DE102007031841A1 - Multi-band coupler structure for e.g. power splitter, has surface plasmon polariton gap wave guide with common layer of metal across entire coupling area, where metallic layer has thickness less than preset value - Google Patents

Abstract

The coupler structure has a surface plasmon polariton gap waveguide (SPP-GWG) provided with a dielectric layer. A nano-optical waveguide is coupled in a coupling area. The gap waveguide comprises a common layer of metal across the entire coupling area. A set of waveguides is provided for transferring electromagnetic energy. The metallic layer has a thickness less than 50 nanometers such that adjacent active boundary layers of the different waveguides in the coupling area are distant from each other in the coupling area.

Description

The The invention relates to coupler structures for use in nano-optical integrated circuits. The couplers are based on specifically excited modes of plasma oscillations in boundary layers between Dielectrics and metals related to surfaces Plasmon Polaritons (Surface Plasmon Polaritons, SPP).

The excitation of SPP to manipulate light fields is known. An overview will be provided by Aussenegg and Ditlbacher in the article: Nanooptik - Plasmons as Light Transporter. In: Physics in Our Time, Issue 5, (2006), Vol. 37, pp. 220-226 , given.

When Plasmons are the collective excitations of free electrons in metals to plasma oscillations against the ion hulls. As quantum mechanical quasiparticles, they pose density fluctuations of charge carriers, so represent vibrations in the FermiGas of metals.

One Polariton is a quasiparticle that interacts with an elementary Excitation in the solid state (plasmon) with electromagnetic fields (Photons) occurs.

Surface plasmons are surface waves in which the longitudinal electrical vibrations are excited parallel to the surface of a metal. The resulting field strength is measurable in the space above the metallic surface. 1 schematically shows the typical course of the electric field strength, as caused by such plasma oscillations along an interface between metal and dielectric.

SPP can be stimulated with coherent light (LASER). Due to its dispersion relation, the wave vector of the exciting light has to be adapted for this purpose. This can be done in different ways. Known methods are the prism coupling according to Otto or Kretschmann-Räther, the excitation of local defects of the metal surface and the lattice coupling. Another efficient method is the so-called end-fire technique used by Stegeman, Wallis and Maradudin in the article: Excitation of surface polaritons by end-fire coupling. In: Optics Letters, Issue 7, (1983), Vol. 8, pp. 386-388 , first described.

A Nano-optics based on conventional optical concepts is not feasible due to the validity of the Abbe limit. The propagation of light fields is due to the diffraction of the light in classic optical elements impossible, their dimensions is less than half the wavelength of light.

With Help the excitation of SPP by (modulatable) LASER light can but also light fields, with a transversal extension the is significantly less than half the wavelength of the light, exist. As a result, a targeted light field manipulation in the sub-wavelength range contrary to the original restrictions the abbe limit is possible in the first place.

The problem with the Abbe limit is by Krenn and Aussenegg in the article: Nano-Optics with Metallic Structures - On Handling Light Beyond the Abbe Limits. In: Physics Journal 1 (2002) No. 3, pp. 39-45 , extensively discussed.

SPP are at the interface between a metal and a Dielectric bound. The lateral extent of the fields hangs thereby of the wavelength of the stimulating light beam and highly dependent on the respective matter. in principle can be found that the average penetration depth in metal is significantly lower than in a dielectric.

there is used as a measure of the penetration depth of the waste the amplitude of the respective field strength on the 1 / e - th Part considered.

2 schematically shows the different material-dependent penetration depths of the associated with the plasma oscillations lateral magnetic field strength. As metals, it is presently preferred to use precious metals such as gold or silver. For silver, the average penetration depth of the magnetic field of the plasma oscillations at a wavelength of the exciting light of 780 nm (near infrared) is about 30 nm. In a typically used for the technological production of the interface used dielectric such as silicon dioxide (SiO 2), the average penetration depth of magnetic field of the plasma oscillations at a wavelength of the exciting light of 780 nm (near infrared) about 400 nm, that is about an order of magnitude more than in metal. The fields are coupled together, and due to the attenuation of the fields by the metal necessarily used, the entire field energy of the plasma oscillations in the longitudinal propagation direction is inevitably attenuated as well.

The mean propagation length of these plasma oscillations in the longitudinal propagation direction is therefore in a simple interface, as shown in FIG 2 is shown, only a few hundred microns, so about 400 microns at an exciting wavelength of the light of 780 nm and an interface of the materials silver and silicon dioxide. To increase the longitudinal range of the plasma oscillations by a further order of magnitude is usually a double Grenzflä A dielectric-metal dielectric (IMI) dielectric material may be used, which may be considered as a strip-guided SPP (surface-plasmon-polariton stripe waveguide, SPP-SWG) waveguide. By careful choice of the dimensions of the strip thickness, the strip width and the materials can then be achieved that only those modes exist on the SPP SWG, which have a particularly low attenuation in the propagation direction. Such a structure is then commonly referred to as the Wide Area Surface Plasmon Polariton Waveguide (Long Range Surface Plasmon Polariton Wave Guide, LR-SPP-WG). Depending on the excited state, different modes of excitation occur in such a waveguide.

With symmetrical excitation, the fields of magnetic field intensity in the planes overlap parallel to the interfaces in the 3 shown way. This is the even wave type (SPP even mode) and at the same time the fundamental mode. In addition, asymmetrical excitation is also possible, in particular if it is caused, for example, by a discontinuity in the interface (eg coupler structure).

In the case of asymmetrical excitation, the fields of magnetic field strength in the planes are superimposed parallel to the interfaces in the 4 shown way. This is the odd wave type (SPP odd mode). In the development of nano-optical couplers, generally all wave types that can be propagated must be taken into account.

Recent advances in increasing the longitudinal range of plasma oscillations have been made by Guo and Adato in the article: Extended long range plasmon waves in finite-thickness metal film and layered dielectric materials. In: OPTICS EXPRESS 14 (2006) No. 25, pp. 409-418 , reported. By using inhomogeneous, layered dielectric materials, the longitudinal range of the plasma vibrations is greatly increased.

at the use of an outer dielectric layer of silicon nitride (Si 3 N 4) and an inner dielectric layer made of silicon dioxide (SiO 2) and a gold strip of 20 nm thickness become an average propagation length for the fundamental wave type these plasma oscillations in the longitudinal propagation direction of 43 mm (43000000 nm).

On the one hand, because of these achievements in increasing the range of stripe-guided plasma oscillations, and on the other because of the relatively familiar technique, which is very similar to stripline technology known from microwave technology for decades, nano-optic devices and circuit elements become necessary for targeted light field manipulation , currently almost exclusively realized with the help of SPP-SWG. Numerous structures based on the SPP-SWG technique have already been implemented and measured. A nanooptic coupler structure based on the SPP-SWG technique is used by Boltasseva, Nikolajsen, Leosson, Kjaer, Larsen and Bozhevolnyi in the article: Integrated Optical Components Utilizing Long-Range Surface Plasmon Polaritons. In: Journal of Lightwave Technology, Vol. 23 (2005), no. 1, pp. 413-422 , presented. The coupler described therein has to guide the light wave fields metal conductor strips made of gold with a layer thickness of 15 nm and a width (stripe width) of 8 microns for each waveguide. In each case, two such SPP SWGs are brought together in a spatial area with a variable interaction length of 0.1 mm to 1.5 mm in 0.1 mm increments. The distance (separation) between the respective SPP SWGs in the area of the coupling length is investigated for two values, namely 0 μm and 4 μm.

to Examining the frequency dependence will be the distance between the respective SPP SWGs in the range of the coupling length increased to 6 microns and the coupling length even increased to 8 mm. Although the scientists show that with their directional coupler different gradations of the coupling up to the same high power distribution (-3 dB) between can achieve the individual waveguides, this is Directional coupler not better suited because it is in its dimensions way too big.

