Arrangement for an antenna for generating or receiving terahertz radiation, antenna, terahertz system, and method for manufacturing an arrangement for an antenna - Patents.com

Abstract

The present invention relates to an assembly (1) for an antenna (16, 17) for generating or receiving terahertz radiation (12), comprising: a photoactive layer (2) activated by optical radiation (11) in the range of 1200 nm to 1700 nm; a substrate (3) transparent to the optical radiation (11) and on which the photoactive layer (2) is attached; a first adhesion-promoting layer (4) with a thickness of up to 5 μm, disposed between the photoactive layer (2) and the substrate (3), connecting a surface of the photoactive layer to a surface of the substrate; and a support (5) transparent to the optical radiation (11). The substrate (3) is attached to the support (5) and disposed between the photoactive layer (2) and the support (5), the substrate (3) and the support (5) being made of the same material. The present invention also relates to the antenna (16, 17), a terahertz system (20), and a method for manufacturing the assembly (1) described above.

Description

[Technical Field]

[0001] The present invention relates to an arrangement for an antenna for generating or receiving terahertz radiation, an antenna for generating or receiving terahertz radiation, a terahertz system for generating and coherently detecting terahertz radiation, and a method for manufacturing an arrangement for an antenna for generating or receiving terahertz radiation. [Background technology]

[0002] Here, terahertz radiation is considered to be electromagnetic radiation with frequencies between 0.05 THz and 20 THz, with frequencies typically between 0.1 THz and 10 THz. While these frequencies are very high for electronic signal processing, they are still very small compared to typical frequencies in photonics, so the quantum energy of terahertz radiation is still very low. Therefore, it is difficult to realize measurement systems that handle terahertz radiation. Therefore, terahertz radiation is the last region of the electromagnetic spectrum that has not yet been developed sufficiently for practical applications.

[0003] Terahertz systems typically use optoelectronic semiconductor chips to generate and detect terahertz radiation. Terahertz systems typically include a laser light source and two THz antennas. Each of the two THz antennas is optically coupled to a laser light source via an optical fiber and activated by light from the laser light source. The first antenna functions as a transmitting antenna, and the second antenna functions as a receiving antenna. In this case, each THz antenna has a semiconductor chip in contact with an antenna conductor and including at least one photosensitive active layer having a band-edge wavelength longer than the wavelength of the laser light source and at least one layer adjacent to the active layer having a band-edge wavelength shorter than the wavelength of the laser light source. Here, antenna conductors are typically integrated on each semiconductor chip. Laser light sources can generate short pulses or beat signals in the terahertz band by superimposing two laser waves with slightly different wavelengths. Herein, the wavelength of a laser light source is defined as the center of gravity of the wavelength spectrum of the light generated by the laser light source.

[0004] Such a terahertz system allows terahertz radiation to be generated and coherently detected by applying a voltage to the antenna conductor of the transmitting antenna. The transmitting and receiving antennas are activated simultaneously or with an adjustable delay by coherent radiation from a laser source, and the current generated in the receiving antenna is measured by a sensor connected to the antenna conductor of the receiving antenna. In this way, the received signal can be detected for different delays in the light travel time between the laser source and the receiving or transmitting antenna to probe a sample placed between the transmitting and receiving antennas.

[0005] Terahertz systems of this type are known, for example, from DE 10 2007 044 839 A1 and DE 10 2010 049 658 A1. By using optical fibers to connect the laser source to the THz antenna, these terahertz systems can advantageously be realized in a compact, robust and flexible way. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 10 2007 044 839 A1 [Patent Document 2] DE 10 2010 049 658 A1 Summary of the Invention [Problem to be solved by the invention]

[0007] The following is a more detailed discussion of the THz antenna shown in FIG. 1 according to an example of the prior art. The THz antenna 30 of FIG. 1 includes a photoactive layer 21, which has a fast charge carrier recombination time and is produced by epitaxial growth on an electrically insulating substrate 22. Metal structures 23 and 24 are formed on the photoactive layer as a THz antenna using evaporation and lithography processes. The metal structures 23 and 24 can be formed, for example, in the shape of a dipole, a bowtie, or a stripline. The metal structures 23 and 24 have gaps through which short (fs-range) optical pulses 11 can be directed toward the photoactive layer 21. The antenna 20 of FIG. 1 is formed, for example, as a THz transmitter. In the THz transmitter 20, a voltage is applied to the metal structures 23 and 24. Excitation by the optical pulse 11 generates photocharge carriers in the photoactive layer, which are strongly accelerated in an electric field, generating electromagnetic radiation in the THz range (0.1-10 THz). Due to the large refractive index jump with respect to air, the radiation propagates favorably in the semiconductor material of layer 21 and substrate 22. To improve the coupling of the THz waves in air, the antenna chip or substrate 22 is placed on the plane of a hyper-hemispherical Si lens 25 made of high-purity Si with high THz transparency.

[0008] The THz receiver appears essentially identical in structure, except that no voltage is applied. Instead, the THz receiver measures the photocurrent caused by the received THz radiation and excited photocharge carriers. However, a photocurrent only flows if (simultaneously) the received THz radiation applies a voltage and the optical pulse induces photoconduction. Therefore, THz time-domain systems include a delay line in one of the beam paths, which allows the temporal position of the received THz radiation and the scanning fs optical pulse to be changed. This allows for "coherent" detection, where the amplitude and phase of the THz wave are scanned in a pump-sample process, potentially with high sensitivity and high speed.

[0009] The first THz systems used an excitation wavelength of 800 nm because of the availability of powerful pulsed lasers with short pulse durations (fs) and photoconductors with very fast recombination times, made from low-temperature (LT) GaAs grown on GaAs substrates.

[0010] New systems often use excitation wavelengths of 1300 nm and 1550 nm because many components are available in this range due to developments in optical communication technology. 1550 nm femtosecond fiber lasers are now inexpensive and maintenance-free. Optical fibers also allow flexible connections from the laser to moving transmitting and detecting heads. This offers significant advantages for industrial applications of THz sensor technology. However, because GaAs does not absorb at 1550 nm, fast photoconductors for this wavelength range had to be developed first. These are currently realized based on InGaAs, InGaAsP, InAlAs, InGaAlAsP, and InGaAlAs layers grown epitaxially and lattice-matched on InP substrates.

[0011] Typical thicknesses of photoconductor layers are in the range of 1-2 μm, which roughly corresponds to the penetration depth (1 / e) of the excitation light. The thicker the layer, the more effort is required for epitaxial growth. However, further photocharge carriers are hardly generated. This leads to an undesirable increase in background dark current (noise). Furthermore, the long path from the excitation point deep inside the layer to the surface contact has an undesirable effect on the temporal behavior (detection bandwidth).

