Optical Logic Gates

Abstract

An optical logic gate is provided, comprising signal providing means (1.1, 1.2) for providing first and second optical signals having the same phase. The optical logic gate further comprises phase modulation means (2.1, 2.2) and interference means (3). The optical logic gate also comprises an optical nonlinear element (1.3) configured to interact with a pump signal, and to interact with the first and second optical signals whose phases have been shifted by the phase modulation means (2.1, 2.2) and interfered by the interference means (3), and to combine an optical output signal as a result of this nonlinear interaction as a logic output signal.

Description

[Technical Field]

[0001] The present invention relates to optical logic gates and methods of operation thereof.

[0002] The use of optical logic, e.g., optical logic gates, in analog or digital processors promises substantially faster and more efficient performance of arithmetic operations. To ensure this, the optical logic used must meet a number of requirements.

[0003] Therefore, it must be possible to switch optical logic gates as fast as possible using low light intensities. Furthermore, optical logic gates must be flexibly cascadable to allow scaling of the respective processors. Other criteria relate to the possibility of achieving a fan-out of at least two and the possibility of restoring logic levels sufficiently loss-free. Furthermore, it is advantageous to efficiently couple input and output signals and avoid critical operating points or corresponding process parameters. Summary of the Invention [Problem to be solved by the invention]

[0004] However, known prior art techniques do not adequately meet these criteria, either being too slow in switching operation, requiring a lot of energy for efficient use, or not being able to be efficiently scaled or cascaded.

[0005] SUMMARY OF THE INVENTION The object of the present invention is therefore to propose an optical logic gate and a method for its operation that are able to overcome the drawbacks of the prior art and, moreover, to meet many of the requirements mentioned above.

[0006] According to the invention, this object is achieved by a logic gate having the features set forth in the independent claims. Advantageous configurations and developments of the invention are realized by the features set forth in the dependent claims. [Means for solving the problem]

[0007] The optical logic gate according to the present invention comprises a signal supply means for supplying a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal, the phases of the first and second optical signals being the same or identical (modulo 2π).

[0008] The optical logic gate further comprises a phase modulation means for transitioning (shifting) the phase of the first optical signal by a predetermined phase difference relative to the phase of the second optical signal.

[0009] The optical logic gate further comprises interference means for causing the first optical signal and the second optical signal, the phases of which have been shifted by the phase modulation means, to interfere with each other.

[0010] The optical logic gate further comprises an optical nonlinear element configured to interact with the pump signal, configured to interact with the first optical signal and the second optical signal whose phase has been shifted by the phase modulation means and interfered by the interference means, and configured to combine and output the optical output signal as a logic output signal as a result of this nonlinear interaction.

[0011] Here, and hereinafter, the first and second optical signals whose phases have been shifted by the phase modulation means and interfered by the interference means refer to a superimposed signal, which is obtained when the first optical signal, after having shifted or fixed their relative phase by the phase modulation means, is made to interfere with the second optical signal by the interference means, so that the first and second optical signals are superimposed. This superimposed signal can then be coupled to an optical nonlinear element, so that it can interact with it electromagnetically and nonlinearly, e.g., be transmitted, reflected and / or absorbed, either completely or at least partially.

[0012] The proposed optical logic gate is characterized by improved cascadability and scalability. In particular, the optical logic gate can switch independently of the phase of the first and second logic input signals. Furthermore, the optical logic gate is robust against different noise signals that can unexpectedly (e.g., randomly) change the phase and / or intensity of the optical signal.

[0013] Because the optical supply of the (optical) pump signal is selectable independently of the first and second logic input signals, a relatively large fan-out is achieved, allowing a logic gate to be efficiently connected to multiple other logic gates, and in this way logic levels can be restored relatively efficiently and without loss.

[0014] For example, the strength of the logic output signal can be greater than the strength of the first logic input signal and / or the second logic input signal (without the use of additional optical amplifiers), and the relative modulation depth of the optical logic gate does not depend significantly on the strength of the first and second logic input signals.

[0015] Operation Mode and Logic Optical logic gates can be used in purely optical analog or digital modes of operation, in which they can be used as modular logic elements to perform multiple logical operations with different logic states.

[0016] The logic state may be a first logic state or a second logic state, e.g., the first logic state may correspond to a bit having a bit value of 0, and the second logic state may correspond to a bit having a bit value of 1 (or vice versa).

[0017] The different logic states can be encoded into the signal by amplitude or intensity modulation. In the case of amplitude or intensity modulation, the modulated signal can have a first intensity when associated with a first logic state. The modulated signal can have a second intensity when associated with a second logic state. The second intensity of the modulated signal can be different from the first intensity of the modulated signal. For example, the second intensity of the modulated signal can be greater than the first intensity of the modulated signal.

[0018] The modulated signal may be a first or second logic input signal, a first or second optical signal, a superimposed signal, or an optical or logic output signal. The first intensities of the different modulated signals may be different from each other. Similarly, the second intensities of the different modulated signals may be different from each other. For example, the first intensity of the first logic input signal may be different from the first intensity of the first optical signal. The second intensity of the first logic input signal may be different from the second intensity of the first optical signal. Similarly, the same applies to the second logic input signal and the second optical signal.

[0019] The signal providing means may be configured to convey amplitude or intensity modulation of the first and second logic input signals onto the first and second optical signals, such that a logic state of the first logic input signal corresponds to a logic state of the first optical signal and a logic state of the second logic input signal corresponds to a logic state of the second optical signal.

[0020] The predetermined phase difference between the phase of the first optical signal and the phase of the second optical signal is π or can be adjusted accordingly by the phase modulation means.

[0021] In this case, interference of the first and second optical signals by the interference means may be destructive. In particular, if the intensities of the first and second optical signals are the same, the interference may be completely destructive, so that they are associated with the same logic state. The first and second optical signals may then almost completely cancel each other in the interference means and / or the optical nonlinear element with a predetermined phase difference π. The superimposed or interfering signal may then correspond to a first logic state or a 0 signal (i.e., for all practical purposes, a signal whose intensity is equal to 0 or less than the average intensity of the noise).

[0022] However, if the magnitudes of the intensities of the first and second optical signals are different, they may be associated with different logic states. For example, exactly one of the two signals may be a zero signal, but the other signal may not be a zero signal. Therefore, despite the interference in the interference means and / or the optical nonlinear element, the first and second optical signals may not completely cancel each other and may interfere with each other little or not at all. The superimposed or interfering signal may correspond to a second logic state or may primarily correspond to the first or second optical signal before the interference, rather than being a zero signal.

[0023] The strength of the logic output signal may depend on the strength of the superimposed signal and the strength of the pump signal due to the interaction of the pump signal and the superimposed signal with the optical nonlinear element.

[0024] For example, the intensity of the pump signal can be set or the optical nonlinear element can be configured such that the optical nonlinear element is optically saturated when the superimposed signal corresponds to a second logic state or a 0 signal, i.e., when the first optical signal and the second optical signal or the first logical input signal and the second logical input signal have different intensities or correspond to different logic states, in which case the optical output signal has a large intensity, which corresponds to the second intensity of the optical output signal and can be associated with the second logic state.

[0025] Furthermore, when the superimposed signal corresponds to a first logic state or a 0 signal, i.e., when the first optical signal and the second optical signal or the first logical input signal and the second logical input signal have the same intensity or correspond to the same logic state, the intensity of the pump signal can be set or the optical nonlinear element can be configured so that the optical nonlinear element is not optically saturated. In this case, the optical output signal has a small intensity, which corresponds to the first intensity or a 0 signal of the optical output signal and can be associated with the first logic state.

[0026] Furthermore, the above-described functionality corresponds to that of a logical XOR function, and therefore the optical logic gate can be used as an XOR gate.

[0027] In particular, the signal providing means, together with the optical nonlinear element, may be configured to associate the intensity of the logic output signal with the intensity of each of the first and second logic input signals, such that the logic output signal in response to the first and second logic input signals is the result of a logical XOR function, wherein the logic states of each of the first and second logic input signals and the logic output signal may be amplitude modulated or intensity modulated.

[0028] If the first logic input signal and the second logic input signal have different intensities or are associated with different logic states, it is preferable that the signal supply means and the optical nonlinear element can be configured such that the phase of the logic output signal is always the same regardless of which logic state the first logic input signal and the second logic input signal are respectively associated with.

[0029] In this case, a purely optical XOR function can be realized, in which the phase of the logic output signal is combined or always the same, regardless of the phase and / or intensity of the first logic input signal and the second logic input signal or the first optical signal and the second optical signal. In particular, the phase of the logic output signal can correspond to the phase of the pump signal.

[0030] This is particularly achieved by first introducing the superimposed signal together with the pump signal into an optical nonlinear element before the logic output signal resulting from the nonlinear interaction is generated and combined. For example, the material of the optical nonlinear element can be selected so that the nonlinear interaction is phase-insensitive, e.g., corresponds to an effective Kerr nonlinearity. The optical nonlinear element preferably comprises or is configured with an optical saturable absorber mediating the interaction.

