Optical logic gate and method for the operation thereof

Abstract

An optical logic gate, which comprises signal-providing means (1.1, 1.2) for providing a first optical signal and a second optical signal having identical phases, is provided. The optical logic gate also comprises a phase modulation means (2.1, 2.2) and an interference means (3). The optical logic gate also comprises an optically non-linear element (1.3), which is configured to interact with a pump signal and with the first and second optical signals shifted with respect to their phases by the phase modulation means (2.1, 2.2) and brought into interference by the interference means (3) and to couple out an optical output signal as a logic output signal as a result of this non-linear interaction.

Description

[0001] Optical logic gate and method for its operation

[0002] The invention relates to an optical logic gate and a method for its operation.

[0003] The use of optical logic, such as optical logic gates, in analog or digital processors promises significantly faster and more efficient execution of computing operations. To ensure this, the optical logic used must meet a number of requirements.

[0004] For example, an optical logic gate should be able to switch as quickly as possible and using low light intensity. Furthermore, optical logic gates should be flexibly cascadable to enable scaling of the respective processor. Further criteria include the ability to achieve a fan-out of at least 2 and to restore the logic level with as little loss as possible. Furthermore, effective isolation of input and output signals and the avoidance of critical operating points or corresponding process parameters are advantageous. However, the current state of the art only inadequately meets these criteria; its switching behavior is too slow, it consumes too much power for efficient use, or it cannot be efficiently scaled or cascaded.

[0005] It is therefore an object of the invention to propose an optical logic gate and a method for its operation with which the disadvantages of the prior art can be overcome and a plurality of the requirements mentioned above can be met.

[0006] According to the invention, this object is achieved with a logic gate having the features of claim 1 and a method having the features of claim 12. Advantageous embodiments and further developments of the invention can be realized with features defined in subordinate claims.

[0007] The optical logic gate according to the invention comprises signal providing means for providing a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal. The respective phases of the first and second optical signals are equal or identical (modulo 2n).

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

[0009] The optical logic gate further comprises an interference means configured to interfere with each other the first and second optical signals shifted in phase by the phase modulation means.

[0010] The optical logic gate also comprises an optically non-linear element which is configured to interact with a pump signal and with the first and second optical signals which have been phase-shifted by means of the phase modulation means and caused to interfere by means of the interference means, and to couple out an optical output signal as a logic output signal as a result of this non-linear interaction. The first and second optical signals which have been phase-shifted by means of the phase modulation means and caused to interfere by means of the interference means here and below refer to the superposition signal which is obtained when the first optical signal is caused to interfere with the second optical signal after their relative phase has been shifted or fixed by means of the phase modulation means and thus superposed. This superposition signal can then be input or output.couple to the optically non-linear element and thus interact with it electromagnetically and non-linearly, for example being completely or at least partially transmitted, reflected and / or absorbed.

[0011] The proposed optical logic gate is characterized by improved cascading 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 various interference signals that could otherwise unpredictably (e.g., randomly) change the phase and / or intensity of an optical signal.

[0012] Since the light supply can be selected independently of the first and second logic input signals using the (optical) pump signal, a comparatively high fan-out is achieved, allowing the logic gate to be efficiently interconnected with several other logic gates. The logic level can thus be restored comparatively efficiently and losslessly.

[0013] For example, the intensity of the logic output signal can be greater than the intensity of the first and / or second logic input signal (even without using an additional optical amplifier). Furthermore, the relative modulation depth of the optical logic gate is largely independent of the intensity of the first and second logic input signals.

[0014] Operating mode and logic

[0015] The optical logic gate can be used in a purely optical analog or digital mode of operation. In digital mode of operation, it can be used as a modular logic element for performing a variety of logical operations with different logical states. A logical state can be a first logical state or a second logical state. For example, a first logical state can correspond to a bit with a bit value of 0 and a second logical state can correspond to a bit with a bit value of 1 (or vice versa).

[0016] Different logical states can be encoded into a signal using amplitude or intensity modulation. With amplitude or intensity modulation, a modulated signal may have a first intensity when associated with a first logical state. The modulated signal may have a second intensity when associated with a second logical state. The second intensity of the modulated signal may be different from the first intensity of the modulated signal. For example, the second intensity of the modulated signal may be greater than the first intensity of the modulated signal.

