Tuning the emission wavelength of quantum light emitters via phase change materials

Abstract

A device is prepared having a layered structure including a layer of phase change material and a layer of matrix material having embedded quantum emitters. An electric field is applied through the layer of matrix material and the layer of phase change material to change the emission wavelength of the quantum emitters. The phase of the phase change material is non-volatilely changed in each of one or more localized regions of the phase change material to form localized changes opposing those of each of the quantum emitters in the layer of matrix material, locally changing the electric field at each quantum emitter.

Description

Technical Field

[0001] The project leading to this application has received funding from Switzerland (QuantERA project "RouTe", Swiss National Science Foundation grant agreement 20QT21_175389).

[0002] This disclosure relates to adjusting the emission wavelength of quantum emitters, and more specifically to phase change materials that locally vary the electric field of quantum emitters.

Background Art

[0003] Some quantum information processing concepts involve single photon emitters (e.g., quantum emitters such as molecules and quantum dots), and are based on (i) coupling the on-chip emission of a single quantum emitter to a optical resonator mode, or (ii) coupling individual quantum emitters to each other.

Summary of the Invention

[0004] According to embodiments, methods, apparatuses, and devices are disclosed.

[0005] According to a first aspect, the present disclosure is embodied as a method of adjusting the emission wavelength of a quantum emitter. This method depends on a device having a layered structure, e.g., a two-layer structure. This layered structure includes a layer of a phase change material and a matrix material layer, the latter embedding one or more quantum emitters. Next, an electric field is applied through the matrix material layer and the phase change material layer to vary the emission wavelength of the quantum emitter by the Stark effect or other related effects. Finally, the phase of the phase change material (PCM) changes non-volatilely in each of one or more local regions of the PCM, e.g., from amorphous to crystalline. That is, the phase of the PCM in the local region is preferably changed from an essentially amorphous structure to an essentially crystalline structure such that the remainder of the PCM has an essentially amorphous structure.

[0006] These local regions form local phase shifts that are opposite (e.g., opposite) to the phase shifts of each quantum emitter within the matrix material layer. This causes a local change in the electric field at each quantum emitter. As a result, by controlling the phase in selected regions of the PCM layer, it becomes possible to individually, for example, programmatically, adjust the emission wavelength of the quantum emitters.

[0007] Changes in the electric field at the emitter position occur, for example, due to changes in the static dielectric constant after a phase change following the arrival of the crystalline phase. This makes it possible to change the local electric field strength experienced by each emitter, and therefore the intensity of the Stark effect. This allows for individual tuning of the emission wavelength of each quantum emitter. The degree of tuning depends on the shape of the local region (where the phase is changed) and the degree to which the phase changes (e.g., the degree of crystallinity of the PCM in these regions).

[0008] Accordingly, the above method can be advantageously used, for example, in quantum information processing applications, more generally, in applications that require (i) coupling the electromagnetic radiation of individual quantum emitters with each other, (ii) coupling individual quantum emitters with light of a predetermined wavelength (e.g., coupling with a distant quantum emitter), or (iii) coupling a predetermined quantum emitter with one or more optical cavity modes of a cavity including a layered structure, as in the embodiment.

[0009] Preferably, one or more local regions are first regions that cause a first local phase change, and the method further includes reconstructing the PCM layer as follows: (i) Before changing the phase of each of the one or more second local regions of the PCM from an amorphous structure to a crystalline structure, the phase of each of the one or more first regions is returned to an amorphous structure. Similar to the first regions, the second local regions cause a second local phase change, which is opposite to that of each quantum emitter in the matrix material layer, but different in size and number. This causes the electric field at each quantum emitter to change locally again, although to a different degree than before.

[0010] In a preferred embodiment, the PCM is such that, after changing the phase of the PCM in each of one or more local regions, the average static relative permittivity of the local region is at least 1.5 times greater than the average static relative permittivity of the rest of the PCM layer.

[0011] Preferably, the phase of the PCM is changed in each local region using a radiating element that is controllably moved relative to the PCM layer. The radiating element includes one of a laser device and a heated nanoscale probe tip.

[0012] In a preferred embodiment, the electric field is applied parallel to the matrix material layer. In a modified example, the electric field is applied transversely to the layer structure.

[0013] In another embodiment, the present disclosure is embodied as an apparatus comprising a light-emitting device, an electrical circuit, and a radiating device. The light-emitting device comprises two electrodes and a layered structure. The latter comprises a PCM layer and a matrix material layer in which quantum emitters are embedded. The matrix material layer extends on the PCM layer and further extends between the two electrodes, for example, vertically or horizontally (e.g., laterally). The electrical circuit is connected to the two electrodes and configured to generate an electric field through the matrix material layer and the phase-change material layer via the two electrodes to change the emission wavelength of the quantum emitters. The radiating device is configured to non-volatilely controllably change the phase of the PCM in each of one or more local regions of the PCM. As in the first embodiment of the present disclosure, the local regions are opposite (e.g., facing) those of each of the quantum emitters in the matrix material layer. Changing the phase of the PCM in these regions causes a locally changing electric field of each quantum emitter during operation.