[0012] In the advantageously thin layer, the excitation radiation is not completely absorbed. This is not a problem in 800 nm systems because the GaAs substrate also absorbs, and for typical substrates with thicknesses of 300–500 μm, the excitation radiation is completely removed from the system. However, InP substrates are typically transparent to wavelengths above 1000 nm. Therefore, residual light not absorbed by the photoactive layer (i.e., hidden in the photoconductor) is not absorbed downstream by the substrate and remains in the system, potentially impairing its function. This is particularly important if residual light pulses activate the transmitting or receiving antennas at the wrong time. Thus, the laser pulses that excite the transmitting antenna can also reach the receiving antenna via the THz imaging optics. To block this path, prior art techniques use optical filters in the THz beam path. However, what these external filters cannot achieve is blocking interfering pulses caused by internal reflections at interfaces within the THz antenna.

[0013] Such internal optical reflections are shown by dashed lines in Figure 2, which shows a structure similar to that of Figure 1. These laser pulses can severely impair the function of the THz sensor system if they re-excite the photoconductor layer with an undesired time delay, thereby generating "echo" THz pulses 27. Measurements of prior art systems show these interfering pulses very clearly (see echo pulses 27 in Figure 3). It would therefore be advantageous to avoid or at least reduce these THz echo pulses 27 caused by optical reflections, since even echo pulses of the smallest amplitude can significantly interfere with measurements.

[0014] The disturbance due to light reflections will be evaluated below. Note that when evaluating the disturbance caused by light reflections, not only the amplitude but also the time position of the echo pulse must be taken into account, i.e. 1. Comparing the spatial extent of the light pulse, and 2. It relates to the time position of the measurement window.

[0015] First, as an example, the perturbation of the echo pulse is estimated based on the spatial extent of the optical pulse and its proximity to the interface. The spatial width of a commonly used 100-femtosecond laser pulse is 30 μm in air and approximately 10 μm in a semiconductor with a refractive index close to n = 3 (InP: 3.167 at 1550 nm) (derived from the speed of light). Therefore, for a typical photoconductor layer with a thickness of 2–3 μm, a pulse expanded to a spatial width of 10 μm will further excite photoconduction. Reflections at or near the photoconductor interface are not perceived as separate echoes but become part of a slightly wider excitation pulse. Therefore, a free photoconductor layer does not generate echoes despite a large refractive index jump at the interface. However, such layers are not mechanically stable enough.

[0016] The perturbation of the echo pulse with respect to the time position of the measurement window and with respect to the distant interface can be estimated as follows: Reflections at more distant interfaces typically result in echo pulses far outside the measurement window. Therefore, reflections outside the Si lens (see lens 25 in Figure 1) relative to air have very high amplitudes due to the high refractive index jump Δn of approximately 2.5 (the refractive index of Si is 3.478 at a wavelength of 1550 nm, while the refractive index of air is approximately 1 at a wavelength of 1550 nm). The distance between the photoconductor layer and the outside of the Si lens is quite large at 7.35 mm (we assumed the InP substrate thickness to be approximately 350 μm and the Si lens thickness to be approximately 7 mm). Because the echo pulse travels this path twice, the additional travel distance relative to the original pulse is approximately 14.7 mm. Taking into account the refractive index of approximately 3.4, there is even an additional optical path length of approximately 50 mm, thus resulting in a delay of the echo pulse of approximately 150 ps. Therefore, these echo pulses are outside the normal measurement window and do not usually interfere with the measurement.

[0017] An InP substrate (n = 3.167 at 1550 nm) and a Si lens (n ​​= 3.478 at 1550 nm) exhibit a refractive index jump Δn = 0.311 when in flush contact. However, this areal contact is difficult to achieve due to the limited planarity of the particularly fragile InP substrate. As a result, air gaps form between the InP and Si in some areas, and a fairly high reflectivity is expected at the semiconductor-air interface. However, the width of the air gap relative to the wavelength also plays a role. For terahertz waves with wavelengths in the 100 μm range (3 THz), the terahertz waves attenuate relatively slowly and jump across the sub-μm gap into the second semiconductor material and propagate there, so a high reflectivity is not yet formed here. However, for example, in the case of a pump laser pulse with a wavelength of 1.5 μm, the first cavity mode with the highest reflection is already formed at a gap width of 0.75 μm (half the wavelength), so that an increase in reflection already begins at smaller gap widths. Thus, while a small air gap on the submicron scale exhibits high reflection for optical pump pulses, it has almost no effect on terahertz waves because their wavelengths are orders of magnitude different.

[0018] In summary, in the above THz system with long-wave excitation at 1.5 μm wavelength of an epitaxial layer on an InP substrate transparent to this wavelength, optical reflection at the interface between the InP substrate and the Si lens (see interface 26 in Figure 2) leads to an interference echo pulse. The echo pulse impinges on the photoactive layer a second time with a delay, exciting it. This causes the THz transmitter to emit an echo pulse, and at the receiver, the received THz signal is scanned a second time. Thus, a time-delayed replica of the THz signal pattern is created.

[0019] For example, we can state the timing of light reflection at the interface between an InP substrate and a Si lens as follows: The InP substrate shown in Figures 1 and 2 is typically 350 μm thick, resulting in a round trip of 700 μm. Including the speed of light in InP via the refractive index, the delay of the echo relative to the main pulse is approximately 7 ps. This delay of the echo pulse can be measured and is clearly seen in Figure 3.

[0020] For example, when measuring a sample with a multilayer structure with layer thicknesses in the range of several hundred microns, the pulses reflected before and after the layer (200 microns for the outbound and return paths) are also separated by several picoseconds (assuming the sample refractive index is 1.5). Considering the multilayer structure of the sample, the width of the THz pulse, and the small amplitude of reflections at inner paint interfaces, it becomes clear that echo pulses with this timing significantly impair measurement accuracy.

[0021] As also shown by measurements using a THz antenna in a time-domain system, the reflection between the InP substrate and the Si lens is indeed an important reflection (see Figure 3). Pre- and post-pulses are observed at a distance of approximately 7 ps from the main pulse. As mentioned before, these 7 ps correspond exactly to the time delay of the echo pulse due to the reflection of the laser pulse at the interface between the InP substrate and the Si lens. Due to differences in the thickness of the InP substrate (nominal 350 μm), the timing of one pulse will differ slightly when comparing different THz transmitting chips.

[0022] The echo pulses on the opposite side of the time axis (see Figure 3) are generated by the reflection of the fs laser at the THz receiver. The receiver is the same for all measurements. This is why the associated echo pulses also overlap sufficiently. In principle, these echo pulses can be calculated with a fixed measurement system. However, this becomes important when a weak measurement signal is close to one of the echo pulses. This is illustrated by an important application example.

[0023] An important field of application arises from the fact that THz radiation (0.1 THz to 30 THz) can penetrate many dielectric materials that are opaque to visible light, such as plastics, paints, and paper. This opens up possibilities for applications in non-destructive material testing. For example, there is a need to measure the thickness of individual layers of plastic material in composites, preferably contactlessly, already during the manufacturing process (e.g., during the extrusion process).

