array of pillars has an index of refraction that is ≥1.8 across the visible spectrum of light.
18. A metasurface optical device comprising:
a transparent substrate including a first-side and a second-side opposite of the first-side;
a blocking-layer on the substrate, the blocking-layer configured to block light from transmitting therethrough;
an array of pillars located on the first-side of the substrate adjacent to the blocking-layer, the array of pillars including different pillars with different dimensions with respect to each other; and
the blocking-layer includes an absorptive-layer configured to absorb the light and a reflective-layer configured to reflect the light, the absorptive-layer includes a first-absorptive-layer and a second-absorptive-layer, and the reflective-layer is sandwiched between the first-absorptive-layer and a second-absorptive-layer.
19. The device of claim 18 , wherein:
the first-absorptive-layer and the second-absorptive-layer each include germanium, silicon, carbon, or combinations thereof; and
the array of pillars comprises niobium oxide, titanium oxide, silicon nitride, or combinations thereof.
20. A metasurface optical device comprising:
a transparent substrate including a first-side and a second-side opposite of the first-side;
a blocking-layer on the substrate, the blocking-layer configured to block light from transmitting therethrough;
an array of metasurface structures located on the first-side of the substrate adjacent to the blocking-layer, the array of metasurface structures including different structures with different dimensions with respect to each other; and
the blocking-layer includes an absorptive-layer configured to absorb the light and a reflective-layer configured to reflect the light the absorptive-layer includes a first-absorptive-layer and a second-absorptive-layer, and the reflective-layer is sandwiched between the first-absorptive-layer and a second-absorptive-layer.