[0014] In the embodiment, the radiating device includes a radiating element, which is one of a laser device and a heatable nanoscale probe tip. The device is configured to move the radiating element in a controllable manner relative to a layered structure, allowing for easy change of the phase of the PCM in a localized region.

[0015] For example, the apparatus may be configured to scan the layered structure together with the radiating elements by moving the layered structure or the radiating elements or both laterally. The distance characterizing the lateral accuracy (in terms of resolution) is preferably smaller than the average lateral separation distance between quantum emitters. The lateral separation distance is measured along a direction parallel to the average plane of the layered structure.

[0016] In the final embodiment, the present disclosure is embodied as a light-emitting device. The device comprises a layered structure having a PCM layer and a matrix material layer in which one or more quantum emitters are embedded. The matrix material layer extends over the PCM layer. Furthermore, the device includes two electrodes positioned on either side of the matrix material layer. These electrodes can generate an electric field through the matrix material layer and the phase-change material layer, thereby changing the emission wavelength of the quantum emitters. As in other embodiments of the present disclosure, the PCM further includes one or more local regions facing each of the quantum emitters in the matrix material layer. The local regions have a different phase from the rest of the PCM layer. As a result, the local regions locally change the electric field at each quantum emitter when the device is in operation.

[0017] Light-emitting devices typically include a substrate on which a PCM layer extends. For example, the PCM layer lies between the substrate and a matrix material layer. As described above in relation to embodiments prior to this disclosure, the electrodes may have a vertical or horizontal (e.g., transverse) configuration. For example, in a transverse configuration, the electrodes may be patterned directly onto the substrate such that a layered structure extends between the electrodes.

[0018] Preferably, the PCM contains GeSbTe or HfO2. Alternatively, the matrix material layer may consist of, for example, a crystalline material or a polymer material, and the quantum emitter may include an organic emitter containing epitaxially grown semiconductor quantum dots, colloidal quantum dots, or other emitters such as dyes and oligomers. Other material combinations are also possible.

[0019] In a preferred embodiment, the average static relative permittivity of the local region is at least twice that of the average static relative permittivity of the rest of the region.

[0020] In the embodiment, the average distance between quantum emitters within the matrix material layer is 50 nm or more. Furthermore, the average in-plane dimension of the local region is preferably 50 to 5000 nm. All in-plane dimensions are measured along a direction parallel to the average plane of the matrix material layer (or layered structure). On the other hand, the average thickness of the local region is preferably 1 nm or more, and this thickness is measured perpendicular to the matrix material layer from the interface between the matrix material layer and the PCM layer.

[0021] The average thickness of the PCM layer is preferably between 50 nm and 200 nm, and the average thickness of the matrix material layer is preferably between 20 nm and 200 nm. Here again, such thicknesses are measured perpendicular to each layer.

[0022] The above summary is not intended to describe each illustrated embodiment or all embodiments of the present disclosure.

[0023] The drawings included in this application are incorporated herein by reference and constitute part of this specification. They illustrate embodiments of the disclosure and, together with this specification, serve to illustrate the principles of the disclosure. The drawings are illustrative of specific embodiments and do not limit the disclosure. [Brief explanation of the drawing]

[0024] [Figure 1A]A two-dimensional cross-sectional view of a light-emitting device according to some embodiments of the present disclosure. [Figure 1B] A two-dimensional top view of a light-emitting device according to some embodiments of the present disclosure. [Figure 2A] Shows selected components of a device according to some embodiments of the present disclosure. [Figure 2B] A diagram showing selected components of a device according to some embodiments of the present disclosure. [Figure 3] A flowchart showing a method for tuning the emission wavelength of a quantum emitter according to some embodiments of the present disclosure.

[0025] The present invention is subject to various changes and alternative forms. Specific embodiments are illustrated in the drawings and will be described in detail. However, it should be understood that the intention is not to limit the present invention to the specific embodiments described. On the contrary, the intention is to cover all changes, equivalents, and alternatives falling within the spirit and scope of the present invention.

Embodiments for Carrying Out the Invention

[0026] Aspects of the present disclosure relate to adjusting the emission wavelength of a quantum emitter, and more particular aspects relate to phase change materials for locally varying the electric field in a quantum emitter. The present disclosure is not necessarily limited to such applications, but various aspects of the present disclosure can be understood through discussion of various examples using this context.

[0027] Some quantum information processing concepts involve single photon emitters (e.g., quantum emitters such as molecules and quantum dots), and are based on (i) on-chip coupling of the emission of a single quantum emitter to a optical resonator mode, or (ii) coupling individual quantum emitters to each other.

[0028] Each quantum emitter may depend on resonance with cavity modes or other quantum emitters. Most quantum emitters may have slightly different emission wavelengths, resulting in a non-uniform spectral width of ensemble emission. To achieve the desired coupling, the spectrally narrow emission spectra of individual quantum emitters may need to overlap with the emission spectra of other quantum emitters or cavity mode spectra.