The Cause in the relatively large dimensions of the described Kopplers is of a fundamental nature and is primary in the use of a quasi-planar SPP-SWG technique, i. H. the coupler structures and waveguide strips are as in the stripline technique in a common plane.

in the Related to the explanation of edge coupling or broadside coupling becomes the resulting problem discussed again in detail below. The focus on the LR-SPP, which are guided with the help of metal strips, leads circuitry into a physical condition Limitation of the minimal design, since those with the SPP-SWG led Lightwave fields are laterally extended very far. The maximum achievable packing density of the individual nano-optical circuit components is due to the inevitably resulting crosstalk limits the signals between adjacent SPP SWGs.

So is in the worst case, the frequency-dependent crosstalk the described coupler structure at one wavelength from 1600 nm about -3 dB at a distance of at least 6 μm, d. H. because of the large penetration depth of the strip-guided Light wave fields in the low-damping surrounding dielectric is still in spite of a relatively large distance of 6000 nm transfer half of the injected energy to the other waveguide. Thus, an ultra-compact nano-optics can not be realized. For reliable and reliable miniaturization of nano-optical circuit components must break new ground become! It must be remembered that it is the primary task nanooptical circuits is as much functionality as possible with the lowest possible space available to deliver. The low-loss transport of energy over long distances is by no means the task of nano-optics.

One to the conventional SPP SWG dual waveguide is the key for miniaturization!

to Targeted guidance of the plasma oscillations becomes one double interface of metal-dielectric-metal (metal Insulator Metal, MIM) used as a gap-guided SPP waveguides (surface-plasmon-polariton gap waveguide, SPP-GWG) can be viewed. By careful choice of dimensions the gap height, the gap thickness and the materials can then be achieved that such modes exist on the SPP-GWG, the one sufficiently low attenuation in the propagation direction have. Depending on the state of excitement, it also happens in one Waveguides to different excitation modes, as they are in principle already described in connection with the SPP SWG. SPP-GWG are so tiny, filled with dielectric gaps between metal strips, which may be arbitrarily thick.

The Light energy is almost completely concentrated in the gap and the lateral metal walls dampen the lateral Field relatively strong, because the penetration depth in metal is only low.

Such SPP-GWG are known, they have already been manufactured and measured. Liu, Zhanghua and Sailing describe the excellent isolation of such waveguides in the article: Novel surface plasmon waveguide for high integration. In: OPTICS EXPRESS 13 (2005) No. 17, pp. 6645-6650 , On substrates of quartz glass (fused silica) as a carrier of the entire test arrangement, metal films with a layer thickness of 60 nm or 200 nm are first applied to different test structures, then with the help of electron beam lithography and a reactive ion etching the 50 nm thick column inserted into the metal film. As a dielectric for filling the gap is simply a standard in semiconductor technology used Abdecklaack (PMMA) applied. Thus, the nano-optical test structure is already finished. The authors point out that the layer thickness of the metal layer must not be too high, because otherwise disturbing higher modes are capable of propagation.

Even though this is the case with the light waves guided here by the SPP-GWG because of the metal edging exclusively around short range Surface Plasmon Polariton (Short Range Plasmon Polariton, SR-SPP) Wave types, so-called SR-SPP modes is, results at a gap thickness of 50 nm and a height of the metal of 200 nm has a propagation length of 2.86 μm. The experiments have shown that even at an approximation the SPP-GWG up to 150 nm, the coupling length 15 microns long would have to be a significant crosstalk the light signals from one SPP-GWG to the adjacent SPP-GWG to effect.

in principle It is noted that a compromise must be found between the losses of SPP-GWG, those with greater thickness of the gap become smaller and the integration density, which coincides with Lesser gap thickness significantly increased and thus simultaneously also reduces the lateral dimensions.

The experiments described above have shown that the separated SPP-GWG have only very low couplings. To make a SPP-GWG compatible coupler, some difficulties have to be overcome. One approach to calculating a coupler is by Wang, Islam and Eleftheriades in the article: An ultra-short contra-directional coupler using surface plasmon polaritons at optical frequencies. In: OPTICS EXPRESS 16 (2006) No. 16, pp 7279-7290 , described. There, both SPP-GWG and SPP-SWG are simultaneously simulated to calculate the coupler. The calculations are based on a complicated six-layer structure in which a layer of 15 nm quartz glass with a permittivity number of 2.09 and then a metal layer of 20 nm silver is deposited on a silver plate. This will initially shape the SPP-GWG.

About that Then there is a layer of 20 nm thick glass with a Permittivity number of 4.2. Above it is a 15 nm thick layer of silver and then over again a layer of glass with a permittivity number of 4.2. This will then form the SPP SWG.

It will now be between the two optical Waveguide types, namely SPP-GWG and SPP-SWG coupled. The length of the coupling path is, however, 1000 nm. Although the authors have impressively shown that for a highly integrated nanooptic circuit, both optical waveguide types in fact coexist and can be used simultaneously, the coupler presented in this article is not better suited because the layer structure for Making the coupler too complicated, the lateral dimensions of the coupler are too large and the coupling of the coupled energy is on the same side as the coupling (contra-directional SPP coupler).

The Although the typical coupler behavior, as z. B. from Waveguide couplers in the microwave range forth, leads but here too significant technical problems, because the boundary layer of the SPP-GWG from the boundary layer of the SPP-SWG only 40 nm away is. Of this route then there is half made of low-damping dielectric. This means that between the injected signal and the extracted signal only a metal layer thickness of 68 silver atom diameters is. This certainly leads to problems, if at one eventual realization of this assumption for computational simulation Coupler circuit distinguish the individual signals from each other should be.

A exclusively in SPP-GWG technology constructed broadside-coupled Ultra-compact multi-band coupler structure is not known!

Of the The invention defined in claim 1 is based on the problem Broadband coupled ultra-compact multi-band coupler structures based solely on SPP-GWG technology, d. H. in Split-guided surfaces of plasmon polaritons Waveguide technology, with the smallest possible dimensions build.

This Problem is indicated by the in claim 1 Characteristics solved.

The particular advantages of the invention are that the coupling length slightly by orders of magnitude can be shortened because the SPP-GWG based coupler structures in a simple way broadside-coupled (broadside-coupled) constructed whereas known couplers use SPP-SWG technology So far edge-coupled (edge-coupled) have been built. With the SPP-GWG based broadside coupling, the fields are over the entire metallization coupled together. When coupling SPP-SWG based fields are in one plane merely approximating the respective edges of the metal strips, resulting in a significantly lower degree of coupling per unit length and thus significantly longer coupling lengths leads.

One Another advantage of using the SPP-GWG technology to build the Coupler is the larger field concentration in the lead Dielectric between the metal sidewalls, which is generally leads to more compact components. The one on these waveguides used straight (short range) wave type can also be efficient and easy with the help of proven end-fire technology stimulate. It can alternatively but also the one-sided classic wave type (Single interface mode, SI-mode), which leads to the leadership only one single interface of the SPP-GWG needed, isolated be stimulated and used.

