OPTICAL PHASED ARRAY, LASER DEVICE, AND METHOD OF OPERATION THEREOF

Abstract

The present invention relates to an optical phased array comprising a signal input for providing useful light of a first wavelength and a first modulation input for providing modulated light of a second wavelength. A first waveguide array having at least one signal output is connected to the signal input and comprises a material transparent to the useful light and having a first band gap. A second waveguide array connected to the first modulation input is located and designed in the vicinity of the first waveguide array to guide the modulated light to the first waveguide array. The first band gap is smaller than the energy of the modulated light.

Description

[Technical field]

[0001] The present invention claims priority from German application DE 10 2022 109 220.8 filed on April 14, 2022, the disclosure of which is incorporated herein by reference in its entirety.

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

[0003] Edge-emitting lasers are based on laser diodes and are now available for a wide frequency spectrum. The high power and mass production of edge-emitting lasers make them interesting for many applications. In addition to edge-emitting lasers, VCSELs and microLEDs (μLEDs) with their small étendue can also be used to couple light into a waveguide. These are commonly referred to as optoelectronic components.

[0004] Moreover, such optoelectronic components are distinguished by larger linewidths in the range of a few nanometers, and in addition the output frequency varies as a function of current and temperature, which, on the one hand, allows tuning, but on the other hand influences the output power of the laser and necessarily requires increased circuit costs to compensate for or suppress undesirable effects.

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

[0006] On the other hand, other applications value the possibility of directing the light beam, i.e. covering a defined field of view with a predefined resolution. Examples of such applications are RGB projection or LIDAR. Directing the light beam is achieved, for example, by components that expand the laser beam to cover a high-resolution LCD, SLM (Spatial Light Modulator) or DLP display. Alternatively, deflection of the laser or light beam may be performed using movable mirrors, either MEMS or macromechanical type. Neither technology is an ideal compromise. Pixel array projection is less efficient and lacks contrast and sharpness, while mechanically moving elements often have robustness problems or add complexity.

[0007] There is therefore a demand for non-mechanical beam control or scanning options which can be easily integrated into a housing, thereby allowing a clear reduction in the volume of the structure. Summary of the Invention

[0008] This need is taken into account with the subject matter of the independent patent claims. Further developments and embodiments of the proposed principle are set out in the dependent claims.

[0009] In this regard, the inventors propose an optical phased array (OPA) that is optically controlled and 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 can also be driven in a very fast and wear-free manner according to the proposed principles.

[0010] In particular, the inventors take advantage of the fact that in optical components of the above-mentioned kind, the refractive index is particularly influenced by free charge carriers. The optical components can therefore have a transparent semiconductor material in which free charge carriers are generated by absorption of photons with energy higher than the band gap. These photons are provided via so-called modulated light. The photon flux is the basis for active modulation of the optical components and can be provided, for example, by a second planar waveguide component below and / or above the optical components, which directs the modulated light to the optical components to be modulated.

[0011] This achieves a modulation of the refractive index, the modulation speed of which is essentially limited by the lifetime of the charge carriers in the material. In particular, in the narrow sense of the optical phased array, a waveguide ensemble is provided that is dedicated to the desired phase shift function. A high-frequency, intensity-modulated controlled laser or a laser diode (or possibly several of them) provides the required photon flux.

[0012] In some aspects of the principles presented herein, optical phased arrays are proposed. In this case, the term "optical phased array" should not be understood in the narrow sense. Rather, it refers to a component whose optical behavior can be adjusted in a desired way by changing the refractive index. The change in the refractive index is achieved by a further element of the phased array, which deflects the modulated light, so that the modulated light generates charge carriers that change the refractive index by absorption. Such components with an advantageously tunable refractive index are optical phased arrays in the narrow sense, i.e. optical phased arrays with several waveguides of different lengths, optical resonators, especially ring oscillators, Mach-Zehnder modulators, or directional optical couplers, to name a few examples.

[0013] The tunable optical phased array comprises a signal input for providing useful light of a first wavelength and a first modulation input for providing modulated light of a second wavelength. A first waveguide array is connected to the signal input, the first waveguide array including at least one signal output and a material transparent to the useful light and having a first band gap. The second waveguide array is connected to the first modulation input and is arranged in the vicinity of the first waveguide array so that the modulated light can be guided to the first waveguide array. In this case, the first band gap 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 to form charge carriers. In addition, in the above-mentioned broad understanding of the optical phased array, the term waveguide array should not be understood too narrowly, but rather as an optical component that provides a certain functionality.