[0029] Techniques for tuning the emission wavelength of quantum emitters include strain tuning and field tuning. However, these techniques cannot be used to individually tune multiple single emitters to overcome the detrimental effects of non-uniform broadening.

[0030] Referring to Figures 1 to 3, one aspect of the present disclosure is first described, which relates to a method for tuning the emission wavelength of a quantum emitter 16.

[0031] Figures 2A and 2B can show selected components of the apparatus according to the embodiments. These apparatuses each include a light-emitting device 1, as shown in Figures 1A and 1B, and radiating elements 37, 38. In each embodiment, the light-emitting device 1 can be moved laterally relative to the radiating elements 37 / 38, thereby locally changing the phase of one or more layers.

[0032] By carrying out the method, it is possible to obtain a light-emitting device 1, in particular, as shown in Figures 1A and 1B. The method can be carried out using apparatus 101 or 102, or both, as shown in Figures 2A and 2B, respectively. In Figure 2A, the radiating elements 37 / 38 may be heated nanoscale probe tips, while in Figure 2B, the radiating elements 37 / 38 may be laser devices. The method and its variations are collectively referred to as "the Method". All references Sn refer to method steps in the flowchart of Figure 3, and numerical references relate to physical parts or components of device 1 and apparatus 101, 102 shown in Figures 1 and 2. Device 1 and apparatus 101, 102 relate to other aspects of the present disclosure, which will be described in detail later.

[0033] The methods shown in Figures 2A and 2B may depend on a light-emitting device, for example, as provided in step S10 of the flowchart in Figure 3. The light-emitting device 1 may have layered structures 12, 15 comprising a phase-change material (PCM) layer 12 and a matrix material layer 15. The layered structures 12, 15 may be simply two-layer structures, as assumed in the accompanying drawings. However, the layered structures 12, 15 may include an additional intermediate layer between the PCM layer 12 and the matrix material layer 15. This intermediate layer may be, for example, an adhesive layer or a protective layer. However, the intermediate layer may be very thin, for example less than 10 nm thick, in order to retain the desired properties of the structures 12, 15, as described below.

[0034] The matrix material layer 15 may have one or more quantum emitters 16 embedded within it. For example, at least one quantum emitter 16 is involved, but the matrix material layer 15 may contain multiple (one or more) quantum emitters 16, as shown in Figures 1A and 1B. A quantum emitter 16 (also called a single-photon source) can facilitate the emission of one photon at a time, in contrast to classical light. Several types of active nanomaterials are known, and these can be designed as single quantum emitters 16, allowing for the tuning of spontaneous emission by varying the local density of optical states in the dielectric nanostructure. A quantum emitter is, for example, a single atom, ion, molecule, or defect center. In this specification, a quantum emitter can include quantum dots, color centers, organic emitters, and solid emitters such as carbon nanotubes. In some embodiments, the quantum emitter may be an epitaxially grown semiconductor quantum dot, a colloidal quantum dot, or an organic emitter such as an organic dye, as described later with reference to another aspect of this disclosure.

[0035] In step S20, an electric field is applied through the matrix material layer 15 and the PCM layer 12. The applied electric field may be constant, for example, static, and is usually constant. The applied electric field may cause a change in the emission wavelength of the quantum emitter 16 due to the Stark effect or other related effects.

[0036] The electric field may be applied by an electrical circuit 32 (see Figures 2A and 2B) via two electrodes 10 (see Figures 1A and 1B). In the example of Figures 1A and 1B, the light-emitting device 1 may include an optically and electrically passive substrate. In some embodiments, the substrate may not emit light and may be electrically insulating. The electrodes 10 of a conductive material may be patterned directly onto this substrate 11. Thus, a voltage can be applied locally through the electrodes 10. The applied voltage can be in the range of 1 to 100 V.

[0037] Furthermore, in step S30, the phase of the PCM 12 may be altered (e.g., non-volatilely) in each of one or more local regions 14 of the PCM. These regions form local phase changes (e.g., local patterns), which are opposite to those of each quantum emitter 16 in the matrix material layer 15. Local phase changes may be formed by a single local region 14 (as assumed in Figures 1A and 1B) or by two or more such local regions. Local regions can also have a variety of possible shapes. For example, a local alteration may be formed by a single local region having a substantially cylindrical shape (as assumed in Figures 1A and 1B). However, a local alteration may also be formed by two or more local regions with altered phases. Furthermore, each local region may have a specific shape. For example, a local alteration may be achieved thanks to two (possibly separate) regions having a bowtie shape. Such structures may be sought to maximize the dielectric strengthening effect with respect to a simple cylindrical (or some circular) structure 14. More generally, the shape and number of local regions can be optimized to form an electric field, adjust its intensity, or both.

[0038] In all cases, region 14 forms a local phase change related to the quantum emitter. That is, the local phase change surrounds or includes the orthogonal projection of the emitter 16 in the PCM layer 12, as assumed in Figures 1A and 1B. In the example of a bowtie change (not shown) formed by laterally opposed regions with phase changes, the electric field hotspot is located between the two local regions (having a triangular in-plane shape). In this case, the orthogonal projection of the emitter is ideally located between the two opposing bowtie regions.

