Surface plasmon polariton band gap structures
First Claim
1. A device for guiding surface plasmon polaritons (SPPs) having a first frequency, said waveguide device comprising,a first medium having a first interface to a second medium, said interface being adapted to guide surface plasmon polaritons and being at least substantially plane, and a plurality of scattering centres, each scattering centre being a region whose cross section in a plane at least substantially parallel to the first interface is an area having a complex dielectric constant different from the complex dielectric constants of the surrounding areas in said plane, wherein projections of said scattering centres at least substantially perpendicularly onto the first interface define one or more non-transmitting parts and one or more transmitting parts on the first interface by forming predetermined, at least substantially periodic patterns of projected scattering centres in said non-transmitting parts, thereby making the non-transmitting parts SPPBG (surface plasmon polariton band gap) regions adapted to at least substantially prohibit the propagation of SPPs having the first frequency, and by not forming the predetermined pattern in the one or more transmitting parts, and wherein the plurality of scattering centres are positioned so as to define at least one transmitting part being at least partially surrounded by one or more non-transmitting parts on the first interface.
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Abstract
The present invention provides a method and devices for controlling the propagation of Surface Plasmon Polaritons (SPPs) using Surface Plasmon Polariton Band Gap (SPPBG) regions. The SPPBG regions are regions of one or more interfaces supporting the propagation of SPPs on which SPPs experience a periodic modulation of the dielectric properties of the media into which its electromagnetic field extend. The frequency range of the band gap is determined by the period of the modulation. SPPBG regions prohibit propagation of SPPs having a frequency within its band gap.
By forming transmitting regions in the SPPBG regions the present invention provides ultra-compact SPP waveguides. The present invention can be utilised to form compact integrated SPP/optical circuits. Also, the present invention provides cavities supporting standing SPP-waves for field localisation. Such field localisation can provide very high field intensities and can be used in various sensor applications.
The devices of the present invention provide a number of advantages over photonic components since SPPs propagates on 2-dimensional interfaces, and only confinement in the plane of propagation is needed. This allows for a very simple production of the devices according to the present invention.
60 Citations
45 Claims
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1. A device for guiding surface plasmon polaritons (SPPs) having a first frequency, said waveguide device comprising,
a first medium having a first interface to a second medium, said interface being adapted to guide surface plasmon polaritons and being at least substantially plane, and a plurality of scattering centres, each scattering centre being a region whose cross section in a plane at least substantially parallel to the first interface is an area having a complex dielectric constant different from the complex dielectric constants of the surrounding areas in said plane, wherein projections of said scattering centres at least substantially perpendicularly onto the first interface define one or more non-transmitting parts and one or more transmitting parts on the first interface by forming predetermined, at least substantially periodic patterns of projected scattering centres in said non-transmitting parts, thereby making the non-transmitting parts SPPBG (surface plasmon polariton band gap) regions adapted to at least substantially prohibit the propagation of SPPs having the first frequency, and by not forming the predetermined pattern in the one or more transmitting parts, and wherein the plurality of scattering centres are positioned so as to define at least one transmitting part being at least partially surrounded by one or more non-transmitting parts on the first interface.
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25. A method for controlling the propagation of surface plasmon polaritons (SPPs) propagating on an at least substantially planar interface between a first and a second medium, said method comprising the steps of:
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providing the first medium, the first medium comprising a first material layer having a first complex dielectric constant ∈
1 with a negative real part, Re(∈
1)<
0, in a first frequency range and having a first surface abutting the interface,providing the second medium, the second medium having, in at least some parts abutting the interface, a second complex dielectric constant ∈
2 with a positive real part, Re(∈
2)>
0, in a second frequency range at least in one or more parts abutting the interface,propagating an SPP at the interface, said SPP having a first frequency comprised in the first and second frequency range, defining a propagation layer comprising the interface and surrounding regions, wherein every point is subject to an electromagnetic field of the SPP having a strength not less than 1% of an electromagnetic field at the interface when the SPP propagates on the part of the interface closest to the point, and confining the SPP to a transmitting part of the interface by providing one or more non-transmitting parts of the interface being SPPBG (surface plasmon polariton band gap) regions at least substantially inaccessible to SPPs having a frequency within a third frequency range comprising the first frequency, said SPPBG regions being defined by a plurality of scattering centres in the propagation layer forming a predetermined, at least substantially periodic pattern when projected at least substantially perpendicularly onto the first interface, each scattering centre being a region whose cross section, in a plane at least substantially parallel to the interface, is an area having one or more complex dielectric constants different from the complex dielectric constant of the surrounding areas in said plane. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34)
propagating the SPP on the transmitting part of the interface, and whenever the SPP propagates from the transmitting part of the interface into a non-transmitting part of the interface, then reflecting at least part of the SPP on the non-transmitting part of the interface and propagating the reflected part of the SPP on the transmitting part of the interface. -
27. A method according to claim 25, wherein the transmitting part of the interface comprises a pattern of projected scattering centres different from the predetermined pattern.
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28. A method according to claim 25, wherein the transmitting part of the interface is at least substantially void of projected scattering centres.
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29. A method according to claim 25, wherein the scattering centres are structures formed at the interface in the first and/or second media.
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30. A method according to claim 25, further comprising the step of forming the SPP by coupling one or more photons to the interface.
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31. A method according to claim 25, further comprising the step of coupling at least part of the SPP to one or more photons.
