Device for forming an outgoing electromagnetic wave from an incident electromagnetic wave
An optical device forming an outgoing electromagnetic wave from an incident electromagnetic wave is disclosed. Such a device comprises at least one unit cell comprising:—at least two optical elements, an optical element being characterized by a type of optical response to said incident electromagnetic wave;—selection means enabling selective excitation of at least one optical element among the at least two optical elements, in response to said incident electromagnetic wave as a function of a wavelength of said incident electromagnetic wave, wherein said selection means comprise at one nanojet-based dielectric deflector compound of at least two dielectric material having different refractive indexes, and wherein said optical elements are placed at a distance from said nanojet-based dielectric deflector.
1. An optical device for forming an outgoing electromagnetic wave from an incident electromagnetic wave, wherein the optical device comprises at least one unit cell, the unit cell comprising:
at least two optical elements; and
a nanojet-based dielectric deflector configured to enable selective excitation of at least one optical element among the at least two optical elements, in response to the incident electromagnetic wave, the excitation being a function of a wavelength of the incident electromagnetic wave,
wherein the nanojet-based dielectric deflector comprises at least one nanojet-based dielectric deflector compound of at least two dielectric materials comprising at least a first part of dielectric material having a first refractive index n 2 and a second part of dielectric material having a second refractive index n 3 ,
wherein the first part and the second part are embedded in a dielectric host medium having a third refractive index n 1 ,
wherein n 1 <n 3 <n 2 , and
wherein the optical elements are placed at a distance from the nanojet-based dielectric deflector.
2. The optical device of claim 1 ,
wherein the optical device is associated with a three-dimensional cartesian coordinate system defined by axis x, y and z with the z-axis being normal to the optical device, the first part and the second part of the nanojet-based dielectric deflector being positioned side by side along the x-axis, and
wherein nanojet-based dielectric deflectors of the optical device are separated along the x-axis by a layer of the dielectric host medium.
3. The optical device of claim 2 , wherein according to a cross section with a plane xz:
the first part having a first width W 1 along the x-axis,
the second part having a second width W 2 along the x-axis,
wherein the width W 1 and W 2 respectively equals to or is higher than half of the wavelength of the incident electromagnetic wave propagating respectively in the first part and in the second part,
the first part and the second part have a same height H along the z-axis, with
H
≈
W
1
+
W
2
tan
θ
B
1
+
tan
θ
B
3
,
θ B1 being the radiation angle of a first nanojet beam generated by a first edge along the z-axis of the nanojet-based dielectric deflector given by
θ
B
1
≈
90
°
-
sin
-
1
(
n
1
n
2
)
2
,
the first edge being between the first part and the host medium and θ B3 being the radiation angle of a second nanojet beam generated by a second edge along the z-axis of the nanojet-based dielectric deflector given by
θ
B
3
≈
90
°
-
sin
-
1
(
n
1
n
3
)
2
,
the second edge being between the second part and the host medium.
4. The optical device of claim 3 ,
wherein the distance is lower than or equals to H C -H B , and
wherein H C and H B are distances between a bottom of the nanojet-based dielectric deflector and intersection points of nanojet beams associated with edges of the first and second parts of the nanojet-based dielectric deflector with
H
B
≈
W
1
+
W
2
tan
θ
B
1
+
tan
θ
B
3
,
and
H
C
≈
W
2
tan
θ
B
3
-
tan
θ
B
2
with θ B2 being the radiation angle of a third nanojet beam generated by an edge along the z-axis of the nanojet-based dielectric deflector, the edge being between the first part and the second part of the nanojet-based dielectric deflector and
θ
B
2
≈
90
°
-
sin
-
1
(
n
3
n
2
)
2
.
5. The optical device of claim 2 , wherein a distance W 3 between two nanojet-based dielectric deflectors along the x-axis in the optical device is higher than or equals half of a wavelength corresponding to a wavelength for the blue color.
6. The optical device of claim 2 , wherein the refractive index n 3 of the second part of the nanojet-based dielectric deflector is such that n 3 >√{square root over (n 1 ×n 2 )}.
7. The optical device of claim 2 ,
wherein the first part and the second part of the nanojet-based dielectric deflector have a shape of cuboids, or
wherein the nanojet-based dielectric deflector has a shape of a half cylinder having an axis along the z-axis, with the second part being a half cylinder of radius R 2 surrounding the first part being a half cylinder of radius R 1 .
8. The optical device of claim 7 , wherein if the nanojet-based dielectric deflector has a shape of a half cylinder, the radius R 1 and R 2 of the first part and the second part are such that R 2 −R 1 <R 1 and n 3 <√{square root over (n 1 ×n 2 )}.
9. The optical device of claim 2 , wherein all optical elements are located at a same distance along the z-axis from a top surface of the nanojet-based dielectric deflector.
10. The optical device of claim 2 ,
wherein each optical element of the unit cell belong to a different set of optical elements, a set of optical elements being characterized by a type of optical response to the incident electromagnetic wave, and
wherein the nanojet-based dielectric deflector is configured to selectively excite all optical elements belonging to a given set.
11. The optical device of claim 10 ,
wherein optical elements of a same set are located at a same distance along the z-axis from a top surface of the nanojet-based dielectric deflector, and
wherein the sets of optical elements are positioned at different distances along the z-axis from the top surface of the nanojet-based dielectric deflector.
12. The optical device of claim 10 , wherein heights along the z-axis of optical elements of a first set are different from heights of optical elements of a second set.
13. The optical device of claim 1 , wherein the optical elements belong to a group comprising:
metallic particles;
dielectric particles;
semiconductor particles;
optical resonators; and
optical antennas.
14. The optical device of claim 1 , wherein the optical elements are assembled on or inside a dielectric substrate.
15. The optical device of claim 14 , wherein the nanojet-based dielectric deflector is placed at a distance below a surface of the dielectric substrate on which the optical elements are assembled.
16. The optical device of claim 1 , wherein the nanojet-based dielectric deflector is a nanojet microlens embedded in the dielectric host medium or placed on a dielectric substrate acting as a support layer.
17. The optical device of claim 1 , wherein the optical device belongs to an eyewear optical device or to a display device.