[0039] Note that the number reference 1 may indicate a light-emitting device obtained after locally changing the phase of a selected region 14 of the PCM layer 12.

[0040] When the phase of the PCM is changed in these regions 14, the electric field at each quantum emitter 16 changes locally, as shown in Figures 1A and 1B. The applied electric field is depicted as a dashed line 20. For example, in these examples, the electric field is schematically visualized as a set of lines like line 20, where the direction at each point is the same as the direction of the electric field. The electric field changes in the vicinity of the quantum emitter thanks to the phase-changed PCM regions 14.

[0041] By changing the field, it becomes possible to programmatically adjust the emission wavelength of the quantum emitter individually. For example, the dimensions and crystal state of the local region 14 can be changed as needed to achieve a desired emission wavelength. Note that the emission spectrum of the quantum emitter may be monitored in real time (e.g., during S30 when programming the PCM layer 12) in order to appropriately adjust the emission wavelength. In some embodiments, the programming step S30 is combined with a spectrum measurement step to gradually (e.g., stepwise) adjust the emission wavelength. In some embodiments, the relevant procedure is applied in S30 to directly form a region 14 of known dimensions by, for example, applying a predetermined amount of radiation (heat or light) for a predetermined duration.

[0042] The PCM region 14 is preferably obtained in S30 using radiating elements 37, 38 such as a heated nanoscale probe tip 37 (Figure 2A) or a laser device 38 (Figure 2B). The radiating elements 37, 38 can nonvolatably and locally change the phase of the PCM (e.g., from amorphous to crystalline). This is equivalent to "programming" the PCM layer 12. The fact that the change is "nonvolatility" means that the phase change remains stable even after radiation (light or heat) is blocked. As will be described later with reference to some embodiments, the device 1 can be reprogrammed as needed to operate the layered structures 12, 15. Therefore, the PCM can be selected such that the phase change region 14 is stable but not necessarily irreversible.

[0043] Step S30 may be performed after step S20. In some embodiments, the electric field may be applied after the phase of the PCM in the local region 14 has been changed (step S30) (step S20).

[0044] Changes in the electric field at the emitter 16 can occur, for example, upon reaching the crystalline phase, due to the resulting change in static dielectric constant. This allows for variations in the local electric field strength experienced by each emitter 16, and therefore, the intensity of the Stark effect. This ability to vary the electric field may enable the ability to individually tune the emission wavelength of each quantum emitter 16. The degree of tuning may be related to the geometric shape and the degree to which the phase of the (phase-changed) local region 14 is altered, for example, the degree of crystallinity of the PCM in these regions.

[0045] Referring here to Figures 1A and 1B, the phases of PCMs 12 and 14 may be changed in the local region 14 from an amorphous structure, or essentially an amorphous structure, to a crystalline structure, or essentially a crystalline structure, as described above S30. As a result, the remaining portion 12 of the PCM may include an amorphous structure.

[0046] A sufficient difference in the static relative permittivity between the two phases of PCM12 can be obtained. The relative permittivity of a material with respect to zero frequency is known as its static relative permittivity. In particular, the PCM can be advantageously selected such that, after changing the phases of PCM12,14 in each local region 14 at S30, the static relative permittivity of the local region 14 is at least 1.5 times (or at least 2 times) greater than the static relative permittivity of the remaining portion 12. Note that, in this specification, the static relative permittivity may also be the effective (or average) permittivity. The static relative permittivity between the two phases of PCM12,14 may differ by a coefficient of at least 1.5, if not 2, in order to produce a sufficient change in electric field density. However, this factor may actually be slightly less than 2, while still providing satisfactory results.

[0047] For example, in PCMs such as Ge2Sb2Te5, the static dielectric constant of the amorphous phase is about 16, while the static dielectric constant of the tetragonal phase is about 30. Such materials allow for a sufficient change in electric field density at a ratio of about 1.875. In some embodiments, performance can be achieved by using HfO2, in which case the static dielectric constant of the amorphous phase is about 25, while the static dielectric constant of the tetragonal phase is about 125, a ratio of about 5.

[0048] The method of the present invention can be used in applications that require (i) coupling the electromagnetic radiation of individual quantum emitters with one another, (ii) coupling individual quantum emitters with light of a predetermined wavelength (e.g., from a distant quantum emitter), or (iii) coupling one of the quantum emitters with a layered optical resonator mode, as shown by step S40 in the flowchart of Figure 3.