[0031] The optical output signal may correspond to a portion of the pump signal that is not absorbed by the optical nonlinear element and / or the optical saturable absorber, or may correspond to a portion of the pump signal that is transmitted through the optical nonlinear element. The phase of the optical output signal may correspond to the phase of the pump signal. The intensity of the optical output signal may be less than the intensity of the pump signal as a result of interaction with the optical nonlinear element. The intensity of the optical output signal may also depend on the intensity of the superimposed signal and / or the optical saturation of the optical nonlinear element.

[0032] In the sense of the present invention, the signal may be pulsed, the interaction may be simultaneous, and in particular the interaction of the pump signal and the superimposed signal with the optical nonlinear element may be simultaneous or at least overlapping in time.

[0033] The simultaneous interaction of the pump signal and the superimposed signal with the optical nonlinear element can be performed such that the pump signal and the superimposed signal reach or couple to the optical nonlinear element and interact therewith simultaneously or at least overlapping in time, for example, the pump signal and / or the superimposed signal can be fully or at least partially absorbed by an optical saturable absorber within the optical nonlinear element.

[0034] However, the pump signal may arrive only after the superimposed signal first reaches the optical nonlinear element, or couples to or interacts with the optical nonlinear element. For example, the superimposed signal may first be fully or at least partially absorbed by an optical nonlinear element or an optical saturable absorber within the optical nonlinear element and electromagnetically excite it. During this excitation or absorption, the optical saturable absorber may become saturated. The pump signal may then pass almost fully or at least partially through the optical saturable absorber within the optical nonlinear element, thereby transmitting through the optical nonlinear element. Thus, the pump signal may be converted into an optical output signal as a result of the simultaneous interaction of the pump signal and the superimposed signal with the optical nonlinear element.

[0035] The pump signal can pass almost completely, partially, or completely through the optical nonlinear element to realize the logic function of the optical logic gate, independent of the degree of absorption of the superimposed signal and / or excitation or saturation of the optical nonlinear element by the superimposed signal.

[0036] This significantly increases the scalability of the optical logic gate, or the optical processor in which it is implemented or incorporated. For example, the phase and / or intensity of the logic output signal can be adjusted or adapted by selecting the phase and / or intensity of the pump signal. In particular, the phase of the logic output signal can correspond to the phase of the pump signal, independent of the respective logic function. The logic output signal can then be directly used as another input signal in another logic element or component of the optical processor.

[0037] signal supply The first optical signal may correspond to or be the same as a first logical input signal, and the second optical signal may correspond to or be the same as a second logical input signal.

[0038] However, the signal providing means may comprise other optical components or optical elements, by means of which the first logical input signal or its logical state can be transferred to the first optical signal and / or the second logical input signal or its logical state can be transferred to the second optical signal, in which case the first optical signal may be different from the first logical input signal and the second optical signal may be different from the second logical input signal.

[0039] The signal providing means may comprise a first additional optical nonlinear element and a second additional optical nonlinear element.

[0040] The first additional optical nonlinear element may be configured to interact with the first additional (optical) pump signal and the first logical input signal, and configured to provide a first optical signal as a result of this nonlinear interaction. The interactions of the first additional (optical) pump signal and the first logical input signal with the first additional optical nonlinear element may occur simultaneously.

[0041] The first optical signal may correspond to a portion of a first additional pump signal transmitted through the first additional optical nonlinear element, and the phase of the first optical signal may correspond to the phase of the first additional pump signal.

[0042] The second additional optical nonlinear element may be configured to interact with the second additional (optical) pump signal and the second logic input signal, and configured to provide a second optical signal as a result of this nonlinear interaction. The interactions of the second additional (optical) pump signal and the second logic input signal with the second additional optical nonlinear element may occur simultaneously.

[0043] The second optical signal may correspond to a portion of a second additional pump signal transmitted through a second additional optical nonlinear element, and the phase of the second optical signal may correspond to the phase of the second additional pump signal.

[0044] Preferably, the first additional pump signal and the first logic input signal propagate within the first additional optical nonlinear element, propagate in opposite directions through the first additional optical nonlinear element, or propagate in opposite directions to the first additional optical nonlinear element as a pair.

[0045] The second additional pump signal and the second logic input signal preferably propagate within the second additional optical nonlinear element, propagate in opposite directions through the second additional optical nonlinear element, or propagate in opposite directions to the second additional optical nonlinear element as a pair.

[0046] Optical Nonlinearity The optical nonlinear element materials of the first additional optical nonlinear element and / or the second additional optical nonlinear element may be selected such that the respective nonlinear interactions are phase insensitive and preferably correspond to an effective Kerr nonlinearity.

[0047] The optical nonlinear element, the first additional optical nonlinear element and / or the second additional optical nonlinear element may comprise or consist of an optical saturable absorber or Kerr medium that mediates the nonlinear interaction.

[0048] Preferably, the optical nonlinear element, the first additional optical nonlinear element, and / or the second additional optical nonlinear element each have a nonlinear input / output characteristic, where the intensity of the emitted or coupled-out optical signal or electromagnetic radiation exhibits a nonlinear relationship depending on the sum of the intensities of the simultaneously input or coupled-in optical signals. For example, the nonlinear input / output characteristic may exhibit a sigmoid function or an S-shaped (bistable) curve.

[0049] In particular, the input / output characteristic may have a (critical) threshold for the sum of the intensities of simultaneously input or combined optical signals, such that a total intensity of simultaneously input optical signals less than the threshold results in only low or zero (0 signal) intensity of the emitted (emitted) optical signal, while a total intensity of simultaneously input optical signals greater than the threshold results in high intensity of the emitted optical signal. If the total intensity is greater than the threshold, the optical nonlinear element or its optical saturable absorber may become optically saturated.

[0050] Preferably, the intensity of the pump signal is selected or the optical nonlinear element is configured such that when the first optical signal and the second optical signal are associated with different logical states or have different intensities, the optical nonlinear element or its optical saturable absorber is optically saturated by interaction (and therefore does not completely cancel each other out through interference), and when the first optical signal and the second optical signal are associated with the same logical state or have the same intensities, they are not optically saturated (and therefore, in the case of a relative phase or a predetermined phase difference π, they completely cancel each other out through destructive interference).

[0051] The optical output signal may correspond to a portion of the pump signal that propagates or is transmitted through the optical nonlinear element and / or a portion of the pump signal that is not absorbed by the optical saturable absorber of the optical nonlinear element. In the case of optical saturation, the pump signal may pass almost completely through or propagate through the optical nonlinear element. The optical output signal may then correspond to a second logic state having a second intensity or a high intensity.

[0052] When the optical nonlinear element or its optical saturable absorber is not saturated, the pump signal may at least not pass through the optical nonlinear element completely, or not pass through at all. Alternatively, the pump signal may be nearly completely absorbed by the optical saturable absorber. The optical output signal may then correspond to a first logic state having a first intensity or a low intensity.

[0053] Preferably, the intensity of the first additional pump signal is selected or the first additional optical nonlinear element is configured such that when the first logic input signal is associated with a first logic state, the first additional optical nonlinear element or its optical saturable absorber is not optically saturated by the interaction, and is optically saturated when the first logic input signal is associated with a second logic state.

[0054] The first optical signal may correspond to a portion of the first additional pump signal propagating or transmitted through the first additional optical nonlinear element and / or a portion of the first additional pump signal not absorbed by the optical saturable absorber of the first additional optical nonlinear element. In the case of optical saturation, the first additional pump signal may pass almost completely through or propagate through the first additional optical nonlinear element. And, the first optical signal may correspond to a second logic state having a second intensity or a high intensity.

[0055] When the first additional optical nonlinear element or its optical saturable absorber is not saturated, the first additional pump signal may not pass through at least the first additional optical nonlinear element at all, or may not pass through at all. Alternatively, the first additional pump signal may be nearly completely absorbed by the optical saturable absorber. The first optical signal may then correspond to a first logic state having a first intensity or a low intensity.

[0056] It is preferable that the intensity of the second additional pump signal is selected or the second additional optical nonlinear element is configured so that the second additional optical nonlinear element or its optical saturable absorber is not optically saturated by the interaction when the second logic input signal is associated with a first logic state, and has a first intensity or is optically saturated corresponding to a zero signal when the second logic input signal is associated with a second logic state.

[0057] The second optical signal may correspond to a portion of the second additional pump signal that is propagated or transmitted through the second additional optical nonlinear element and / or a portion of the second additional pump signal that is not absorbed by the optical saturable absorber of the second additional optical nonlinear element. In the case of optical saturation, the second additional pump signal may pass almost completely through or propagate through the second additional optical nonlinear element. The second optical signal may correspond to a second logic state having a second or high intensity.

[0058] If the second additional optical nonlinear element or its optical saturable absorber is not saturated, the second additional pump signal may not pass through at least the second additional optical nonlinear element at all, or may not pass through at all. Alternatively, the second additional pump signal may be nearly completely absorbed by the optical saturable absorber. The second optical signal may then correspond to a first logic state having a first intensity or a low intensity.

[0059] graphene Preferably, the optical nonlinear element, the first additional optical nonlinear element and / or the second additional optical nonlinear element have or are formed from graphene or a graphene layer as an optical saturable absorber or medium mediating the respective nonlinear interactions.