[0024] Another example is measuring the thickness of a paint layer 32 (see FIG. 4), especially in a multi-layer system, when the paint is still wet. This allows, for example, control of the ongoing painting process of an automobile body. For this measurement, a THz pulse 12 is directed toward a painted metal surface 33. Different interfaces of multiple paint layers 32 (typically anti-corrosion, filling, pigmented paint, and clear coat) as well as the metal carrier 33 generate reflections 34 at different time positions. The reflected THz pulse 34 is directed toward a receiving antenna 31, where the time offset of the reflected THz pulse is measured with the scanning laser pulse. Knowing the refractive index of the layer 32 allows the thickness of each layer assembly to be determined. The refractive index of paint is often in the range of 1.5 to 1.6 for terahertz radiation.

[0025] It should be noted that the refractive indices of the paints differ only slightly from each other, so the reflection amplitude at internal interfaces is small, while much stronger reflections occur at interfaces between air and paint or paint and metal. This THz reflection pattern 34 is depicted schematically in Figure 4.

[0026] When the THz transmitter 30 emits an echo pulse via optical multiple excitation, a time-delayed replica 35 of the reflection pattern 34 is generated (see Figure 5). In the replica 35, a strong reflection at the air boundary can be located immediately next to a weak reflection of the main pulse at an internal interface (see Figure 5). Furthermore, the echo pulse in the receiver 31 can generate a strong reflection at the paint-metal interface that falls exactly within the time window where the main pulse scans the weak reflection at the transition between the individual paint layers.

[0027] It is therefore clear from the above that the measurement quality can be significantly affected even by weak echo pulses, and therefore echoes at the THz antennas (both transmitter 30 and receiver 31) should be avoided at all costs.

[0028] The above example is intended to demonstrate the importance of echo cancellation. However, echo pulses can also interfere significantly in transmission arrangements or measurement systems in spectroscopy, where the Fourier transform of the detected pulse train is used, and these interference effects cannot always be calculated. In so-called "continuous wave" THz systems (CW THz systems), the echo signals are less obvious, but they still naturally distort the phase and shape of the optical beat signal and the THz wave.

[0029] The object of the present invention is to design an arrangement which allows at least partly to solve the above problems. It would be particularly advantageous to provide an arrangement which allows the aforementioned echo pulses to be prevented or at least reduced. Furthermore, it would be advantageous to provide a method for manufacturing the arrangement. [Means for solving the problem]

[0030] This object is achieved according to the invention by an arrangement, an antenna, a terahertz system and a method as set forth in the independent claims. Improvements are set forth in the dependent claims and in the following description.

[0031] According to one aspect of the present invention, there is provided an arrangement for an antenna for generating or receiving terahertz radiation, the arrangement comprising: - a photoactive layer activated by optical radiation in the range of 1200 nm to 1700 nm; a substrate transparent to said optical radiation and on which said photoactive layer is attached; a carrier transparent to said optical radiation, said substrate being attached to said carrier and being arranged between said photoactive layer and said carrier;

[0032] The substrate and the carrier are made of the same material, and the arrangement further includes a first adhesion-promoting layer disposed between the photoactive layer and the substrate, connecting them flatly to each other, the first adhesion-promoting layer having a thickness of 5 μm or less.

[0033] Because the thickness of the first adhesion-promoting layer is small, the time it takes for the light to reach the substrate interface and return is relatively short. Therefore, the light reflection caused by the first adhesion-promoting layer excites the photoactive layer almost simultaneously with the excitation light. Therefore, spatially separated echo pulses can be avoided.

[0034] Because the substrate and carrier are made of the same material, they have the same refractive index. As a result, there is no refractive index jump at the material transition. This significantly reduces reflections at the material interface, reducing the aforementioned optical reflection or optical echo pulse.

[0035] The first adhesion-promoting layer allows the photoactive layer and the substrate to come into close surface contact. This prevents or reduces air gaps between the photoactive layer and the substrate. The thin thickness of the adhesion-promoting layer allows the interface to be close to the photoactive layer, so that the pulse reflected at the interface between the substrate and the adhesion-promoting layer falls within the pulse width of the original light pulse. This prevents the reflected light pulse from merging with the original pulse to form a separate echo pulse.

[0036] A material or component is herein considered transparent if it is capable of transmitting at least 90%, and / or at least 95%, and / or 99% of incident radiation in the range of the electromagnetic spectrum of interest.

[0037] The photoactive layer may have a thickness less than the thickness of the substrate. For example, the photoactive layer may have a thickness of at most 10 μm, particularly at most 0.5 μm. In particular, the thickness may be in the range of 1 μm to 2 μm. However, such a thickness is often not sufficiently mechanically stable. Therefore, the substrate mainly serves to mechanically stabilize the photoactive layer.

[0038] The substrate may have a thickness at least 10 times or at least 100 times that of the photoactive layer. The substrate may have a thickness of at most 1 mm, particularly at most 0.5 mm, and / or at least 0.2 mm, particularly at least 0.3 mm. Such substrate thicknesses are typical for semiconductor disks or wafers. Thus, the substrate can be made from a semiconductor disk, particularly a wafer or semiconductor chip. The photoactive layer attached to the wafer can then be subjected to conventional wafer processing, allowing various structures to be processed in parallel. The side of the substrate opposite the photoactive layer is preferably directly adjacent to the carrier. This also reduces unwanted reflections.

[0039] According to one variant, the carrier has a carrier thickness of at least 3 mm, particularly at least 5 mm, and particularly at least 7 mm. Therefore, the substrate thickness is usually smaller than the carrier thickness. For example, the carrier thickness may be at least five times the substrate thickness. Because the carrier thickness is relatively large compared to the layer thickness and the substrate thickness, the optical travel time of the optical radiation within the carrier may be relatively long, which means that the optical reflection may be shifted in time. Therefore, the unavoidable reflective interface away from the photoactive layer can be shifted outside the measurement window of interest by increasing the thickness of the adjacent carrier, so that the measurement is not affected.

[0040] In this specification, thickness or layer thickness is in particular measured perpendicular to the layer plane and / or perpendicular to the plane. Usually, all thicknesses and layer thicknesses are measured in the same direction.

[0041] The side of the photoactive layer opposite the substrate is uncoated in at least some areas and is in particular exposed to ambient air. Due to the manufacturing process (see below), the side of the photoactive layer opposite the substrate may contain InP residues in some areas.

