Device for deviating and focusing light
A device includes a host medium having a first refractive index value; a first layer comprising a first dielectric material having a second refractive index value, wherein the second refractive index value is greater than the first refractive index value, and wherein the first layer comprises a first step structure at a boundary between the first layer and the host medium; and a second layer comprising a second dielectric material and comprising a second step structure, the second layer having a third refractive index value higher than the first refractive index value of the host medium, wherein the second step structure is stacked on the first step structure, and, in response to an incident electromagnetic wave reaching the device, a first nanojet beam generated by the first step structure and a second nanojet beam generated by the second step structure are combined and focused around a first focusing point.
1. A device for generating and guiding nanojet beams from an incident electromagnetic wave that is incident on the device, the device comprising:
a host medium having a first refractive index value;
a first layer comprising a first dielectric material having a second refractive index value, wherein the second refractive index value is greater than the first refractive index value, and wherein the first layer comprises a first step structure and a third step structure at a boundary between the first layer and the host medium, wherein the first step structure and the third step structure face each other and are separated from each other by a first distance; and
a second layer comprising a second dielectric material and comprising a second step structure and a fourth step structure at a boundary between the second layer and the host medium, the second layer having a third refractive index value higher than the first refractive index value of the host medium, wherein the second step structure and the fourth step structure face each other and are separated from each other by a second distance that is smaller than the first distance, wherein the second step structure is stacked on the first step structure and wherein the fourth step structure is stacked on the third step structure, wherein each of the first step structure, the second step structure, the third step structure, and the fourth step structure is configured such that, in response to the incident electromagnetic wave reaching the device in a direction from the first layer toward the second layer, nanojet beams originating from edges of the first step structure, the second step structure, the third step structure, and the fourth step structure are combined at a focal spot to form a single high-intensity nanojet beam.
2. The device of claim 1 , wherein:
the incident electromagnetic wave is a plane wave,
the device is configured such that the plane wave incident on the device is normal to the first layer,
the first step structure includes a first edge, a first bottom surface, and a first base angle between the first edge and the first bottom surface,
the second step structure includes a second edge, a second bottom surface, and a second base angle between the second edge and the second bottom surface, and
the first base angle and second base angle are equal to 90 degrees.
3. The device of claim 2 ,
wherein the first step structure further comprises a first top surface and the second step structure further comprises a second top surface;
wherein the first bottom surface of the first step structure and the first top surface of the first step structure are parallel to a first plane, and the first edge of the first step structure is parallel to an axis perpendicular to the first plane; and
wherein the second bottom surface of the second step structure and the second top surface of the second step structure are parallel to the first plane; and
wherein the second edge of the second step structure is parallel to the axis.
4. The device of claim 1 , wherein the first step structure and the third step structures have a same first height H 1 , wherein the second step structure and the fourth step structure have a same second height H 2 , wherein the second height H 2 has a value around
(
d
1
2
)
·
γ
1
-
H
1
,
wherein d 1 is the first distance, and γ 1 is around
1
tan
Θ
B
1
,
where Θ B1 is a nanojet beam radiation angle generated by the first step structure and the third step structure, wherein
Θ
B
1
≈
9
0
∘
-
Θ
TIR
1
2
where
Θ
TIR
1
=
sin
-
1
(
n
1
n
2
)
is a first critical angle of refraction, n 1 is the first refractive index value of the host medium, n 2 is the second refractive index value of the first layer, wherein
(
d
2
2
)
has a value around H 2 /γ 2 , wherein d 2 is the second distance, γ 2 is around
1
tan
Θ
B
2
,
where Θ B2 is a nanojet beam radiation angle generated by the second step structure and the fourth step structure, and wherein
Θ
B
2
≈
9
0
∘
-
Θ
TIR
2
2
where
Θ
TIR
2
=
sin
-
1
(
n
1
n
3
)
is a second critical angle of refraction, and n 3 is the third refractive index value of the second layer.
5. The device of claim 1 , wherein:
the device is configured such that the incident electromagnetic wave is a plane wave that is normal to the first layer and the second layer,
the first step structure includes a first edge, a first bottom surface, and a first base angle between the first edge and the first bottom surface,
the second step structure includes a second edge, a second bottom surface, and a second base angle between the second edge and the second bottom surface, and
the first base angle and the second base angle are equal to an angle α.