[0060] For example, the Fermi level of graphene can be set or selected, e.g., by doping, so that graphene has a particularly strong or effective detectable absorber. On the other hand, the relaxation time of graphene's saturable absorber can be made sufficiently small, allowing fast switching. On the other hand, the relaxation time of graphene's saturable absorber can also be made sufficiently large to provide a sufficiently long time window for the pump signal, the first additional pump signal, and / or the second additional pump signal, so that, for example, the optical nonlinear element, the first additional optical nonlinear element, and / or the second additional optical nonlinear element can be passed through, or propagated through, the first logic input signal and the second logic input signal (or the first optical signal and the second optical signal) largely independent of the pulse shape, or as soon as they are optically saturated. This also allows for the phase, pulse shape, and / or intensity of the first optical signal, the second optical signal, and / or the logic output signal or logic level to be effectively recovered, thus further contributing to effective scalability.

[0061] The relaxation time of graphene's saturable absorber can be less than 1 picosecond, thus enabling clock rates of optical logic gates greater than 1 THz.

[0062] The use of graphene or graphene layers also enables integrated and / or CMOS-based structures of optical logic gates or optical nonlinear elements, or first additional optical nonlinear elements and / or second additional optical nonlinear elements.

[0063] Hereinafter, the graphene layer of the first additional optical nonlinear element may be referred to as the first graphene layer or the first additional graphene layer. Hereinafter, the graphene layer of the second additional optical nonlinear element may be referred to as the second graphene layer or the second additional graphene layer.

[0064] The lengths of the graphene layer, the first additional graphene layer, and / or the second additional graphene layer may be different and may be flexibly configured such that the threshold and / or propagation loss of each of the saturable absorbers corresponds to a target specification for the strength of the signal coupled out of each graphene layer, thereby flexibly configuring different logic functions of the optical logic gate. The lengths may be selected to avoid critical points, e.g., bistable phases.

[0065] The length of the graphene layer, the first additional graphene layer, and / or the second additional graphene layer may be 1 to 50 micrometers, preferably 5 to 15 micrometers. Therefore, the total intensity or power of the supply of the pump signals (total intensity of the pump signal, the first additional pump signal, and the second additional pump signal) may be less than 100 mW. The intensity of the first logic input signal and / or the second logic input signal may be less than 20 mW.

[0066] Waveguide The optical logic gate may further comprise at least one waveguide for receiving the pump signal, the optical output signal, and / or the first and second optical signals that have been phase shifted and interfered by the interference means.

[0067] At least one waveguide may extend through and / or connect to the optical nonlinear element, and at least one waveguide may be connected or coupled at one end to a pump or light providing and / or pump signal combining element that provides a pump signal, and at the other end to a logic output that provides a logic output signal.

[0068] Preferably, the pump signal can propagate in a first direction, and the first and second optical signals, whose phases have been shifted by the phase modulation means and interfered by the interference means, can propagate in at least one waveguide through an optical nonlinear element in a second direction opposite to the first direction, or can be coupled to the optical nonlinear element by such propagation.

[0069] At least one waveguide may be configured to receive a pump signal (e.g., a pump signal from a pump source) propagating in a first direction and to fully or at least partially couple it to the optical nonlinear element or its optical saturable absorber or its Kerr medium.

[0070] At least one waveguide may further be configured to receive the phase-shifted, interfered / interfered first and second optical signals propagating in a second direction opposite to the first direction, and to fully or at least partially couple them to the optical nonlinear element, its optical saturable absorber or its Kerr medium.

[0071] At least one waveguide may be further configured to receive an optical output signal, where the optical output signal may be coupled out of the optical nonlinear element, its optical saturable absorber or its Kerr medium, propagate in a first direction, and / or send it to a logic output.

[0072] Additional Waveguides a) Connecting waveguide The optical logic gate may further comprise a first connecting waveguide and / or a second connecting waveguide.

[0073] The first connecting waveguide may extend through the first additional optical nonlinear element and connect it to the phase modulation means, the interference means, the optical nonlinear element and / or at least one waveguide, wherein the first connecting waveguide may be configured to receive the first additional pump signal and couple it to the first additional optical nonlinear element or its optical saturable absorber, and / or may be configured to receive the first optical signal and send it to the phase modulation means, the interference means, the optical nonlinear element and / or at least one waveguide.

[0074] The first connecting waveguide may be configured to receive a first additional pump signal and / or a first optical signal propagating in a first direction.

[0075] The second connecting waveguide may extend through the second additional optical nonlinear element and connect it to the phase modulation means, the interference means, the optical nonlinear element and / or at least one waveguide, and the second connecting waveguide may be configured to receive a second additional pump signal and couple it to the second additional optical nonlinear element or its optical saturable absorber, and / or may be configured to receive a second optical signal and send it to the phase modulation means, the interference means, the optical nonlinear element and / or at least one waveguide.

[0076] The second connecting waveguide may be configured to receive a second additional pump signal and / or a second optical signal propagating in the first direction.

[0077] The phase modulation means and / or the interference means may be arranged on or connected / coupled to the first connecting waveguide and / or the second connecting waveguide.

[0078] b) Input waveguide The optical logic gate may further comprise a first logic input for providing a first (optical) logic input signal. The first logic input may be connected or coupled to a first additional optical nonlinear element via a first input waveguide. The first input waveguide may be configured to receive the first logic input signal (from the first logic input) and to couple the first logic input signal to the first additional optical nonlinear element.

[0079] The first input waveguide can be connected to the first connecting waveguide via a first waveguide connecting element, which can be disposed between the first additional optical nonlinear element, the phase modulation means or the first heating element and the interference means or the optical nonlinear element.

[0080] The first waveguide connection element may be configured to propagate at least a portion of the first logic input signal, or a signal present at the first logic input in the first input waveguide coming from the first logic input, to the first connecting waveguide and also to propagate it to the first additional nonlinear element.

[0081] If the first waveguide connection element propagates only a portion of the signal present at the first logic input to the first connection waveguide, only this portion may be understood as the first logic input signal for the purposes of this application.

[0082] The first waveguide connection element may be configured to propagate the first optical signal or part of the signal coupled from the first additional optical nonlinear element as a result of nonlinear interactions in the first connection waveguide from the first additional optical nonlinear element and / or the phase modulation means and / or the first heating element back to the first connection waveguide and propagate it further to the interference means and / or the optical nonlinear element.

[0083] If the first waveguide connection element passes only a portion of the signal coupled out as a result of the nonlinear interaction from the first additional optical nonlinear element to the first connecting waveguide toward the optical nonlinear element, only this portion may be understood as the first optical signal for the purposes of this application.

[0084] The first input waveguide may extend through the first additional optical nonlinear element and / or may be coupled to the first additional optical nonlinear element or its optical saturable absorber and / or may extend away from and to the first connecting waveguide and / or the first additional pump waveguide.

[0085] For example, a first logic input signal propagating in a second direction opposite to the first direction in the first input waveguide or the first connecting waveguide can be coupled to a first additional optical nonlinear element.

[0086] The first input waveguide may be connected to and / or may extend through a phase modulation means, for example to shift the phase of the first logic output signal.

[0087] The optical logic gate may further comprise a second logic input for providing a second (optical) logic input signal. The second logic input may be connected or coupled to a second additional optical nonlinear element via a second input waveguide. The second input waveguide may be configured to receive the second logic input signal (from the second logic input) and couple the second logic input signal to the second optical nonlinear element.

[0088] The second input waveguide can be connected to the second connecting waveguide via a second waveguide connecting element, which can be disposed between the second additional optical nonlinear element, the phase modulation means or the second heating element and the interference means or the optical nonlinear element.

[0089] The second waveguide connection element may be configured to propagate at least a portion of a signal present at the second logic input in the second input waveguide from the second logic input signal or the second logic input to the second connecting waveguide and further propagate it to the second additional nonlinear element.

[0090] If the second waveguide connection element propagates only a portion of the signal present at the second logic input to the second connection waveguide, only this portion may be understood as the second logic input signal within the meaning of the present application.

[0091] The second waveguide connection element may be configured to propagate the second optical signal or a portion of the signal coupled out from the second additional optical nonlinear element as a result of a nonlinear interaction in the second connection waveguide and coming from the second additional optical nonlinear element and / or the phase modulation means and / or the second heating element back into the second connection waveguide and propagate it further to the interference means and / or the optical nonlinear element.

[0092] If the second waveguide connection element only propagates a portion of the signal coupled out as a result of nonlinear interactions within the second connection waveguide from the second additional optical nonlinear element towards the optical nonlinear element, only this portion may be understood as the second optical signal within the meaning of the present application.

[0093] The second input waveguide may extend through the second additional optical nonlinear element and / or connect to the second additional optical nonlinear element or its optical saturable absorber and / or extend away from the second connecting waveguide and / or the second additional pump waveguide.

[0094] For example, a second logic input signal propagating in a second direction opposite to the first direction in the second input waveguide or the second connecting waveguide can be coupled to a second additional optical nonlinear element.

[0095] The second input waveguide may further be connected to and / or extend through a phase modulation means, for example to shift the phase of the second logic output signal.

[0096] c) Output waveguide The optical logic gate may further comprise an output waveguide that couples out and receives the logic output signal from the optical nonlinear element and propagates or passes the logic output signal to the logic output.