[0014] In this context, the first and second waveguide arrays may have the same or at least similar form. In particular, the second waveguide array should be designed to be able to better deflect the modulated light into the first waveguide array, i.e. the first component with the refractive index to be changed. Accordingly, in some embodiments, the first and second waveguide arrays are intended to be arranged one above the other in two essentially parallel planes and to overlap in some regions. The overlapping of the first and second waveguide arrays increases the efficiency, since the modulated light can be better injected into the first waveguide array. The waveguides of the second waveguide array are tuned to the first waveguide array, so that the individual waveguides of the first array experience the desired refractive index change at a predetermined intensity of the modulated light.

[0015] The intensity of the modulating light adjusts the rate of charge carrier generation, thereby modulating the refractive index in the first array of waveguides. The modulation can be done digitally, for example by a pulse modulated signal, or as an amplitude modulated signal.

[0016] In some embodiments, the first waveguide array of the optical phased array comprises a plurality of waveguides essentially in one plane, with a defined optical transit time difference between them, for example achieved by different lengths of the waveguides. The optical transit time difference creates a phase difference at the output of the array, which leads to superposition and therefore interference. Using modulation of the refractive index according to the proposed principles, the phase difference can be controlled, which allows the light beam emitted from the array to be controlled.

[0017] In a further aspect, the second waveguide array also comprises a plurality of waveguides essentially in one plane and including a defined optical transit time difference between them, again achieved by the waveguides having different lengths.

[0018] In a further aspect, the optical phased array includes a further second modulation input for supplying modulated light of a second wavelength or a third wavelength. The modulated light of the third wavelength is also richer in energy than the band gap of the material of the first waveguide array, and is therefore absorbed to generate free charge carriers. The second modulation input is connected to the third waveguide array and is located in the vicinity of the first waveguide array such that the modulated light can be directed to the first waveguide array. In this way, the flexibility is increased and also the range of modulation of the refractive index by charge carrier generation is increased. Here, the first waveguide array can be located 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 be overlapping or arranged as mirror images of each other depending on the embodiment.

[0019] In a further aspect, the second and / or third waveguide arrays are provided with out-coupling structures, in particular in the form of diffractive optics. The out-coupling structures serve to extract the modulated light from the waveguide arrays in a defined manner. In this case, the diffractive optics or out-coupling structures can also be responsible for guiding light, so that the modulated light can be guided to the first waveguide. In some embodiments, the out-coupling structures face the first waveguide array. The out-coupling structures allow for a locally limited extraction of a definable portion of the modulated light. In another embodiment, the second and / or third waveguide arrays are slightly separated from the first waveguide array, for example by less than 300 nm, in particular by less than 100 nm. This allows a part of the light (part of the light field) to reach the first waveguide array as evanescent light. For example, the waveguide arrays are close to each other, which leads to crosstalk of the modulated light into the first waveguide array.

[0020] Another aspect deals with improving the optical coupling of the modulated light into the first waveguide array. In one aspect, a particularly planar DBR structure is provided, in particular for reflecting back the modulated light. The DBR structure is arranged in the first waveguide array opposite the second waveguide. The modulated light can thereby be absorbed or reflected back. In a further embodiment, it is conceivable to provide a planar distribution layer arranged 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 in the first waveguide array. A uniform distribution of the charge carriers is useful for generating a uniform change in the refractive index.

[0021] Some embodiments address the selection of appropriate materials. In some embodiments, a semiconductor material is used as the material of the first waveguide array. The semiconductor material can have a direct or indirect band gap, but the direct or indirect band gap is selected so that the semiconductor material is essentially transparent to the useful light. In one embodiment, the material includes InP, Si, GaAs, AlGaAs, AlGaP, or GaN. However, these materials are not transparent to the second wavelength of light. Therefore, the modulated light is absorbed and generates charge carriers in the material. However, the material of the second or third waveguide array should be transparent to the modulated light. For this reason, the material of the second or third waveguide array generally has a higher band gap than the material of the first waveguide array. AlN, SiNx, Al2O3, or SiO2 can be materials that can be tuned to the material of the first waveguide array.

