Plasmonic transducer having two metal elements with a gap disposed therebetween
A plasmonic transducer includes at least two metal elements with a gap therebetween. The metal elements are elongated along a plasmon-enhanced, near-field radiation delivery axis. Cross sections of the metal elements in a plane normal to the delivery axis vary in shape along the delivery axis. A waveguide is disposed along an elongated side of the plasmonic transducer. The waveguide is optically coupled to the plasmonic transducer along the elongated side.
1. An apparatus comprising:
a plasmonic transducer that includes at least two metal elements with a gap therebetween, wherein the metal elements are elongated along a plasmon-enhanced, near-field radiation delivery axis, and wherein cross sections of the metal elements in a plane normal to the delivery axis vary in shape along the delivery axis; and
a waveguide disposed along an elongated side of the plasmonic transducer and overlapping the plasmonic transducer on a substrate-parallel plane, wherein the waveguide is optically coupled to the plasmonic transducer along the elongated side.
2. The apparatus of claim 1 wherein the cross sections become narrower in a down track direction at an output end of the plasmonic transducer.
3. The apparatus of claim 2 , wherein the gap becomes narrower in a cross track direction at the output end of the plasmonic transducer.
4. The apparatus of claim 3 , wherein each of the metal elements comprise a tip of constant cross-sectional shape along the delivery axis separated by the narrowed gap at the output end of the plasmonic transducer.
5. The apparatus of claim 1 , wherein the metal elements each comprise:
a tip portion proximate an output end of the plasmonic transducer;
a taper portion coupled to the tip portion and increasing in cross sectional area away from the output end; and
a coupling portion coupled to the taper portion and disposed along the waveguide to receive energy from the waveguide.
6. The apparatus of claim 5 , wherein the coupling portion has a constant cross sectional area along the delivery axis.
7. The apparatus of claim 1 , wherein the waveguide extends to an output end of the plasmonic transducer.
8. The apparatus of claim 1 , wherein the metal elements are co-planar on the substrate-parallel plane.
9. An apparatus comprising:
a plasmonic transducer that includes at least two metal elements with a gap therebetween, wherein the metal elements are elongated along a plasmon-enhanced, near-field radiation delivery axis and each comprise:
a tip portion proximate an output end of the plasmonic transducer and having a first cross sectional area relative to a plane normal to the delivery axis;
a coupling portion at an input end of the plasmonic transducer and having a second cross sectional area relative to the plane that is greater than the first cross sectional area; and
a taper portion coupled between the tip portion and the coupling portion, wherein the taper portion varies from the first to the second cross sectional area along the delivery axis.
10. The apparatus of claim 9 , further comprising a channel waveguide disposed along the delivery axis proximate at least the elongated coupling portions of the metal elements.
11. The apparatus of claim 10 , further comprising a dielectric layer disposed between a core of the waveguide and the metal elements.
12. The apparatus of claim 9 , wherein the gap is 40 nm or less at the output end, and wherein the tip portions has a side dimension proximate the gap of 40 nm or less.
13. An apparatus comprising:
a plasmonic transducer that includes at least two metal elements with a gap therebetween, wherein the metal elements are elongated along a plasmon-enhanced, near-field radiation delivery axis and each comprise:
a tip portion proximate an output end of the plasmonic transducer and having a first cross sectional area relative to a plane normal to the delivery axis;
a coupling portion at an input end of the plasmonic transducer and having a second cross sectional area relative to the plane that is greater than the first cross sectional area and
a taper portion coupled between the tip portion and the coupling portion, wherein the taper portion varies from the first to the second cross sectional area along the delivery axis, wherein a combined length of the coupling and taper portions along the delivery axis is at least 30 times a length of the tip portion along the delivery axis.
14. The apparatus of claim 9 , wherein the metal elements are co-planar on a substrate-parallel plane.
15. The apparatus of claim 9 , further comprising a waveguide disposed along an elongated side of the plasmonic transducer and overlapping the plasmonic transducer on a substrate-parallel plane.
16. The apparatus of claim 13 , further comprising a waveguide disposed along the delivery axis proximate at least the elongated coupling portions of the metal elements and overlapping the plasmonic transducer on a substrate-parallel plane.
17. The apparatus of claim 16 , further comprising a dielectric layer disposed between a core of the waveguide and the metal elements.
18. The apparatus of claim 13 , wherein the gap is 40 nm or less at the output end, and wherein the tip portions has a side dimension proximate the gap of 40 nm or less.
19. The apparatus of claim 13 , wherein the metal elements are co-planar on a substrate-parallel plane.