[0097] The output waveguide can directly connect the optical nonlinear element to the logic output, or the output waveguide can connect or couple the optical nonlinear element to the interferometric means and / or the interferometric means to the logic output.

[0098] The output waveguide may also correspond to or be contiguous with a portion or section of at least one waveguide.

[0099] d) Pump supply The optical logic gate may further comprise a pump waveguide for receiving a pump signal and coupling the pump signal to the optical nonlinear element. The pump waveguide may be a portion or section of, or may be contiguous with, at least one of the waveguides.

[0100] The pump waveguide, the at least one waveguide and / or the output waveguide may be a waveguide and a part / section of the same waveguide, respectively.

[0101] The optical logic gate may further comprise a first additional pump waveguide for receiving a first additional pump signal and coupling the first additional pump signal to the first additional optical nonlinear element, which may be part or section of or continuous with the first connecting waveguide (e.g., in the first additional optical nonlinear element).

[0102] The optical logic gate may further comprise a second additional pump waveguide for receiving a second pump signal and for coupling the second additional pump signal to the second additional optical nonlinear element, which may be part or section of or continuous with the second connecting waveguide (e.g., in the second additional optical nonlinear element).

[0103] The optical logic gate may also comprise an (optical) pump signal supply or an optical supply for supplying the pump signal, the first additional pump signal, the second additional pump signal and / or the total pump signal.

[0104] The optical logic gate can also include a pump connection element configured to split an overall pump signal provided by the pump signal supply into a pump signal, a first additional pump signal, and a second additional pump signal, pass the pump signal to the pump waveguide, pass the first additional pump signal to the first additional pump waveguide, and send the second additional pump signal to the second additional pump waveguide. For example, the pump connection element can be configured as a multi-mode interferometer having one input and three outputs.

[0105] The length of the pump waveguide, or the length of the optical path along which the pump signal propagates from the pump connection element to the optical nonlinear element, can be longer than the length of the first additional pump waveguide, or the length of the optical path along which the first additional pump signal propagates from the pump connection element to the first additional optical nonlinear element, and the length of the second additional pump waveguide, or the length of the optical path along which the second additional pump signal propagates from the pump connection element to the second additional optical nonlinear element, can be longer than the length of the first additional pump waveguide, or the length of the optical path along which the second additional pump signal propagates from the pump connection element to the second additional optical nonlinear element.

[0106] A waveguide in the sense of the present application may be a bidirectional waveguide, and thus the direction or propagation direction in the waveguide may be defined by the sign of the respective occupied Fourier mode (k-mode).

[0107] CMOS The optical logic gates may comprise or be integrated into a CMOS-based layer structure.

[0108] The graphene layer and at least one waveguide of the optical nonlinear element can be integrated into a CMOS-based layer structure and can be arranged to overlap or overlap each other to ensure electromagnetic coupling.

[0109] The graphene layer can be disposed in or correspond to a first layer of a CMOS-based layer structure. The at least one waveguide can be disposed in a second layer above or below the graphene layer. The first and second layers can also be disposed relative to one another such that the graphene layer and the at least one waveguide contact each other.

[0110] The graphene layers can be configured as stripes, and the longitudinal axes of the graphene stripes and the at least one waveguide can extend parallel within the optical nonlinear element. The graphene or graphene stripes can cover at least one waveguide within the optical nonlinear element along its longitudinal axis.

[0111] The length of the graphene stripe can be selected so that the threshold, propagation loss, and / or intensity of the optical output signal of the optical nonlinear element correspond to target values. Thus, the threshold, saturable absorption, and / or propagation loss points can be flexibly adapted to other configurations or designs of the optical logic gate. For example, the target values ​​can be selected so that the optical logic gate does not operate within a critical point, e.g., the bistable region, of the graphene or optical nonlinear element.

[0112] The features or embodiments mentioned regarding the configuration of the optical nonlinear element can be similarly applied or adapted to the first other optical nonlinear element and the second other optical nonlinear element.

[0113] The first other graphene layer and the first connecting waveguide and / or the first input waveguide may be integrated into a CMOS-based layer structure and overlap or are superimposed on each other.

[0114] The first other graphene layer of the first other optical nonlinear element may cover and / or be electromagnetically coupled to the first connecting waveguide and / or the first input waveguide.

[0115] Preferably, the first other graphene layer of the optical saturable absorber, Kerr medium and / or first other optical nonlinear element covers the first input waveguide, the first other pump waveguide and / or the first connecting waveguide.

[0116] The second other graphene layer and the second connecting waveguide and / or the second input waveguide may be incorporated into a CMOS-based layer structure and overlap or are superimposed on each other.

[0117] The second additional graphene layer of the second additional optical nonlinear element may cover and / or be electromagnetically coupled to the second connecting waveguide and / or the second input waveguide.

[0118] Preferably, the second additional graphene layer of the optical saturable absorber, Kerr medium and / or second additional optical nonlinear element covers the second input waveguide, the second additional pump waveguide and / or the second connecting waveguide.

[0119] Interference methods The interferometer may be a multimode interferometer. The multimode interferometer as the interferometer may be switched or arranged outside the optical nonlinear element and the phase modulation means and / or between the optical nonlinear element and the phase modulation means.

[0120] The multimode interferometer or interference means may further be configured to interfere with the first optical signal and the second optical signal from the phase modulation means, the relative phases of which have been shifted, and then propagate the corresponding interfered superimposed signal or interfering superimposed signals towards the optical nonlinear element into at least one waveguide.

[0121] The interferometric means may be configured to propagate the optical output signal in at least one waveguide and route it from the optical nonlinear element to a logic output.

[0122] The interferometric means may be part of an optical nonlinear element or a region of an optical nonlinear element, for example the interferometric means may be configured as a waveguide connecting element.

[0123] For example, the at least one waveguide may comprise a first waveguide for receiving the first optical signal, a second waveguide for receiving the second optical signal, and a third waveguide for receiving the pump signal and / or for receiving the optical output signal.

[0124] The first waveguide, the second waveguide, and / or the third waveguide may each extend apart from one another through the optical nonlinear element, or may extend apart next to the optical nonlinear element. The third waveguide may be disposed in the optical nonlinear element between the first waveguide and the second waveguide.

[0125] In this case, the interference means can be formed as a waveguide connection element by a region of the optical nonlinear element, where the first waveguide and the second waveguide are respectively connected to or arranged in proximity to a third waveguide, and the first optical signal and the second optical signal, the relative phases of which have been shifted, are interfered with or superimposed on each other in the third waveguide. The superimposed signal thus formed can be coupled to the optical nonlinear element, its optical saturable absorber, or its Kerr medium.

[0126] The graphene layer of the optical nonlinear element can completely cover at least the third waveguide, and the graphene layer can be used to ensure simultaneous interaction of the pump signal with the first and second optical signals whose phases have been shifted and which have been interfered with by the interference means. The graphene layer of the optical nonlinear element can further cover the first and second waveguides.

[0127] The first waveguide may for example correspond to or be continuous with a part / section of the first connecting waveguide.

[0128] The second waveguide may for example correspond to or be continuous with a part / section of the second connecting waveguide.

[0129] The pump waveguide and / or the output waveguide may each correspond to or be contiguous with a portion / section of a third waveguide.

[0130] Phase Modulation Means The phase modulation means may comprise at least one heating element, which may be suitable for shifting or changing the phase of the first and / or second optical signals such that the relative phase of the first and / or second optical signals corresponds to a predetermined phase difference. To this end, the at least one heating element may be arranged on or thermally coupled to the first and / or second connecting waveguide.

[0131] The phase modulation means may be arranged or connected between the signal supply means or the first additional optical nonlinear element and / or the second additional optical nonlinear element and the interference means and / or the optical nonlinear element. The phase modulation means may be part of the signal supply means.

[0132] Additionally, at least one heating element may be disposed on or thermally coupled to the first input waveguide or the second input waveguide.

[0133] Advantageously, the at least one heating element comprises a first heating element for modifying the phase of the first optical signal and a second heating element for modifying the phase of the second optical signal. The first heating element can then be arranged on or thermally coupled to the first connecting waveguide, and the second heating element can be arranged on or thermally coupled to the second connecting waveguide. This allows for very precise adjustment of the phase difference between the first and second optical signals, or for corresponding fine adjustment.

[0134] Preferably, the phase modulation means, the at least one heating element and / or the first heating element are integrated together with the first additional optical nonlinear element, the first connecting waveguide and / or the first input waveguide into a CMOS-based layer structure.

[0135] The phase modulation means, the at least one heating element and / or the second heating element may be integrated into a CMOS-based layer structure together with the second additional optical nonlinear element, the second connecting waveguide and / or the second input waveguide.

[0136] Instead of a heating element, at least one electro-optical modulator can also be used as the phase modulation means.

[0137] method The present invention also relates to a method of operating an optical logic gate as described above, said method comprising the steps of: providing, by a signal providing means, a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal, wherein the phases of the first optical signal and the second optical signal are the same; shifting the relative phase of the first optical signal and the second optical signal by a predetermined phase difference using a phase modulation means; after the transition of the relative phase, interfering the first optical signal with the second optical signal by an interference means; The method includes a step of using the optical nonlinear element to cause the pump signal to interact with the first optical signal and the second optical signal interfered by the interference means, and as a result of this nonlinear interaction, combining and outputting an optical output signal as a logic output signal from the optical nonlinear element.