[0022] In some embodiments, a resonator device is proposed, comprising a waveguide with a signal input for providing useful light of a first wavelength and a signal output. The device further comprises a resonator, in particular a ring resonator, optically coupled to the waveguide in order to amplify the frequency mode of the useful light in the waveguide. Above the resonator, a device designed to inject modulated light of a second wavelength into the resonator is arranged. The resonator is further formed by a material that is essentially transparent to the useful light and has a band gap that absorbs the modulated light to form charge carriers. In this way, a tunable resonator device is implemented, which allows in particular a mode-stable but tunable laser. Applications of such resonator devices can be in the fields of coherent distance measurement, high-resolution spectroscopy, or image projection, for example 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 with diffractive optics designed to direct the modulated light in the second waveguide to the resonator. As in the case of optical phased arrays, a DBR structure, particularly a flat DBR structure, may be provided that is arranged opposite the second waveguide to reflect the modulated light back to the resonator.

[0024] A further aspect relates to a laser device using an optical component according to the proposed principle, the laser device comprising a first laser device for generating useful light and a second laser device for generating modulated light. The modulated light is intensity modulated by the second laser device. The two laser devices are connected to an optical phased array, an optical component, or a resonator device.

[0025] A further aspect relates to the operation of an optical phased array, the phased array including a signal input for providing useful light at a first wavelength and a first waveguide array having at least one signal output. The first waveguide array is connected to the signal input and has a material transparent to the useful light and having a first band gap. In the method, the useful light is incident on the first waveguide array. Similarly, modulated light is generated and at least a portion is coupled to the first waveguide array. Absorption of the incident modulated light generates charge carriers in the first waveguide array, which change the refractive index in a characteristic manner. The variation in the refractive index is controlled by changing the intensity of the modulated light.

[0026] In one aspect, the coupling of the modulated light is performed using a second waveguide array disposed in the vicinity of the first waveguide array so that the modulated light can be guided to the first waveguide array. The first and second waveguide arrays have different properties and characteristics depending on the optical components. In some aspects, the first waveguide array comprises a plurality of waveguides essentially in one plane with a defined optical propagation time difference between each other. The second waveguide array can be similarly designed and can comprise a plurality of waveguides essentially in one plane with a defined optical propagation time difference between each other. In some embodiments, the propagation time difference in the waveguides of the first or second waveguide array is formed by the different lengths of the waveguides. [Brief description of the drawings]

[0027] Further aspects and embodiments in accordance with the proposed principles will be disclosed by reference to the various embodiments and examples described in detail in conjunction with the accompanying drawings. [Figure 1] FIG. 1 illustrates an embodiment of an optical phased array. [Diagram 2] FIG. 1 shows in plan view an embodiment of a phased array according to the proposed principles. [Diagram 3]FIG. 3 is a cross-sectional view of the phased array of FIG. 2 with some aspects of the proposed principles. [Figure 4] FIG. 2 illustrates a second embodiment of an optical phased array with some aspects of the proposed principles. [Diagram 5] 5 is another embodiment of FIG. 4. [Figure 6] FIG. 6 is a cross-sectional view of the phased array of FIG. 4 or FIG. 5 to illustrate some aspects of the proposed principles. [Figure 7] FIG. 13 shows a cross-sectional view of a further embodiment of a phased array according to the proposed principles. [Figure 8] FIG. 13 shows a further cross-sectional view of an embodiment of a phased array according to the proposed principles. [Figure 9] FIG. 13 illustrates a third embodiment of an optical phased array with some aspects of the proposed principles. [Figure 10] 10A-10C are different cross-sectional views of an embodiment of a phased array according to the principles of FIG. [Figure 11] 10A-10C are different cross-sectional views of an embodiment of a phased array according to the principles of FIG. [Figure 12] 10A-10C are different cross-sectional views of an embodiment of a phased array according to the principles of FIG. [Figure 13] 1 is an example of a method involving some aspects of the proposed principles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The following embodiments and examples show various aspects and their combinations according to the proposed principles. The embodiments and examples are not necessarily drawn to scale. Similarly, various elements may be shown enlarged or reduced in size 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 each other without thereby violating the principles of the present invention. Some aspects have regular structures or forms. It should be noted that in practice slight deviations from the ideal form may occur, but do not contradict the spirit of the present invention.

[0029] In addition, individual figures, features, and aspects are not necessarily shown to scale, and the proportions between individual elements may not be essentially correct. Some aspects and features are emphasized by being shown enlarged. However, terms such as "top," "upper," "lower," "lower," "greater," "lesser," and the like are correctly indicated with respect to elements in the figures. Thus, such relationships between elements can be derived based on the drawings.

