Optical phased array, laser device, and method of operating the same

Abstract

The present invention relates to an optical phased array having a signal input section for supplying effective light of a first wavelength, and a first modulation input section for supplying modulated light of a second wavelength. A first waveguide array having at least one signal output section is connected to the signal input section and comprises a material that is transparent to the effective light and has a first bandgap. A second waveguide array connected to the first modulation input section is positioned and designed in the vicinity of the first waveguide array to guide the modulated light to the first waveguide array. The first bandgap is smaller than the energy of the modulated light. [Effect] By purely optical means, it is possible to induce a change in the refractive index of an optical component, thereby influencing the functionality of the optical component. The change in refractive index is essentially caused by the intensity modulation of modulated light, which can reach high speeds in the range of several hundred MHz.

Description

[Technical Field]

[0001] This invention claims priority to German first application DE 10 2022 109 220.8 dated April 14, 2022, the disclosures of which are incorporated herein in their entirety by reference.

[0002] The present invention relates to an optical phased array, a resonator apparatus, and a laser apparatus (Laseranordnung) having an optical phased array or a resonator apparatus. The present invention further relates to a method for operating an optical phased array or a resonator apparatus. [Background technology]

[0003] End-emitting lasers (EDMs) are based on laser diodes and are now available for a wide frequency spectrum. The high power output and mass production capabilities of EDMs have made them attractive for many applications. In addition to EDMs, VCSELs and micro-LEDs (μLEDs) with small etendues can also be used to couple light into waveguides. These are generally referred to as optoelectronic components.

[0004] Furthermore, such optoelectronic components stand out for having larger linewidths within the range of a few nanometers, and in addition, their output frequency varies with current and temperature. This allows for tuning (Abstimmungsmoglichkeit) on the one hand, but on the other hand, the laser output is affected, inevitably leading to increased circuit costs (Schaltungsaufwand) to compensate for or suppress undesirable effects.

[0005] However, many applications require lasers with narrow linewidths, as well as high stability in emission wavelength and performance. This necessitates stabilization of end-emitting lasers. Stabilization of end-emitting lasers can be achieved, on the one hand, by a DBR structure along the laser resonator, but this is costly. One alternative to the DBR structure along the laser resonator is to couple the laser device to an external cavity with a tunable etalon, a Bragg grating, or a micro-resonator with a small form factor. All of these achieve linewidths of just a few kHz.

[0006] On the other hand, in other applications, the ability to direct the light beam, that is, to cover a defined field of view with a predetermined resolution, is important. Examples of such applications include RGB projection and LiDAR. Light beam direction is achieved by components that extend the laser beam to cover high-resolution LCDs, SLMs (spatial light modulators), or DLP displays. Alternatively, the laser beam or light beam may be deflected using MEMS or movable mirrors of the macromechanical type. Neither technique is an ideal compromise. Pixel array projection is inefficient and lacks contrast and sharpness, while mechanically moving elements often have robustness issues and increase complexity.

[0007] Therefore, there is a demand for non-mechanical beam control or scanning options that can be easily incorporated into the housing, thereby enabling a significant reduction in structural volume (Bauvolumen). [Overview of the project]

[0008] This demand is taken into consideration along with the subject matter of the independent patent claim. Further developments and embodiments of the proposed principle are described in the dependent claims.

[0009] In this regard, the inventors propose an optically controlled optical phased array (OPA) that enables a large modulation bandwidth in a very small form factor. In addition to the optical phased array, other optical components such as resonators, modulators, or optical switches are also driven (ansteuern) in a very fast and wear-free manner according to the proposed principle.

[0010] In particular, the inventors utilize the fact that the refractive index in the above-described type of optical component is particularly influenced by free charge carriers. Therefore, the optical component may have a transparent semiconductor material in which free charge carriers are generated by the absorption of photons having energy higher than the band gap. These photons are provided via so-called modulated light (Modulationslicht). The photon flux is the basis for active modulation of the optical component and may be provided, for example, by a second flat waveguide component located below and / or above the optical component, directing the modulated light towards the optical component to be modulated.

[0011] This achieves refractive index modulation, and the modulation rate is essentially limited by the lifetime of the charge carriers in the material. Particularly in the narrow sense of optical phased arrays, a waveguide assembly is provided that is configured for the desired phase shift function. A high-frequency, intensity-modulated laser or laser diode (or, in some cases, some of them) provides the required photon flux.

[0012] In some aspects of the principles presented herein, optical phased arrays are proposed. In this context, the term “optical phased array” should not be understood in a narrow sense. Rather, an optical phased array refers to a component whose optical behavior can be tuned in a desired manner by changing its refractive index. The change in refractive index is achieved by further elements of the phased array that deflect the modulated light, and as a result, the modulated light generates charge carriers that change the refractive index by absorption. Examples of components that have a favorably tuneable refractive index include, to list a few, optical phased arrays in the narrow sense, i.e., optical phased arrays with several waveguides of different lengths, optical resonators, in particular ring oscillators, Mach-Zehnder modulators, or directional optical couplers.