[0138] This method may, for example, include, as an initial step: In a digital mode of operation, the method includes operating the optical logic gate using amplitude or intensity modulation, where the predetermined phase difference is π.

[0139] In digital operation mode, Associating a first logic state with a first magnitude of each of the first logic input signal, the second logic input signal, and the logic output signal; and associating a second logic state with a second magnitude of each of the first logic input signal, the second logic input signal, and the logic output signal, where the second magnitude is different from the first magnitude.

[0140] The association may be such that the logic output signal in response to the first logic input signal and the second logic input signal is the result of a logic XOR function.

[0141] The logic state of the first logic input signal may be conveyed to the first optical signal by the signal providing means, and the logic state of the second logic input signal may be conveyed to the second optical signal by the signal providing means.

[0142] In particular, if the first logic input signal and the second logic input signal have different magnitudes or are associated with different logic states, the phase of the logic output signal may always be the same regardless of the logic states to which the first logic input signal and the second logic input signal are respectively associated.

[0143] The intensity of the pump signal may be selected such that the optical nonlinear element or its optical saturable absorber is optically saturated by simultaneous interaction when the first logical input signal or optical signal and the second logical input signal or optical signal are associated with different logical states, and is not optically saturated when the first logical input signal or optical signal and the second logical input signal or optical signal are associated with the same logical state.

[0144] Prior to transitioning the relative phase of the first optical signal and the second optical signal, the method further comprises: interacting the first additional pump signal and the first logic input signal using a first additional optical nonlinear element, and coupling out a first optical signal from the first additional optical nonlinear element as a result of the nonlinear interaction, which interaction may occur simultaneously; The method includes using a second additional optical nonlinear element to interact with the second additional pump signal and the second logic input signal, and as a result of the interaction, coupling out a second optical signal from the second additional optical nonlinear element, wherein the interactions can occur simultaneously.

[0145] In this method, the intensity of the pump signal can be selected such that the optical nonlinear element or its optical saturable absorber is optically saturated by interaction when the first logic input signal and the second logic input signal are associated with different logic states, and is not optically saturated when the first logic input signal and the second logic input signal are associated with the same logic state.

[0146] The intensities of the first additional pump signal and / or the first logic input signal may be selected such that the first additional optical nonlinear element or its optically saturable absorber is optically saturated by the interaction when the first logic input signal is associated with the second logic state, and is not optically saturated when the first logic input signal is associated with the first logic state.

[0147] The intensities of the second additional pump signal and / or the second logic input signal may be selected such that the second additional optical nonlinear element or its optically saturable absorber is optically saturated by the interaction when the second logic input signal is associated with the second logic state, and is not optically saturated when the second logic input signal is associated with the first logic state.

[0148] Additional information The present invention provides optical logic gates and methods of operation that allow optical or electro-optical processors to operate efficiently and be scalable or perform corresponding arithmetic operations.

[0149] In particular, efficient input / output coupling is ensured, since light or optical signals do not need to flow directly from the logic input to the logic output. The relative modulation depth of an optical logic gate is also largely independent of the (absolute) strength of the signals provided at the first and second logic inputs.

[0150] The optical logic gate and its operating method according to the present invention may also be used in various optical or electro-optical circuits in the fields of network technology and measurement or sensor technology.

[0151] Furthermore, the present invention is applicable to a variety of optical logic input signals, which may correspond to classical or quasi-classical states of light or electromagnetic radiation, or even quantum states, i.e., individual photons or coherent signals with very weak intensities (e.g., corresponding microwave signals).

[0152] Furthermore, it should be noted that the term "light" in the sense of the present invention generally refers to electromagnetic radiation and should not be understood as limiting the frequency range of electromagnetic radiation used. For example, the input or output signals of an optical logic gate or its components, such as the signal supply means and / or the optical nonlinear element, may be microwave radiation or electromagnetic radiation in the THz range. For example, the optical nonlinear element may be formed of a superconducting circuit including at least one Josephson contact (microwave radiation) or a terahertz resonator or a terahertz metal. Therefore, the present invention can be applied and implemented in a wide range of the electromagnetic spectrum. [Brief explanation of the drawings]

[0153] An exemplary embodiment The optical logic gate and its method of operation will now be described in detail by way of example. [Figure 1] FIG. 1 shows a schematic diagram of an exemplary embodiment of an optical logic gate. [Figure 2] FIG. 2 shows a schematic diagram of another exemplary embodiment of an optical logic gate. [Figure 3] Figure 3 shows the logic truth table of the optical logic gate. [Figure 4] 4a, 4b and 4c show schematic cross-sectional views of a CMOS layer structure with graphene and waveguides. [Figure 5] 5a, 5b and 5c show schematic cross-sections of a CMOS layer structure with graphene and two waveguides. [Figure 6] 6a, 6b and 6c show schematic cross-sections of a CMOS layer structure with graphene and three waveguides. [Figure 7] Figure 7a shows a schematic cross-section of a CMOS layer structure with a phase modulation means and a waveguide, and Figure 7b shows a schematic cross-section of a CMOS layer structure with a phase modulation means and two waveguides. [Figure 8] 8a shows the nonlinear input / output characteristics of the optical nonlinear element, and FIG. 8b shows the transmittance of the optical nonlinear element. DETAILED DESCRIPTION OF THE INVENTION

[0154] The optical logic gate shown in Figure 1 comprises signal supply means 1.1, 1.2 for supplying a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal, the phases of the first and second optical signals being the same or identical (modulo 2π).

[0155] The optical logic gate further comprises phase modulation means 2.1, 2.2 for shifting the phase of the first optical signal by a predetermined phase difference relative to the phase of the second optical signal.

[0156] The optical logic gate further comprises interference means 3 configured to cause the first and second optical signals, the phases of which have been shifted by the phase modulation means 2.1, 2.2, to interfere with each other.

[0157] The optical logic gate further comprises an optical nonlinear element 1.3 configured to interact with the pump signal and also configured to interact with the first and second optical signals whose phases have been shifted by the phase modulation means 2.1, 2.2 and interfered by the interference means 3, and configured to combine and output the optical output signal as a logic output signal as a result of this nonlinear interaction.

[0158] The signal supply means 1.1, 1.2 comprises a first additional optical nonlinear element 1.1 and a second additional optical nonlinear element 1.2.

[0159] The phase modulation means 2.1, 2.2 comprises a first heating element 2.1 and a second heating element 2.2.

[0160] The interferometer means 3 is configured as a multimode interferometer and is connected on one side between the first heating element 2.1 and the second heating element 2.2 and on the other side to the optical nonlinear element 1.3.

[0161] The first connecting waveguide C1 connects or couples the first additional optical nonlinear element 1.1, the first heating element 2.1 and the interferometric means 3. The second connecting waveguide C2 connects or couples the second additional optical nonlinear element 1.2 to the second heating element 2.2 and the interferometric means 3.

[0162] The first input waveguide E1 connects or couples the first logic input IN1 to the first connection waveguide C1 via a first waveguide connection element 5.1, and the second input waveguide E2 connects or couples the second logic input IN2 to the second connection waveguide C2 via a second waveguide connection element 5.2.

[0163] At least one waveguide W connects or couples the interference means 3 to and extends through the optical nonlinear element 1.3. In this example, the at least one waveguide W consists of a single waveguide, hereafter referred to as the through waveguide W.

[0164] An output waveguide Wa connects or couples the interferometer means 3 to a logic output OUT.

[0165] A pump signal supply P is connected or coupled to the pump waveguide P3, the first additional pump waveguide P1 and the second additional pump waveguide P2 via a pump connection element 4. The pump connection element 4 is likewise configured as a multimode interferometer.

[0166] The pump signal feed provides a total pump signal, which is split by pump connection element 4 into a pump signal, a first additional pump signal, and a second additional pump signal. The pump signal is received by pump waveguide P3 and propagates to or couples with through waveguide W and optical nonlinear element 1.3. The first additional pump signal is received by pump waveguide P1 and propagates to or couples with first additional optical nonlinear element 1.1. The second additional pump signal is received by second additional pump waveguide P2 and propagates to or couples with second additional optical nonlinear element 1.2.

[0167] The first additional pump waveguide P1 is continuous with the first connecting waveguide C1, and the second pump waveguide is continuous with the second connecting waveguide C2.

[0168] The first logic input IN1 provides a first logic input signal, which is received by the first input waveguide E1, propagates via the first waveguide connection element 5.1 to the first connection waveguide C1, and propagates or couples to the first additional optical nonlinear element 1.1 via the first heating element 2.1.

[0169] The second logic input IN2 provides a second logic input signal, which is received by the second input waveguide E2 and propagates via the second waveguide connection element 5.2 to the second connection waveguide C2 and propagates or couples to the second additional optical nonlinear element 1.2 via the second heating element 2.2.