[0030] FIG. 1 shows a device of a so-called optical phased array in the narrow sense, i.e. a device in which beamforming can be achieved by means of a phase shift generated by several optical waveguides of different lengths.

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

[0032] In operation of the device, useful light NL is injected and distributed to the various branches 11a-11g of the optical phased array 3''. Due to the different lengths of the individual branches, signals with a phase shift between each other arise at the respective output 12'. These signals interfere with each other. By appropriately adjusting the length based on the frequency or wavelength of the scattered useful light, constructive or destructive interference occurs. The position of the constructive interference on the screen S at position P1 or position P2 as illustrated in FIG. 1 can be adjusted by various means. In general, the position of this constructive interference depends on the geometric parameters as well as the refractive index of the waveguides 11a-11g. By changing the refractive index of the material, the position P1 or position P2 on the screen S can be controlled, so that a "scanning" of the screen is achieved with the interfering output light.

[0033] Conventional methods in this regard use, for example, thermal techniques, in which the optical phased array 3'' is heated or cooled, thereby changing the refractive index of each of the waveguides in a characteristic way. However, such processes are 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 represents an improvement over thermal techniques, but requires relatively high voltages to generate the required electric fields. Therefore, such approaches are expensive to implement, especially in applications where the available operating voltage is low.

[0034] Figure 2 shows one embodiment of the proposed principle, where the refractive index of the optical component is adjusted not by thermal or electro-optical means, but by purely optical means. Here, it is exploited that the material of the waveguides 11a-11g, i.e. the material of the optical component 3, also has a band gap and is thereby able to absorb light. The waveguides 11a-11g are transparent to the useful light, but free charge carriers can be generated by the absorption of photons of higher energy in the waveguides. These free charge carriers then cause a change in the refractive index in a characteristic way. Figure 2 shows one possible embodiment of this principle.

[0035] The device according to the proposed principle comprises an optical component 3, which in this embodiment is also formed as an optical phased array in the narrow sense. Here, a laser device 1 is arranged at a signal input coupled to a waveguide 11. The laser device 1 may be an edge-emitting laser, a laser diode or a laser device not based on a semiconductor structure. The optical phased array comprises a number of waveguides 11a, 11b-11g, which are connected to each other at the input side and each lead to a signal output 12' at the output side. The lengths of the respective waveguides between the signal input and the signal output are different and are mutually tuned such that an interference pattern of the incident light at the output on the screen is generated similar to that of FIG. 1.

[0036] According to the invention, the optical component 3 comprises a second signal input connected to a second laser diode 2 for supplying the modulated light ML. This modulation input is connected to a number of waveguides 21a, 21b to 21g. The waveguides also form a waveguide structure for the modulated light ML, with each individual waveguide 21a, 21b to 21g being designed above a part of the waveguides 11a, 11b to 11g.

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

[0038] In operation of the proposed device, modulated light ML is incident with a photon energy larger than the band gap of the material in the waveguides 11a, 11b-11g. In the following, for the purpose of explaining the principles of the invention, it is conveniently assumed that the band gap is constant and there are no differences with respect to crystal orientation or direct / indirect band gap. In fact, the principles of the invention are possible when light is absorbed in or around the material of the waveguide and then generates free charge carriers in the material of the waveguide.

[0039] The modulated light ML is emitted from the existing extraction optics and optically absorbed by the waveguides 11a, 11b-11g. The absorption generates charge carriers in the conduction band of the material of the waveguides 11a, 11b-11g, which changes the refractive index of this material. Due to the length of the individual waveguides 21a, 21b-21g for the modulated light ML, shown in the plan view of FIG. 2, the intensity-dependent incidence and the resulting absorption take place in a defined manner, which results in a characteristic change in the refractive index in the individual waveguides 11a, 11b-11g for the useful light NL. A change in the intensity of the modulated light ML also changes the refractive index. Thus, the intensity modulation of the light ML causes a modulation of the refractive index in a characteristic manner.

[0040] In this case, the material of the waveguide for the modulated light ML is selected such that the material is transparent to the modulated light ML itself. However, due to the very high energy of the photons of the modulated light ML, the modulated light ML exceeds the band gap of the waveguides 11a-11g and is thus absorbed in the waveguides 11a-11g, generating free charge carriers. By adjusting the intensity of the modulated light, the generation of charge carriers and thus the resulting change in the refractive index can be adjusted or varied. In this way, the interference pattern at the output of the optical component 3 can be adjusted, for example, to achieve the effect shown in FIG. 1, such as changing the constructive interference maximum along the position.