[0013] A tunable optical phased array comprises a signal input section for supplying active light (Nutzlicht) of a first wavelength and a first modulation input section for supplying modulated light of a second wavelength. A first waveguide array is connected to the signal input section, and the first waveguide array includes at least one signal output section and a material that is transparent to the active light and has a first bandgap. A second waveguide array is connected to the first modulation input section and positioned near the first waveguide array so that the modulated light can be guided into the first waveguide array. In this case, the first bandgap is smaller than the photon energy of the modulated light. In other words, the material of the first waveguide array is selected to absorb light of the second wavelength and form charge carriers. Furthermore, in the broad understanding of optical phased arrays described above, the term waveguide array should not be understood overly narrowly, but rather as an optical component that provides a certain kind of functionality.

[0014] In this context, the first waveguide array and the second waveguide array may have the same or at least similar configurations. In particular, the second waveguide array should be designed to deflect the modulated light well to the first waveguide array, i.e., the first component having the refractive index to be changed. Accordingly, in some embodiments, the first waveguide array and the second waveguide array are intended to be positioned above and below each other in two essentially parallel planes and to overlap in some regions. Since the modulated light can be better incident on the first waveguide array, the overlap of the first and second waveguide arrays increases efficiency. The waveguides of the second waveguide array are tuned to the first waveguide array, and as a result, in the individual waveguides of the first array, a desired change in refractive index occurs at a predetermined intensity of modulated light.

[0015] The intensity of the modulated light adjusts the rate of charge carrier generation, thereby modulating the refractive index within the first waveguide array. Modulation can be performed digitally, for example, by a pulse-modulated signal or as an amplitude-modulated signal.

[0016] In some embodiments, the first waveguide array of an optical phased array comprises a plurality of waveguides that are essentially in a single plane, each containing a defined optical propagation time difference between them. This optical propagation time difference is achieved, for example, by different waveguide lengths. The optical propagation time difference creates a phase difference at the output of the array, which in turn causes superposition and interference. By using refractive index modulation according to the proposed principle, the phase difference can be controlled, and as a result, the optical beam emitted from the array can be controlled.

[0017] In a further embodiment, the second waveguide array also comprises a plurality of waveguides that are essentially in a single plane, including a defined difference in optical propagation time between them. This difference in optical propagation time is also realized by the different lengths of the waveguides.

[0018] In a further embodiment, the optical phased array includes a further second modulation input for supplying modulated light of a second or third wavelength. The modulated light of the third wavelength is also more energetic than the band gap of the material of the first waveguide array and is therefore absorbed, generating free charge carriers. The second modulation input is connected to the third waveguide array and positioned near the first waveguide array so that the modulated light can be directed to the first waveguide array. In this way, flexibility is increased, and the range of refractive index modulation due to charge carrier generation is further increased. Here, the first waveguide array can be positioned between the second and third waveguide arrays so that the modulated light can be directed to the first waveguide array from both sides. The second and third waveguide arrays can overlap or be positioned as mirror images of each other, depending on the embodiment.

[0019] In further embodiments, the second and / or third waveguide arrays include an extraction structure, particularly in the form of a diffractive optical system. This extraction structure helps to extract the modulated light from the waveguide arrays in a defined manner. In this case, the diffractive optical system or extraction structure can also act as a light guide, thus guiding the modulated light to the first waveguide. In some embodiments, the extraction structure faces the first waveguide array. The extraction structure allows for the localized extraction of a defined portion of the modulated light. In another embodiment, the second and / or third waveguide arrays are located only a short distance from the first waveguide array, for example, less than 300 nm, particularly less than 100 nm. This allows some of the light (part of the optical field) to reach the first waveguide array as evanescent light. For example, crosstalk of the modulated light to the first waveguide array occurs because the waveguide arrays are in close proximity to each other.

[0020] Another embodiment deals with improvements to the optical coupling of modulated light to the first waveguide array. In one embodiment, a particularly planar DBR structure is provided, specifically for reflecting back the modulated light. The DBR structure is located in the first waveguide array, opposite the second waveguide. This allows the modulated light to be absorbed or reflected back. In a further embodiment, a planar distribution layer may be provided in the first waveguide, opposite the second waveguide, which is formed to reflect back the modulated light or to distribute the charge carriers generated by the modulated light within the first waveguide array. Uniformly distributing the charge carriers is useful for producing a uniform change in refractive index.

[0021] In some embodiments, appropriate material selection is addressed. In some embodiments, semiconductor materials are used as the material for the first waveguide array. Semiconductor materials may have a direct or indirect band gap, the direct or indirect band gap being selected such that the semiconductor material is essentially transparent to effective light. In one embodiment, the material includes InP, Si, GaAs, AlGaAs, AlGaP, or GaN. However, these materials are not transparent to light of a second wavelength. Therefore, the modulated light is absorbed, generating charge carriers within the material. However, the material for the second or third waveguide array should be transparent to modulated light. For this reason, the material for the second or third waveguide array generally has a higher band gap than the material for the first waveguide array. AlN, SiNx, Al2O3, or SiO2 may be materials that can be tuned to the material for the first waveguide array.

