Spectral filter, and image sensor and electronic device including the spectral filter
Provided is a spectral filter including a first Bragg reflective layer, a second Bragg reflective layer that is spaced apart from the first Bragg reflective layer and includes a cavity, the first resonance layer being provided between the first Bragg reflective layer and the second Bragg reflective layer, a second resonance layer including at least a portion of the first Bragg reflective layer, the second Bragg reflective layer, and the cavity, a third Bragg reflective layer, a fourth Bragg reflective layer spaced apart from the third Bragg reflective layer, wherein the second resonance layer is provided between the third Bragg reflective layer and the fourth Bragg reflective layer.
1. A spectral filter comprising:
a first Bragg reflective layer;
a second Bragg reflective layer spaced apart from the first Bragg reflective layer;
a first resonance layer provided between the first Bragg reflective layer and the second Bragg reflective layer, the first resonance layer comprising a cavity;
a second resonance layer comprising at least a portion of the first Bragg reflective layer, the second Bragg reflective layer, and the cavity;
a third Bragg reflective layer; and
a fourth Bragg reflective layer spaced apart from the third Bragg reflective layer,
wherein the second resonance layer is provided between the third Bragg reflective layer and the fourth Bragg reflective layer, and
wherein the first Bragg reflective layer contacts the third Bragg reflective layer and the second Bragg reflective layer contacts the fourth Bragg reflective layer.
2. The spectral filter of claim 1 , wherein each of the first Bragg reflective layer, the second Bragg reflective layer, the third Bragg reflective layer, and the fourth Bragg reflective layer comprises a plurality of material layers having different refractive indices that are alternately stacked.
3. The spectral filter of claim 1 , wherein each of the first Bragg reflective layer, the second Bragg reflective layer, the third Bragg reflective layer, and the fourth Bragg reflective layer comprises a distributed Bragg reflector.
4. The spectral filter of claim 1 , wherein the first Bragg reflective layer and the second Bragg reflective layer are symmetrical with respect to the first resonance layer.
5. The spectral filter of claim 1 , wherein the third Bragg reflective layer and the fourth Bragg reflective layer are symmetrical with respect to the second resonance layer.
6. The spectral filter of claim 1 , wherein a thickness of a material layer included in the first Bragg reflective layer and the second Bragg reflective layer is different from a thickness of a material layer included in the third Bragg reflective layer and the fourth Bragg reflective layer.
7. The spectral filter of claim 1 , wherein a thickness of a material layer included in the first Bragg reflective layer and the second Bragg reflective layer is less than a thickness of a material layer included in the third Bragg reflective layer and the fourth Bragg reflective layer.
8. The spectral filter of claim 1 , wherein the second resonance layer comprises the first Bragg reflective layer and the second Bragg reflective layer.
9. The spectral filter of claim 8 , wherein a first surface of the first Bragg reflective layer and a first surface of the second Bragg reflective layer are in contact with the first resonance layer.
10. The spectral filter of claim 9 , wherein a second surface of the first Bragg reflective layer opposite to the first surface of the first Bragg reflective layer and a second surface of the second Bragg reflective layer opposite to the first surface of the second Bragg reflective layer are in contact with the third Bragg reflective layer and the fourth Bragg reflective layer, respectively.
11. The spectral filter of claim 1 , wherein the second resonance layer comprises one of the first Bragg reflective layer and the second Bragg reflective layer.
12. The spectral filter of claim 11 , wherein one of the first Bragg reflective layer and the second Bragg reflective layer is in contact with the first resonance layer.
13. The spectral filter of claim 11 , wherein the other one of the first Bragg reflective layer and the second Bragg reflective layer is spaced apart from the first resonance layer, and
wherein one of the third Bragg reflective layer and the fourth Bragg reflective layer is provided between the other of the first Bragg reflective layer and the second Bragg reflective layer and the first resonance layer.
14. The spectral filter of claim 1 , wherein a wavelength of light passing through the spectral filter is determined by at least one of an effective refractive index of the cavity and a thickness of the cavity.