[0041] The change in refractive index due to charge carriers is essentially determined by three effects. On the one hand, the filling of the density of states by free charge carriers according to Burstein-Moss, or the filling of allowed band states, which generally leads to a change in the refractive index towards lower values. However, a normalization of the band gap, or a slight change in the band gap towards smaller energies, leads to a change in the refractive index towards larger values. Finally, via 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 is changed towards smaller values. In the proposed principle, these three aspects act in combination. The free charge carrier absorption according to the Drude model is then the main aspect.

[0042] In this case, the charge carriers absorb light particles in the medium, which raise them to a higher energy state. Charge carriers in the valence band rise to the conduction band, which creates electron-hole pairs. In this way, freely moving electrons are created in the conduction band, which acts similarly to an eh plasma. This plasma generates a characteristic absorption band in the IR range that can be explained by the Drude model. The characteristic absorption band leads to a decrease in the refractive index at short wavelengths, according to the so-called Kramers-Kronig relation. The Drude model, expressed by equation (1),

number

number

[0043] The change in the refractive index here is negative. That is, the refractive index decreases due to the absorption of light in the waveguide. Furthermore, the change in the refractive index is proportional to the square of the wavelength λ. This basically means that the longer the wavelength, i.e., the lower the energy, the higher the change in the refractive index.

[0044] In the following, the charge carrier generation upon incidence of modulated light is estimated and the resulting change in the refractive index is at least qualitatively explained. In this estimation, the modulated light is generated by a laser with a power of 100 mW and a beam diameter of d=100 μm. The wavelength of the modulated light is λ=400 nm. As waveguide material for the optical components, a combination of InP and GaP is used, the parameters used refer 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 the laser beam decreases exponentially in the material, i.e., its intensity decreases with e (-z / z0) (where z0 is the absorption length). The absorption length is approximately proportional to the absorption length when the light intensity becomes 1 / e of the original I (or 1 / e 2 ) corresponds to the length z when the temperature drops to 100°C. This gives us approximately

number

[0046] The decrease in light means that charge carriers are then generated. Thus, the number of charge carriers in the absorption length is

number

[0047] So this is about 10 26 1 / (scm 3 ) range. This means that for an injection period of about 1 ns,

number

[0048] The electron-hole plasma thus generated recombines, which reduces the number of free charge carriers again. The recombination rate here follows different mechanisms. These mechanisms are, on the one hand, recombination that occurs with direct recombination, i.e. electrons and holes combine together again to generate corresponding photons, plasmons or phonons. Alternatively, so-called Auger recombination is possible, but since Auger recombination is several orders of magnitude lower than direct recombination, it does not have to be taken into account in the discussion.

[0049] Thus, the recombination rate R results from the concentrations n, p of the available charge carriers and the material-dependent parameters C that characterize the two mechanisms mentioned above in the respective material.

number

[0050] The indicated charge carrier density n=p is 6×10 17 1 / cm 3 In the range of 10-11 cm, the parameter C indicating direct recombination is 6*. 3 / s, from equation (4) we get 2×10 16 1 / nscm 3 Thus, if the recombination rate remains approximately constant, the generated charge carriers are therefore fully combined after about 10 ns.

[0051] The generation and recombination rates of charge carriers can also be expressed using the differential equation shown in Equation (5). Thus, the generation rate,

number

number

[0052] The solution to this differential equation is a function that increases with time from 0 and reaches equilibrium after about 15 ns. Equilibrium between charge carrier generation and recombination occurs when the modulated light is continuously incident, or when the intensity of the incident modulated light is modulated with a frequency significantly less than the recombination rate. The intensity at equilibrium essentially scales with the square root of the charge carriers commanded by recombination.

number

[0053] For the example laser with the power mentioned above, the charge carrier density at equilibrium is approximately 10 18 1 / cm 3 is in the range.

[0054] From the above differential equations and assumptions about the incident modulated light and other parameters, 3 10 per 17 ~10 19 This produces a charge carrier concentration in the range of 10 -2 The change in refractive index is estimated to be in the range of 100 nm, i.e., a few percent. As the intensity of the modulated light increases, the absorption in the material increases, and so does the charge carrier concentration, leading to an increased change in the refractive index.

