Optical coupling device having diffraction gratings for coupling light with a light guide and fabrication method thereof
An optical coupler device for coupling light with a light guide is provided. The device includes a first layer having a plurality of first diffraction gratings spaced apart via first trenches, the first diffraction gratings and the first trenches forming first periodic units. The device also includes a second layer having a plurality of second diffraction gratings spaced apart via second trenches, the second diffraction gratings and the second trenches forming second periodic units. Additionally, the second periodic units are offset in a lateral axis of the optical coupler device relative to the first periodic units by a relative shift distance S 2 that is in a range from about 10 nm to about 600 nm.
1. An optical coupler device for coupling light with a light guide, comprising:
a first layer comprising a plurality of first diffraction gratings spaced apart via first trenches, the first diffraction gratings and the first trenches forming first periodic units;
a second layer comprising a plurality of second diffraction gratings spaced apart via second trenches, the second diffraction gratings and the second trenches forming second periodic units; and
a first fill layer disposed between the first layer and the second layer, the first fill layer having a thickness from about 100 nm to about 260 nm,
wherein the second periodic units are offset in a lateral axis of the optical coupler device relative to the first periodic units by a relative shift distance S 2 that is in a range from about 10 nm to about 600 nm.
2. The optical coupler device of claim 1 , wherein a width of the first diffraction gratings is different from a width of the second diffraction gratings.
3. The optical coupler device of claim 1 , where a thickness of the first diffraction gratings is different from a thickness of the second diffraction gratings.
4. The optical coupler device of claim 1 , wherein a width of the first periodic unit is substantially equal to a width of the second period unit.
5. The optical coupler device of claim 1 , wherein the relative shift distance S 2 is in a range from about 100 nm to about 400 nm.
6. The optical coupler device of claim 1 , wherein a material of the first diffraction gratings and of the second diffraction gratings has a refractive index in a range from about 1.5 to about 2.0.
7. The optical coupler device of claim 6 , wherein the material of the first diffraction gratings and the second diffraction gratings has a refractive index in a range from about 1.7 to about 2.0.
8. The optical coupler device of claim 1 , wherein a material of the first trenches and of the second trenches has a refractive index of less than about 1.5.
9. The optical coupler device of claim 8 , wherein the material of the first trenches and the second trenches has a refractive index in a range from about 1.0 to about 1.3.
10. The optical coupler device of claim 1 , wherein a material of the first and second trenches is the same as a material of the first fill layer.
11. The optical coupler device of claim 1 , further comprising a third layer comprising a plurality of third diffraction gratings spaced apart via third trenches, the third diffraction gratings and the third trenches forming third periodic units, wherein the third periodic units are offset in a lateral axis of the optical coupler device relative to the first periodic units by a relative shift distance S 3 .
12. The optical coupler device of claim 11 , further comprising a second fill layer disposed between the second layer and the third layer.
13. The optical coupler device of claim 12 , wherein a material of the first, second, and third trenches is the same as a material of the second fill layer.
14. The optical coupler device of claim 1 , wherein the optical coupler device is an input coupler configured to couple light into the light guide.
15. The optical coupler device of claim 1 , wherein the optical coupler device is an output coupler configured to couple light out of the light guide.
16. The optical coupler device of claim 1 , wherein the first diffraction gratings and the second diffraction gratings comprise one or more of one or more of silicon nitride (Si 3 N 4 ), niobium pentoxide (Nb 2 O 5 ), titanium dioxide (TiO 2 ), tantalum pentoxide (Ta 2 O 5 ), hafnium (IV) oxide (HfO2), hatrium dioxide (ScO 2 ), scandium dioxide (SiN), silicon nitride (SiO x N), and aluminum oxygen nitride (AlO x N).
17. The optical coupler device of claim 1 , wherein the first trenches and the second trenches comprise one or more of silicon dioxide (SiO 2 ) glass, magnesium fluoride (Mgf 2 ) glass, or fused silica glass.
18. An optical device comprising a light guide and the optical coupler device of claim 1 .