Optical filter and sensor system
An optical filter having a passband at least partially overlapping with a wavelength range of 800 nm to 1100 nm is provided. The optical filter includes a filter stack formed of hydrogenated silicon layers and lower-refractive index layers stacked in alternation. The hydrogenated silicon layers each have a refractive index of greater than 3 over the wavelength range of 800 nm to 1100 nm and an extinction coefficient of less than 0.0005 over the wavelength range of 800 nm to 1100 nm.
1. An article, comprising:
a plurality of hydrogenated silicon layers, and
a plurality of lower-refractive-index layers, wherein the plurality of lower-refractive-index layers include at least one oxide other than silicon dioxide,
wherein the plurality of lower-refractive-index layers include at least one of aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), niobium pentoxide (Nb 2 O 5 ), tantalum pentoxide (Ta 2 O 5 ), or a mixture thereof.
2. The article of claim 1 , wherein
the article has a passband at least partially overlapping with a wavelength range of 800 nm to 1100 nm, and
the passband has a center wavelength that shifts by less than 20 nm in magnitude with a change in an incidence angle between 0° to 30°.
3. The article of claim 2 , wherein the passband has a center wavelength that shifts by less than 13 nm in magnitude with a change in an incidence angle between 0° to 30°.
4. The article of claim 2 , wherein the passband has a center wavelength that shifts by about 12.2 nm in magnitude with a change in an incidence angle between 0° to 30°.
5. The article of claim 1 , wherein the plurality of hydrogenated silicon layers have a refractive index of greater than 3.6 at a wavelength of 830 nm.
6. The article of claim 1 , wherein at least one of the plurality of hydrogenated silicon layers is larger than at least one of the plurality of lower-refractive-index layers.
7. The article of claim 1 , further comprising:
a first filter stack, wherein at least one of the plurality of lower-refractive-index layers is disposed between two hydrogenated silicon layers of the plurality of hydrogenated silicon layers.
8. The article of claim 7 , further comprising:
a second filter stack.
9. An article, comprising:
a plurality of hydrogenated silicon layers, and
a plurality of lower-refractive-index layers, wherein at least one of the plurality of hydrogenated silicon layers is thicker than at least one of the lower-refractive-index layers,
wherein the plurality of hydrogenated silicon layers have a refractive index of greater than 3.65 at a wavelength of 800 nm.
10. The article of claim 9 , wherein the plurality of hydrogenated silicon layers have a refractive index of greater than 3 over a particular wavelength range.
11. The article of claim 9 , wherein the plurality of hydrogenated silicon layers have an extinction coefficient of less than 0.0005 over a particular wavelength.
12. The article of claim 9 , wherein the plurality of lower-refractive-index layers include at least one oxide.
13. The article of claim 12 , wherein the plurality of lower-refractive-index layers include at least one of silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), niobium pentoxide (Nb 2 O 5 ), tantalum pentoxide (Ta 2 O 5 ), or a mixture thereof.
14. The article of claim 9 , wherein the article has a passband that has a center wavelength that shifts by less than 13 nm in magnitude with a change in an incidence angle between 0° to 30°.
15. The article of claim 9 , wherein the article has a passband that has a center wavelength that shifts by about 12.2 nm in magnitude with a change in an incidence angle between 0° to 30°.
16. The article of claim 9 , wherein the plurality of hydrogenated silicon layers have a refractive index of greater than 3.6 at a wavelength of 830 nm.
17. The article of claim 9 , further comprising:
a first filter stack, wherein at least one of the plurality of lower-refractive-index layers is disposed between two hydrogenated silicon layers of the plurality of hydrogenated silicon layers.
18. The article of claim 17 , further comprising:
a second filter stack.
19. The article of claim 18 , wherein
the first filter stack defines a low pass filter with a low pass cutoff wavelength,
the second filter stack defines a high pass filter with a high pass cutoff wavelength, and
the article has a passband defined between the high pass cutoff wavelength and the low pass cutoff wavelength.
20. An optical filter, comprising:
a first filter stack on a first side of a substrate, the first filter stack includes alternating layers of hydrogenated silicon and layers of a lower-refractive-index material; and
a second filter stack on a second, opposite side of the substrate,
the second filter stack including at least two, different oxides.
21. The optical filter of claim 20 , wherein the second filter stack includes a least one of silicon dioxide (SiO 2 ) or Tantalum pentoxide (Ta 2 O 5 ).
22. The optical filter of claim 20 , wherein the second filter stack has a thickness of 0.1 μm to 1 μm.
23. The optical filter of claim 20 , wherein the optical filter has a total coating thickness of less than 10 μm.
24. The optical filter of claim 20 , wherein the layers of hydrogenated silicon have a refractive index of greater than 3.6 at a wavelength of 830 nm.
25. The optical filter of claim 20 , wherein at least one of the layers of hydrogenated silicon is thicker than at least one of the layers of the lower-refractive-index material.
26. The optical filter of claim 20 , wherein
the first filter stack defines a low pass filter with a low pass cutoff wavelength,
the second filter stack defines a high pass filter with a high pass cutoff wavelength, and
the optical filter has a passband defined between the high pass cutoff wavelength and the low pass cutoff wavelength.
27. An optical filter, comprising
a plurality of layers, wherein the plurality of layers include hydrogenated silicon layers and lower-refractive-index layers, and wherein the optical filter has a passband that has a center wavelength that shifts by less than 13 nm in magnitude with a change in an incidence angle from 0° to 30°.
28. The optical filter of claim 27 , wherein the passband shifts by less than 12.5 nm in magnitude with a change in the incidence angle.
29. The optical filter of claim 27 , wherein at least one of the hydrogenated silicon layers is thicker than at least one of the lower-refractive-index layers.
30. The optical filter of claim 27 , wherein a refractive index of the hydrogenated silicon layers is greater than 3.