[0042] Optical radiation in this context is understood to be the electromagnetic radiation required to excite the photoactive layer so that electron-hole pairs are generated therein. The excitation energy of the optical radiation depends on the band gap of the photoactive material used, i.e., the distance between the valence band and the conduction band. Conversely, the photoactive material of the photoactive layer can be selected so that its band gap is tailored to a specific excitation energy. As long as the band gap is temperature-dependent, its value, defined in the usual way at the operating temperature, is typically between 10°C and 50°C, in particular between 15°C and 25°C. To be able to rely on known components of optical communication technology, the photoactive layer has a band gap of at least 1200 nm, in particular at least 1250 nm, and / or at most 1700 nm, in particular at most 1650 nm, corresponding to the excitation wavelength. For example, the photoactive layer can be made at least predominantly of semiconductor materials such as InGaAs, InAlAs, InGaAsP, InGaAlAs, InGaAlAsP, and / or GaAlAs, or can include a combination of several semiconductors. The semiconductors used are typically doped with a transition metal, particularly Fe, Rh, or Ru. The concentration of the transition metal in the photoactive layer is at least 10 18 cm -3 Concentration of, in particular, at least 10 19 cm -3 The concentration may be

[0043] In particular, the photoactive layer is formed from a single layer of photoactive material.

[0044] Alternatively, the photoactive layer may include multiple sub-layers. For example, it may have at least one active layer and one adjacent layer. In principle, an active layer or each of the active layers is embedded between two adjacent layers. Here, the adjacent layers function as recombination layers. The photoactive layer may also have a periodic layer structure with multiple alternating active and recombination layers. For example, more than 100 active layers may be provided.

[0045] The effect of residual echo pulses can be further minimized or reduced by restricting the extent of the photoactive layer to the area where it is absolutely necessary. The photoactive layer should be no larger than 1 mm. 2 , especially up to 0.1 mm 2 , preferably at most 0.01 mm 2 The vertical projection of the photoactive layer onto the substrate may be at most 1 mm 2 , especially up to 0.1 mm 2 , preferably at most 0.01 mm 2 The above-mentioned projection perpendicular to the substrate is here a parallel projection, i.e. the projection rays emitted from the photoactive layer, called projection lines, are parallel to one another. The photoactive layer may have a lateral extent measured parallel to the substrate and / or a diameter of at most 1 mm, preferably at most 0.1 mm. In particular, the photoactive layer may be in the form of a mesa structure.

[0046] The substrate can be embodied, for example, as a plane-parallel plate. The carrier can be formed as a plane parallel body or a wedge-shaped body. The substrate can be directly adjacent to the carrier (i.e., without any adhesive or layer in between). In another embodiment, a second adhesion-promoting layer is provided, which is disposed between the substrate and the carrier and connects them flatly to each other.

[0047] The first and second adhesion promotion layers can be made of the same material or can comprise different materials. Various materials are conceivable for the various adhesion promotion layers. On the one hand, the components to be connected must be flat and tightly connected by the material. On the other hand, the material should be transparent to THz radiation and / or optical radiation. In one embodiment, the first and / or second adhesion promotion layer is an adhesive layer (e.g., a layer made of benzocyclobutene (BCB)). Other suitable materials are also conceivable.

[0048] In one embodiment, the substrate is a silicon wafer. The carrier can be embodied as a silicon body. The silicon wafer and silicon body can be prepared with high surface flatness. Furthermore, thin Si wafers (0.2 mm to 1 mm) are typically stretchable, bendable, and conform well to adjacent silicon bodies (i.e., carriers). In some embodiments, van der Waals / cohesion forces can be used to create a gapless Si-Si connection between the substrate embodied as a Si wafer and the carrier embodied as a Si body. This advantageously prevents air gaps and therefore refractive index jumps between the carrier and the substrate.

[0049] The arrangement can also include a lens for terahertz radiation. Convex lenses, especially plano-convex lenses, are usually used. Hemispheric or hyperhemispheric lenses are often used. According to one embodiment, the lens is attached to a carrier. The lens can be adjacent to the carrier. However, a third adhesion-promoting layer can be provided between the carrier and the lens, connecting them flush with each other. Alternatively, the lens can form the carrier. In this case, the substrate is therefore attached directly to the lens without an additional carrier. According to one variant, the lens is made of the same material as the substrate and / or carrier. Alternatively, the lens can be made of a polymer material, such as polymethylpentene (also called TPX or PMP). The lens thickness (usually measured at its thickest point) can be at least 2 mm, especially at least 3 mm. The lens thickness and the carrier thickness can be the same.

[0050] The substrate and / or carrier and / or lens are typically made of an electrically insulating material. The substrate and / or carrier and / or lens are typically transparent to the generated terahertz radiation. Furthermore, the lens is typically transparent to optical radiation.

[0051] According to another aspect of the present invention, an antenna for generating or receiving terahertz radiation is provided. The antenna includes an arrangement of the type described above. The antenna further includes an antenna conductor having a first substructure and a second substructure. The first substructure and the second substructure are separated by a gap and are in contact with the photoactive layer. Here, the substructures may be in electrical and mechanical contact with the photoactive layer. The antenna conductor is typically made of one metal, but in this case, it may have two metal structures. In particular, the antenna conductor can be formed by evaporated or sputtered metal. Depending on the shape of the substructures, for example, a dipole antenna, a bowtie antenna, or a so-called stripline antenna can be formed.

[0052] Typically, at least the receiving antenna of a THz system is based on a photoconductor. The transmitting antenna may also be based on a photodiode instead of a photoconductor (see DE 10 2010 049 658 A1). By using a photodiode, a particularly high efficiency of the transmitting antenna can be achieved.

[0053] The photoactive layer may be in contact with the antenna conductor at its surface or lateral end faces. For example, the antenna conductor may be disposed on the side of the photoactive layer opposite the substrate or on the side of the photoactive layer facing the substrate. Alternatively, the first and second substructures may be disposed adjacent to the photoactive layer on the substrate. In this case, the photoactive layer may be disposed between the two structures.

[0054] According to a further aspect, a terahertz system for generating and coherently detecting terahertz radiation is proposed, the terahertz system comprising a laser light source and two THz antennas, each optically coupled to the laser light source and activatable by optical radiation from the laser light source, the first antenna functioning as a transmitting antenna and the second antenna functioning as a receiving antenna, the transmitting antenna and / or the receiving antenna each comprising an antenna of the type described above.

[0055] The light from the laser source has in particular a wavelength of at least 1200 nm, typically at least 1250 nm, and / or at most 1700 nm, typically at most 1680 nm. According to some embodiments, a pulsed laser is used as the laser source. Alternatively, a continuous wave laser (CW laser) can be used.

[0056] The wavelength of the laser source of the terahertz system may be in one of the telecommunication bands (e.g., O-band, E-band, S-band, C-band, L-band, and / or U-band in the wavelength range between 1260 nm and 1675 nm, in particular between 1300 nm and 1550 nm). The use of a pulsed laser as a laser source for activating a THz antenna may be advantageous. It is particularly advantageous if both THz antennas are based on photoconductors, since high transmission power and high reception sensitivity can be achieved particularly well using pulsed lasers. In the embodiment of the terahertz system as a pulsed system, femtosecond pulsed lasers with wavelengths between 1200 nm and 1700 nm can be used. The duration of the femtosecond pulses is less than 1 picosecond, for example, 10 fs to 990 fs.