[0055] Thus, for example, to achieve a phase shift of π between two waveguides based on a change in refractive index, a waveguide having a length of about 100 μm is prepared and a 10 18 ~about 10 19It is sufficient to generate a charge carrier density in the range of π = 1.0, so that by additional modulated light from an individual additional laser or several lasers, a sufficient charge carrier concentration of free charge carriers can be generated in the material of the optical component to generate the necessary change in refractive index for a phase shift of π, which corresponds to 180°.

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

[0057] In this regard, Fig. 4 shows a further embodiment that achieves greater flexibility in tuning the refractive index by using several additional laser devices to generate modulated light ML, which may have different wavelengths, and furthermore, such an embodiment also allows for a certain symmetrical morphology, resulting in a uniform charge carrier distribution.

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

[0059] Here again, it can be seen that the first waveguide structure with the waveguides 11a, 11b to 11g is arranged in one plane. In contrast, the two waveguide structures with the branches 21a, 21b to 21g for the modulated light ML and the branches 21a', 21b' to 21g' for the modulated light ML' are arranged above and below the first waveguide structure, respectively. In other words, the waveguides 11a, 11b to 11g are surrounded on both sides by corresponding modulated waveguide structures. When the modulated light ML is switched on, as indicated here by the arrows in FIG. 6, the light is guided as uniformly as possible by the outcoupling structure 22 into the first waveguide structure. This results in the scattered modulated light ML being distributed uniformly in the waveguide structure with the waveguides 11a, 11b to 11g, which leads to a more uniform charge carrier distribution. Furthermore, in this embodiment, a significantly larger refractive index increase can occur depending on the absorption, since the intensity is adjusted according to the intensity increase that can be brought about by the waveguides 21a', 21b' to 21g' over a larger area.

[0060] A variation in this respect is shown in Fig. 5. Here, the waveguide structure for the modulated light ML or the waveguide structure for the modulated light ML' is provided above or below the waveguide structure for the useful light NL in mirror symmetry. Thus, the lengths of the individual waveguides 21a, 21b to 21g or 21a', 21b' to 21g' are different above or below the respective waveguides 11a, 11b to 11g. This provides a degree of freedom in adjusting the interference pattern and the change in the refractive index.

[0061] In yet another embodiment, further mirrors or other optical or electro-optical structures are shown above or below the waveguide structure for the useful light, which may help to produce a more uniform light distribution and also a more uniform charge carrier distribution, ultimately improving the signal quality.

[0062] FIG. 7 shows in cross section an embodiment in which two further DBR structures 31 and 31′ are arranged above and below the plane of the waveguide structure for the useful light NL. The DBR structures are designed in such a way that the absorption of the modulated light ML is enhanced in the waveguide structure with the waveguides 11a, 11b-11g, thereby increasing the 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 completely absorbed by the waveguide structure for the useful light.

[0063] FIG. 8 shows another embodiment in which the plane of the waveguide structure for the useful light NL and the plane of the waveguide structure for the modulated light ML are arranged as close to each other as possible. In this embodiment, the distance between the waveguides 11a, 11b-11g and the waveguides 21a, 21b-21g for the modulated light is only a few tens to a few hundreds of nm. The modulated light is thereby directly coupled into the waveguide structure with the waveguides 11a, 11b-11g by evanescent coupling and is at least partially absorbed in the waveguide structure. This embodiment has the advantage that basically no further coupling structure 22 or DBR structure is required, which simplifies the manufacturing. However, also in this embodiment, there may be one DBR structure below the waveguides 11a, 11b-11g.

[0064] 9 shows a further embodiment with different optical components compared to the above embodiment. The background to this is the fact that the basic principle of the change in refractive index in optical components due to the additionally introduced modulated light is not limited to optical phased arrays in the narrow sense, as already mentioned. Rather, it is also possible to, for example, reduce the linewidth of edge-emitting lasers, stabilize edge-emitting lasers, or flexibly adjust other optical functionalities by them.

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

[0066] Above or below this ring resonator 32, a partially ring-shaped waveguide element 21 is further provided, at the end 33 of which a mirror or an absorbing element is arranged. A device with a mirror has the advantage that the light that is not absorbed is reflected back into the curved waveguide 21 and can be absorbed again in the ring resonator. As in the other embodiments, the ring-shaped structure above the ring resonator also has an extraction structure, by which the modulated light ML provided by the laser diode 1 is injected into the ring resonator, where free charge carriers are generated. These are caused by a change in the refractive index in the ring resonator, and the selected mode is shifted by the optical coupling D. The intensity of the injected modulated light is modulated to change the refractive index, and with it the frequency modulation of the scattered useful light is realized at the output 12.