[0049] The PCM may, in some cases, be reprogrammed as shown in Figure 3, for example. That is, after locally modifying the PCM to obtain a first local region 14 of the changed phase, the PCM layer 12 may be reconstructed by S60, which changes the phase in part or each of the first region 14 and returns them to their amorphous structure. For example, the initial state of the PCM is restored before S20, which changes the PCM phase in each of one or more second local regions 14 from amorphous to crystalline. Like the first local modification caused by the first local region, the second local modification caused by the second local region 14 is related to each quantum emitter 16 in the layer 15. In this case as well, it is possible to locally modify the electric field in the quantum emitter 16. That is, the second modification is typically formed in relation to the quantum emitter 16 thanks to the crystalline region in the second local region, and the second modification may partially surround or include the orthogonal projection of the quantum emitter in the PCM layer. The second region may be larger (or smaller) and thicker (or thinner), but may be nearly identical to the first region. Furthermore, the reprogramming may involve separate regions. For example, the PCM may be reprogrammed to change its phase in more (or fewer) second regions 14 compared to a previous programming cycle, or in completely different regions (forming local changes in relation to different quantum emitters). If necessary, the electric field may be switched off before the change S60 that returns the phase of the local region 14 to its initial (amorphous) phase (step S50).

[0050] Referring more specifically to Figures 2A and 2B, the phases of the PCMs 12 and 14 can be changed in S30 using radiating elements 37 and 38 that are controllably moved relative to the PCM layer 12. The radiating elements may include, in particular, a heated nanoscale probe tip 37 or a laser device 38. That is, the phase of the PCM can be changed, for example, by locally applying energy in the form of light or heat to each of one or more localized regions 14 through the matrix material layer 15 (or substrate 11).

[0051] In the example of Figure 2B, the phase change is achieved by a laser beam generated by the laser device 38. In this example, the laser beam strikes the PCM layer 12 from above through the matrix layer 15. In a variation, the PCM layer 12 may be structured by striking it with a laser beam from below, for example, through a sufficiently transparent substrate 11. In the example of Figure 2A, the localized region 14 is obtained by a heated nanoscale probe tip 37. Like the laser device 38, the probes 33 and 37 can be independently controlled and operated within the apparatus 101. It is also possible to use multiple probe tips simultaneously. However, embodiments that rely on a single probe tip 37 are also conceivable, for example, when a relatively small number of regions 14 (typically on the order of 100 or less) are to be formed, or when a region 14 that may have a small volume is to be formed, or both. The time required for precise localized manipulation may be on the order of less than one second. The probes 33 and 37 may be heated via a heating element (not shown) that is in thermal contact with the probe tip, or by applying an electrical signal to the probe 33 to heat it by Joule heating. Generally, techniques derived from scanning tunneling microscopes (STMs) and atomic force microscopes (AFMs) can be used.

[0052] Another aspect of this disclosure may relate to apparatus 101, 102 that may be used to carry out the methods according to this disclosure. Two examples of such apparatus are described herein with reference to Figures 2A and 2B.

[0053] These devices 101 and 102 may include a light-emitting device 1, an electrical circuit 32, and a radiation device. Furthermore, devices 101 and 102, like the moving stage, may include various control devices 34 and 35 and electrical circuits.

[0054] The light-emitting device 1 may include two electrodes 10 and layered structures 12, 15. The electrodes 10 may be formed on-chip. The layered structure may include a PCM layer 12 and a matrix material layer 15 extending above the PCM layer 12. The quantum emitter 16 may be embedded in the matrix material layer. Note that the fact that the matrix material layer 15 extends above the PCM layer 12 may indicate, depending on the selected orientation, that it is either above or below the PCM layer 12.

[0055] Layer 15 may further extend between the two electrodes 10, for example, vertically or horizontally (laterally). That is, the electrodes may be positioned on each side (upper and lower) of the layer structure in the lateral direction. Since layers 12 and 15 are preferably in direct contact with each other (and thus form a two-layer structure), the electrodes may sandwich both layers 12 and 15 in either a vertical or lateral configuration. The light-emitting device 1 shown in Figures 1A and 1B depicts an exemplary horizontal configuration.

[0056] The electrical circuit 32 can be connected to the two electrodes 10. This circuit 32 is configured to generate an electric field through the matrix material layer 15 and the PCM layer 12 via the two electrodes 10. In operation, the electric field can cause a change in the emission wavelength of the quantum emitter 16, as described earlier.

[0057] The radiating device may be configured to nonvolatilically and controllably change the phase of the PCM in a selected local region 14 of the PCM. As previously described, such a region 14 may be formed opposite each of the quantum emitters 16 in the matrix material layer 15 to locally change the electric field at each quantum emitter 16 during operation. This can be achieved, for example, using radiating elements 37, 38. In some embodiments, the radiating element may be a laser device 38. In other embodiments, the radiating element may be a heatable nanoscale probe tip 37, for example, the tip 37 may be mounted on a cantilever 33 (Figure 2A) as commonly associated with SPL technology. In any case, the devices 101, 102 can be configured to controllably move the radiating elements 37, 38 relative to the layered structures 12, 15. That is, the layered structures 12, 15 and the radiating elements 37, 38 can be controlledly moved relative to each other so that a selected region 14 with a changed phase can be obtained.