[0170] Thus, the first logic input signal and the first additional pump signal propagate in opposite directions (positive and negative k modes, respectively) in the first connecting waveguide C1 and the first additional optical nonlinear element 1.1, and the second logic input signal and the second additional pump signal also propagate in opposite directions (positive and negative k modes, respectively) in the second connecting waveguide C2 and the second additional optical nonlinear element 1.2.

[0171] The first additional optical nonlinear element 1.1 has a first additional graphene layer 1.1.1 as an optical saturable absorber. The first additional graphene layer 1.1.1 is configured as a stripe that extends along its longitudinal axis parallel to, above, and covering the first connecting waveguide C1. The first additional pump signal and the first logic input signal are coupled to the first additional graphene layer 1.1.1 by the first connecting waveguide C1 in the first additional optical nonlinear element 1.1 and interact simultaneously.

[0172] As a result of this nonlinear interaction, the first additional optical nonlinear element 1.1 couples and feeds a first optical signal into the first connecting waveguide C1. The first optical signal corresponds to the portion of the first additional pump signal that is not absorbed by the first additional graphene layer 1.1.1 or corresponds to the portion of the first additional pump signal that is transmitted through the first additional optical nonlinear element 1.1. The phase of the first optical signal corresponds to the phase of the first additional pump signal.

[0173] The second additional optical nonlinear element 1.2 has a second additional graphene layer 1.2.1 as an optical saturable absorber. The second additional graphene layer 1.2.1 is configured as a stripe that extends along its longitudinal axis parallel to and covers the second connecting waveguide C2. The second additional pump signal and the second logic input signal are coupled to the second additional graphene layer 1.2.1 by the second connecting waveguide C2 of the second additional optical nonlinear element 1.2 and interact simultaneously.

[0174] As a result of this nonlinear interaction, the second additional optical nonlinear element 1.2 couples and feeds a second optical signal into the second connecting waveguide C2. The second optical signal corresponds to the portion of the second additional pump signal that is not absorbed in the second additional graphene layer 1.2.1 or corresponds to the portion of the second additional pump signal that passes through the second additional optical nonlinear element 1.2. The phase of the second optical signal corresponds to the phase of the second additional pump signal.

[0175] The first optical signal propagates in the first connecting waveguide C1 to the first heating element 2.1, and the second optical signal propagates to the second heating element 2.2. The first 2.1 heating element and the second 2.2 heating element are configured to adjust a predetermined phase difference or relative phase between the first and second optical signals. The predetermined phase difference or relative phase is π. The first and second optical signals, shifted in their relative phase, propagate to the interference element 3 via the first 5.1 waveguide connecting element and the second 5.2 waveguide connecting element.

[0176] The interference element 3 superimposes or interferes the first and second optical signals and directs the corresponding superimposed signal to the through-hole waveguide W, where it further propagates to the optical nonlinear element 1.3. The superimposed signal or the first and second optical signals, whose phases have been shifted and interfered by the interference element 3, and the pump signal propagate in opposite directions (positive and negative k modes, respectively) through the through-hole waveguide W and the optical nonlinear element 1.3.

[0177] The optical nonlinear element 1.3 comprises a graphene layer 1.3.1 as an optically saturable absorber, configured as a stripe that extends along its longitudinal axis parallel to and covers a through-guide W. The pump signal and the superimposed signal are coupled to and simultaneously interact with the graphene layer 1.3.1 by the through-guide W of the optical nonlinear element 1.3.

[0178] As a result of this nonlinear interaction, the graphene layer 1.3.1 or the optical nonlinear element 1.3 couples the optical output signal into the through waveguide W, where it propagates towards the interferometric means 3 and is further guided by the interferometric means 3 to the output waveguide Wa and the logic output OUT.

[0179] The optical output signal is substantially identical to the logical output signal (excluding propagation losses in the waveguide etc.) and corresponds to the portion of the pump signal that is not absorbed in the graphene layer 1.3.1 or that passes through the optical nonlinear element 1.3. The phase of the logical output signal corresponds to the phase of the pump signal.

[0180] The waveguide shown in Figure 1 is made of silicon nitride.

[0181] The reference numerals shown in FIG. 1 are used in the following figures.

[0182] The example of an optical logic gate shown in Figure 2 differs from the example shown in Figure 1 in that the first input waveguide E1 extends away from the first connecting waveguide 1 through a first additional optical nonlinear element 1.1 and a first heating element 2.1. A first additional graphene layer 1.1.1 covers both the first input waveguide E1 and the first connecting waveguide C1 at the first additional optical nonlinear element 1.1.

[0183] The second input waveguide E2 extends away from the second connecting waveguide C2 via the second additional optical nonlinear element 1.2 and the second heating element 2.2. A second additional graphene layer 1.2.1 covers both the second input waveguide E2 and the second connecting waveguide C2 in the second additional optical nonlinear element 1.2.

[0184] In Figure 2, at least one waveguide W includes a first waveguide W1, a second waveguide W2, and a third waveguide W3. A first connecting waveguide C1 is continuous with the first waveguide W1. A second connecting waveguide C2 is continuous with the second waveguide W2. A pump waveguide P3 is continuous with the third waveguide W3. The third waveguide W3 is continuous with the output waveguide Wa.

[0185] The first waveguide W1, the second waveguide W2, and the third waveguide W3 extend away from each other through the optical nonlinear element 1.3, and the third waveguide W3 is disposed between the first waveguide W1 and the second waveguide W2 in the optical nonlinear element 1.3.

[0186] The interference means 3 is a part or region of the optical nonlinear element 1.3 as a waveguide connecting element.

[0187] In this region, the first waveguide W1 and the second waveguide W2 each connect to the third waveguide W3 or extend adjacent to the third waveguide W3, so that the first optical signal and the second optical signal, which have been shifted in terms of their relative phases, interfere with or are superimposed on each other in the third waveguide W3.

[0188] In this region, the graphene layer 1.3.1 of the optical nonlinear element 1.3 also covers the first waveguide W1, the second waveguide W2 and the third waveguide W3, allowing the pump signal and the first and second optical signals whose phases have been shifted and interfered by the interference means 3 to interact with the graphene layer 1.3.1.

[0189] The optical logic gates shown in the examples of Figures 1 and 2 operate in a digital mode of operation: the first and second logic states are encoded using amplitude or intensity modulation.

[0190] A first logic state having a bit value of 0 is associated with the first and second logic input signals and the logic output signal when they each have a first strength, and a second logic state having a bit value of 1 is associated with the first and second logic input signals and the logic output signal when they each have a second strength, where the second strength of the signals is greater than the first strength of the signals.

[0191] The signal supplying means 1.1, 1.2 and the optical nonlinear element 1.3 are configured to correlate the strength of the logic output signal at the logic output OUT with the respective strengths of the first and second logic input signals at the first and second logic inputs IN1 and IN2, such that the logic output signal in response to the first and second logic input signals is the result of a logical XOR function.

[0192] The intensities of the first additional pump signal and the first additional graphene layer 1.1.1 are configured such that the first additional graphene layer 1.1.1 or the first additional optical nonlinear element 1.1 is not optically saturated when the first logic input signal has a first intensity of the first logic input signal or corresponds to a first logic state (bit value 0). In particular, when the first logic input signal corresponds to the first logic state, the total intensity, i.e., the sum of the intensities of the first additional pump signal and the first logic input signal, is less than the threshold of the first additional graphene layer 1.1.1. In this case, the intensity of the coupled-out first optical signal or the intensity of the supplied first optical signal is similarly low, corresponding to a 0 signal. The first optical signal then has a first intensity of the first optical signal or is associated with a first logic state (bit value 0).

[0193] The intensities of the first additional pump signal and the first additional graphene layer 1.1.1 are further configured such that the first additional graphene layer 1.1.1 or the first additional optical nonlinear element 1.1 is optically saturated when the first logic input signal has a second intensity of the first logic input signal or corresponds to a second logic state (bit value 1). In particular, the total intensity, i.e., the sum of the intensities of the first additional pump signal and the first logic input signal, is greater than the threshold of the first additional graphene layer 1.1.1 when the first logic input signal corresponds to the second logic state. In this case, the intensity of the coupled-out first optical signal or the supplied first optical signal is large and does not correspond to a 0 signal. In this case, the first optical signal has a second intensity of the first optical signal or corresponds to a second logic state (bit value 1).

[0194] The intensities of the second additional pump signal and the second additional graphene layer 1.2.1 are configured such that the second additional graphene layer 1.2.1 or the second additional optical nonlinear element 1.2 is not optically saturated when the second logic input signal has a first intensity of the second logic input signal or corresponds to a first logic state (bit value 0). In particular, the total intensity, i.e., the sum of the intensities of the second additional pump signal and the second logic input signal, is less than the threshold of the second additional graphene layer 1.2.1 when the second logic input signal corresponds to the first logic state. In this case, the intensity of the coupled-out or supplied second optical signal is similarly low or corresponds to a 0 signal. The second optical signal has a first intensity of the second optical signal or is associated with a first logic state (bit value 0).

