Device for near-field focusing and beam forming
An optically-transparent device ( 100 ) is disclosed which comprises a main part ( 10 ) of dielectric material having a refractive index n 2 , said device being configured for forming a field intensity distribution in a near zone of said device from electromagnetic waves incidentally illuminating said device, when said device is embedded into a dielectric material having a refractive index n 1 lower than said refractive index n 2 . Said device ( 100 ) further comprises at least one insert ( 11 ) of dielectric material having a refractive index n 3 higher than said refractive index n 2 , said at least one insert being at least partly inserted into said main part, said refractive index n 1 being different from said refractive index n 3 , and wherein Formula (I) with W 2 being a half width of said insert and Formula (II), Formula (III) with W 1 being a half width of said main part and Formula (IV), with λ being the wavelength of the electromagnetic wave propagating in the dielectric material having refractive index n 1 .
1. An optical device for near-field focusing and beam forming, said device being configured to form, in a near field zone at a second surface of the device opposite to a first surface of the device, a field intensity distribution from an incident electromagnetic wave of visible light at the surface of said device, wherein said device is embedded in a first dielectric material having a first refractive index n 1 , said device comprising:
a main part, said main part made of a second dielectric material having a second refractive index n 2 ,
wherein said second refractive index n 2 is higher than said first refractive index n 1 ; and
at least one insert, said at least one insert made of a third dielectric material having a third refractive index n 3 that is higher than said second refractive index n 2 ,
wherein said at least one insert is at least partially within said main part, said first refractive index n 1 being different from said third refractive index n 3 ,
wherein
W
1
≥
λ
1
4
,
with W 1 being a half width of said main part and λ 1 being a first wavelength of the incident electromagnetic wave of visible light in said main part,
wherein
W
2
≥
λ
2
4
with W 2 being a half width of said at least one insert and λ 2 being a second wavelength of the incident electromagnetic wave of visible light in said at least one insert,
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite first edges of the main part of the optical device to form a first nanojet beam having a focal point in the near field zone at the second surface of the optical device, the first nanojet beam being formed from a crossing, at the focal point, of individual first nanojet beams from each of the opposite first edges of the main part, and
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite second edges of the at least one insert to form a second nanojet beam at the focal point in the near field zone at the second surface of the optical device, the second nanojet beam being formed from a crossing, at the focal point, of individual second nanojet beams from each of the opposite second edges of the at least one insert, the first and the second nanojet beam thereby forming a single high-intensity nanojet beam at the focal point in the near field zone at the second surface of the optical device.
2. The optical device according to claim 1 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a bottom surface of said device and the second surface corresponds to a top surface of the device, and when, at the top surface, a top edge of said at least one insert is above or coincides with a top edge of said main part, said half-width W 2 of said at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
-
H
1
+
H
2
)
,
where H 1 corresponds to a first height of said main part and H 2 corresponds to a second height of said at least one insert, where θ B2 is given by:
θ
B
2
≈
90
°
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
3. The optical device according to claim 1 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a top surface of said optical device and the second surface corresponds to a bottom surface of the optical device, and when, at the top surface, a top edge of said at least one insert is above or coincides with a top edge of said main part, said half-width W 2 of said at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
)
,
where θ B2 is given by:
θ
B
2
≈
9
0
∘
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
4. An optically-transparent device according to claim 1 , wherein each of a shape of said main part and a shape of said at least one insert is selected from the group consisting of: a cuboid, a cylinder, a cone, and a prism.
5. An optically-transparent device according to claim 1 , wherein each of said main part and said at least one insert has a shape with non-vertical lateral surfaces.
6. An optically-transparent device according to claim 1 , wherein a top edge of said at least one insert coincides with a top edge of said main part and a first height of said at least one insert equals to a second height of said main part.
7. An optically-transparent device according to claim 1 , wherein said main part and said at least one insert share at least one same axis of symmetry.
8. An optically-transparent device according to claim 1 , wherein a first axis of symmetry perpendicular to a top surface of said at least one insert is shifted from a second axis of symmetry perpendicular to a top surface of said main part.
9. The optical device according to claim 1 , wherein said second dielectric material of said main part or said third dielectric material of said at least one insert is selected from the group consisting of: glass, plastic, and a polymer material.
10. A system comprising:
a dielectric host medium with a first refractive index n 1 ;
an optical device for near-field focusing and beam forming,
wherein the optical device is configured to form, in a near field zone at a second surface of the optical device opposite to a first surface of the optical device, a field intensity distribution from an incident electromagnetic wave of visible light at the first surface of the optical device, and
wherein the optical device is embedded in said dielectric host medium, said optical device comprising:
a main part, said main part is made of a second dielectric material having a second refractive index n 2 ,
wherein said second refractive index n 2 is higher than said first refractive index n 1 ; and
at least one insert, said at least one insert made of a third dielectric material having a third refractive index n 3 that is higher than said second refractive index n 2 ,
wherein said at least one insert is at least partially within said main part, said first refractive index ni being different from said third refractive index n 3 ,
wherein
W
1
≥
λ
1
4
,
with W 1 being a halt width of said main part and λ 1 being a first wavelength of the incident electromagnetic wave in said main part, and
wherein
W
2
≥
λ
2
4
,
with W 2 being a half width of said at least one insert and λ 2 being a second wavelength of the incident electromagnetic wave in said at least one insert; and
a support layer made of a dielectric substrate with a fourth refractive index n 4 ,
wherein said optical device is on said support layer,
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite first edges of the main part of the optical device to form a first nanojet beam having a focal point in the near field zone at the second surface of the optical device, the first nanojet beam being formed from a crossing, at the focal point, of individual first nanojet beams from each of the opposite first edges of the main part, and
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite second edges of the at least one insert to form a second nanojet beam at the focal point in the near field zone at the second surface of the optical device, the second nanojet beam being formed from a crossing, at the focal point. of individual second nanojet beams from each of the opposite second edges of the at least one insert, the first and the second nanojet beam thereby forming a single high-intensity nanojet beam at the focal point in the near field zone at the second surface of the optical device.