15. The spectral filter of claim 1 , further comprising:
a first unit filter configured to transmit light of a first wavelength; and
a second unit filter configured to transmit light of a second wavelength that is different from the first wavelength.
16. The spectral filter of claim 15 , wherein an effective refractive index of the cavity included in the first unit filter and an effective refractive index of the cavity included in the second unit filter are different from each other.
17. The spectral filter of claim 16 , wherein a material pattern of the cavity included in the first unit filter and a material pattern of the cavity included in the second unit filter are different from each other.
18. An image sensor comprising:
a spectral filter configured to transmit light; and
a pixel array configured to receive the light transmitted through the spectral filter,
wherein the spectral filter comprises:
a first Bragg reflective layer;
a second Bragg reflective layer spaced apart from the first Bragg reflective layer;
a first resonance layer provided between the first Bragg reflective layer and the second Bragg reflective layer, the first resonance layer comprising a cavity;
a second resonance layer comprising at least a portion of the first Bragg reflective layer, the second Bragg reflective layer, and the cavity;
a third Bragg reflective layer; and
a fourth Bragg reflective layer spaced apart from the third Bragg reflective layer,
wherein the second resonance layer is provided between the third Bragg reflective layer and the fourth Bragg reflective layer, and
wherein the first Bragg reflective layer contacts the third Bragg reflective layer and the second Bragg reflective layer contacts the fourth Bragg reflective layer.
19. The image sensor of claim 18 , wherein each of the first Bragg reflective layer, the second Bragg reflective layer, the third Bragg reflective layer, and the fourth Bragg reflective layer comprises a distributed Bragg reflector (DBR).
20. The image sensor of claim 18 , wherein a thickness of a material layer included in the first Bragg reflective layer and the second Bragg reflective layer is different from a thickness of a material layer included in the third Bragg reflective layer and the fourth Bragg reflective layer.
21. The image sensor of claim 18 , wherein the second resonance layer comprises the first Bragg reflective layer and the second Bragg reflective layer.
22. The image sensor of claim 21 , wherein a first surface of the first Bragg reflective layer and a first surface of the second Bragg reflective layer are in contact with the first resonance layer, and
wherein a second surface of the first Bragg reflective layer opposite to the first surface of the first Bragg reflective layer and a second surface of the second Bragg reflective layer opposite to the first surface of the second Bragg reflective layer are in contact with the third Bragg reflective layer and the fourth Bragg reflective layer, respectively.
23. The image sensor of claim 18 , wherein the second resonance layer comprises one of the first Bragg reflective layer and the second Bragg reflective layer.
24. The image sensor of claim 23 , wherein one of the first Bragg reflective layer and the second Bragg reflective layer is in contact with the first resonance layer.
25. An electronic device comprising an image sensor, the image sensor comprising:
a spectral filter configured to transmit light; and
a pixel array configured to receive the light transmitted through the spectral filter,
wherein the spectral filter comprises:
a first Bragg reflective layer;
a second Bragg reflective layer spaced apart from the first Bragg reflective layer;
a first resonance layer comprising a cavity, the first resonance layer being provided between the first Bragg reflective layer and the second Bragg reflective layer;
a second resonance layer comprising at least a portion of the first Bragg reflective layer, the second Bragg reflective layer, and the cavity;
a third Bragg reflective layer; and
a fourth Bragg reflective layer spaced apart from the third Bragg reflective layer,
wherein the second resonance layer is provided between the third Bragg reflective layer and the fourth Bragg reflective layer, and
wherein the first Bragg reflective layer contacts the third Bragg reflective layer and the second Bragg reflective layer contacts the fourth Bragg reflective layer.
26. The electronic device of claim 25 , comprising one of a mobile phone, a smartphone, a tablet, a smart tablet, a digital camera, a camcorder, a notebook computer, a television, a smart television, a smart refrigerator, a security camera, a robot, or a medical camera.