[0057] In other embodiments, the laser light source may be an optical beat source. For example, the laser light source may be provided by a dual-mode laser or a two-laser system configured to generate a beat signal of two laser waves. The beat frequency of this beat signal should be at least 0.05 THz to generate terahertz radiation of the appropriate frequency and wavelength, typically between 0.05 THz and 20 THz, and more particularly between 0.1 THz and 10 THz. Embodiments with a dual-mode laser or a two-laser system and activation of a THz antenna by the corresponding beat signal can provide satisfactory results, especially when the transmitting antenna is photodiode-based. This is because photodiode-based transmitting antennas avoid the problem of excessively low transmit power, which is particularly severe when activated by a beat signal.

[0058] In particular, a lens arrangement is provided for focusing laser light onto the photoactive layer. Typically, laser light or optical radiation is not completely absorbed by the photoactive layer, so the remaining light passes through the photoactive layer and downstream layers (substrate, adhesion-promoting layer, carrier, and / or THz lens). The optical echo pulse reflected at a certain distance typically impinges divergently on the photoactive layer, where it can regenerate photocharge carriers over a large area. Even at a certain distance from the antenna guide substructure, these photocharge carriers can activate the antenna guide and generate THz echo pulses. Therefore, it is advantageous to limit the lateral extent of the photoactive layer so that the divergently reflected echo pulses no longer impinge on the photoactive layer. To achieve this, the photoactive layer may be formed, for example, as a mesa structure. The substructures can then be formed as side contacts. In this case, the photoelectric effect does not occur outside the mesa, and therefore the majority of the optical echo pulse remains ineffective with respect to excitation of the photoactive layer. See above dimensions for preferred maximum lateral or areal extents of the photoactive layer.

[0059] According to a further aspect, there is provided a method for manufacturing an arrangement for an antenna for generating or receiving terahertz radiation, the method comprising at least the following steps: - producing a photoactive layer on a support substrate made at least predominantly of InP; - connecting the photoactive layer flatly to the substrate by means of a first adhesion-promoting layer having a layer thickness of at most 5 μm; - removing said auxiliary substrate, in particular by chemical etching; - attaching the substrate to a carrier such that the substrate is positioned between the photoactive layer and the carrier;

[0060] The photoactive layer may be activatable by optical radiation in the range of 1200 nm to 1700 nm. Furthermore, the substrate and carrier are made of the same material. The substrate and carrier are transparent to the optical radiation.

[0061] In particular, the photoactive layer can be epitaxially grown lattice-matched on an InP support substrate. Suitable materials for the photoactive layer having the required bandgap may include InGaAs, InAlAs, InGaAsP, InGaAlAs, InGaAlAsP, and / or GaAlAs. See above for other properties of the photoactive layer.

[0062] The disadvantages of InP-based substrates are as described above (e.g., the refractive index jump from InP to Si; InP is often brittle, resulting in air gaps at component interfaces). Therefore, according to the present invention, the InP material is used only as an auxiliary substrate for growing the photoactive layer. After the photoactive layer is formed, the InP auxiliary substrate is removed. This is typically done by chemical etching. Alternatively, the auxiliary substrate can be removed by mechanical etching. In particular, the auxiliary substrate is completely removed. Although the goal is to completely remove the auxiliary substrate, in arrangements produced by the described method, the photoactive layer may have detectable material residues of the auxiliary substrate on the side opposite the substrate. Photoactive layers grown on InP auxiliary substrates are usually not sufficiently mechanically stable by themselves, since the layer thickness of the photoactive layer is often up to several micrometers. For this reason, the photoactive layer is bonded to a substrate before removing the InP auxiliary substrate, thereby stabilizing the photoactive layer. Before removing the auxiliary substrate, the substrate and the auxiliary substrate usually sandwich the photoactive layer.

[0063] According to one variant, the photoactive layer is grown by means of molecular beam epitaxy at a temperature between 200° C. and 450° C., in particular at 400° C. According to another variant, the photoactive layer is epitaxially grown and is doped with a transition metal such as Fe, Rh or Ru, in particular at a temperature between 10° C. and 200° C. 18 cm -3 It is doped at a concentration exceeding .

[0064] This method can be completed with the following process steps: - applying an antenna conductor having a first substructure and a second substructure to the photoactive layer such that the first substructure and the second substructure are spaced apart from each other and in contact with the photoactive layer.

[0065] Here, the step of attaching the antenna conductor to the photoactive layer can be performed before connecting the photoactive layer to the substrate, or after removing the auxiliary substrate.

[0066] If necessary, the lateral extent of the photoactive layer can be reduced, for example, to form a mesa structure. This can be done, for example, by wet chemical and / or dry etching processes. In one variation of this method, a surface passivation can be provided on the photoactive layer. The surface passivation can include, for example, silicon nitride and / or silicon oxide.

[0067] The substrate can still exist as an unprocessed wafer with at least one structure disposed thereon before being attached to the carrier. Thus, at least one structure (subassembly) including a photoactive layer, a first adhesion-promoting layer, and / or an antenna conductor can be attached to the substrate. Typically, multiple separate structures, e.g., at least 5, at least 10, at least 50, or even at least 100 structures, are disposed on the substrate. This allows for the active layer on the substrate to be processed using established semiconductor manufacturing techniques, allowing for the design of various different structures in parallel. This allows for the various processed structures to be individualized or separated from one another. In particular, the substrate wafer can be divided into individual chips. Thus, the method can be completed by separating the processed structures on the substrate and attaching the substrate with the processed structures to a carrier to form the above-mentioned assembly.

[0068] The method is particularly suitable for manufacturing the above-mentioned arrangement and the above-mentioned antenna. Features mentioned in relation to the arrangement and the antenna may also be claimed for the method and vice versa.

[0069] Exemplary embodiments of the arrangement, antenna, and terahertz system are illustrated in the accompanying figures and explained in more detail in the following description. [Brief explanation of the drawings]

[0070] [Figure 1]1 is a schematic diagram of a photoconductive THz antenna according to the prior art. [Figure 2] This is a schematic diagram of the photoconductive THz antenna in Figure 1, with optical reflection added. [Figure 3] FIG. 1 shows normalized terahertz amplitudes from different THz transmitters plotted over delay time and measured with a prior art THz receiving antenna. [Figure 4] FIG. 1 shows a schematic diagram of a setup for measuring the thickness of a paint layer. [Figure 5] This is a diagram of the mechanism in Figure 4 with a THz echo pulse added. [Figure 6] 1 is a schematic diagram of a THz antenna according to an embodiment of the present invention; [Figure 7] 1 is a schematic diagram of a further THz antenna according to an embodiment of the present invention; [Figure 8] 1 is a schematic diagram of a further THz antenna according to an embodiment of the present invention; [Figure 9] 1 is a schematic diagram of a further THz antenna according to an embodiment of the present invention; [Figure 10] 1 is a schematic diagram of a further THz antenna according to an embodiment of the present invention; [Figure 11] 1 is a schematic diagram of a terahertz system for generating and coherently detecting terahertz radiation according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0071] 11 includes a laser source 15, a transmitting antenna 16, and a receiving antenna 17. The transmitting antenna 16 and the receiving antenna 17 are each a THz antenna activated by light from the laser source 15. For this purpose, a beam splitter 28 is connected after the output of the laser source 15. The transmitting antenna 16 and the receiving antenna 17 are connected to two outputs of the beam splitter 28 by optical fibers 18, respectively.