11. An optical sensor device, comprising:
a first dielectric material having a first refractive index n 1 ; and
an optical device for near-field focusing and beam forming,
wherein the optical device is configured to form, in a near field zone at a second surface of the optical device opposite to a first surface of the optical device, a field intensity distribution from an incident electromagnetic wave of visible light at the first surface of said optical device, and
wherein said optical device is embedded in said first dielectric material, said optical device comprising:
a main part, said main part made of a second dielectric material having a second refractive index n 2 ,
wherein said second refractive index n 2 is higher than said first refractive index n 1 ; and
at least one insert, said at least one insert made of a third dielectric material having a third refractive index n 3 that is higher than said second refractive index n 2 ,
wherein said at least one insert is at least partially within said main part, said first refractive index n 1 being different from said third refractive index n 3 ,
wherein
W
1
≥
λ
1
4
,
with W 1 being a half width of said main part and λ 1 being a first wavelength of the incident electromagnetic wave of visible light in said main part, and
wherein
W
1
≥
λ
1
4
,
with W 2 being a half width of said at least one insert and λ 2 being a second wavelength of the incident electromagnetic wave of visible light in said at least one insert,
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite first edges of the main part of the optical device to form a first nanojet beam having a focal point in the near field zone at the second surface of the optical device, the first nanojet beam being formed from a crossing, at the focal point, of individual first nanojet beams from each of the opposite first edges of the main part, and
wherein the incident electromagnetic wave of visible light at the first surface of the optical device is guided by opposite second edges of the at least one insert to form a second nanojet beam at the focal point in the near field zone at the second surface of the optical device, the second nanojet beam being formed from a crossing, at the focal point, of individual second nanojet beams from each of the opposite second edges of the at least one insert, the first and the second nanojet beam thereby forming a single high-intensity nanojet beam at the focal point in the near field zone at the second surface of the optical device.
12. The system according to claim 10 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a bottom surface of said optical device and the second surface corresponds to a top surface of the optical device, and when, at the top surface, a top edge of said insert is above or coincides with a top edge of said main part, said half-width W 2 of said one at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
-
H
1
-
+
H
2
)
,
where H 1 corresponds to a first height of said main part and H 2 corresponds to a second height of said at least one insert, θ B2 is given by:
θ
B
2
≈
9
0
∘
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
13. The system according to claim 10 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a top surface of said optical device and the second surface corresponds to a bottom surface of the optical device, and when, at the top surface, a top edge of said at least one insert is above or coincides with a top edge of said main part, said half-width W 2 of said at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
)
,
where θ B2 is given by:
θ
B
2
≈
9
0
∘
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
14. The system according to claim 10 , wherein said half-width W 2 of said at least one insert depends at least in part on (i) said half-width W 1 of said main part and (ii) a first ratio between said second and third refractive indexes n 2 and n 3 and a second ratio between said first and second refractive indexes n 1 and n 2 .
15. A system according to claim 10 , wherein each of said main part and said at least one insert has a shape with non-vertical lateral surfaces.
16. The optical sensor device according to claim 11 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a bottom surface of said optical device and the second surface corresponds to a top surface of the device, and when, at the top surface, a top edge of said at least one insert is above or coincides with a top edge of said main part, said half-width W 2 of said at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
-
H
1
+
H
2
)
,
where H 1 corresponds to a first height of said main part and H 2 corresponds to a second height of said at least one insert, θ B2 is given by:
θ
B
2
≈
9
0
∘
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
17. The optical sensor device according to claim 11 , wherein, in an X, Y, Z coordinate system, where the first surface corresponds to a top surface of said optical device and the second surface corresponds to a bottom surface of the optical device, and when, at the top surface, a top edge of said at least one insert is above or coincides with a top edge of said main part, said half-width W 2 of said at least one insert is given by:
W
2
≈
tan
θ
B
2
×
(
W
1
tan
θ
B
1
)
,
where θ B2 is given by:
θ
B
2
≈
9
0
∘
-
sin
-
1
(
n
2
n
3
)
2
,
and where θ B1 is given by:
θ
B
1
≈
9
0
∘
-
sin
-
1
(
n
1
n
2
)
2
.
18. An optical sensor device according to claim 11 , wherein each of said main part and said at least one insert has a shape with non-vertical lateral surfaces.
19. The optical sensor device according to claim 11 , wherein said half-width W 2 of said at least one insert depends at least in part on (i) said half-width W 1 of said main part and (ii) a first ratio between said second and third refractive indexes n 2 and n 3 and a second ratio between said first and second refractive indexes n 1 and n 2 .
20. The optical device according to claim 1 , wherein said half-width W 2 of said at least one insert depends at least in part on (i) said half-width W 1 of said main part and (ii) a first ratio between said second and third refractive indexes n 2 and n 3 and a second ratio between said first and second refractive indexes n 1 and n 2 .