This opens up additional degrees of freedom in circuit technology Application of these nano-optical circuit components.

One Another advantage is that the distance to the reliable Avoiding crosstalk between the individual waveguides is smaller by several orders of magnitude in the SPP-GWG, as for the same degree of isolation in the SPP SWG is required. So the four gates of a coupler from each other To isolate are significantly shorter distances in SPP-GWG based couplers necessary, as is the case with the SPP-SWG based couplers. For this reason alone, a SPP-GWG based coupler together with its incoming and outgoing waveguides orders of magnitude smaller than it was based on the SPP SWG Coupler is the case.

In summary, there is the advantage that the planar dimensions of the here presented for the first time coupler structures in SPP-GWG based technology with the same functionality is about one million times smaller than is possible in the SPP-SWG technique previously used. So is in the above-mentioned article of Boltasseva et. al. the shortest coupling length of the SPP-SWG based coupler with comparable optical properties as the couplers described here, in the best case 0.8 mm, that is whopping 800000 nm.

at the novel coupler structures presented here according to the invention, based on the SPP-GWG technique, this is the Pair required length because of the ones used here Broadside coupling in one of the structures only 36 nm, the means it is more than twenty thousand times shorter. If this shortening factor for a length parameter tends to be applied in the area opened very clearly the miniaturization potential of the here favored Slit-guided waveguide technique.

advantageous Embodiments of the invention can be found in the subclaims.

embodiments The invention are illustrated in the drawings and are in Described in more detail below.

It shows

1 schematically the typical course of the electric field strength, as it is caused by plasma oscillations along an interface between metal and dielectric,

2 schematically the different material-dependent penetration depths of the associated with the plasma oscillations lateral magnetic field strength,

3 schematically shows the course of the magnetic field strength laterally to the propagation direction of the first straight wave mode (SPP even mode) along a strip-guided surface plasmon polariton waveguide (SPP-SWG) for a relatively thick strip,

4 schematically shows the course of the magnetic field strength laterally to the propagation direction of the first odd mode along a strip-guided surface plasmon polariton waveguide (SPP-SWG) for a relatively thick strip,

5 schematically the course of the magnetic field strength laterally to the direction of propagation of the classical wave mode (single interface mode, SI-mode) with only one-sided excitation along a strip-guided surface plasmon polariton waveguide (SPP-SWG) for a relative thick stripes,

6 schematically the layer structure and the course of the magnetic field strength laterally to the propagation direction of the fundamental wave type in the SPP-SWG,

7 schematically the layer structure and the course of the magnetic field strength laterally to the propagation direction of the fundamental wave type in the SPP-GWG, with the gap thickness (G) and the gap height (H),

8th 1 is a schematic plan view of an exemplary first embodiment of a 4-port coupler structure with the respective signal ports of the coupler,

9 1 is a schematic plan view of an exemplary first embodiment of a 4-port coupler structure with the most important dimensions,

10 1 schematically the incomplete unstructured layer sequence for producing an exemplary first embodiment of the 4-port coupler,

11 2 schematically the partially structured layer sequence for producing an exemplary first embodiment of the 4-port coupler,

12 1 schematically the complete structured layer sequence for producing an exemplary first embodiment of the 4-port coupler,

13 1 is a schematic side view of an exemplary first embodiment of the 4-port coupler with the two signal ports of the shortened version of this coupler with excitation by SI modes;

14 the course of the magnetic fields (SI mode) along the inner boundary surfaces of the individual waveguides of an exemplary shortened first embodiment of the 4-port coupler,

15 1 is a schematic plan view of an exemplary embodiment of a measuring arrangement for measuring the 4-port coupler structures (DUT) with all the signal ports of the respective coupler,

16 2 schematically shows the plan view of an exemplary embodiment of a normalizing 4-port auxiliary structure for the measuring arrangement for measuring the 4-port coupler structures, with the most important dimensions,

17 the frequency-dependent course of the magnitude of the most important scattering parameters of a tested 4-port coupler in the shortened first embodiment,

18 the frequency-dependent course of the magnitude of the most important scattering parameters of a tested 4-port coupler in the non-shortened first embodiment,

19 the course of the magnetic fields of the symmetric fundamental wave type along the individual waveguides (SPP-GWG) of an exemplary non-shortened first embodiment of the 4-port coupler at a frequency of about 250 THz, with a nearly complete coupling between port 1 and port 4,

20 the course of the magnetic fields of the symmetric fundamental wave type along the individual waveguides (SPP-GWG) of an exemplary unabridged first embodiment of the 4-port coupler at a frequency of about 350 THz, with a nearly equal coupling between port 1 and port 4 and between port 1 and port 3,

21 the course of the magnetic fields of the symmetric fundamental wave type along the individual waveguides (SPP-GWG) of an exemplary non-shortened first embodiment of the 4-port coupler at a frequency of about 440 THz, with a nearly complete coupling between port 1 and port 3,

22 the typical cross-section of the coupling region of SPP-SWG-based coupler structures, as previously realized by other scientists,

23 the typical cross section of the coupling region of the broadside coupling used here of SPP-GWG based coupler structures, with the most important dimensions,

24 1 is a schematic plan view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler,

25 1 is a schematic side view of an exemplary second embodiment of a 4-port coupler structure with the coupler's two first signal ports and the region of the coupling;

26 1 is a schematic plan view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with a signal gate angled 90 degrees in the plane;

27 1 is a schematic plan view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with two signal ports angled 90 degrees in the plane,

28 1 is a schematic plan view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with four signal gates angled 90 degrees in the plane,

29 1 is a schematic plan view of an exemplary second embodiment of a 6-port coupler structure with the respective signal ports of the coupler,

30 schematically the side view of an exemplary second embodiment of a 6-port coupler structure with the two first signal ports and the fifth signal port of the coupler and the region of the coupling.

The typical course of the electric field strength, as it is caused by plasma oscillations along an interface between metal and dielectric, is in 1 shown schematically.

in principle There are two different materials to recognize, namely on the one hand metal (hatched area) and on the other dielectric (dotted area). By the periodic shifting of the charge centers of the electron surrounding the atomic hulls of the metal the plasma oscillations are generated. The periodic shift of the respective charge centers is here by the characters + and - hinted. Initially, the Electrons on the surface of the metal, so those which is directly in the interface between the metal and the dielectric. To excite the plasma oscillations the coherent light of a LASER is used. once stimulated, the plasma oscillations propagate until, the field energy is consumed by loss mechanisms.

The electromagnetic fields associated with these plasma oscillations in the interface have both electrical and magnetic field components. Therefore, it is easy to see that the field strengths of both coupled fields in the conductive metal decay much faster than in the non-conductive dielectric. The field lines in the metal are thus more closed than in the dielectric, where they can still be detected relatively far away from the interface. While 1 shows the longitudinal course of the electric field strength in the propagation direction is in 2 the lateral penetration depth is shown transversely to the propagation direction. As a measure of the penetration depth, the fall in the amplitude of the field strength to the 1 / th part is usually used. The penetration depth thus defined depends on the material used. For silver (Ag), the average penetration of the magnetic field of the plasma oscillations at a wavelength of the exciting light of 780 nm (near infrared) is about 30 nm. For silicon dioxide (SiO 2), the average penetration of the magnetic field of the plasma oscillations at a wavelength of the exciting Light of 780 nm (near infrared) about 400 nm, about ten times more.