[0017] The modulated signal can be the first or second logic input signal, the first or second optical signal, the superimposed signal, or the optical output signal or logic output signal. The respective first intensities of different modulated signals can be different from one another. The second intensities of different modulated signals can also be different from one another. For example, the first intensity of the first logic input signal can be different from the first intensity of the first optical signal. The second intensity of the first logic input signal can be different from the second intensity of the first optical signal. The same applies analogously to the second logic input signal and the second optical signal.

[0018] The signal providing means can be configured such that an amplitude or intensity modulation of the first and second logic input signals is transferred to the first and second optical signals. This can be done such that the logical state of the first logic input signal corresponds to the logical state of the first optical signal and the logical state of the second logic input signal corresponds to the logical state of the second optical signal.

[0019] The predetermined phase difference between the phase of the first optical signal and the phase of the second optical signal can be n or can be adjusted accordingly by means of the phase modulation means.

[0020] In this case, the interference of the first optical signal and the second optical signal by means of the interference means can be destructive. The interference can in particular be completely destructive if the intensities of the first and second optical signals are the same, so that they are associated with the same logical states. The first optical signal and the second optical signal can then almost completely cancel each other out at a predetermined phase difference n in the interference means and / or optically non-linear element. The heterodyne or interference signal can then correspond to the first logical state or to a zero signal (i.e. for all practical purposes, a signal with an intensity equal to zero or less than an average noise intensity).

[0021] If, however, the intensities of the first and second optical signals differ, they can be associated with different logical states. For example, exactly one of the two signals can be a zero signal and the other not. In this case, despite the interference in the interference means and / or optically nonlinear element, the first and second optical signals cannot completely cancel each other out and can interfere with each other only slightly or not at all. The superposition or interference signal can then correspond to the second logical state or largely correspond to the first or second optical signal before the interference, which is not a zero signal.

[0022] The intensity of the logic output signal may depend on the intensity of the beat signal and the intensity of the pump signal due to the interaction of the pump signal and the beat signal with the optically nonlinear element.

[0023] For example, the intensity of the pump signal can be adjusted, or the optically nonlinear element can be configured, such that the optically nonlinear element optically saturates when the heterodyne signal corresponds to the second logical state or to a non-zero signal, i.e., when the first and second optical signals, or the first and second logic input signals, have different intensities or correspond to different logical states. In this case, the optical output signal can have a high intensity, which can correspond to the second intensity of the optical output signal, and can be associated with the second logical state.

[0024] The intensity of the pump signal can also be adjusted, or the optically nonlinear element can also be configured, such that the optically nonlinear element does not optically saturate when the heterodyne signal corresponds to the first logical state or a zero signal, i.e., when the first and second optical signals or the first and second logic input signals have the same intensities or correspond to the same logical states. In this case, the optical output signal can have a low intensity, which can correspond to the first intensity of the optical output signal or a zero signal, and can be associated with the first logical state.

[0025] The functionality described above corresponds to that of a logical XOR function. Thus, the optical logic gate can be used as an XOR gate.

[0026] In particular, the signal providing means, together with the optically non-linear element, can be configured to link the intensity of the logic output signal to the respective intensities of the first and second logic input signals such that the logic output signal as a function of the first and second logic input signals is the result of a logical XOR function, wherein the respective logical states of the first and second logic input signals and the logic output signal can be amplitude- or intensity-modulated.

[0027] Preferably, the signal providing means together with the optically non-linear element can be configured such that when the first and second logic input signals have different intensities or are associated with different logic states, the phase of the logic output signal is always the same regardless of which logic states the first and second logic input signals are respectively associated with.

[0028] In this case, a purely optical XOR function can be implemented in which the phase of the logic output signal is decoupled or always the same, independent of the phases and / or intensities of the first and second logic input signals or the first and second optical signals. In particular, the phase of the logic output signal can correspond to the phase of the pump signal.

[0029] This is achieved in particular by first feeding the superposition signal together with the pump signal into the optical nonlinear element before the logic output signal is generated and coupled out as a result of the nonlinear interaction. For example, the material of the optical nonlinear element can be selected such that the nonlinear interaction is phase-insensitive, e.g., corresponding to an effective Kerr nonlinearity. Preferably, the optical nonlinear element comprises or consists of an optically saturable absorber for mediating the interaction.