[0058] In some embodiments, the devices 101, 102 may be configured to scan the radiating elements 37, 38 relative to the layered structures 12, 15. Note that the distance characterizing the lateral accuracy (in terms of resolution) may be smaller (or substantially smaller) than the average lateral separation distance between the quantum emitters 16. This lateral separation distance may be measured along a direction parallel to the average plane of the layered structures, for example, parallel to the plane (x,y) in the example of Figures 1 and 2. For example, the devices 101, 102 may consist of a holder 31 on which the light-emitting device 1 can be mounted. The holder may be attached to the xy stage 31 itself, or may form part of it, for example in Figures 2A and 2B. The xy stage 31 may be connected to a control system 35. Furthermore, a control device 34 may be connected to both the control system 35 and the radiating elements 37, 38 to vertically move the radiating elements 37, 38 to an optimal vertical position above the layered structures 12, 15.

[0059] Next, another embodiment of the light-emitting device 1 will be described with reference to Figures 1A and 1B. As previously described, the device 1 may include a layered structure, for example, a matrix material layer 15 having PCM layers 12, 14 and a quantum emitter 16 embedded therein, where the matrix material layer 15 may extend on the PCM layers 12, 14. Furthermore, the device 1 may include two electrodes 10 positioned on either side of the layered structure in either a vertical or horizontal (e.g., transverse) configuration.

[0060] The electrode 10 can generate an electric field through the matrix material layer 15 to change the emission wavelength of the quantum emitter 16 during operation. Furthermore, as a result of programming the PCM layers 12 and 14, the light-emitting device 1 may include one or more local regions 14 in the matrix material layer 15 that are opposite to each of the quantum emitters 16. The phase of the local regions 14 may differ from the phase of the rest of the PCM layer 12, which may cause local modifications to the electric field at each emitter 16 during operation.

[0061] The electrodes 10 can take on various shapes. In some embodiments, the electrodes 10 may be in the shape of opposing parallelepipeds. In some embodiments, the electrodes 10 may form a concentric ring, or may include two or more electrodes, or both. For example, there may be four electrodes on both sides of the layered region, thereby allowing the electric field direction to be set in any direction in a plane parallel to the layered structure. In some embodiments, the electrodes 10 can form an array for subdividing the layered region into smaller sub-regions, for example, so that the direction of the field can be changed locally. Furthermore, such subdivision can be used to dynamically change the emission wavelength of only a subset of the quantum emitter by changing the voltage applied to each electrode 10. In a horizontal arrangement, the distance between the electrodes 10 may be between 2 and 1000 micrometers. The distance between the electrodes 10 may be between 10 and 100 micrometers. The distance between the electrodes 10 may allow for a sufficiently high electric field (0.1 to 1 MV / cm). By arranging the electrodes vertically, a more compact structure can be achieved.

[0062] As previously mentioned, PCM12,14 may include hafnium(IV) oxide (HfO2) in particular. In some embodiments, the PCM layer includes a germanium-antimony-tellurium alloy (GeSbTe, or abbreviated as GST), or more generally, an alloy containing Ge, Sb, and Te respectively, as well as additional elements such as Se. The PCM layer may include, for example, Ge2Sb2Te5 as previously mentioned. In some embodiments, the PCM layer may include Ge2Sb2Se4Te1, which combines broadband transparency (1 to 18.5 μm) with high optical contrast (Δn = 2.0). As previously stated, such materials make it possible to achieve a factor of about 1.5 (or more) between the effective static dielectric constant in the local region 14 and the rest of the portion 12.

[0063] The matrix material layer 15 may be, for example, a crystalline material or a polymer material. Suitable examples of crystalline materials include crystalline semiconductors and organic crystals such as pentacene, dibenzoterylene, and terylene. Suitable examples of polymers include polystyrene, poly(methyl methacrylate), and styrene-ethylene-butylene-styrene.

[0064] The quantum emitter 16 may include or consist of epitaxially grown semiconductor quantum dots, e.g., InAs / GaP quantum dots, or other relevant quantum dots suitable for electric field tuning. In some embodiments, the quantum emitter 16 may include or consist of colloidal quantum dots, e.g., II-VI or III-V semiconductors, or perovskites. The emitter 16 may include cadmium selenide (CdSe), e.g., n-type II-VI semiconductors, or metal halide perovskites (APbX3, where A=Cs, CH3NH3, or (NH2CHNH2)1-x(CH3NH2)x, 0≦x≦1, and X=Cl, Br, or I). In some embodiments, a single molecule (e.g., an organic dye) may be used. Other examples of quantum emitters may be contemplated as listed above.

[0065] The layered structures 12, 14, and 15 can be supported by an optically and electrically passive substrate 11, such as a substrate containing one or more layers. These substrates may be Si, GaAs, GaP, InP, oxides (such as SiO2 or Al2O3), or glass. The substrate can provide mechanical stability to the device 1. For completeness, the electrical contacts (electrodes) 10 may be composed of any suitable electrical conductor, such as gold, silver, aluminum, indium tin oxide (ITO), tungsten, or a doped semiconductor.