[0022] In some aspects, a resonator device is proposed, which comprises a waveguide having a signal input section for supplying effective light of a first wavelength, and a signal output section. The device further comprises a resonator, in particular a ring resonator, optically coupled to the waveguide for amplifying the frequency modes of the effective light within the waveguide. Arranged above the resonator is a device designed to cause modulated light of a second wavelength to enter the resonator. Furthermore, the resonator is formed of a material that is essentially transparent to the effective light and has a band gap that absorbs the modulated light to form charge carriers. In this way, a tunable resonator device is implemented that enables a laser which is in particular mode-stable (modenstabil) and wavelength-tunable (durchstimmbar). Applications of such a resonator device may include those in the fields of coherent distance measurement, high-resolution spectroscopy, or image projection, for example image projection for AR or VR projection.

[0023] In one embodiment, the device arranged above the resonator comprises one or more deflection mirrors. Alternatively, the device may have a second waveguide provided with a diffractive optical system designed to direct the modulated light in the second waveguide towards the resonator. As in the case of an optical phased array, a DBR structure, particularly a flat DBR structure, which is particularly configured for reflecting the modulated light back, can be provided, the DBR structure being arranged on the opposite side of the resonator from the second waveguide.

[0024] A further aspect relates to a laser device using an optical component according to the proposed principle. In this case, the laser device comprises a first laser device (Laservorrichtung) for generating effective light, and a second laser device for generating modulated light. The intensity of the modulated light is modulated by the second laser device. The two laser devices are connected to an optical phased array, the optical component, or the resonator device.

[0025] A further embodiment relates to the operation of an optical phased array, in which the phased array includes a signal input section for supplying effective light of a first wavelength and a first waveguide array having at least one signal output section. The first waveguide array is connected to the signal input section and has a material that is transparent to the effective light and has a first bandgap. In this method, effective light is incident on the first waveguide array. Similarly, modulated light is generated and at least a portion of it is coupled to the first waveguide array. Absorption of the incident modulated light generates charge carriers within the first waveguide array, which change the refractive index in a characteristic manner. The change in refractive index is controlled by a change in the intensity of the modulated light.

[0026] In one embodiment, the coupling of modulated light is performed using a second waveguide array positioned near a first waveguide array so that the modulated light can be guided into the first waveguide array. The first and second waveguide arrays have different properties and features depending on their optical components. In some embodiments, the first waveguide array comprises a plurality of waveguides essentially in one plane, with a defined optical propagation time difference between them. The second waveguide array can be designed similarly and comprises a plurality of waveguides essentially in one plane, with a defined optical propagation time difference between them. In some embodiments, the propagation time difference in the waveguides of the first or second waveguide array is formed by different waveguide lengths. [Brief explanation of the drawing]

[0027] Further aspects and embodiments in accordance with the proposed principle are disclosed by reference to various embodiments and examples described in detail with the accompanying drawings. [Figure 1] This figure shows one embodiment of an optical phased array. [Figure 2] This figure shows a plan view of one embodiment of a phased array according to the proposed principle. [Figure 3]Figure 2 shows a cross-sectional view of a phased array with several embodiments of the proposed principle. [Figure 4] This figure shows a second embodiment of an optical phased array with several aspects of the proposed principle. [Figure 5] This is another embodiment shown in Figure 4. [Figure 6] Figure 4 or 5 shows a cross-sectional view of a phased array to illustrate some aspects of the proposed principle. [Figure 7] This is a cross-sectional view of a further embodiment of a phased array according to the proposed principle. [Figure 8] This is a further cross-sectional view of an embodiment of a phased array according to the proposed principle. [Figure 9] This figure shows a third embodiment of an optical phased array with several aspects of the proposed principle. [Figure 10] Figure 9 shows a different cross-sectional view of an embodiment of a phased array according to the principle. [Figure 11] Figure 9 shows a different cross-sectional view of an embodiment of a phased array according to the principle. [Figure 12] Figure 9 shows a different cross-sectional view of an embodiment of a phased array according to the principle. [Figure 13] This is an embodiment of a method involving several aspects of the proposed principle. [Modes for carrying out the invention]

[0028] The following embodiments and examples illustrate various aspects and combinations thereof in accordance with the proposed principle. The embodiments and examples are not necessarily to scale. Similarly, various elements may be shown enlarged or reduced to emphasize individual aspects. It goes without saying that the individual aspects and features of the embodiments and examples shown in the drawings can be easily combined with one another without compromising the principle of the invention. Some aspects have a regular structure or form. It should be noted that slight deviations from the ideal form may occur in practice, but this will not be inconsistent with the spirit of the invention.

[0029] In addition, individual drawings, features, and aspects are not always shown in the correct size, and the proportions between individual elements may not be fundamentally correct. Some aspects and features are emphasized by being shown in enlarged form. However, terms such as "up," "above," "down," "below," "greater," and "smaller" are correctly indicated in relation to the elements in the drawings. Therefore, such relationships between elements can be derived from the drawings.