3 shows a structure with two interfaces. When a metal strip is embedded in a dielectric and both interfaces are excited, the electromagnetic fields may be superimposed and form various propagatable modes or modes. 3 shows schematically the course of the magnetic field strength laterally to the propagation direction of the first straight wave mode (SPP even mode) along a strip-guided surface plasmon polariton waveguide (SPP-SWG) for a relatively thick strip. An opposite overlay of the fields is possible. 4 schematically shows the course of the magnetic field strength laterally to the propagation direction of the first odd mode along a strip-guided surface plasmon polariton waveguide (SPP-SWG) for a relatively thick strip. Such odd modes are mostly disturbing and undesirable. By reducing the conductor thickness, these modes can be suppressed. 5 shows schematically the course of the magnetic field strength laterally to the propagation direction of the classical wave type (single interface mode, SI-mode) with only one-sided excitation (here) along a strip-guided surface plasmon polariton waveguide (SPP-SWG ) for a relatively thick strip. The problem of stimulating this wave type without at the same time conforming to the even wave type 3 can be solved by irradiating only a single interface with the laser.

In order to reduce the losses in the metal and to reduce the number of modes or modes carried by the interfaces, metal strips with narrow lateral dimensions are typically used in practice. Structures have emerged known as strip-guided surfaces plasmon polariton waveguide (SPP-SWG). The 6 schematically shows the layer structure of the SPP-SWG and the course of the magnetic field strength laterally to the propagation direction of the fundamental wave type.

For However, the invention presented here becomes another nanooptic Waveguide favored: To reduce the dimensions of nano-optical Structures and reduce the number of the interfaces guided wave types or fashions, are in practice typically used in column metal with narrow lateral dimensions. Thus, 50 nanometers is a typical value for the gap thickness (G) and 200 nanometers a typical value for the gap height (H).

It Structures have established themselves as gap-guided Surface plasmon polariton waveguide (surface-plasmon-polariton gap waveguide, SPP-GWG).

In the same relative scale as in 6 is in 7 schematically the layer structure and the course of the magnetic field strength shown laterally to the propagation direction of the fundamental wave type in SPP-GWG. SPP-SWG and SPP-GWG are mutually dual structures. In principle, they can also be used simultaneously in a complex nano-optical circuit.

So it is conceivable and certainly advantageous that SPP-GWG was based Structures for the construction of individual ultra-compact nano-optical function blocks be used and for connecting and transporting the respective Signals between more distant function blocks can then SPP SWG can be used. Such a hybrid technique with both dual forms of nanooptic waveguide has more complex Circuit structures in the future certainly have many advantages. One such ultra-compact nano-optical function module is, for example one of the broadside-coupled shown here according to the invention ultra-compact multi-band coupler structures in gap-guided Surface plasmon polariton waveguide technology (SPP-GWG Technology).

A split-guided surface plasmon polariton waveguide (SPP-GWG) consists, as in 7 represented in a limited area of the height (H) of three layers, wherein the first layer of metal, the second layer of a dielectric having the thickness (G) and the third layer is again made of metal, whereby two plane-parallel interfaces between the different materials are formed, which have the distance (G) from each other. Depending on the respective geometrical dimensions, namely the height (H) and the thickness (G) and the respective characteristic properties of the materials used to construct the SPP-GWG, different types of propagating modes can be excited, each one depending on the type overlapping the fields also involves both interfaces of the SPP-GWG simultaneously. At this point it should be mentioned in addition, that in connection with 2 and 5 Of course, the classical wave mode (SI-mode) can also excite plasmon polariton gap waveguide (SPP-GWG) in the gap-guided surface if the lateral metal walls are sufficiently far away, ie if the gap thickness (G ) is chosen very large. This is used in the shortened first embodiment of the coupler structures presented here.

8th schematically shows the top view of an exemplary coupler structure of the first embodiment with the four signal ports of the coupler. In this representation, one looks from above onto the dielectric with the gap thickness (G). The drawing is not to scale. It can be seen in the drawing that two SPP-GWG initially relative have a large distance from each other, then run next to each other over a certain distance (the coupling path) closely adjacent and then again have a relatively large distance from each other.

At The ends of the SPP-GWG marked here are the four signal gates of the thus designed coupler defined. Gate 1 is the entrance gate (input port) of the coupler. Here, the signal energy is actively supplied. Gate 2 is the isolated port for this coupler. The lightwave fields are superimposed with appropriate Dimensioning the coupler dimensions so that in this gate the Signal energy largely disappears. That's why this first Embodiment of the coupler also as a unidirectional Type can be designated. The isolated gate would be in microwave engineering correspond to the fumbled gate. Gate 3 is the passage gate (through port). Here, the part of the signal energy fed into port 1 becomes decoupled, which is not coupled in Tor 4. gate 4 is the coupled port. Here is the part of signal energy fed into port 1 is decoupled from the other SPP-GWG is over-coupled.

A nano-optical coupler in this first embodiment can be excited by different modes. For relatively large thicknesses of the dielectric gap in the SPP-GWG, the in 2 and 5 shown classical, not superimposed surfaces SPP wave type (SI-mode) exist.

In this case, the door handle must be specified. Then, the mutually adjacent inner boundary surfaces of the two SPP-GWG are to be regarded as the actual signal gates. This is in 8th indicated that the Torbezeichnung has been placed on the then relevant interface and not in the middle of the respective dielectric of the SPP-GWG.

Of the Coupler is basically symmetrical, d. H. it can also use any other gate to feed the signal become. The other goals then arise accordingly.

9 shows schematically the top view of an exemplary 4-port coupler structure of the first embodiment with the most important characteristic dimensions. The thickness of the dielectric filled gap is denoted by (G). At a height (H) of the metal layer of the noble metal silver of 200 nm, a value of about 50 nm for the thickness (G) of the gap is to be selected for a typical SPP-GWG for high packing density. In principle, however, the dimensioning of the gap thickness (G) offers an additional degree of freedom in the design of nano-optical circuit components. The distance (W) between the interfaces of the two SPP-GWG should be at least 150 nm. Then, according to the above-referenced investigations, no significant crosstalk of the signals takes place between the individual SPP-GWGs. The actual coupling length is denoted by (L) and the coupling distance is denoted by (D). Both are carefully dimensioned values that significantly influence the electro-optical behavior of the couplers, thus determining the characteristic quantities such as coupling attenuation, decoupling (isolation) and directivity. The total length of the couplers is the coupler length and is denoted by (T). Here it plays a role that the SPP-GWG need not be separated at right angles, but in slightly curved shape with not too small radius of curvature, otherwise the attenuation in the SPP-GWG may be too large.

In order to manufacture such a 4-port coupler of the first embodiment, it is advisable to resort to the well-established methods of conventional semiconductor technology. 10 schematically shows an initially incomplete and unstructured layer sequence of a generated by oxidation of a semiconductor wafer of silicon dielectric layer, as a basis for producing an exemplary embodiment of the 4-port coupler of the first embodiment. The silicon wafer not shown here, which is located under the dielectric sketched here, also serves as a carrier plate for the nano-optical test structures to be produced, which can then be brought to the desired manipulable sizes of the respective test structures in a known manner, such as chips. In the 10 The lower layer shown is a dielectric, which consists of silicon dioxide (SiO 2), which adheres firmly and securely to the silicon wafer, not shown here, which acts as a carrier plate. On the silicon dioxide, a 200 nm high metal layer of silver (Ag) is vapor-deposited or better sputtered on. With the help of electron beam lithography, the metal layer is now masked and patterned by reactive ion etching. The 11 schematically shows the still incompletely structured layer sequence for producing an exemplary first embodiment of the 4-port coupler. In the metal, the gaps were etched in a high vacuum using ions accelerated in an electric field. The coupling distance (D) is a critical parameter because the ratio of the metallization height to the width of the non-etched residual ridge between the two later completed SPP-GWG is very unfavorable (coupling distance (D) = 15 nm, metal layer height or gap height (H) = 200 nm).