[0072] The laser source 15 is a pulsed laser, and its wavelength is between 1200 nm and 1700 nm, in particular 1300 nm or 1550 nm. A controllable optical delay circuit 19 can be placed at the input or in the path of the optical fiber 18 to shift the relative timing of the optical control signals for activating the two THz antennas 16, 17. For this purpose, the optical delay circuit 19 can comprise, for example, a delay line to which a variable electric field can be applied. Finally, a sample 29 is also shown, positioned between the transmitting antenna 16 and the receiving antenna 17. The sample 29 can be examined with the terahertz system 20.

[0073] The pulsed laser forming the laser source 15 can be, for example, an erbium-doped fiber pulsed laser or a semiconductor pulsed laser, for example based on the InGaAsP / InP material system.

[0074] For further details of the terahertz system 20, reference is made to DE 10 2010 049 658 A1.

[0075] In the following, individual times of the THz antennas 16 and 17 of the terahertz system 20 will be described. Figures 6 to 10 show schematic diagrams of THz antennas according to embodiments of the present invention. For clarity, only the THz transmitting antenna 16 is shown here. However, it will be apparent that the THz transmitting antennas shown in Figures 6 to 10 can also be used as THz receiving antennas.

[0076] 6 shows a schematic representation of an arrangement 1 that is part of an antenna 16 for generating terahertz radiation 12. The arrangement 1 comprises a photoactive layer 2, a substrate 3, a first adhesion promoting layer 4, and a carrier 5.

[0077] The photoactive layer 2 can be activated by optical radiation 11 from a laser source 15 in the range of 1200 nm to 1700 nm and therefore has a corresponding bandgap. Suitable semiconductors for the photoactive layer 2 are, for example, InGaAs, InAlAs, InGaAsP, InGaAlAs, InGaAlAsP, or GaAlAs. The semiconductors used for the photoactive layer 2 typically have a bandgap of at least 10 18 cm -3 , especially at least 10 19 cm -3 The photoactive layer 2 is doped with a transition metal, such as Fe, Rh or Ru, at a concentration of 0.5 μm. For the generation of THz radiation, a layer thickness of the photoactive layer 2 of at most 10 μm, and at least 0.5 μm, is advantageous. In the exemplary embodiment shown, the total layer thickness may be between 1 μm and 2 μm. In particular, the photoactive layer 2 consists of a single layer of photoactive material. Alternatively, the photoactive layer 2 may comprise several sublayers. For example, there may be at least one active layer and one adjacent layer.

[0078] The photoactive layer 2 is attached to a substrate 3. A first adhesion-promoting layer 4, applied over the entire surface, serves for this purpose. The first adhesion-promoting layer 4 is therefore located between the photoactive layer 2 and the substrate 3, connecting them evenly and flush. The adhesion-promoting layer 4 largely avoids air gaps between the substrate 3 and the photoactive layer 2. To further suppress back-reflection of the laser light 12, the adhesion-promoting layer 4 should have a layer thickness of up to 5 μm. Layer thicknesses in the range of 0.5 μm to 2 μm are conceivable. A suitable material for the adhesion-promoting layer 4 (also called adhesive layer) is, for example, BCB (benzocyclobutene), which is often used in the prior art for so-called wafer bonding.

[0079] The substrate 3 is made of a material, particularly silicon, that is transparent to the laser radiation 11 and the THz radiation 12. The substrate 3 is also electrically insulating. The substrate 3 ensures the mechanical stability of the photoactive layer 2, particularly during the fabrication of the device 1 (see the fabrication method below). The substrate 3 is typically embodied as a plane-parallel plate. The substrate 3 can be advantageously fabricated from chips of commercially available silicon wafers. This allows the application of established wafer processing techniques and the parallel production of multiple structures on one substrate. The first side of the substrate 3, facing the photoactive layer 2, is therefore planar. On the second side of the substrate 3, facing away from the photoactive layer 2, the substrate is attached to the carrier 5. The substrate 3 is therefore positioned between the photoactive layer 2 and the carrier 5. The side of the substrate 3 facing the carrier 5 is also particularly planar. The substrate 3 has a substrate thickness (measured perpendicular to the substrate plane from the first side to the second side of the substrate 3) that is substantially greater than the layer thickness of the photoactive layer 2. The substrate 3 may have a thickness of, for example, up to 1 mm, but typically at least 0.2 mm. In the exemplary embodiment shown, the substrate 3 has a thickness in the range of 300 μm to 500 μm. After wafer processing is complete, the structure is separated and mounted on a carrier.

[0080] The carrier 5 is made of the same material as the substrate 3 but is much thicker. In the illustrated exemplary embodiment, the carrier 5 is embodied as a plane-parallel silicon body or silicon block. Therefore, a first side of the carrier 5 facing the substrate 3 is planar. Furthermore, a second side of the carrier 5 opposite the substrate 3 is embodied as a flat surface. The THz radiation 12 generated by the antenna 16 leaves the carrier 5 via the first side of the carrier 5 opposite the substrate 3. The carrier 5 has a carrier thickness (measured from the first side to the second side of the carrier 5) that is substantially greater than the thickness of the substrate and the thickness of the photoactive layer 2. This allows optical reflections at the carrier 5-air interface (i.e., the second side of the carrier 5) to be delayed in time and therefore outside the measurement window of interest. An exemplary carrier thickness is at least 5 mm, in particular at least 8 mm. Because the carrier 5 and the substrate 3 are made of the same material, reflections of the optical radiation 11 at the interface between the substrate 3 and the carrier 5 are strongly suppressed.

[0081] The carrier 5 and the substrate 3 are connected flat, with their sides placed flat against each other, for example by press contact. Thus, the carrier 5 can be directly adjacent to the substrate 3. Alternatively, a second adhesion-promoting layer (not shown) can be provided between the substrate 3 and the carrier 5, which connects the substrate 3 and the carrier 5 flat and flush against each other. The second adhesion-promoting layer can be made of a polymer material such as BCB.

[0082] The antenna conductor 6 further comprises a first substructure 7 and a second substructure 8. The first substructure 7 and the second substructure 8 are separated from each other by a gap 9. The photoactive layer 2 is uncoated in the region of the gap 9 and is exposed to the ambient air. Optical radiation 11 from the laser 15 is incident on the photoactive layer 2 through the gap 9. Both substructures 7 and 8 are in electrical and mechanical contact with the photoactive layer 2. The substructures 7 and 8 are typically formed as metal structures and are formed by vapor deposition or sputtering of metal onto the photoactive layer 2. In the embodiment of FIG. 6, the substructures 7 and 8 are located on the side of the photoactive layer 2 opposite the substrate 3.