[0030] The optical output signal can correspond to the portion of the pump signal not absorbed by the optically nonlinear element and / or the optically saturable absorber, or to the portion of the pump signal transmitted through the optically nonlinear element. The phase of the optical output signal can correspond to the phase of the pump signal. The intensity of the optical output signal can be smaller than the intensity of the pump signal due to the interaction with the optically nonlinear element. The intensity of the optical output signal can also depend on the intensity of the beat signal and / or the degree of optical saturation of the optically nonlinear element.

[0031] A signal within the meaning of this invention can be pulsed. The interaction can occur simultaneously. In particular, the interaction of the pump signal and the heterodyne signal with the optically nonlinear element can occur simultaneously or at least with temporal overlap.

[0032] Simultaneous interaction of the pump signal and the beat signal with the optically nonlinear element can occur such that the pump signal and the beat signal arrive at the optically nonlinear element simultaneously or at least overlapping in time, or couple to and interact with it. For example, the pump signal and / or the beat signal can be completely or at least partially absorbed by an optically saturable absorber in the optically nonlinear element.

[0033] However, it is also possible for the beat signal to arrive at the optically nonlinear element first, or to couple into or onto the optically nonlinear element and interact with it, and only then does the pump signal arrive. For example, the beat signal may first be completely or at least partially absorbed by the optically nonlinear element or an optically saturable absorber in the optically nonlinear element, thereby electromagnetically exciting it. During and due to this excitation or absorption, the optically saturable absorber may be saturated. The pump signal may then pass almost completely or at least partially through the optically saturable absorber in the optically nonlinear element, thereby transmitting through the optically nonlinear element.The pump signal can thus be transformed into the optical output signal as a result of a simultaneous interaction of the pump signal and the heterodyne signal with the optically nonlinear element.

[0034] Depending on the degree of absorption of the beat signal and / or the excitation or saturation of the optically nonlinear element by the beat signal, the pump signal can pass through the optical nonlinear element almost completely, partially or not at all in order to realize a logical function of the optical logic gate.

[0035] This significantly improves the scalability of the optical logic gate or an optical processor in which the optical logic gate can be implemented or integrated. 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, regardless of the respective logic function. The logic output signal can then be used directly as an additional input signal in another logic element or component of the optical processor.

[0036] Signal provision

[0037] The first optical signal may correspond to or be identical to the first logic input signal. The second optical signal may correspond to or be identical to the second logic input signal.

[0038] However, the signal-providing means may also comprise additional optical components or elements with which the first logic input signal or its logical state can be transferred to the first optical signal and / or the second logic input signal or its logical state can be transferred to the second optical signal. In this case, the first optical signal may be different from the first logic input signal. The second optical signal may be different from the second logic input signal.

[0039] The signal providing means may comprise a first and a second further optically non-linear element.

[0040] The first further optically nonlinear element can be configured to interact with a first further (optical) pump signal and the first logic input signal, and to extract and provide the first optical signal as a result of this nonlinear interaction. The interaction of the first further (optical) pump signal and the first logic input signal with the first further optically nonlinear element can occur simultaneously.

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

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

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

[0044] Preferably, the first further pump signal and the first logic input signal propagate in the first further optically non-linear element or through the first further optically non-linear element in opposite directions or couple into or to the first further optically non-linear element while propagating in opposite directions.

[0045] Preferably, the second further pump signal and the second logic input signal propagate in the second further optically non-linear element or through the second further optically non-linear element in opposite directions or couple into or to the second further optically non-linear element while propagating in opposite directions.

[0046] Optical nonlinearity

[0047] The material of the optically nonlinear element, the first and / or second further optically nonlinear element can each be selected such that the respective nonlinear interaction is phase-insensitive, preferably corresponding to an effective Kerr nonlinearity.

[0048] The optically nonlinear element, the first and / or second further optically nonlinear element may comprise or consist of an optically saturable absorber or a Kerr medium for mediating the nonlinear interaction.