Here are narrow, reproducible process parameters, variably dimensioned mask dimensions (ie, in practice, the mask dimensions will vary slightly around the target dimensions.) to compensate for unforeseen process tolerances and thereby achieve a higher yield) and some luck necessary to obtain a satisfactory yield of test structures. The required tiny structures are still a major challenge for the currently available technological appliances and by no means comply with the established specifications. However, this problem will be solved in the future if the increased demand for such structures will enable the economic production of suitable technologies and processes.

12 schematically shows the complete, fully structured layer sequence for producing an exemplary first embodiment of the 4-port coupler. With the application of the dielectric covering varnish (PMMA) on the spin coater, drying and curing, the manufacturing process is in principle completed.

13 schematically shows the side view of an exemplary first embodiment of the 4-port coupler with two signal ports of the coupler. Again, for clarity, the inner interfaces of the SPP-GWG are characterized as the gates for large gap thicknesses (G) as used for the shortened first embodiment using an SI mode for excitation. In the non-shortened, normal first embodiment of the coupler, the thickness (d) of the gap is significantly less than the height (H) of the metallization, and the symmetrical fundamental mode (even mode) is achieved by central stimulation of the entire gap region by means of the final fire technique excited. For this case, then the entire cross-sectional area of the dielectic in the gap is considered as a gate in this plane.

To illustrate the electro-optical processes in such a 4-port coupler is in 14 the course of the lateral magnetic field strength at a frequency of about 685 THz along the individual branches of an exemplary, shortened first embodiment of a 4-port coupler structure when excited by a classical SI mode shown. This frequency and the chosen dimensions are a 3 dB coupler.

This has the following dimensions in detail: thickness of the gap (G) 360 nm, distance between the inner interfaces (W) = 180 nm, coupling length (L) = 36 nm, coupling distance (D) = 15 nm and total length of the coupler (T) = 530 nm.

The Splitting of the incident in Tor 1 electro-optical wave classical Wave type (SI mode) with unilateral excitation along the inner Interface of the SPP-GWG in two electro-optical waves with equal amplitudes at gate 3 and gate 4 is clear to recognize. The extinction of the wave amplitudes is also clear to recognize at gate 2. The fields along the interfaces have well recognizable different penetration depths in the respective ones Media. Such a 4-port coupler structure is too tiny to handle easy and direct to measure on a measuring station. For measuring the characteristic parameters of the respective coupler structures an adapter circuit is necessary which the tiny dimensions of the signal gates of the nanooptic Circuit structure in manageable orders of magnitude adapts.

15 schematically shows the top view of an exemplary embodiment of a measuring arrangement for measuring the 4-port coupler structures with all the signal ports of the coupler. The respective object to be measured (device under test, DUT) is integrated in this adapter, ie for measuring the DUT, z. B. the coupler together with the measuring adapter as a complete unit completely constructed as a nano-optical circuit structure. So you get a chip that can be fixed and aligned with the usual in semiconductor technology manipulators. This makes it possible to conveniently handle and measure the 4-port coupler.

So can, as in 15 indicated, for. For example, the thickness of the gap filled with dielectric can be increased so far that with the help of a focused laser beam with a relatively large diameter of about 1 micron and the end-fire technique, the most diverse modes targeted and separately on the with the 4-port coupler connected SPP-GWG can be stimulated. The feeding SPP-GWG need not necessarily be widened. If z. B. only the straight fundamental mode (even mode) should be performed by the SPP-GWG, as is the case in the other embodiments of coupler structures presented here, the thickness of the SPP-GWG may well remain to the outer edge with the original dimensions ,

to Calibration of the calibration certificate will require calibration standards. These should coincide with the manufacture of the adapter integrated into the adapter Couplers are also manufactured as separate measurement objects.

For this purpose, the marked with DUT area instead of a 4-port coupler, for example, with the in 16 to provide schematically illustrated 4-port waveguide structure. This normalizing auxiliary structure is composed of two simple, homogeneous, continuous and non-coupled SPP-GWGs how undisturbed transmission lines work. The outer dimensions (HP) and (BP) are identical to the corresponding dimensions of the respective couplers to be measured. The distance (SP) of the SPP-GWG from each other corresponds to the distance (W) of the interfaces of the coupler. The thicknesses (WP) of the column must also be identical to the gap thicknesses (G) in the coupler structures. With otherwise identical structure of the adapter structure with the integrated coupler and the adapter structure with the integrated instead of the 4-port coupler, in 16 As shown, simple waveguide transmission lines as the line losses or losses, which additionally arise in the coupler can be detected by simple comparison measurements with the continuous transmission lines, metrologically.

As already known from the microwave technology, can also with nano-optical circuit components scattering parameters (S-parameters) used to characterize the optoelectronic properties be, where the reflected from the respective gates or to other goals transmitted power waves as a basis serve the measuring method.

17 shows the frequency-dependent course of the magnitude of the main scattering parameters of the examined coupler in the shortened first embodiment, stimulated by the unilateral classic wave mode (single interface mode, SI-mode).

The scattering parameter amounts are reproduced in the frequency range from about 400 THz to over 700 THz, which characterize the transmissions of the power waves from one gate to the other. As reference planes for the scattering parameters, the planes have been chosen after the slightly curved separation of the SPP-GWGs, which include the complete coupler. Their mutual distance therefore corresponds to the total length of the coupler of the shortened first embodiment and is (T) = 530 nm. The designation of the scattering parameters is assigned to the numbering of the gates as follows: The amount of the scattering parameter S21 indicates how much of the inward gate ( Input Port) Gate 1 is fed to port 2, the isolated port (isolated port). 17 shows a progression below 20 dB for the entire frequency range, ie less than 1 of the signal power fed into the input port Tor 1 is transmitted to the decoupled gate.

The amount of the scattering parameter S31 indicates how much of the signal power fed to the gate Tor 1 is transmitted to the port 3, the through port, and the amount of the scattering parameter S41 indicates how much of the gate input Tor 1 fed signal power to the gate 4, the coupled port (coupled port) is transmitted. There is a significant frequency dependence in the transmission behavior. Depending on the frequency range, once more signal power is transmitted to the one and sometimes more signal power to the other gate. For five signal frequencies, the power distribution in the frequency range under consideration is the same, which makes this coupler a multi-band module. For each of these signal frequencies, the coupler investigated here functions as a power splitter or -3 dB coupler; so z. B. also at 685 THz, as in 14 shown. If one looks closely at the course of the scattering parameter amounts, it can be seen that the respective power levels are rather at -5 dB instead of the theoretical optimum of -3 dB. This is because the waveguides leading to the actual coupler region are lossy. Thus, the slightly curved incoming and outgoing SPP-GWG used here have a relatively high attenuation of 1 dB, which explains the higher losses. Here an optimization of the course of the gap-guided waveguides could cause a reduction of the losses.