[0030] Figure 1 shows a so-called optical phased array device in the narrow sense, that is, a device that can achieve beamforming using phase shifts (Phasenversatz) generated by several optical waveguides of different lengths.

[0031] The device includes, for example, an end-emitting laser 1 in the form of a laser diode or another laser device. An optical phased array 3'' is connected to the output section of this laser device. The optical phased array 3'' includes a waveguide 11 connected to a signal input section, which, as it extends, divides into several individual branches 11a, 11b to 11g. Each of these individual branches has a different length and leads to a corresponding signal output section 12'.

[0032] In the operation of this device, useful light NL is incident and distributed to various branches 11a to 11g of the optical phased array 3''. Because the lengths of the individual branches differ, signals with phase shifts between them are generated at each output section 12'. These signals interfere with each other. Constructive or destructive interference can be produced by appropriately adjusting the lengths based on the frequency or wavelength of the scattered (eingestreut) effective light. The location of the constructive interference on the screen S at position P1 or position P2, as illustrated in Figure 1, can be adjusted by various means. Generally, the location of this constructive interference depends on geometric parameters and the refractive indices of the waveguides 11a to 11g. By changing the refractive index of the material, position P1 or position P2 on the screen S can be controlled, and as a result, "scanning" of the screen is achieved using the interfering output light.

[0033] In this regard, conventional methods employ a thermal approach, for example, in which the optical phased array 3'' is heated or cooled, thereby changing the refractive index of each waveguide in a characteristic manner. However, such a process is relatively slow and can only be controlled to a limited extent. Alternatively, it is possible to change the refractive index of individual regions by applying a constant electric field. This offers an improvement over the thermal approach, but requires a relatively high voltage to generate the necessary electric field. Therefore, such an approach is costly to implement, especially in applications where the available operating voltage is low.

[0034] Figure 2 shows one embodiment of the proposed principle in which the refractive index of the optical components is adjusted using purely optical methods, rather than by thermal or electro-optical methods. Here, it is utilized that the materials of waveguides 11a-11g, i.e., the materials of optical component 3, also have a band gap and can thereby absorb light. Waveguides 11a-11g are transparent to effective light, but free charge carriers can be generated by the absorption of higher energy photons in the waveguides. These free charge carriers then cause a characteristic change in refractive index. Figure 2 shows one possible embodiment of this principle.

[0035] The apparatus according to the proposed principle also comprises an optical component 3 formed as a narrowly defined optical phased array. A laser device 1 is placed in the signal input section coupled to the waveguide 11. The laser device 1 may be an end-emitting laser, a laser diode, or a laser device not based on a semiconductor structure. The optical phased array comprises a plurality of waveguides 11a, 11b to 11g that are connected to each other on the input side and lead to the signal output section 12' on the output side. The lengths of the waveguides between the signal input section and the signal output section are different and are tuned to each other so that the interference pattern of incident light at the output on the screen is generated in the same way as in Figure 1.

[0036] According to the present invention, the optical component 3 includes a second signal input section connected to a second laser diode 2 for supplying modulated light ML. This modulation input section is connected to a plurality of waveguides 21a, 21b-21g. ​​The waveguides also form a waveguide structure for the modulated light ML, in which the individual waveguides 21a, 21b-21g are designed to be above a portion of the waveguides 11a, 11b-11g.

[0037] In this regard, Figure 3 shows a cross-sectional view of the apparatus according to the proposed principle. Here, it can be seen that the individual waveguides 11a, 11b-11g for useful light NL are essentially arranged along one plane. Above this plane, the waveguide structures 21a, 21b-21g for modulated light ML are also provided in one plane. Each of these waveguides 21a, 21b-21g of the structure for modulated light ML has an extraction optical system (Auskoppeloptik) 22 facing the respective waveguide 11a, 11b-11g.

[0038] In the operation of the proposed apparatus, modulated light ML having a photon energy greater than the band gap of the material in waveguides 11a, 11b-11g is incident. In this regard, for the purpose of explaining the principle of the present invention, it is conveniently assumed below that the band gap is constant and there is no difference with respect to the crystal direction or direct / indirect band gap. In fact, the principle of the present invention is possible when light is absorbed in or around the waveguide material, and then the light generates free charge carriers within the waveguide material.

[0039] Modulated light ML is emitted from the existing extraction optical system and optically absorbed by waveguides 11a, 11b-11g. Absorption generates charge carriers in the conduction band of the materials in waveguides 11a, 11b-11g, thereby changing the refractive index of these materials. As shown in the plan view of Figure 2, the lengths of the individual waveguides 21a, 21b-21g for the modulated light ML determine the intensity-dependent incidence and the resulting absorption, resulting in characteristic changes in the refractive index in the individual waveguides 11a, 11b-11g for the useful light NL. Changes in the intensity of the modulated light ML also change the refractive index. Therefore, intensity modulation of light ML causes characteristic modulation of the refractive index.