6. The device of claim 5 , wherein the first step structure and the third step structure have a same first height H 1 , wherein the second step structure and the fourth step structure have a same second height H 2 , wherein the second height H 2 has a value around
(
d
1
2
)
·
γ
1
-
H
1
,
wherein d 1 is the first distance, and γ 1 is around
1
tan
Θ
B
1
,
where Θ B1 is a nanojet beam radiation angle generated by the first step structure and the third step structure, wherein
Θ
B
1
≈
9
0
∘
-
Θ
TIR
1
+
α
2
where
Θ
TIR
1
=
sin
-
1
(
n
1
n
2
)
is a first critical angle of refraction, n 1 is the first refractive index value of the host medium, n 2 is the second refractive index value of the first layer, wherein
(
d
2
2
)
has a value around H 2 /γ 2 , wherein d 2 is the second distance, γ 2 is around
1
tan
Θ
B
2
,
where Θ B2 is a nanojet beam radiation angle generated by the second step structure and the fourth step structure, and wherein
Θ
B
2
≈
9
0
∘
-
Θ
TIR
2
+
α
2
where
Θ
TIR
2
=
sin
-
1
(
n
1
n
3
)
is a second critical angle of refraction, and n 3 is the third refractive index value of the second layer.
7. The device of claim 5 ,
wherein the first step structure further comprises a first top surface and the second step structure further comprises a second top surface;
wherein the first bottom surface of the first step structure and the first top surface of the first step structure are parallel to a first plane, and the first edge of the first step structure is non-perpendicular to the first top surface and the first bottom surface; and
wherein the second bottom surface of the second step structure and the second top surface of the second step structure are parallel to the first plane, and the second edge of the second step structure is non-perpendicular to the second top surface and the second bottom surface.
8. The device of claim 1 , wherein:
the device is configured such that the incident electromagnetic wave is a plane wave that hits the device at an angle of incidence Θ i , and
the first step structure includes a first edge, a first bottom surface, and a first base angle between the first edge and the first bottom surface,
the second step structure includes a second edge, a second bottom surface, and a second base angle between the second edge and the second bottom surface, and
the first base angle and the second base angle are equal to 90 degrees.
9. The device of claim 8 , wherein the second refractive index value of the first layer is equal to the third refractive index value of the second layer, wherein the first step structure and the third step structure have a same first height H 1 , and wherein the second distance d 2 is described according to
(
d
2
2
)
=
-
(
d
1
2
)
-
H
1
·
tan
Θ
B
1
′
+
tan
Θ
B
1
″
2
,
wherein
Θ
B
1
′
≈
9
0
∘
-
Θ
TIR
2
+
Θ
i
2
,
and
Θ
B
1
″
≈
9
0
∘
-
Θ
TIR
2
-
Θ
i
2
,
where d 1 is the first distance, and
Θ
TIR
=
sin
-
1
(
n
1
n
2
)
is a critical angle of refraction, n 1 is the first refractive index value of the host medium, and n 2 is the second refractive index value of the first layer.
10. The device of claim 1 , wherein the third refractive index value of the second layer is smaller than the second refractive index value of the first layer.
11. The device of claim 1 , wherein the incident electromagnetic wave has a wavelength equal to a value between 390 and 700 nm.
12. The device of claim 1 , wherein the second layer has a shape that is selected from the group consisting of a cuboid shape, a cylinder shape, and a prism shape.
13. The device of claim 1 , wherein the host medium comprises a homogenous dielectric host medium.
14. The device of claim 1 , wherein the host medium functions as an embedding layer in which at least the second layer comprising the second step structure is embedded.
15. The device of claim 1 , wherein the first step structure has a first height, wherein the second step structure has a second height, and wherein the second height is based on the first height, the first refractive index value, and the second refractive index value.
16. The device of claim 1 , wherein the first step structure and the third step structure have a first height, wherein the second step structure and the fourth step structure have a second height, and wherein the second height is based on the first height, the first refractive index value, and the second refractive index value.
17. The device of claim 1 , wherein the device receives the incident electromagnetic wave as a plane wave normal to the first layer.
18. The device of claim 1 , wherein the focal spot is beyond the second layer.
19. The device of claim 1 , wherein the first step structure and the third step structure have a same first height, wherein the second step structure and the fourth step structure have a same second height;
wherein the second height is based on the first height, the first distance, and a nanojet beam radiation angle generated by the first step structure and the third step structure; and
wherein the second distance is based on the second height and a nanojet beam radiation angle generated by the second step structure and the fourth step structure.