[0083] The THz antenna 16 shown in FIG. 7 differs from the THz antenna shown in FIG. 6 in that the substructures 7, 8 of the antenna conductor 6 are positioned laterally adjacent to the photoactive layer 2. That is, the photoactive layer 2 is centrally located between the substructures 7, 8. The photoactive layer 2 is located inside the gap 9, completely filling the gap. In particular, the photoactive layer 2 in the embodiment of FIG. 7 is embodied as a mesa structure with dimensions measured perpendicular to the layer thickness of at most 100 μm×100 μm. The footprint of the mesa structure is therefore at most 0.01 mm 2 7, the vertical projection of the photoactive layer 2 onto the substrate has a reduced area, so that only a small portion of the divergent radiation of the optical radiation 11 at the interface between the substrate 3 and the carrier 5 impinges on the back surface of the photoactive layer 2. As a result, significantly fewer charge carriers are generated in the photoactive layer 2, which can effectively minimize the THz echo pulse. Apart from the arrangement of the substructures 7, 8 relative to the photoactive layer 2 and the embodiment of the photoactive layer 2 as a mesa structure, the antenna 16 shown in FIG. 7 has the same characteristics as the antenna of FIG. 6.

[0084] FIG. 8 shows an antenna 16 in addition to the antenna 16 of FIG. 6, which has a lens 13 for the THz radiation 12. The lens 13 couples the THz radiation 12 from the antenna 16 and, in the exemplary embodiment of FIG. 8, is formed as a plano-convex lens, in particular a hemispherical or hyper-hemispherical lens. The lens 13 is attached to the carrier 5 with its planar side connected to a second planar side of the carrier 5. In particular, the lens 13 is made of the same material as the carrier 5 and the substrate 3, i.e., Si in the exemplary embodiment shown. In this case, the lens 13 can be connected to the carrier 5, for example, by pressure contact and can be directly adjacent to the carrier 5. Alternatively, other materials can be used for the lens 13. For example, polymer materials such as polymethylpentene are conceivable. In this case, the lens 13 can be connected flush and flush to the carrier 5 by a third adhesion-promoting layer (for example, an adhesive layer made of BCB). The lens thickness is in particular at least 2 mm, in particular at least 3 mm. The lens 13 can have the same thickness as the carrier 5.

[0085] In another embodiment, the lens may form the carrier. This embodiment of the antenna 16 is shown in FIG. 9. Here, the substrate 3 is attached directly to the lens 14, resulting in no additional carrier. The lens 14 can be adjacent to the substrate 3, or a fourth adhesion-promoting layer can be placed between the lens 14 and the substrate 13, resulting in a flush and tight connection between the flat side of the lens 14 and the substrate 3. The lens 14 is made of the same material as the substrate 3. For further characteristics of the lens 14, see lens 13 above.

[0086] In the antenna 16 of Figure 9, the photoactive layer 2 and the metal structures 7, 8 of the antenna conductor 6 are constructed in a similar manner to the antenna of Figure 7. However, it will be clear that the structure of the photoactive layer 2 and the metal structures 7, 8 of Figure 6 can also be used.

[0087] The antenna 16 shown in FIG. 10 has a similar structure to the antenna of FIG. 8 and differs from it only in the arrangement of the metal structures 7 and 8. The metal structures 7 and 8 of the antenna conductor 6 in FIG. 10 are arranged on the side of the photoactive layer 2 facing the substrate 3, whereas in FIG. 6 they are arranged on the side of the photoactive layer opposite the substrate 3. In FIG. 10, the first adhesion promotion layer 4 is arranged between the metal structures 7 and 8 and the substrate 3, connecting the metal structures 7 and 8 flush to the substrate 3. Therefore, the first adhesion promotion layer 4 has a reduced layer thickness in the area of ​​the metal structures 7 and 8. The advantage of the arrangement shown in FIG. 10 is that reflected light radiation does not strike the opaque metal structures 7 and 8 and, as a result, does not generate free charge carriers in the photoactive layer 2. The side of the photoactive layer 2 opposite the substrate 3 is completely uncoated and exposed to the ambient air.

[0088] The antenna 16 of FIGS. 6-10 is preferably used in the terahertz system 20 of FIG.

[0089] A method for manufacturing the arrangement 1 or for manufacturing the antenna 16 is described below.

[0090] First, an auxiliary substrate (not shown) made of InP is prepared. Next, the photoactive layer 2 is produced. The photoactive layer 2 is produced by epitaxial growth on the InP auxiliary substrate. Typically, the photoactive layer 2 is grown by molecular beam epitaxy at a temperature between 200°C and 450°C. The temperature is particularly 400°C. During the epitaxial growth, the photoactive layer 2 is grown at a temperature of, in particular, 10 18 cm -3 The doping is performed with a transition metal at a concentration of .

[0091] After the photoactive layer 2 has been produced, the side of the photoactive layer opposite the auxiliary substrate may be connected over its entire surface to a silicon wafer. The silicon wafer has a diameter of at least 2 inches, in particular at least 3 inches, and a thickness of between 0.2 mm and 1 mm. A first adhesion-promoting layer 4 is used for the connection. The silicon wafer and the auxiliary substrate are now located on either side of the photoactive layer 2. The auxiliary substrate is then completely removed, in particular by chemical etching. Alternatively, the auxiliary substrate may be removed mechanically.

[0092] In an additional step, the antenna conductor 6 is brought into contact with the photoactive layer 2. The antenna conductor 6, which comprises a first substructure 7 and a second substructure 8, is applied to the photoactive layer 2 in such a way that the two substructures are spaced apart from each other and in contact with the photoactive layer 2. The antenna conductor 6 is applied in particular in a so-called lift-off process by evaporation or sputtering of metal.

[0093] Here, the antenna conductor 6 can be applied just before the photoactive layer 2 is connected to the substrate 3 (i.e. before the auxiliary substrate is removed) or only after the auxiliary substrate is removed.

[0094] To produce the mesa structure of the photoactive layer 2 shown in Figures 7 and 9, the photoactive layer 2 may be etched in the areas after the removal of the auxiliary substrate. This is usually done by wet chemical etching and dry etching processes. Metal structures 7 and 8 can then be applied as described above. Alternatively, the mesa structure of the photoactive layer 2 can be generated before connecting the photoactive layer 2 to the silicon wafer. The metal structures 7 and 8 are then applied to the photoactive layer 2 by evaporation or sputtering. A first adhesion-promoting layer 4 is then applied to the metal structures 7 and 8 and the photoactive layer 2. The silicon wafer is then connected to the photoactive layer 2 via layer 4. In a further step, the auxiliary substrate is removed, particularly completely.