[0066] In some embodiments, as shown in Figures 1A and 1B, the substrate 11 supports layered structures 12, 14, and 15. The PCM layers 12 and 14 may be sandwiched between the substrate 11 and the matrix material layer 15. The electrodes 10 may be patterned laterally on the substrate 11; that is, the layered structures 12 and 15 extend laterally between the electrodes 10. In this case, the electric field is applied parallel to the layered structures 12, 14, and 15 in S20. As a variation, a perpendicular electrode configuration is also conceivable, in which the electrodes are made from a sufficiently transparent material such as ITO, or a doped semiconductor, allowing the electric field to be applied perpendicular to the substrate surface.

[0067] That is, in the examples of Figures 1A and 1B, device 1 may include a matrix layer 15 on top of PCM layers 12 and 14 on the substrate 11. However, in a modification, a separate sequence may be envisioned in which the PCM layer itself is on top of the matrix layer on the substrate. Any such structure can have a lateral electrode configuration. Furthermore, a vertical configuration is also conceivable in which, for example, the upper electrode layer extends over a two-layer structure (matrix-PCM or PCM-matrix) and itself extends over the lower electrode layer and the substrate. In that case, the upper electrode can be fabricated from an optically transparent material (e.g., ITO) to allow laser programming and light extraction from the quantum emitter.

[0068] The quantum emitters 16 may be spaced at least 50 nm (average) apart in the matrix layer 15, for example, in some embodiments where the limited resolution of the radiating elements 37, 38 is used to form a local region 14. In some embodiments, the quantum emitters 16 may be spaced at least 50 nm (average) apart laterally. That is, the separation distance measured parallel to the (x,y) plane may be greater than or equal to 50 nm. The separation distance may facilitate the individual tuning of the emission wavelengths of the quantum emitters 16, which are individually addressable with respect to the PCM programming S30, by electric field tuning. In some embodiments, smaller separation distances are possible when a smaller radiative resolution is available.

[0069] The average in-plane dimensions of the local region 14 may be greater than the average in-plane dimensions of the quantum emitters, for example, when the local variations are each formed by a single region 14, as in the examples of Figures 1A and 1B. For example, the local region may have an approximately cylindrical shape. Nevertheless, as mentioned above, the local regions may have any suitable shape and may be grouped to form a local pattern (e.g., alteration) that surrounds or includes the projection position of each quantum emitter. For example, the average in-plane dimensions of the local region 14 may be between 50 and 5000 nm. The in-plane dimensions are measured along a direction parallel to the average plane of the matrix material layer 15 (or layered structure), for example, parallel to (x,y) in Figures 1A and 1B. In some embodiments, the region 14 may be formed in relation to a single quantum emitter, and the in-plane dimensions of this region may be of the same order as the average in-plane spacing between quantum emitters. However, a single region 14 may overlap with multiple quantum emitters 16 (thus tuning multiple emitters at once).

[0070] In some embodiments, the average thickness (or depth) of the local region 14 is typically greater than or equal to 1 nm. This thickness is measured perpendicular to the matrix material layer 15, for example, along the direction z in the attached drawing. Furthermore, since the region 14 is typically formed directly below the interface with the matrix material layer 15, the thickness of the region can be measured from the interface between the matrix material layer 15 and the PCM layer 12.

[0071] The depth of region 14 may be equal to the thickness of PCM layers 12 and 14, as assumed in Figure 1A. PCM light absorption at the emission wavelength of the quantum emitter can be kept small, for example, by using a material with low absorption at the emitter wavelength, a sufficiently thin layer, or both. As a result, the average thickness of PCM layers 12 and 14 may be between 50 nm and 200 nm, and in some embodiments, less than 100 nm. On the other hand, the average thickness of the matrix material layer 15 may be between 20 nm and 200 nm.

[0072] While this disclosure has been described with reference to a limited number of embodiments, modifications, and accompanying drawings, those skilled in the art will understand that various modifications may be made and equivalents may be substituted without departing from the scope of this disclosure. In particular, any given embodiment, modification, or feature (such as a device or method) shown in the drawings may be combined with or replaced with another embodiment, modification, or other feature in the drawings without departing from the scope of this disclosure. Various combinations of features described with respect to any of the above embodiments or modifications may be contemplated, within the scope of the accompanying claims. Furthermore, many minor modifications can be made to adapt the teachings of this disclosure to specific circumstances or materials without departing from the scope of this disclosure. Thus, this disclosure is not limited to any particular embodiment disclosed, and is intended to include all embodiments that fall within the scope of the accompanying claims. In addition, many modifications other than those expressly mentioned above may be conceivable. For example, materials other than those expressly mentioned herein may be conceivable, and further device (and electrode) shapes may be used.

[0073] The descriptions of various embodiments of the present invention are presented for illustrative purposes only and are not intended to be exhaustive or to limit the disclosed embodiments. It will be apparent to those skilled in the art that many modifications and changes are possible without departing from the scope and spirit of the invention. The terms used herein have been selected to best describe the principles of the embodiments, their practical application to market-based technologies or technical improvements, or to enable those skilled in the art to understand the embodiments described herein.