[0195] The intensities of the second additional pump signal and the second additional graphene layer 1.2.1 are further configured such that the second additional graphene layer 1.2.1 or the second additional optical nonlinear element 1.2 is optically saturated when the second logic input signal has a second intensity of the second logic input signal or corresponds to a second logic state (bit value 1). When the second logic input signal corresponds to the second logic state, the total intensity, i.e., the sum of the intensities of the second additional pump signal and the second logic input signal, is greater than the threshold of the second additional graphene layer 1.2.1. In this case, the intensity of the coupled-out or supplied second optical signal is large or does not correspond to a 0 signal. The second optical signal has a second intensity of the second optical signal or is associated with a second logic state (bit value 1).

[0196] The nonlinear interaction mediated by the first and second additional graphene layers 1.1.1 and 1.2.1 is phase independent. Therefore, the logic states of the first and second logical input signals are transferred by the signal providing means 1.1, 1.2 to the first and second optical signals, respectively, with the same phase regardless of the phase of the first and second logical input signals. This allows for accurate and efficient transition of the relative phase by the first and second heating elements 2.1, 2.2.

[0197] After fixing or shifting the relative phase of the first and second optical signals by the first heating element 2.1 and the second heating element 2.2, the first and second optical signals arrive at the interference means 3 simultaneously, whereby the first and second optical signals interfere or are superimposed, and if the first and second optical signals are associated with the same logic state, the superimposed signal corresponds to a 0 signal (total destructive interference), and the superimposed signal itself is associated with a first logic state (low intensity or 0 signal) (bit value 0).

[0198] If the first and second optical signals are associated with different logic states, the superimposed signal does not correspond to a 0 signal. In one embodiment, the signal providing means 1.1, 1.2 are configured such that the first intensity of the first and second optical signals, respectively, corresponds to a 0 signal (first logic state). The superimposed signal then corresponds exactly to the first or second optical signal corresponding to a second logic state of high intensity. The superimposed signal itself then corresponds to the second logic state (high intensity) (bit value 1).

[0199] The superimposed signal is then coupled simultaneously with the pump signal into the optical nonlinear element 1.3 or its graphene layer 1.3.1.

[0200] The intensities of the pump signal and the graphene layer 1.3.1 are configured such that the graphene layer 1.3.1 or the optical nonlinear element 1.3 is not optically saturated when the superimposed signal corresponds to a first logic state (bit value 0). In particular, the total intensity, i.e. the sum of the intensities of the pump signal and the superimposed signal, is less than the threshold of the graphene layer 1.3.1 or the optical nonlinear element 1.3 when the superimposed signal corresponds to the first logic state. In this case, the intensity of the combined optical output signal is likewise low or corresponds to a zero signal. The optical output signal then has a first intensity of the optical output signal or is associated with the first logic state (bit value 0).

[0201] The intensities of the pump signal and the graphene layer 1.3.1 are further configured such that the graphene layer 1.3.1 or the optical nonlinear element 1.3 is optically saturated when the superimposed signal corresponds to a second logic state (bit value 1). The total intensity, i.e., the sum of the intensities of the pump signal and the superimposed signal, is greater than the threshold of the graphene layer 1.3.1 or the optical nonlinear element 1.3 when the superimposed signal corresponds to the second logic state. In this case, the intensity of the combined output optical signal is greater or does not correspond to a 0 signal. The optical output signal then has a second intensity of the optical output signal or is associated with the second logic state (bit value 1).

[0202] FIG. 3 shows a logical truth table corresponding to the logical XOR function described above.

[0203] The first column corresponds to the logic states or bit values ​​of the first logic input signal at the first logic input IN1. The second column corresponds to the logic states or bit values ​​of the second logic input signal at the second logic input IN2. The third column corresponds to the logic states or bit values ​​of the optical output signal or logic output OUT. The fourth column corresponds to the phase of the logic output signal.

[0204] The phase φ of the logic output signal is always the same regardless of the logic states of the first and second logic input signals, respectively. The phase φ corresponds to the phase of the pump signal.

[0205] This greatly enhances the modularity and scalability of optical logic gates.

[0206] Figures 4, 5 and 6 show schematic cross-sections of optical logic gates with a CMOS layer structure, where a graphene layer (hatched areas) covers one, two or three waveguides (black areas), respectively.

[0207] The graphene layer 1.3.1 as part of the optical nonlinear element 1.3, the first additional graphene layer 1.1.1 as part of the first additional optical nonlinear element 1.1, and the second additional graphene layer 1.2.1 as part of the second additional optical nonlinear element 1.2 are each configured as stripes, and the cross sections shown correspond to the normal plane to the layer plane of the graphene or to the longitudinal axis of the graphene stripes and waveguides shown.

[0208] 4a, 4b and 4c correspond to the exemplary embodiment shown in FIG.

[0209] In Figures 4a, 4b and 4c, the graphene layer 1.3.1 is arranged or connected to at least one waveguide or through-waveguide W. Similarly, the first other graphene layer 1.1.1 is arranged or connected to a first connecting waveguide C1. The second other graphene layer 1.2.1 is arranged or connected to a second connecting waveguide C2.

[0210] In FIG. 4a, a graphene layer 1.3.1 is arranged on at least one waveguide or through waveguide W, a first additional graphene layer 1.1.1 is arranged on a first connecting waveguide C1, and a second additional graphene layer 1.2.1 is arranged on a second connecting waveguide C2.

[0211] 4b, at least one waveguide or through waveguide W, a first connecting waveguide C1 and a second connecting waveguide C2 are respectively composed of upper and lower layers, and each graphene layer is disposed between the upper and lower layers and connected to the first and second partial layers.

[0212] In Fig. 4c, the graphene layer 1.3.1, the first additional graphene layer 1.1.1 and the second additional graphene layer 1.2.1 each consist of at least two sub-layers or layers of graphene with a corresponding passivation GP between the two sub-layers or layers, which may be made of or consist of silicon nitride or silicon oxide.

[0213] 5a, 5b and 5c correspond to schematic cross-sectional views of CMOS layer structures with graphene, similar to FIGS. 4a, 4b and 4c, respectively, but each with two waveguides according to the exemplary embodiment shown in FIG. 2. In this case, a first additional graphene layer 1.1.1 is arranged directly on the first connecting waveguide C1 and the first input waveguide E1. A second additional graphene layer 1.2.1 is arranged directly on the second connecting waveguide C2 and the second input waveguide E2.

[0214] Figures 6a, 6b and 6c correspond to schematic cross-sectional views of CMOS layer structures with graphene, similar to Figures 4a, 4b and 4c, respectively, but each having three waveguides according to the exemplary embodiment shown in Figure 2. In this case, the graphene layer 1.3.1 of the optical nonlinear element 1.3 is located directly on the first waveguide W1, the second waveguide W2 and the third waveguide W3.

[0215] 7a and 7b are schematic cross-sectional views of the phase modulation means 2.1, 2.2.

[0216] The first heating element 2.1 and the second heating element 2.2 have metal layers (dotted lines) that are electrically connected and can be heated by them. When power is applied, the electrical resistance of each metal layer heats the respective waveguide located underneath, causing a change in refractive index.

[0217] The cross section shown in FIG. 7 corresponds to the plane normal to the plane of the metal layer and the longitudinal axis of the waveguide.

[0218] FIG. 7a shows a cross section of a CMOS-based layer structure of the phase modulation means 2.1, 2.2 according to the embodiment shown in FIG.

[0219] The first heating element 2.1 has a metal layer arranged above and spaced apart from the first connecting waveguide C1, and is integrated with the first connecting waveguide C1 in the CMOS layer structure.

[0220] The second heating element 2.2 has a metal layer arranged above and spaced apart from the second connecting waveguide C2 and is integrated with the second connecting waveguide C2 in the CMOS layer structure.

[0221] FIG. 7b shows a cross-sectional view of the CMOS layer structure of the phase modulation means 2.1, 2.2 of the embodiment shown in FIG.

[0222] The first heating element 2.1 has a metal layer arranged above the first connecting waveguide C1 and the first input waveguide E1 and spaced apart from each other, and is integrated with the first connecting waveguide C1 and the first input waveguide E1 in the CMOS layer structure.

[0223] The second heating element 2.2 has a metal layer arranged above and spaced apart from the second connecting waveguide C2 and the second input waveguide E2, and is integrated with the second connecting waveguide C2 and the second input waveguide E2 in the CMOS layer structure.

[0224] 8a and 8b show the nonlinear input / output characteristics and transmission rate of the optical nonlinear element 1.3.

[0225] FIG. 8a shows the total intensity I of the simultaneously combined or interacting input signals. in Optical output signal I according to out The intensity of the entire I in is the pump signal I P and the intensity of the superimposed signal. The vertical dotted line corresponds to the threshold of the saturable absorber of the optical nonlinear element 1.3 or of the graphene layer 1.3.1.

[0226] The total strength I of the simultaneously coupled or interacting input signals in is less than the threshold, the optical output signal I outis very low (e.g., a zero signal), and the optical output signal has a first optical output signal intensity or corresponds to a first logic state, when the first logic input signal and the second logic input signal correspond to different logic states.

[0227] The total strength I of the simultaneously coupled or interacting input signals in is greater than the threshold, the optical output signal I out is high (no 0 signal), and the optical output signal has a second optical output signal strength, or corresponds to a second logic state, when the first logic input signal and the second logic input signal correspond to the same logic state.