[0095] Optionally, a surface passivation, for example made of silicon nitride or silicon oxide, may be applied to the photoactive layer 2 and / or the metal substructures 7,8.

[0096] After the photoactive layer 2, wafer, adhesion promotion layer 4 and metal structures 7, 8 have been placed relative to one another, the silicon wafer can be cut to form a plurality of chips, each comprising a silicon substrate 3, an adhesion promotion layer 4 and metal structures 7, 8. In this way, a Si wafer is used to manufacture a plurality of substrates 3. Of course, at the start of the method, substrates 3 in the form of chips can also be used instead of wafers.

[0097] The substrate 3 is then fixed onto the carrier 5 or onto the lens 14 formed as a carrier. If necessary, the lens 13 is connected to the carrier 5.

[0098] The described method is particularly suitable for manufacturing the above arrangement 1 and described antenna 16 of Figures 6 to 10. Features mentioned only in relation to the arrangement and antenna may also be claimed for the method and vice versa. [Explanation of symbols]

[0099] Arrangement for 1 THz antenna 2 Photoactive layer 3. Circuit Board 4 Adhesion promotion layer 5. Career 6 Antenna conductor 7 Metal structure 8 Metal structure 9. Gap 10 flat surface 11 fs laser pulse 12 THz pulse 13 Lens 14 Lenses 15 Laser 16 transmitting antennas 17 Receiving antenna 18 Optical Fiber 19 Delay Circuit 20 Terahertz System 21 Photoactive layer 22 PCB 23 Metal structures 24 Metal structures 25 Career 26 Interface 27 Echo Pulse 28 Beam Splitter 29 Samples 30 THz transmitter 31 THz receiver 32 Paint layer 33 Metal Carrier 34 THz reflection pattern 35 Replica 36 samples

Claims

1. An arrangement (1) for an antenna (16, 17) for generating or receiving terahertz radiation (12), comprising: a photoactive layer (2) activated by optical radiation (11) in the range of 1200 nm to 1700 nm; a substrate (3) transparent to said optical radiation (11) and on which said photoactive layer (2) is attached; a carrier (5) transparent to said optical radiation (11), Including, The substrate (3) is attached to the carrier (5) and is disposed between the photoactive layer (2) and the carrier (5), the substrate (3) and the carrier (5) are made of the same material; A first adhesion-promoting layer (4) is disposed between the photoactive layer (2) and the substrate (3) to connect them flatly to each other; Arrangement (1), characterized in that the first adhesion-promoting layer (4) has a layer thickness of 5 μm or less.

2. the photoactive layer (2) has a layer thickness of at most 10 μm, in particular at least 0.5 μm, and / or the substrate (3) has a thickness of at most 1 mm, in particular at least 0.2 mm; and / or The carrier (5) has a carrier thickness of at least 3 mm, in particular at least 5 mm. Arrangement (1) according to claim 1 .

3. the carrier (5) and the substrate (3) are made of silicon, and / or The photoactive layer (2) consists at least in large part of InGaAs, InAlAs, InGaAsP, InGaAlAs, InGaAlAsP, and / or GaAlAs, in particular doped with a transition metal.

3. Arrangement (1) according to claim 1 or 2.

4. The substrate (3) is embodied as a plane-parallel plate and / or the carrier (5) is embodied as a plane-parallel body. Arrangement (1) according to any one of claims 1 to 3.

5. a lens (13) for said terahertz radiation (12), in particular a plano-convex, hemispherical or hyper-hemispherical lens, The lens (13) is attached to the carrier (5) or the lens (13) forms the carrier (5). Arrangement (1) according to any one of claims 1 to 4.

6. The face of the photoactive layer (2) opposite the substrate (3) is uncoated in at least some areas and is in particular exposed to the ambient air. Arrangement (1) according to any one of claims 1 to 5.

7. An antenna (16, 17) for generating or receiving terahertz radiation (12), An arrangement (1) according to any one of claims 1 to 6, an antenna conductor (6) having a first substructure (7) and a second substructure (8); Including, The first substructure (7) and the second substructure (8) are separated from each other by a gap (9) and are in contact with the photoactive layer (2). An antenna (16, 17) characterized in that

8. The antenna conductor (6) is disposed on the surface of the photoactive layer (2) opposite to the substrate (3) or on the surface of the photoactive layer (2) facing the substrate (3). Antenna (16, 17) according to claim 7.

9. The first substructure (7) and the second substructure (8) are arranged on the substrate (3) on the sides of the photoactive layer (2), and the photoactive layer (2) is arranged between the first substructure (7) and the second substructure (8). Antenna (16, 17) according to claim 7.

10. The photoactive layer (2) has a thickness of up to 1 mm ２ , especially up to 0.1 mm ２ , especially up to 0.01 mm ２ has a footprint of Antenna (16, 17) according to claim 9.

11. A terahertz system (20) for generating and coherently detecting terahertz radiation (12), comprising: a laser light source (15) and two THz antennas (16, 17), each of the THz antennas (16, 17) optically coupled to the laser light source and activatable by the optical radiation (11) from the laser light source; One of the THz antennas (16, 17) functions as a transmitting antenna (16) and the other functions as a receiving antenna (17); The transmitting antenna (16) and / or the receiving antenna (17) each constitute an antenna according to any one of claims 8 to 10. A terahertz system (20) characterized by:

12. The optical radiation (11) of the laser light source has a wavelength of at least 1200 nm and / or at most 1700 nm.

12. The terahertz system of claim 11.

13. 1. A method for manufacturing an arrangement (1) for an antenna (16, 17) for generating or receiving terahertz radiation (12), comprising: - producing a photoactive layer (2) on an auxiliary substrate made at least predominantly of InP; - connecting said photoactive layer (2) flatly to said substrate (3) by means of a first adhesion-promoting layer (4) with a layer thickness of at most 5 μm; removing said auxiliary substrate, in particular by chemical etching; - attaching said substrate (3) to a carrier (5) so that said substrate (3) is located between said photoactive layer (2) and said carrier (5); and the photoactive layer (2) is activatable by optical radiation (11) in the range of 1200 nm to 1700 nm; The substrate (3) and the carrier (5) are made of the same material and are transparent to the optical radiation (11). A method characterized by:

14. The photoactive layer (2) is grown by molecular beam epitaxy at a temperature between 200° C. and 450° C., and / or the photoactive layer is epitaxially grown and has a thickness of at least 10 １８ cm －３ is doped with a transition metal at a concentration of 14. The method of claim 13.

15. The method further comprises attaching an antenna conductor (6) having a first substructure (7) and a second substructure (8) to the photoactive layer (2) such that the first substructure (7) and the second substructure (8) are spaced apart from each other and in contact with the photoactive layer (2); The step of attaching the antenna conductor (6) to the photoactive layer (2) is performed either before connecting the photoactive layer (2) to the substrate (3) or after removing the auxiliary substrate.

15. The method according to claim 13 or 14.

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