[0040] In this case, the waveguide material for the modulated light ML is selected such that the material is transparent to the modulated light ML itself. However, because the photons of the modulated light ML have very high energy, the modulated light ML exceeds the band gap of waveguides 11a to 11g, and as a result is absorbed by waveguides 11a to 11g, generating free charge carriers. By adjusting the intensity of the modulated light, the generation of charge carriers, and consequently the resulting change in refractive index, can be adjusted or altered. In this way, the interference pattern at the output of optical component 3 can be adjusted, and effects such as changing the constructive interference maximum along the position (konstruktives Interferenzmaxima), as shown in Figure 1, can be achieved.

[0041] The change in refractive index due to charge carriers is essentially determined by three effects. On the one hand, there is the filling of the state density by free charge carriers, or the filling of allowed band states, according to Burstein-Moss, which generally leads to a change in refractive index to lower values. However, normalization of the band gap, or a slight (leicht) change in the band gap toward lower energies, leads to a change in refractive index toward higher values. Ultimately, through the generation of free charge carriers and the subsequent characteristic absorption in the IR region, the refractive index in the transparent region of interest of the EM spectrum changes toward lower values. In the proposed principle, these three aspects act in combination, with free charge carrier absorption according to the Drude model being the primary consideration.

[0042] In this process, charge carriers absorb light particles in the medium, thereby rising to higher energy states. Charge carriers in the valence band rise to the conduction band, thereby forming electron-hole pairs. In this way, freely moving electrons are generated in the conduction band and behave similarly to an EH plasma. This plasma generates a characteristic absorption band in the IR region that can be explained by the Drude model. The characteristic absorption band leads to a decrease in refractive index at short wavelengths, according to the so-called Kramers-Kronig relation. The Drude model is represented by equation (1),

number

number

[0043] The change in refractive index here is negative. That is, the refractive index decreases due to the absorption of light within the waveguide. Furthermore, the change in refractive index is proportional to the square of the wavelength λ. From this, it follows that, basically, the longer the wavelength, that is, the lower the energy, the greater the change in refractive index.

[0044] The following describes the estimation of charge carrier generation upon incidence of modulated light, and at least qualitatively explains the resulting change in refractive index. In this estimation, the modulated light is generated by a laser with an output of 100 mW and a beam diameter of d = 100 μm. The wavelength of the modulated light is λ = 400 nm. A combination of InP and GaP is used as the waveguide material for the optical components, and the parameters used are related to InP. For InP, the refractive index at λ = 400 nm is equal to n = 4.4. On the other hand, GaP has a refractive index n = 4.2 at λ = 400 nm. Its intensity I is:

number

[0045] The intensity of a laser beam decreases exponentially within a material. That is, its intensity decreases exponentially. (-z / z0) (where z0 is the absorption length) is approximately proportional to the light intensity being 1 / e of the original I (or, in this case, 1 / e with respect to I). 2 This corresponds to the length z when it decreases to ). This means that, approximately,

number

[0046] The decrease in light means that charge carriers were generated at that time. In this way, the number of charge carriers at the absorption length is

number

[0047] Therefore, this is approximately 10 26 1 / (scm 3 This is within the range of ). Therefore, when the incidence period is approximately 1 ns,

number

[0048] The electron-hole plasma generated in this way recombines, which in turn reduces the number of free charge carriers again. In this process, the recombination rate follows different mechanisms. On one hand, these mechanisms include recombination that occurs via direct recombination. That is, electrons and holes recombine together again to generate corresponding photons, plasmons or phonons. Alternatively, so-called Auger recombination is also possible, but since the scale of Auger recombination is several orders of magnitude lower than that of direct recombination, it does not need to be considered in the discussion.

[0049] Therefore, the recombination rate R is derived from the available charge carrier concentrations n and p, and the material-dependent parameter C that characterizes the two aforementioned mechanisms in respective materials. [Math.]

[0050] Within the range where the specified charge carrier density n=p is 6×10 17 1 / cm 3 , when the parameter C representing direct recombination is 6*10-11 cm 3 / s, a recombination rate R in the range of 2×10 16 1 / (ns·cm 3 ) is obtained from formula (4). Therefore, if the recombination rate remains substantially constant, the generated charge carriers will be completely recombined after approximately 10 ns.

[0051] The generation rate and recombination rate of charge carriers can also be expressed using the differential equation shown in formula (5). Therefore, the generation rate, [Math.] corresponds to the charge carrier density, and corresponds to a constant value obtained from the parameter α derivable from formula (3) and the intensity I obtained by subtracting the product of the recombination rate and the number of charge carriers over time. The following applies: [Math.]

[0052] The solution to this differential equation is a function that increases with time from 0 and reaches equilibrium after approximately 15 ns. When modulated light is continuously incident, or when the intensity of the incident modulated light is modulated, and the frequency is clearly smaller than the recombination rate, an equilibrium is reached between charge carrier generation and recombination. The intensity at equilibrium essentially corresponds to the square root of the charge carriers indicated by recombination.

number

[0053] In the example of the laser with the output described above, the charge carrier density at equilibrium is approximately 10 18 1 / cm 3 It is within the range.