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32. A method according to claim 25, further comprising the step of propagating a second SPP on the interface, said second SPP having a second frequency outside the third frequency interval.
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33. A method according to claim 32, wherein the step of confining the SPP to the transmitting part of the interface further comprises the step of propagating the second SPP on one of the one or more non-transmitting parts of the interface.
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34. A method according to claim 25, further comprising the steps of
providing a gain medium in the second medium for coupling energy to SPP modes supported by the first interface, said gain medium defining a transmitting part of the first interface when projected perpendicularly onto the first interface, pumping the gain medium electrically or optically, and amplifying the guided SPP by coupling energy from the gain medium to the mode containing the SPP.
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35. A method for manufacturing a device for controlling the propagation of a SPP (surface plasmon polariton) having a first frequency and propagating on an at least substantially planar interface, said method comprising the steps of:
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providing a substrate having an at least substantially planar surface, forming, in one or more parts of the substrate surface, a predetermined and at least substantially periodic pattern of structures which are concave or convex with respect to the substrate surface so as to define one or more non-transmitting parts of an interface between the substrate and a first material layer to be held by the substrate surfaces, providing the first material layer abutting the substrate surface so as to form convex or concave structures in the first layer which are associated with the concave or convex structures of the substrate surface, the first material layer having a complex dielectric constant ∈
1 with a negative real part, Re(∈
1)<
0, in a first frequency range comprising the first frequency, said at least substantially planar interface being an upper or a lower surface of the first material layer,wherein the interface is adapted to support the propagation of SPPs, and wherein the one or more non-transmitting parts of the interface forms one or more surface plasmon polariton band gap regions on the interface, and wherein the pattern of structures is formed to define one or more transmitting parts on the interface without said predetermined pattern, and so that said one or more non-transmitting parts at least partly surround said one or more transmitting parts to form an SPP waveguide in the non-transmitting parts of the interface.
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36. A method for manufacturing a device for controlling the propagation of an SPP (surface plasmon polariton) having a first frequency and propagating on an at least substantially planar interface, said method comprising the steps of:
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providing a first material layer having a complex dielectric constant ∈
1 with a negative real part, Re(∈
1)<
0, in a first frequency range comprising the first frequency, said at least substantially planar interface being a plane associated with an upper or a lower surface of the first material layer, andremoving, or altering the complex dielectric constant of, selected regions of the first layer so as to form a predetermined, at least substantially periodic pattern of selected regions in the first layer, the selected regions thereby obtaining a complex dielectric constant different from ∈
1,wherein the selected regions define, in the interface, one or more non-transmitting parts with said at least substantially periodic pattern and one or more transmitting parts without said at least substantially periodic pattern, wherein the interface is adapted to support the propagation of SPPs, and wherein the one or more non-transmitting parts of the interface forms one or more surface plasmon polariton band gap regions on the interface, and wherein said one or more non-transmitting parts at least partly surround the one or more transmitting parts of the interface.
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39. A method for manufacturing a device for controlling the propagation of an SPP (surface plasmon polariton) having a first frequency and propagating on an at least substantially planar interface between a material layer and a medium, said method comprising the steps of:
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providing the substrate having a surface abutting the material layer, the substrate having a complex dielectric constant >
2 with a positive real part, Re(∈
2)∈
0, in a second frequency range comprising the first frequency, andaltering the complex dielectric constant of a plurality of regions in the substrate to a complex dielectric constant different from ∈
2, said plurality of regions being positioned so as to, when projected at least substantially perpendicularly onto the interface, form one or more predetermined, at least substantially periodic patterns defining one or more non-transmitting parts of the interface.providing the material layer on the surface of the substrate, said material layer having a first complex dielectric constant ∈
1 with a negative real part, Re(∈
1)<
0, in a first frequency range comprising the first frequency and having an upper and a lower surface, the interface being defined as the plane associated with the upper or the lower surface of the material layer,wherein the one or more predetermined patterns define one or more transmitting parts of the interface without the predetermined pattern, said transmitting parts being at least partly surrounded by the one or more non-transmitting parts. - View Dependent Claims (37, 38)
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- 43. A method according to claim 43, wherein the plurality of regions are positioned so as to define one or more transmitting parts forming an SPP waveguide in the non-transmitting parts on the interface.
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45. A method for manufacturing a device for controlling the propagation of a SPP (surface plasmon polariton) having a first frequency and propagating on an at least substantially planar interface, said method comprising the steps of:
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providing a substrate having an at least substantially planar surface. forming, in one or more parts of the substrate surface, a predetermined and at least substantially periodic pattern of structures which are concave or convex with respect to the substrate surface so as to define one or more non-transmitting parts of an interface between the substrate and a first material layer to be held by the substrate surface, providing the first material layer abutting the substrate surface so as to form convex or concave structures in the first layer which are associated with the concave or convex structures of the substrate surface, the first material layer having a complex dielectric constant ∈
1 with a negative real part, Re(∈
1)<
0, in a first frequency range comprising the first frequency, said at least substantially planar interface being an upper or a lower surface of the first material layer.wherein the interface is adapted to support the propagation of SPPs, and wherein the one or more non-transmitting parts of the interface forms one or more surface plasmon polariton band gap regions on the interface, and wherein the pattern of structures is formed to define one or more transmitting parts on the interface without said predetermined pattern, and so that said one or more non-transmitting parts at least partly surround said one or more transmitting nails to form an SPP cavity in the non-transmitting parts of the interface.
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Specification