[0067] The proposed optical component can be implemented in various ways, in particular with regard to the supply of modulated light. In this respect, Fig. 10, Fig. 11 and Fig. 12 show different embodiments, each with a cross-sectional view. In Fig. 10, the 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 arranged on a laterally arranged further carrier at the height of the optical element 3'. The modulated light is partially reflected at the prism-shaped mirror element 4 towards the ring resonator 32, while a part of the modulated light passes further from the first element and enters the second mirror element 4, where it is reflected. This arrangement has the advantage that it 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 Fig. 11. In this embodiment, above the plane of the ring resonator there is a further waveguide structure 21 with several extraction elements 22. These serve to extract the modulated light ML in the waveguide structure 21 and direct it into the waveguide of the ring resonator 32. Also in this embodiment the modulated light is generated by a second laser diode 2 arranged externally.

[0069] Finally, in a third embodiment, a ring resonator is placed between two DBR structures 31, where 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 ring resonator material. In this embodiment, too, the outcoupling structure 22 serves to couple the light into the DBR structure 31 and the ring resonator material.

[0070] The various implementations and embodiments, together with their individual features, can be combined with one another to generate charge carriers in the optically relevant region upon absorption of modulated light, thereby changing the refractive index within the material as described above, thereby realizing optical components with tunable functionality.

[0071] Finally, Fig. 13 shows an embodiment of a method of operation of an optically tunable component, in which a signal input is provided for feeding useful light of a first wavelength to at least one waveguide. Furthermore, there is a signal output at which the tuned or tunable useful light can be picked up. The optical component comprises a material transparent to the useful light, which material 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 is connected to a first laser device for generating the useful light.

[0072] Further, a second laser device is provided, designed to generate modulated light. The photon energy of the modulated light is greater than the first band gap. In the proposed method, in step S2, useful light is injected into 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. In the second step S2, modulated light is also provided, but in such a way that at least a part of the modulated light is injected into the material of the area associated with the optical component. The optical component may be a waveguide, a resonator, a PIC or PLC, or a waveguide array, as shown in the previous examples.

[0073] The incident modulated light, due to its higher photon energy, is absorbed in this region and generates free charge carriers in this region. Depending on the intensity of the incident modulated light, a balance occurs between charge carrier recombination and charge carrier generation. But at the same time, the free charge carriers change the refractive index of the material, which affects the incident useful light. This change in refractive index is tuned by the intensity of the modulated light over a predefined region, which also changes the functionality of the optical component.

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

[0075] 1 Laser device 2 Laser device 3, 3' Phased Array 3'' Phased Array 4. Mirror 11 Waveguide 11a, 11b waveguide 11c, 11d waveguide 11e, 11f waveguide 11g waveguide 12, 12' Output section 21 Waveguide 21a, 21b waveguide 21c, 21d waveguide 21e, 21f waveguide 21g waveguide 22 Diffractive optics 30 Phased Array Materials 31, 31' DBR structure 32 Ring resonator D-coupling NL Effective light ML Modulated Light

Claims

1. a signal input for providing useful light at a first wavelength; a first waveguide array having at least one signal output connected to said signal input, the first waveguide array comprising a material transparent to said useful light and having a first bandgap; a first modulation input for providing modulated light at a second wavelength; a second waveguide array connected to the first modulation input, the second waveguide array being positioned proximate to the first waveguide array such that modulated light can be directed into the first waveguide array; 1. An optical phased array comprising: the first band gap is smaller than the energy of the modulated light; Optical phased array.

2. 2. The optical phased array of claim 1, wherein the first waveguide array has a plurality of waveguides that lie essentially in one plane and that include a defined optical transit time difference between each other, and optionally the second waveguide array has a plurality of waveguides that lie essentially in one plane and that include a defined optical transit time difference between each other.

3. The first waveguide array comprises the following elements: Optical ring oscillator, Mach-Zehnder Modulator, directional optical coupler, 13. The optical phased array of claim 1, wherein the at least one element is formed as or comprises at least one of the elements.

4. 4. The optical phased array of claim 1, wherein the first waveguide array and the second waveguide array are arranged above each other in two essentially parallel planes.