By Choice of dimensions or for a given structure by selecting the Signal frequency can be the coupling loss in wide ranges depending on the goal from -3 dB to -15 dB or -3 dB to -10 dB. It is about in this 4-port coupler not just a power divider, but a universal multi-band coupler with variable coupling characteristics. Farther can from the fact that the coupler for very different signal frequencies a defined power distribution causes more circuitry Benefit be drawn. So the coupler can quite well as a diplexer or frequency-selective switch can be used.

The previously considered coupler structure of the shortened first Embodiment has as an addition and laxative Waveguide SPP-GWG with relatively large gap thicknesses (G) and was part of the investigations with the classical wave type (SI-mode) by unilateral excitation along the inner interface of the SPP-GWG.

Although this form of 4-port coupler leads to particularly short coupling lengths, because of the large gap thicknesses (G) but only conditionally suitable for an optimally high integration density, because the stray fields in the dielectric are relatively far-reaching, such as 14 impressively proven.

By significantly reducing the gap thicknesses (G) to 25 nm, the classical mode (SI mode) can not be achieved with the available means be stimulated more separately. Rather, when using the end-fire technique to excite the SPP formed by superposition of the two interface vibrational fields of 7 illustrated straight mode (even mode) as the fundamental mode (fundamental mode) for this gap-guided SPP waveguide (SPP-GWG). In order to more conveniently examine the electro-optical processes, a 4-port coupler in a non-shortened first embodiment with relatively large spacing (30 nm) of the coupling waveguides from each other was investigated.

The The 4-port coupler structure examined below has in detail following dimensions: thickness of the gap (G) = 25 nm, distance between the inner interfaces (W) = 400 nm, coupling length (L) = 500 nm, coupling distance (D) = 15 nm and total length of the coupler (T) = 1 μm.

18 shows the frequency-dependent course of the magnitude of the main scattering parameters of the examined here 4-port coupler in the not shortened first embodiment. Because of the related embodiment, the characteristics of the scatter parameter amounts are in principle similar to those already described in connection with the shortened version of this coupler 17 are shown and will therefore not be discussed again here. As significant differences, it can be seen that the transmission losses in this non-shortened first embodiment of the 4-port coupler structure are smaller than in the shortened first embodiment. Although the entire coupler structure is now about twice as long as the shortened version, the transmission loss is only about half as large. This is obviously due to the more concentrated fields of the straight fundamental wave type, which is propagatable by reducing the thickness (G) of the dielectric filled gap in the SPP-GWG used. However, the deterioration of the insulation (S21) that occurs with this coupler structure can be improved, but this should not pose a fundamental problem.

19 Figure 12 shows the course of the SPP even-mode magnetic fields along the individual waveguides (SPP-GWG) of an exemplary non-shortened first embodiment of the 4-port coupler at a frequency of about 250 THz. Noticeable in this and the other two representations is the clearly recognizable high field concentration in the dielectric of the SPP-GWG and the relatively rapid decay of the fields in the surrounding metal. Only in the region of the coupling length of the coupler structure does a violent interaction between the waveguides take place. It can also be seen that at this frequency an almost complete coupling between gate 1 and gate 4 takes place, ie almost the entire signal power fed into port 1 reaches the gate 4, while at gate 2 or gate 3 less than -25 dB, ie approximately in each case only one three-thousandths of the signal power can be coupled out. This behavior changes significantly with frequency.

20 Figure 12 shows the course of the SPP even-mode magnetic fields along the individual waveguides (SPP-GWG) of an exemplary non-shortened first embodiment of the 4-port coupler at a frequency of about 350 THz. It can be seen at this frequency a nearly equal coupling between port 1 and port 4 and between port 1 and port 3. This means that the coupler structure acts at this frequency of the injected signal as a power divider. If the frequency is further increased, the conditions are reversed 19 almost to.

21 Figure 3 shows the course of the SPP even-mode magnetic fields along the individual waveguides (SPP-GWG) of an exemplary non-shortened first embodiment of the 4-port coupler at a frequency of about 440 THz. This time shows a nearly complete coupling between Tor 1 and Tor 3, ie almost the entire fed into Tor 1 signal power reaches the gate 3, while at Tor 2 or Tor 4 less than -25 dB, so about each coupled out only one three thousandths of the signal power can be. This coupler structure can therefore be used in principle as a frequency-selective diplexer or in a more than 4-port embodiment as a frequency-selective multiplexer, as a directional coupler with predetermined coupling loss, as a multi-band coupler and also in particular as a power divider at different frequencies.

As an alternative to the coupler structures already described, a coupler structure is described below as a further embodiment of a broadside-coupled ultra-compact multi-band coupler structure in gap-guided surfaces Plasmon Polariton waveguide technology, which has in principle similar characteristics as the previously described Kopplerstruktur but still compact and low loss is constructed. This second embodiment of coupler structures has as an incoming and outgoing waveguide SPP-GWG with relatively small gap thicknesses (G = 25 nm) and is centrally focused exclusively with the fundamental mode (SPP even mode) by symmetrical excitation of the respective gates by end-fire technology operated in the center of the cross-section of the SPP-GWG. The special feature of the second embodiment is that each individual SPP-GWG has its own level, in which this SPP-GWG can be laid arbitrarily, without crossing another waveguide, because in this level it meets at most itself. The different The planes in which the respective waveguides (SPP-GWG) are located are separated by a very thin (about 15 nm) metal layer, which automatically results in a coupling distance (D) = 15 nm in the coupling region. If two SPP-GWGs lie directly above one another in the different levels in a certain area, the intense coupling of the fields into the individual SPP-GWGs occurs in this area because of the thin metal layer between the dielectrics of the different SPP-GWGs, whereby the respective frequency-dependent characteristic electrical behavior of these coupler structures thus produced depends in a complicated manner on the geometrical dimensions, the material properties of the materials used to construct the structures and on the frequency of the electromagnetic energy supplied for exciting the plasma oscillations.

Both embodiments of the coupler structures, the previously described shortened or non-shortened first embodiments and the second embodiment of the coupler structure are broadside-coupled in the coupling region, which can also be implemented very advantageously by using SPP-GWG as a compact waveguide. Since, in this type of coupling, the effective area provided for inducing the action of the plasma oscillations of one waveguide on the other waveguide and thus the degree of coupling fields is extremely large, the required coupling lengths (L) compared to the strip-guided SPP are Waveguides so low. The difference between the edge coupling and the broadside coupling will be apparent from the following pictures. 22 shows the typical cross section of the coupling region of SPP-SWG based coupler structures, as have been realized by other scientists. In this SPP-SWG technique, first of all, as is customary in microwave stripline technology, printed conductors are applied and patterned on a dielectric carrier material. It also makes sense to realize the coupler as it is known from the microwave stripline technology in that the conductor strips are guided laterally to each other. So here only the lateral edge fields of each guided by the metal strip wave types can couple together. Even if the metal conductor strips are brought together so far that they touch each other directly at the edges, the vectors of the fields guided by the strips are primarily perpendicular to the contact surface. At first, only one advantage is taken of the fact that the amounts of stray fields in the immediate vicinity of the strips are stronger. The stripes can be laterally only approximate until they touch. Due to the forced doubling of the strip width, however, further, possibly disturbing wave types can be stimulated. Therefore, a direct contact of the metal strips should be avoided.