[0228] Figure 8b shows the overall intensity I in 1 shows the transmission factor T of the optical nonlinear element 1.3 as a function of , ie the portion of the pump signal that is not absorbed by the graphene layer 1.3.1 and passes through the optical nonlinear element 1.3.

[0229] The transmission factor T is the pump signal I p and the optical output signal I out is obtained from a comparison of the intensities of out =TI p The transmission rate T has an exponential relationship with the length x of the graphene layer 1.3.1, where T=e -αx , strong propagation loss α=α(I in ) (per micrometer). The transmittance T shows a sigmoid function with the threshold of light saturation as the inflection point.

[0230] Below the threshold, the transmission coefficient T is low and the pump signal is almost completely absorbed in the graphene layer 1.3.1 of the optical nonlinear element 1.3. The logic output signal has a corresponding low intensity, which corresponds to the first intensity of the optical output signal.

[0231] Above the threshold, the transmission factor T has a plateau as a sign of optical saturation of the optical nonlinear element 1.3 or the graphene layer 1.3.1. The pump signal can pass through the optical nonlinear element 1.3 or the graphene layer 1.3.1 without being completely absorbed. The logic output signal has a corresponding high intensity, which corresponds to the second intensity of the optical output signal.

[0232] Individual features or features of the exemplary embodiments shown in Figures 1 to 8 can also be combined with each other.

Claims

1. signal supply means (1.1, 1.2) for supplying a first optical signal based on a first logical input signal and a second optical signal based on a second logical input signal, wherein the respective phases of said first optical signal and said second optical signal are the same; a phase modulation means (2.1, 2.2) for shifting the phase of the first optical signal by a predetermined phase difference with respect to the phase of the second optical signal; an interference means (3) for causing the first optical signal and the second optical signal whose phases have been shifted by the phase modulation means (2.1, 2.2) to interfere with each other; an optical nonlinear element (1.3) configured to interact with a pump signal and to interact with the first and second optical signals whose phases have been shifted by the phase modulation means (2.1, 2.2) and which have been interfered with by the interference means (3), and to combine an optical output signal as a logical output signal as a result of this nonlinear interaction; Optical logic gates with

2. the predetermined phase difference is π; the signal providing means (1.1, 1.2) and the optical nonlinear element (1.3) are configured to correlate the intensity of the logic output signal with the intensities of the first logic input signal and the second logic input signal, respectively, so that the logic output signal in response to the first logic input signal and the second logic input signal is the result of a logic XOR function; 2. The optical logic gate of claim 1, wherein the logic states of each of said first and second logic input signals and said logic output signal are intensity modulated.

3. 3. An optical logic gate according to claim 2, wherein said signal providing means (1.1, 1.2) are configured such that the logic state of said first logic input signal corresponds to the logic state of said first optical signal and the logic state of said second logic input signal corresponds to the logic state of said second optical signal.

4. 4. An optical logic gate according to claim 2 or 3, wherein the signal providing means (1.1, 1.2) and the optical nonlinear element (1.3) are configured such that when the first and second logic input signals have different intensities and / or correspond to different logic states, the phase of the logic output signal is always the same, regardless of the logic states to which the first and second logic input signals are respectively associated.

5. 5. The optical logic gate of claim 1, wherein the optical output signal corresponds to the portion of the pump signal that has passed through the optical nonlinear element (1.3) and / or the phase of the optical output signal corresponds to the phase of the pump signal.

6. The optical logic gate according to any one of claims 1 to 5, wherein the optical nonlinear element (1.3) comprises a graphene layer as an optical saturable absorber (1.3, 1.3.1) mediating nonlinear interactions in the optical nonlinear element (1.3).

7. further comprising at least one waveguide (W, W1, W2, W3) extending through and / or connecting to said optical nonlinear element (1.3), The at least one waveguide (W, W1, W2, W3) coupling said pump signal propagating in a first direction into said optical nonlinear element (1.3); receiving the optical output signal propagating in the first direction from the optical nonlinear element (1.3); a phase modulation means for modulating the first and second optical signals, the first and second optical signals propagating in a second direction opposite to the first direction, the phases of which have been shifted by the phase modulation means (2.1, 2.2) and interfered by the interference means (3), and the first and second optical signals are coupled to the optical nonlinear element (1.3).

7. The optical logic gate according to claim 1.

8. 8. Optical logic gate according to claims 6 and 7, wherein the graphene layer (1.3, 1.3.1) and the at least one waveguide (W, W1, W2, W3) are integrated into a CMOS-based layer structure and are stacked on top of each other so that electromagnetic coupling between the graphene layer (1.3, 1.3.1) and the at least one waveguide (W, W1, W2, W3) is ensured.

9. the signal supply means (1.1, 1.2) comprises a first additional optical nonlinear element (1.1) and a second additional optical nonlinear element (1.2); the first additional optical nonlinear element (1.1) is configured to interact with a first additional pump signal and a first logic input signal, and to provide a first optical signal as a result of this nonlinear interaction, wherein the first optical signal corresponds to a portion of the first additional pump signal transmitted through the first additional optical nonlinear element (1.1) and / or the phase of the first optical signal corresponds to the phase of the first additional pump signal; the second additional optical nonlinear element (1.2) is configured to interact with a second additional pump signal and the second logic input signal and to provide a second optical signal as a result of this nonlinear interaction, the second optical signal corresponding to a portion of the second additional pump signal transmitted through the second additional optical nonlinear element (1.2) and / or the phase of the second optical signal corresponding to the phase of the second additional pump signal; The optical logic gate according to any one of claims 1 to 8.

10. a first connecting waveguide (C1) extending through the first additional optical nonlinear element (1.1) and connecting it to a phase modulation means (2.1, 2.2), an interference means (3), an optical nonlinear element (1.3) and / or at least one waveguide (W, W1, W2, W3), wherein the first connecting waveguide (C1) comprises: receiving the first additional pump signal propagating in a first direction and coupling it to the first additional optical nonlinear element (1.1); configured to receive the first optical signal propagating in the first direction and direct it towards or to a phase modulation means (2.1, 2.2), an interference means (3), an optical nonlinear element (1.3) and / or at least one waveguide (W, W1, W2, W3), a second connecting waveguide (C2) extending through the second additional optical nonlinear element (1.2) and connecting it to the phase modulation means (2.1, 2.2), the interference means (3), the optical nonlinear element (1.3) and / or at least one waveguide (W, W1, W2, W3); Equipped with The second connecting waveguide (C2) is receiving the second additional pump signal propagating in a first direction and coupling it to the second additional optical nonlinear element (1.2); configured to receive the second optical signal propagating in the first direction and direct it towards or to the phase modulation means (2.1, 2.2), the interference means (3), the optical nonlinear element (1.3) and / or the at least one waveguide (W, W1, W2, W3), 10. The optical logic gate of claim 9.

11. the first logic input signal propagates to or towards the first additional optical nonlinear element (1.1) in a second direction opposite to the first direction, 11. The optical logic gate of claim 10, wherein the second logic input signal propagates to or towards the second additional optical nonlinear element (1.2) in a second direction opposite to the first direction.

12. A method for operating the optical logic gate according to any one of claims 1 to 11, comprising: providing, using said signal providing means (1.1, 1.2), a first optical signal based on a first logical input signal and a second optical signal based on a second logical input signal, wherein the phases of said first and second optical signals are the same; shifting the relative phase of the first optical signal and the second optical signal by a predetermined phase difference using the phase modulation means (2.1, 2.2); After the relative phase is shifted, the first optical signal and the second optical signal are interfered with by the interference means (3); using the optical nonlinear element (1.3) to interact with a pump signal and the first and second optical signals interfered by the interference means (3), and combine an optical output signal as a result of this nonlinear interaction as a logical output signal from the optical nonlinear element (1.3); A method of operation including:

13. further comprising operating the optical logic gate in a digital mode of operation using amplitude modulation or intensity modulation; The predetermined phase difference is π, and operating in the digital operating mode comprises: associating a first logic state with a first magnitude of each of the first logic input signal, the second logic input signal, and the logic output signal; and associating second logic states with respective second intensities, wherein the second intensities are different from the first intensities of the first logic input signal, the second logic input signal, and the logic output signal; the association is performed such that a logic output signal responsive to the first logic input signal and the second logic input signal is the result of a logic XOR function.

13. The method of claim 12.

14. 14. The method of claim 13, wherein when the first logic input signal and the second logic input signal have different magnitudes or are associated with different logic states, the phase of the logic output signal is always the same regardless of the logic states with which the first logic input signal and the second logic input signal are respectively associated.

15. The optical nonlinear element (1.3) has an optical saturable absorber (1.3, 1.3.1) that mediates the nonlinear interaction in the optical nonlinear element (1.3), the intensity of the pump signal is selected such that the optical saturable absorber (1.3, 1.3.1) is optically saturated by the interaction when the first logic input signal and the second logic input signal are associated with different logic states, but is not optically saturated when the first logic input signal and the second logic input signal are associated with the same logic state; and / or 15. The method of claim 12, 13 or 14, wherein the optical output signal corresponds to the portion of the pump signal that is not absorbed by the optical saturable absorber (1.3, 1.3.1) and that is transmitted through the nonlinear element (1.3).

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