Near-field optical transducers for thermal assisted magnetic and optical data storage
View Patent ↗An optical transducer comprises an optical element for directing an electromagnetic wave to a focal region and a metallic nano-structure having a longitudinal axis substantially parallel to an electric field of the electromagnetic wave, the metallic nano-structure being positioned outside of the optical element, wherein the electromagnetic wave produces surface plasmons on the metallic nano-structure. A cladding material having a refractive index differing from the refractive index of the optical element can be positioned adjacent to a surface of the metallic nano-structure. Magneto-optical recording heads that include the transducers and disc drives that include the magneto-optical recording heads are also included.
1. An optical transducer comprising:
an optical element for directing an electromagnetic wave to a focal region; and
a metallic nano-structure having a longitudinal axis substantially parallel to an electric field of the electromagnetic wave, the metallic nano-structure being positioned outside of the optical element and separated from the optical element by a gap, wherein the electromagnetic wave produces surface plasmons on the metallic nano-structure.
2. The optical transducer of claim 1 , wherein the metallic nano-structure is evanescently coupled to the electromagnetic wave adjacent to an end of the optical element.
3. The optical transducer of claim 1 , wherein:
the optical element has a first refractive index; and
the metallic nano-structure is surrounded by a material having a second refractive index, with the second refractive index being lower than the first refractive index.
4. The optical transducer of claim 1 , wherein the gap has a width of less than 50 nm.
5. The optical transducer of claim 1 , wherein the nano-structure comprises a metallic pin having an aspect ratio greater than or equal to 2:1.
6. The optical transducer of claim 1 , wherein the nano-structure comprises a pin having a pointed tip.
7. The optical transducer of claim 1 , wherein the nano-structure is dimensioned for resonant coupling of energy into a recording medium.
8. The optical transducer of claim 1 , wherein the optical element comprises one of: a solid immersion lens, a solid immersion mirror, or a planar waveguide.
9. The optical transducer of claim 1 , wherein the electromagnetic wave comprises one of: radially polarized light or split linearly polarized light.
10. A magneto-optical recording head comprising:
a magnetic write pole; and
the optical transducer of claim 1 positioned adjacent to the magnetic write pole.
11. A disc drive comprising:
a storage medium;
the magneto-optical recording head of claim 10 ; and
an arm for positioning the magneto-optical recording head adjacent to the storage medium.
12. An optical transducer comprising:
an optical element having a focal region and a first index of refraction; the means
a metallic nano-structure embedded in the optical element at the focal region; and
a cladding material having a second index of refractive positioned between the optical element and the metallic nano-structure, and separating the metallic nano-structure from the optical element.
13. The optical transducer of claim 12 , wherein the metallic nano-structure is dimensioned to resonantly couple to the electromagnetic wave in the presence of a recording medium.
14. The optical transducer of claim 12 , wherein:
the thickness of the cladding material is less than the thickness of the metallic nano-structure.
15. The optical transducer of claim 12 , wherein:
the difference between the first and second refractive indexes is greater than about 0.5.
16. The optical transducer of claim 12 , wherein:
the thickness of the cladding material is tapered along a surface of the metallic nano-structure.
17. The optical transducer of claim 12 , wherein:
the second refractive index is lower than the first refractive index.
18. An optical transducer comprising:
an optical element having a focal region and a first index of refraction;
a metallic nano-structure positioned in the optical element at the focal region; and
a cladding material having a second index of refraction positioned between the optical element and the metallic nano-structure;
wherein the second index of refraction is greater than the first index of refraction.
19. The optical transducer of claim 12 , wherein the optical element comprises one of: a solid immersion lens, a solid immersion mirror, or a planar waveguide.
20. The optical transducer of claim 12 , wherein electromagnetic wave comprises one of: radially polarized light or split linearly polarized light.
21. A magneto-optical recording head comprising:
a magnetic write pole;
the optical transducer of claim 12 positioned adjacent to the magnetic write pole; and
a polarizer for polarizing the electromagnetic wave.
22. A disc drive comprising:
a storage medium;
the magneto-optical recording head of claim 21 ; and
an arm for positioning the magneto-optical recording head adjacent to the storage medium.