In contrast, shows 23 the typical cross section of the coupling region of the broadside coupling used here of SPP-GWG based coupler structures. It is a large, over the entire height of the SPP-GWG acting coupling area to recognize, which is then maintained over the entire coupling length (L). Both waveguides have in the coupling region a common metal wall, which is only a few atomic layers thick. Obviously, this causes the SPP much more directly, as it were directly excited by the adjacent SPP of the other SPP-GWG, as it is by the adjacent stray fields in the strip-guided structures. First indications give the field pictures in with appropriate interpretation 14 . 19 . 20 and 21 , However, the actual reasons are still research subject.

Around more circuit-engineering degrees of freedom at an even higher level To get degree of integration density, it is necessary to change the directions of In principle, the incoming and outgoing waveguides are arbitrary shape and the number of coupled waveguides increase as needed. This is now a universal developed second embodiment of the coupling structures.

24 schematically shows the top view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler. In order to reduce the losses in the direction of propagation of the wave by abrupt changes in direction of the waveguide, the incoming and outgoing waveguides are guided in gently curved paths here as well. The coupling of the field energies of the respective waveguides takes place over the entire, more or less complicated, bounded area of the coupling, ie wherever the respective SPP-GWG overlap directly. Otherwise, with regard to the basic mode of operation, what has already been discussed above applies.

However, it must be expressly pointed to a principal and very significant difference between the first and the second embodiment of the SPP-GWG based coupler structures, so that one is not misled by the similar images in the understanding. The waveguide structures to be recognized here are compared to 8th and the corresponding previous images are drawn spatially rotated by 90 degrees, ie we no longer look at the dielectric with the thickness (G) but at the dielectric of the height (H)!

This becomes immediately apparent when 25 is looked at. 25 schematically shows the side view of an exemplary second embodiment of a 4-port coupler structure with the two first signal ports of the coupler and the region of the coupling. The gate designations (Gate 1) and (Gate 2) show the dielectric cross-sectional areas of the SPP-GWG. B. have a height (H) of about 200 nm and a thickness (G) of about 25 nm. It can also be clearly seen that the respective SPP-GWG lie in different levels. If these are guided in such a way that they overlap, an intensive coupling of these two waveguides occurs in this overlapping area.

The circuitry advantage of the second embodiment will become apparent in the following pictures. 26 schematically shows the top view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with a 90 degrees angled signal port. As a result, the signal associated with the gate 4 can be fed to a further nano-optical circuit module which may be of any size without running the risk of blocking the door 3 by the area required for this circuit module.

27 schematically shows the top view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with two by 90 degrees angled signal ports. Here, the already begun thought was continued. In the 27 The coupler structure shown can also be cascaded very simply by stringing together a number of further identical coupler structures in a sequential order. For this purpose, a corresponding number of identical or modified coupler structures are connected to one another such that the port 3 of a first coupler structure is connected to the port 1 of a second coupler structure, the port 3 of the second coupler structure is connected to the port 1 of a third coupler structure, etc. Now, the respective port 2 and the respective port 4 of the respective coupler structures are connected to nano-optical circuits. This results in numerous circuit options. If, for example, all coupler structures are constructed as unidirectional directional couplers, signals are fed into the respective ports 4 of the respective coupler structures when a signal is fed into the port 1 of the first coupler structure. If, on the other hand, the signal is fed into the port 3 of the last coupler structure, signals are sent to the respective ports 2 of the respective coupler structures. The various possibilities of realizing nano-optical circuits with the aid of these coupler structures are very numerous. Another variant of the design is shown in the following picture. 28 schematically shows the top view of an exemplary second embodiment of a 4-port coupler structure with the respective signal ports of the coupler, with four by 90 degrees angled signal ports. This coupler structure can be designed as a bidirectional coupler and then interconnect opposing nano-optic circuit devices.

The multi-layer technology makes it possible to link together an arbitrary number of SPP-GWGs. In 29 schematically the top view of an exemplary second embodiment of a 6-port coupler structure with the respective signal ports of the coupler is shown. This coupler structure arises from the fact that additional layers with a third SPP-GWG are added to the known coupler structures of the second embodiment. This third waveguide is then guided in a known manner so that it overlaps with the other waveguides. 30 schematically shows the side view of an exemplary second embodiment of a 6-port coupler structure with the two first signal ports and the fifth signal port of the coupler and the region of the coupling in which the broad sides of the three waveguides overlap. As required, additional levels can be added to link additional waveguides together and increase the number of ports of the couplers.

The for producing such complex structures in the nanometer range required technologies are currently not available. That's why you have to be in the metrological review to wait a bit longer for the calculations of such structures.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - Aussenegg and Ditlbacher in the article: Nanooptik - Plasmons as Lichttransporter. In: Physics in Our Time, Issue 5, (2006), Vol. 37, pp. 220-226 [0002]
• - Stegeman, Wallis and Maradudin in the article: Excitation of surface polarity by end-fire coupling. In: Optics Letters, Issue 7, (1983), Vol. 8, pp. 386-388 [0006]
• - Nano-optics with metallic structures - About the handling of light beyond the Abbe limit. In: Physics Journal 1 (2002) No. 3, pp. 39-45 [0009]
• - Guo and Adato in the article: Extended long range plasmon waves in finite-thickness metal film and layered dielectric materials. In: OPTICS EXPRESS 14 (2006) No. 25, pp. 409-418 [0016]
• - Boltasseva, Nikolajsen, Leosson, Kjaer, Larsen and Bozhevolnyi in the article: Integrated Optical Components Utilizing Long-Range Surface Plasmon Polaritons. In: Journal of Lightwave Technology, Vol. 23 (2005), no. 1, pp. 413-422 [0018]
• - Novel surface plasmon waveguide for high integration. In: OPTICS EXPRESS 13 (2005) No. 17, pp. 6645-6650 [0026]
• - Wang, Islam and Eleftheriades in the article: An ultra-short contra-directional coupler utilizing surface plasmon-polaritons at optical frequencies. In: OPTICS EXPRESS 16 (2006) No. 16, pp 7279-7290 [0029]
• - Boltasseva et. al. [0040]

Claims (12)