[0054] From the differential equations mentioned above and estimations regarding the incident modulated light and other parameters, 1 cm 3 10 17 ~10 19 A charge carrier concentration within the range of charge carriers is generated. From this, the change in refractive index according to the Drude model is 10 -2 It is estimated that the range is within a few percent. As the intensity of the modulated light increases, absorption within the material increases, and consequently the charge carrier concentration also increases, which in turn increases the change in refractive index.

[0055] Therefore, for example, in order to achieve a phase change of π between two waveguides based on a change in refractive index, a waveguide with a length of approximately 100 μm is prepared, and 10 in the waveguide 18 ~about 10 19It is sufficient to generate a charge carrier density within this range. This allows for the generation of free charge carriers with a sufficient charge carrier concentration within the material of the optical component by additional modulated light from individual or several lasers, thereby generating the refractive index change required for a phase shift of π corresponding to 180°.

[0056] According to this principle, various embodiments of optical components are implemented in which charge carriers are formed in a portion of the optical component by supplying energy-rich light, resulting in a change in refractive index.

[0057] In this regard, Figure 4 shows a further embodiment in which greater flexibility is achieved when tuning the refractive index by using several additional laser devices to generate modulated light ML of varying wavelengths. Furthermore, such embodiments also allow for a certain symmetrical form, resulting in a uniform charge carrier distribution.

[0058] Figure 4 shows the optical component 3. Here again, a laser device 1 is connected to the signal input section to supply useful light NL. In this embodiment, two laser devices 2 and 2' are provided, and laser devices 2 and 2' supply modulated light ML and ML' to two additional modulation input sections of the optical component 3, respectively. The waveguide structure to which the modulation input sections are connected is similarly designed and illustrated in the cross-sectional view of Figure 6.

[0059] Here again, we can see that the first waveguide structure having waveguides 11a, 11b-11g is arranged in a single plane. In contrast, the two waveguide structures having branches 21a, 21b-21g for modulated light ML and branches 21a', 21b'-21g' for modulated light ML' are arranged above and below the first waveguide structure, respectively. In other words, waveguides 11a, 11b-11g are surrounded on both sides by the corresponding modulated waveguide structures. When the modulated light ML is turned on (eingeschaltet), as shown by the arrows in Figure 6, the light is guided as uniformly as possible into the first waveguide structure by the extraction structure 22. This results in a more uniform distribution of scattered modulated light ML in the waveguide structure having waveguides 11a, 11b-11g, leading to a more uniform charge carrier distribution. Furthermore, in this embodiment, the intensity is adjusted by the increase in intensity that can be brought about by waveguides 21a', 21b'~21g' in a larger region, so a clearly large increase in refractive index (Brechungsindexsprung) can occur depending on the degree of absorption.

[0060] The changes in this respect are shown in Figure 5. Here, the waveguide structure for modulated light ML or the waveguide structure for modulated light ML' is provided mirror-symmetrically above or below the waveguide structure for useful light NL. Therefore, the lengths of the individual waveguides 21a, 21b-21g or 21a', 21b'-21g' are different above or below the respective waveguides 11a, 11b-11g. This provides a degree of freedom in adjusting the interference pattern and refractive index changes.

[0061] In yet another embodiment, a mirror or other optical or electro-optical structure is shown above or below the waveguide structure for the effective light. This embodiment may help to produce a more uniform light distribution and a more uniform charge carrier distribution, ultimately improving the quality of the signal.

[0062] Figure 7 shows a cross-sectional view of an embodiment in which two further DBR structures 31 and 31' are positioned above and below the plane of the waveguide structure for the active light NL. The DBR structures are designed to enhance the absorption of the modulated light ML within the waveguide structure having waveguides 11a, 11b-11g, thereby improving efficiency in charge carrier generation. In this context, the two flat DBR structures 31 and 31' form a vertical cavity in which the modulated light ML is ideally reflected back and forth several times until it is essentially absorbed by the waveguide structure for the active light.

[0063] Figure 8 shows another embodiment in which the plane of the waveguide structure for useful light NL and the plane of the waveguide structure for modulated light ML are arranged as close to each other as possible. In this embodiment, the distance between waveguides 11a, 11b-11g and waveguides 21a, 21b-21g for modulated light is only a few tens to a few hundred nanometers. As a result, the modulated light is directly coupled to the waveguide structure having waveguides 11a, 11b-11g by evanescent coupling and is at least partially absorbed in the waveguide structure. This embodiment has the advantage of simplifying manufacturing because it basically does not require any further coupling structures 22 or DBR structures. However, even in this embodiment, there may be one DBR structure below waveguides 11a, 11b-11g.

[0064] Figure 9 shows a further embodiment having different optical components from the embodiment described above. The background to this is the fact that, as already mentioned, the basic principle of the change in refractive index in the optical components due to the additionally introduced modulated light is not limited to optical phased arrays in the narrow sense. Rather, it is possible to flexibly adjust other optical functions by, for example, reducing the linewidth of the end-emitting laser, stabilizing the end-emitting laser, or doing so.