5. a second modulation input for providing modulated light at the second wavelength or a third wavelength; a third waveguide array connected to the second modulation input, the third waveguide array being positioned proximate to the first waveguide array such that modulated light of the second wavelength or the third wavelength can be guided to the first waveguide array; Further comprising: the first band gap is smaller than the energy of the light of the third wavelength; The optical phased array according to any one of claims 1 to 4.

6. 6. The optical phased array of claim 5, wherein the first waveguide array is disposed between the second waveguide array and the third waveguide array.

7. 7. The optical phased array of claim 5 or 6, wherein the second waveguide array comprises a plurality of waveguides essentially in one plane and including defined optical transit time differences between each other.

8. 8. The optical phased array of claim 5, wherein the second waveguide array and the third waveguide array are at least partially overlapping and / or arranged as mirror images.

9. 9. The optical phased array of claim 1, wherein the second waveguide array and / or the third waveguide array have an out-coupling structure facing towards the first waveguide array, in particular an out-coupling structure in the form of a diffractive optic.

10. 10. The optical phased array of claim 1, wherein the second waveguide array and / or the third waveguide array are at a distance from the first waveguide array of less than 300 nm, in particular less than 100 nm, in particular less than a wavelength of the modulated light, in particular less than half a wavelength of the modulated light.

11. 11. The optical phased array of claim 1, wherein a 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 lengths of the waveguides being different.

12. 12. The optical phased array of claim 1, further comprising a DBR structure, in particular a flat DBR structure for reflecting back modulated light, the DBR structure being arranged on a side of the first waveguide array opposite the second waveguides.

13. 13. The optical phased array of claim 1, further comprising a particularly flat distribution layer arranged on the first waveguide opposite the second waveguide and shaped to reflect back modulated light or to distribute charge carriers generated by the modulated light in the first waveguide array.

14. The material of the first waveguide array comprises the following components: InP, S. GaAs, AlGaAs, AlGaP, and GaN, and and / or The material of the second and / or third waveguide arrays may comprise the following components: AlN, SiNx, A ２ O ３ , and Yes ２、 At least one of: The optical phased array according to any one of claims 1 to 13.

15. a waveguide coupling a signal input for providing useful light at a first wavelength to a signal output; a resonator, in particular a ring resonator, optically coupled to the waveguide for amplifying a frequency mode of the useful light within the waveguide; a device disposed above the resonator designed to couple modulated light at a second wavelength into the resonator; A resonator device comprising: The resonator includes a material having a band gap, so that the resonator is essentially transparent to useful light and absorbs modulated light to form charge carriers. Resonator device.

16. 16. The resonator device of claim 15, wherein the device disposed above the resonator comprises one or more deflection mirrors, or the device comprises a second waveguide with diffractive optics designed to direct modulated light in the second waveguide to the resonator.

17. 17. The resonator arrangement according to claim 15 or 16, further comprising a DBR structure, in particular a flat DBR structure for reflecting back modulated light, which is arranged on the side of the resonator opposite the second waveguide.

18. a first laser device for generating useful light; a second laser device for generating modulated light; and An optical phased array according to any one of claims 1 to 14 or a resonator device according to any one of claims 15 to 17; A laser device having a

19. Phased array, a signal input for providing useful light at a first wavelength; a first waveguide array having at least one signal output connected to said signal input, the first waveguide array comprising a material transparent to said useful light and having a first bandgap; 1. A method of operating an optical phased array, comprising: A step of inputting useful light into the first waveguide array; directing modulated light such that at least a portion of the modulated light is coupled into the first array of waveguides; generating charge carriers in the first waveguide array by absorption of the coupled modulated light; A method for operating an optical phased array, comprising:

20. 20. The method of claim 19, wherein the step of injecting the modulated light is performed by a second waveguide array positioned proximate to the first waveguide array such that the modulated light can be directed into the first waveguide array.

21. 21. The method of claim 19 or 20, wherein the first waveguide array comprises a plurality of waveguides that are essentially in one plane and that include a defined optical transit time difference between each other, and optionally the second waveguide array comprises a plurality of waveguides that are essentially in one plane and that include a defined optical transit time difference between each other.

22. 22. The method of claim 21, wherein the propagation time differences in the waveguides of the first waveguide array, the second waveguide array, and / or the third waveguide array are formed by the lengths of the waveguides being different.

Images