Coupler structures for use in nano-optical circuits and networks consisting of plasmon polariton waveguide surfaces, in which plasma oscillations are excited in interfaces between a dielectric and a metal to transport electromagnetic energy and signals at optical frequencies, ie at a few hundred terahertz two or more waveguides suitable for transporting electromagnetic energy in the range of optical frequencies, and having at least one coupling region in which the respective waveguides are brought together so closely that the electromagnetic fields guided by the respective waveguides can interact with one another, characterized in that all nano-optical waveguides used to construct the coupler structures invariably consist of the type gap-guided surfaces Plasmon Polariton Waveguide (abbreviated: Surface Plasmon Polariton Gap Wave Guide, abbreviated to: SPP-GWG), - wherein a gap-guided surface plasmon polariton waveguide in a limited range of height (H) consists of three layers, - wherein the first layer of metal, the second layer of a dielectric having the thickness (G) and the third layer is in turn made of metal, - whereby two plane-parallel arranged interfaces between the different materials are formed, which have the distance (G) from each other, - depending on the respective geometric dimensions (H), (G) and the respective Characteristic properties of the materials used to build the SPP-GWG, different types of propagation wave can be excited, depending on the type both one and by overlaying the fields simultaneously involve both interfaces of the SPP-GWG and these used to build the coupler structures nano-optical waveguide always broadside-coupled in the coupling area si nd, - where broadside-coupled means that the waveguides are brought together so far that touch the waveguides and thereby the respective plane-parallel interfaces of the SPP-GWG in the coupling region are again plane-parallel to each other and - wherein each coupled together SPP-GWG on the the entire coupling region has a common layer of metal, this layer usually being very thin, that is to say its thickness is typically less than 50 nanometers, which means that the respective directly adjacent active boundary layers of the respective different waveguides are less in the coupling region than 50 nm apart. Coupler structures according to Claim 1, characterized that over the total length (T) of the coupler is two exactly parallel mutually guided SPP-GWG initially as far apart are removed, that no crosstalk of the signals of the respective SPP-GWG, which then turns these two SPP-GWG into curved, rounded way to be merged so far that they are over an area of coupling length (L) and touch the dielectrics respective SPP-GWG in the coupling length (L) only by a very thin metal layer are separated from each other, then this SPP-GWG in curved, rounded way and Way to be separated again so far, no crosstalk the signals between the respective SPP-GWG can take place, - in which the gap thickness (G) of the SPP-GWG used to construct the coupler so far chosen that a propagator Type of shaft, which only the respective inner, inner interfaces of the coupled SPP-GWG involved (a so-called single Interface mode or SI mode) as fundamental mode (fundamental mode), then the characteristic electromagnetic Behavior of the coupler structure determined in the entire coupling area. Coupler structures according to Claim 1, characterized that over the total length (T) of the coupler is two exactly parallel mutually guided SPP-GWG initially as far apart are removed, that no crosstalk of the signals of the respective SPP-GWG, which then turns these two SPP-GWG into curved, rounded way to be merged so far that they are over an area of coupling length (L) and touch the dielectrics respective SPP-GWG in the coupling length (L) only by a very thin metal layer are separated from each other, then this SPP-GWG in curved, rounded way and Way to be separated again so far, no crosstalk the signals between the respective SPP-GWG can take place, - in which the gap thickness (G) of the SPP-GWG used to construct the coupler is chosen so narrow that a spreadable superimposed Wave type, the same time both internal interfaces the interconnected SPP-GWG involved (a so-called Surface Plasmon Polariton even mode or SPP even mode) as the fundamental mode (fundamental mode) can be stimulated, then the characteristic electromagnetic behavior of the coupler structure in the entire coupling region certainly. Coupler structures according to Claim 1, characterized that over the total length of the coupler structure is two or more SPP-GWG plane-parallel with regard to the respective interfaces but otherwise lying in different levels arbitrarily led to each other and are so far apart from each other that no crosstalk of the signals of the respective SPP-GWG take place can then that these two or more SPP-GWG in curved, rounded way to be merged so far that they are immediately across an area of coupling touch and the dielectrics of the respective SPP-GWG in Area of coupling only by a very thin metal layer from each other are separated, then then this SPP-GWG in curved, rounded Way to be separated again so far that no crosstalk the signals between the respective SPP-GWG can take place, - in which the gap thickness (G) of the SPP-GWG used to construct the coupler is chosen so narrow that a spreadable superimposed Wave type, the same time both internal interfaces the interconnected SPP-GWG involved (a so-called Surface Plasmon Polariton even mode or SPP even mode) as the fundamental mode (fundamental mode) can be stimulated, then the characteristic electromagnetic behavior of the coupler structure in the entire coupling region certainly. Coupler structures according to claim 2 to 4, characterized characterized in that by specific choice of geometrical dimensions and the materials used to construct the coupler structure so designed and by choice and stimulation of a suitable wave type operated at a certain frequency so that in one certain signal port of the coupler structure fed electromagnetic energy on two designated signal gates uniform with shares equally large proportions of energy, the Kopplerstruktur at that frequency then like a power splitter acts. Coupler structures according to claim 2 to 4, characterized characterized in that in particular by selective choice of the geometric Dimensions and materials used to build the coupler structure designed and selected and stimulated by suitable wave types is operated at different frequencies so that the in a given signal gate of the coupler structure fed electromagnetic Energies of different frequencies are limited to two Signal gates each uniform with the same size Divide energy shares, the Kopplerstruktur in these Frequencies then like a multi-band power divider (multi-band power splitter) acts. Coupler structures according to claim 2 to 4, characterized characterized in that by specific choice of geometrical dimensions and the materials used to construct the coupler structure so designed and by choice and stimulation of a suitable wave type operated at a certain frequency so that in one certain signal port of the coupler structure fed electromagnetic energy on two designated signal gates with exactly defined large Divide energy shares, the coupler structure at this frequency then acting as a directional coupler. Coupler structures according to claim 2 to 4, characterized characterized in that by specific choice of geometrical dimensions and the materials used to construct the coupler structure so designed and by choice and stimulation of suitable wave types in particular is operated at different frequencies so that the in a given signal gate of the coupler structure fed electromagnetic Energy for all selected frequencies arises two designated signal gates with precisely defined large Shares energy shares, the coupler structure at these frequencies then like a multi-band directional coupler acts. Coupler structures according to claim 2 to 4, characterized characterized in that by specific choice of geometrical dimensions and the materials used to construct the coupler structure so designed and by choice and stimulation of a suitable wave type is operated so that in this operation the frequency of the stimulating Wave can be chosen so that in a given Signaling gate of the coupler structure fed electromagnetic energy on two dedicated signal gates with over the signal frequency adjustable divides large amounts of energy, the Kopplerstruktur then as a frequency-selective crossover (frequency-selective diplexer) or variable directional coupler with adjustable values of the coupling damping acts. Kopplerstrukturen according to claim 2 to 4, characterized in that the coupler structure designed by selective selection of the geometrical dimensions and the materials used for construction and operated by selecting and exciting suitable modes, in particular at certain frequencies so that in a particular signal port of the coupler structure fed electromagnetic energy for certain frequencies distributed to two dedicated signal ports so that almost all the energy components is distributed to a first output port and the second output port receives no energy portion of the input signal and that for certain other frequencies, the fed electromagnetic energy to exactly swept distributed so that almost the entire energy content is now distributed to the second output port and the first output port no longer receives energy share of the input signal, the coupler structure at these frequencies then each acts as a multi-band crossover (multi-band diplexer). Coupler structures according to Claim 4, characterized that by using more than two SPP-GWG, in general So by the use of N (where N is a natural Number greater than 2 is) SPP-GWG, by targeted choice the geometric dimensions and the materials used for construction the Kopplerstruktur so designed and by choice and suggestion of a suitable mode at a certain frequency so operated that is in a certain signal port of the coupler structure fed electromagnetic energy on each of them certain signal gates with well-defined large amounts of energy split, the coupler structure at this frequency then as an N-port directional coupler acts. Coupler structures according to Claim 4, characterized that by using more than two SPP-GWG, in general So by the use of N (where N is a natural Number greater than 2 is) SPP-GWG, by targeted choice the geometric dimensions and the materials used for construction the Kopplerstruktur so designed and by choice and suggestion of a suitable wave type in particular at certain frequencies so is operated, that in a certain signal gate of the Kopplerstruktur fed electromagnetic energy for certain frequencies distributed on certain signal gates so that almost the entire energy is distributed to a first exit gate and the other output ports receive no energy portion of the input signal and that for certain other frequencies the fed electromagnetic energy is distributed so that almost the entire Energy share is now distributed to another exit gate and both the first and the remaining exit gates now no Energy share of the input signal gets more, and so on, wherein the respective output gate, which almost the entire energy shares of the input signal should be selected using the frequency can be, with the coupler structure at these frequencies then each acts like an N-port power distributor (n-gort multiplexer).