[0065] In this embodiment, the optical component 30' also includes a material 30 in which a waveguide 11 is embedded, extending from a signal input to a signal output 12, as in other embodiments. The waveguide serves to supply and process the active light NL. A resonator element 32 is connected to the waveguide via an optical coupler D. In this embodiment, element 32 is formed as a ring resonator. In the operation of this device, individual modes of scattered active light NL are selected and amplified by the optical coupler D and the geometric parameters of the ring resonator 32 and provided at the output 12. In this way, the end-face emitting laser diode is stabilized against thermal fluctuations on the one hand, and its linewidth is significantly reduced to just a few megahertz on the other hand.

[0066] A partially ring-shaped waveguide element 21 is provided above or below the ring resonator 32, and a mirror or absorbing element is positioned at the end 33 of the waveguide element 21. The device with a mirror has the advantage that unabsorbed light is reflected back to the curved waveguide 21 and can be absorbed again in the ring resonator. As in other embodiments, the ring-shaped structure above the ring resonator also has an extraction structure through which modulated light ML provided by the laser diode 1 is incident on the ring resonator, generating free charge carriers in the ring resonator. These cause a change in the refractive index in the ring resonator, and the selected mode is shifted by the optical coupling D. As the intensity of the incident modulated light undergoes a modulation change, the refractive index changes, and with this, frequency modulation of the scattered effective light is realized in the output unit 12.

[0067] The proposed optical components are implemented in various ways, particularly with respect to the supply of modulated light. In this regard, Figures 10, 11, and 12 show different embodiments, each with cross-sectional views. In Figure 10, coupling to the ring resonator 32 is performed by a further mirror element 4 designed in a prism shape. For this purpose, the modulated light ML is provided by a laser device 2 positioned on a further carrier located laterally at the height of the optical element 3'. The modulated light is partially reflected by the prism-shaped mirror element 4 and heads toward the ring resonator 32, but some of the modulated light continues past the first element and enters the second mirror element 4, where it is reflected. This device has the advantage that the device can be easily mounted on an existing optical component 3', as long as the material forming the optical component is transparent to the modulated light.

[0068] Another embodiment is shown in Figure 11. In this embodiment, there is a further waveguide structure 21 having several extraction elements 22 above the plane of the ring resonator. These help to extract the modulated light ML from the waveguide structure 21 and direct it into the waveguide of the ring resonator 32. In this embodiment as well, the modulated light is generated by a second laser diode 2 located externally.

[0069] Finally, in the third embodiment, the ring resonator is positioned between two DBR structures 31. In this case, one of the DBR structures below the ring resonator is formed as a flat mirror, and the second DBR structure above the ring resonator 32 covers only the material of the ring resonator. In this embodiment as well, the extraction structure 22 helps to illuminate the DBR structures 31 and the material of the ring resonator.

[0070] Various embodiments and designs can be combined with the individual features of each embodiment to generate charge carriers in optically relevant regions by absorbing modulated light, thereby changing the refractive index within the material as described above. This makes it possible to realize optical components with tunable functionality.

[0071] Finally, Figure 13 shows an embodiment of how an optically tunable component operates. This component includes a signal input for supplying effective light of a first wavelength to at least one waveguide. Furthermore, there is a signal output for which the tuned or tunable effective light can be picked up (abgreifbar). The optical component includes a material transparent to the effective light, which has a first band gap or is designed to absorb light smaller than a predetermined wavelength. Such an optical component is provided in step S1 and connected to a first laser device for generating the effective light.

[0072] Furthermore, a second laser device designed to generate modulated light is provided. The photon energy of the modulated light is greater than that of the first bandgap. In the proposed method, in step S2, effective light is incident on the first component and processed in the optical component in a desired manner. The light processed in the optical component can be picked up at the output unit. In the second step S2, modulated light is also supplied, but at least a portion of the modulated light is supplied so as to be incident on the material in the region related to the optical component. The optical component may be a waveguide, a resonator, a PIC or PLC, or a waveguide array, as shown in the above embodiments.

[0073] The incident modulated light, due to its higher photon energy, is absorbed within this region, generating free charge carriers within this region. An equilibrium is reached between charge carrier recombination and charge carrier generation, depending on the intensity of the incident modulated light. However, simultaneously, the free charge carriers alter the refractive index of the material, thereby affecting the incident useful light. This change in refractive index is controlled by the intensity of the modulated light over a predetermined region, thereby also changing the functionality of the optical components.