Claims

1. A method for adjusting the emission wavelength of a quantum emitter, To provide a device having a layered structure including a phase change material layer and a matrix material layer, wherein the matrix material layer embeds one or more quantum emitters, Applying an electric field through the matrix material layer and the phase change material layer in order to change the emission wavelength of the quantum emitter, A method comprising: non-volatilely changing the phase of the phase change material in each of one or more local regions of the phase change material in order to obtain a local phase change opposite to each of the quantum emitters in the matrix material layer and to locally change the electric field in each of the quantum emitters.

2. The method according to claim 1, wherein the phase of the phase-change material in one or more local regions is changed from an essentially amorphous structure to an essentially crystalline structure such that the rest of the phase-change material has an essentially amorphous structure.

3. The one or more local regions are first regions that cause a first local phase change, The above method involves the layer of the phase change material, To obtain a second local phase change opposite to each of the quantum emitters in the matrix material layer, and to locally change the electric field in each of the quantum emitters, the phase of one or more second local regions of the phase change material is changed from an amorphous structure to a crystalline structure. Before that, the phase of each of the first regions is returned to an amorphous structure, The method according to claim 2, further comprising reconstructing by

4. The method according to any one of claims 2 to 3, wherein the phase change material is changed in each of the one or more local regions, and the average static relative permittivity of the local region is at least 1.5 times greater than the average static relative permittivity of the remaining portion.

5. The method according to claim 1, wherein the phase of the phase-change material is changed in each of the one or more local regions using a radiating element that is controllably moved relative to a layer of the phase-change material, the radiating element comprising one of a laser device and a heated nanoscale probe tip.

6. The method according to claim 1, wherein an electric field is applied to change the phase of the phase change material so as to couple the electromagnetic radiation of individual quantum emitters with each other.

7. The method according to claim 1, wherein an electric field is applied to change the phase of the phase change material so as to couple one electromagnetic emission of the quantum emitter with an optical resonator mode of the resonator including the layered structure.

8. The method according to claim 1, wherein the electric field is applied parallel to the matrix material layer.

9. A light-emitting device comprising two electrodes and a layered structure, the latter comprising a layer of phase-change material and a matrix material layer for embedding one or more quantum emitters, wherein the matrix material layer extends over the layer of phase-change material and between the two electrodes, An electrical circuit connected to the two electrodes, configured to generate an electric field through the matrix material layer and the phase change material layer via the two electrodes in such a way as to change the emission wavelength of the quantum emitter during operation, An apparatus comprising: a radiation device configured to non-volatilely control the phase of the phase change material in each of one or more local regions of the phase change material in order to obtain a local phase change opposite to each of the quantum emitters in the matrix material layer and to locally change the electric field at each of the quantum emitters.

10. The radiation device is a radiation element which is one of a laser device and a heatable nanoscale probe chip. The apparatus according to claim 9, wherein the apparatus is configured to controllably move the radiating element relative to the layered structure.

11. The apparatus according to claim 10, further configured to scan the layered structure with the radiating element, wherein the distance indicating the resolution in scanning the radiating element is smaller than the average lateral separation distance between the quantum emitters, and the lateral separation distance is measured along a direction parallel to the average plane of the layered structure.

12. A layered structure comprising a layer of phase change material and a matrix material layer in which one or more quantum emitters are embedded, wherein the matrix material layer extends on top of the layer of phase change material, The layered structure includes two electrodes positioned on both sides of the matrix material layer and the phase change material layer to generate an electric field and change the emission wavelength of the quantum emitter during operation, A light-emitting device wherein the phase change material includes one or more local regions having a phase different from the phase of the rest of the phase change material, thereby forming local phase changes opposite to each of the quantum emitters in the matrix material layer so as to locally change the electric field at each of the quantum emitters during operation.

13. The light-emitting device according to claim 12, wherein the phase change material comprises one of GeSbTe and HfO2.

14. The matrix material layer comprises one of a crystalline material and a polymer material. The light-emitting device according to any one of claims 12 to 13, wherein the quantum emitter includes one of an epitaxially grown semiconductor quantum dot, a colloidal quantum dot, and an organic emitter.

15. The light-emitting device according to claim 12, wherein the average distance between quantum emitters in the matrix material layer is 50 nm or more.

16. The light-emitting device according to claim 12, wherein the average in-plane dimension of the local region is 50 to 5000 nm, and the average in-plane dimension is measured along a direction parallel to the average plane of the matrix material layer.

17. The light-emitting device according to claim 16, wherein the average thickness of the local region is 1 nm or more, and the thickness is measured perpendicular to the matrix material layer from the interface between the matrix material layer and the phase change material layer.

18. The light-emitting device according to claim 12, wherein the average thickness of the phase change material layer is 50 nm to 200 nm, and the average thickness of the matrix material layer is 20 nm to 200 nm.

19. The light-emitting device according to claim 12, wherein the average static relative permittivity of the local region is at least twice the average static relative permittivity of the remaining portion.

20. A substrate having a layer of the phase change material extending thereon, the latter being located between the substrate and the matrix material layer, The light-emitting device according to claim 12, further comprising electrodes, wherein the electrodes are patterned on the substrate and the layered structure extends between the electrodes.

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