[0074] In this way, it is possible to induce a change in the refractive index of an optical component by purely optical means, thereby influencing the functionality of the optical component. Purely optical means include, depending on the application and embodiment, for example, phase shift, frequency modulation, optical switching, or other functions. Unlike other solutions, the change in refractive index is essentially caused by intensity modulation of the modulated light, thereby reaching high speeds in the range of several hundred MHz. Furthermore, complex and additional means related to circuit technology are reduced, and only an additional laser device is required to generate modulated light with a photon energy higher than the effective light. [Explanation of Symbols]

[0075] 1. Laser device 2. Laser device 3, 3' phased array 3'' Phased Array 4 Mirror 11 Waveguides 11a, 11b waveguide 11c, 11d waveguide 11e, 11f waveguide 11g waveguide 12, 12' Output section 21 Waveguides 21a, 21b waveguide 21c, 21d waveguide 21e, 21f waveguide 21g waveguide 22 Diffraction Optical Systems 30 Phased Array Materials 31, 31' DBR structure 32 Ring Resonator D-coupling NL Effective Light ML Modulated Light

Claims

1. A signal input section for supplying effective light of a first wavelength, A first waveguide array having a plurality of parallel waveguides and at least one signal output section, the first waveguide array being connected to the signal input section and comprising a material that is transparent to the effective light and has a first band gap, A first modulation input unit for supplying modulated light of a second wavelength, A second waveguide array connected to the first modulation input unit, having a plurality of parallel waveguides, wherein the plurality of parallel waveguides of the second waveguide array are arranged parallel to the plurality of parallel waveguides of the first waveguide array, such that a portion of the modulated light is coupled from the plurality of parallel waveguides of the second waveguide array to each corresponding one of the plurality of parallel waveguides of the first waveguide array, Equipped with, The first band gap is smaller than the energy of the modulated light. Optical phased array.

2. The first waveguide array comprises a plurality of waveguides that are essentially located in a single plane and have a defined optical propagation time difference between them. The second waveguide array comprises a plurality of waveguides that are essentially located in a single plane and have a defined optical propagation time difference between them. The optical phased array according to claim 1.

3. The first waveguide array comprises the following elements: Optical ring oscillator, Mach-Zehnder modulator, and, directional optical coupler, Formed as at least one of the elements, or comprising at least one of the elements The optical phased array according to claim 1.

4. The first waveguide array and the second waveguide array are arranged vertically relative to each other in two essentially parallel planes. The optical phased array according to claim 1.

5. A second modulation input unit for supplying modulated light of the second or third wavelength, A third waveguide array connected to the second modulation input unit, the third waveguide array being positioned near the first waveguide array such that modulated light of the second wavelength or the third wavelength can be guided to the first waveguide array, Furthermore, The first band gap is smaller than the energy of light of the third wavelength. The optical phased array according to claim 1.

6. The first waveguide array is positioned between the second waveguide array and the third waveguide array. The optical phased array according to claim 5.

7. The second waveguide array comprises a plurality of waveguides that are essentially located in a single plane and have a defined optical propagation time difference between them. The optical phased array according to claim 5.

8. The second waveguide array and the third waveguide array are arranged to overlap at least partially and / or as mirror images. The optical phased array according to claim 5.

9. The second waveguide array and / or the third waveguide array have an extraction structure in the form of a diffraction optical system facing the first waveguide array. The optical phased array according to claim 5.

10. The second waveguide array and / or the third waveguide array are located at a distance of less than 300 nm from the first waveguide array. The optical phased array according to claim 5.

11. The propagation time differences in the plurality of waveguides of the first waveguide array, the second waveguide array, and / or the third waveguide array are formed by the different lengths of the waveguides. The optical phased array according to claim 5.

12. The DBR structure is located on the opposite side of each waveguide of the second waveguide array, with the first waveguide array in between, and further comprises a DBR structure for reflecting and returning the modulated light. The optical phased array according to claim 1.

13. The system further comprises a distribution layer positioned on the opposite side of each waveguide of the second waveguide array, with the first waveguide array in between, and configured to reflect back the modulated light or to distribute the charge carriers generated by the modulated light within the first waveguide array. The optical phased array according to claim 1.

14. The material of the first waveguide array comprises the following components: InP, Si, GaAs, AlGaAs, AlGaP, and, GaN, Includes at least one of the following: and / or, The material of the second waveguide array and / or the third waveguide array comprises the following components: AlN, SiNx, Al ２ O ３ , and, Yes ２、 Including at least one of the following: The optical phased array according to claim 5.

15. A method for operating an optical phased array, The aforementioned optical phased array is A signal input section for supplying effective light of a first wavelength, A first waveguide array having at least one signal output section, connected to the signal input section, and comprising a material that is transparent to the effective light and has a first band gap, A second waveguide array, which is arranged parallel to the first waveguide array, such that a portion of the modulated light is coupled from a plurality of parallel waveguides of the second waveguide array to a corresponding one of a plurality of parallel waveguides of the first waveguide array. Equipped with, The aforementioned method, The steps include: irradiating the first waveguide array with the effective light, The steps include: injecting the modulated light so that at least a portion of the modulated light supplied from the second waveguide array is coupled to the first waveguide array; The steps include generating charge carriers in the first waveguide array by absorbing the coupled modulated light, including, How an optical phased array operates.

16. The first waveguide array comprises a plurality of waveguides that are essentially located in a single plane and have a defined optical propagation time difference between them. The second waveguide array comprises a plurality of waveguides that are essentially located in a single plane and have a defined optical propagation time difference between them. The method according to claim 15.

17. The propagation time difference in the waveguides of the first waveguide array, the second waveguide array, and / or the third waveguide array is formed by the difference in the lengths of the waveguides. The method according to claim 16.

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