[0049] Preferably, the optically nonlinear element, the first and / or second further optically nonlinear element each have a nonlinear input / output characteristic in which the intensity of the outgoing or coupled-out optical signals or the electromagnetic emissions describes a nonlinear relationship as a function of the sum of the intensities of the simultaneously incoming or coupled-in optical signals. For example, the nonlinear input / output characteristic can describe a sigmoid function or an S-shaped (bistable) curve.

[0050] In particular, the input / output characteristic can have a (critical) threshold value for the sum of the intensities of the simultaneously incoming or coupled-in optical signals. A total intensity of the simultaneously incoming optical signals less than the threshold value results in only a low or no (zero signal) intensity of the outgoing (emitted) optical signal, while a total intensity of the simultaneously incoming optical signals greater than the threshold value results in a high intensity of the outgoing optical signal. If the total intensity is greater than the threshold value, the optically nonlinear element or its optically saturable absorber can be optically saturated.

[0051] Preferably, the intensity of the pump signal is selected or the optically non-linear element is configured such that the optically non-linear element or its optically saturable absorber is optically saturated by the interaction when the first optical signal and the second optical signal are associated with different logical states or have different intensities (and therefore do not completely cancel each other out due to the interference), and is not optically saturated when the first optical signal and the second optical signal are associated with the same logical states or have the same intensities (and therefore completely cancel each other out due to the destructive interference in the case of a relative phase or predetermined phase difference of n).

[0052] The optical output signal can correspond to the portion of the pump signal propagated or transmitted by the optically nonlinear element and / or the portion of the pump signal not absorbed by the optically saturable absorber of the optically nonlinear element. In the case of optical saturation, the pump signal can almost completely pass through the optically nonlinear element or propagate through the optically nonlinear element. The optical output signal can then correspond to the second logic state with the second or high intensity.

[0053] If the optically nonlinear element or its optically saturable absorber is not saturated, the pump signal cannot pass through the optically nonlinear element completely or at all. Instead, it can be almost completely absorbed by its optically saturable absorber. The optical output signal can then correspond to the first logical state with the first or low intensity. Preferably, the intensity of the first further pump signal is selected or the first further optically nonlinear element is configured such that the first further optically nonlinear element or its optically saturable absorber is not optically saturated by the interaction when the first logic input signal is associated with the first logical state, and is optically saturated when the first logic input signal is associated with the second logical state.

[0054] The first optical signal can correspond to the portion of the first further pump signal propagated or transmitted by the first further optically nonlinear element and / or the portion of the first further pump signal not absorbed by the optically saturable absorber of the first further optically nonlinear element. In the case of optical saturation, the first further pump signal can almost completely pass through the first further optically nonlinear element or propagate through the first further optically nonlinear element. The first optical signal can then correspond to the second logical state with the second or high intensity.

[0055] If the first additional optically nonlinear element or its optically saturable absorber is not saturated, the first additional pump signal cannot pass through the first additional optically nonlinear element completely or at all. Instead, it can be almost completely absorbed by its optically saturable absorber. The first optical signal can then correspond to the first logical state with the first or lowest intensity.

[0056] Preferably, the intensity of the second further pump signal is selected or the second further optically nonlinear element is configured such that the second further optically nonlinear element or its optically saturable absorber is not optically saturated by the interaction when the second logic input signal is associated with the first logic state or has a first intensity or corresponds to a zero signal, and is optically saturated when the second logic input signal is associated with the second logic state. The second optical signal can correspond to the part of the second further pump signal propagated or transmitted by the second further optically nonlinear element and / or the part of the second further pump signal not absorbed by the optically saturable absorber of the second further optically nonlinear element.In the case of optical saturation, the second pump signal can almost completely pass through the second optically nonlinear element or propagate through the second optically nonlinear element. The second optical signal can then correspond to the second logic state with the second or high intensity.

[0057] If the second additional optically nonlinear element or its optically saturable absorber is not saturated, the second additional pump signal cannot pass through the second additional optically nonlinear element completely or at all. Instead, it can be almost completely absorbed by its optically saturable absorber. The second optical signal can then correspond to the first logical state with the first or low intensity.

[0058] Graphen

[0059] Preferably, the optically non-linear element, the first and / or second further optically non-linear element comprises or is formed from graphene or a graphene layer as an optically saturable absorber or medium for mediating the respective non-linear interaction.

[0060] For example, the Fermi level of the graphene can be adjusted or selected, e.g. by doping, such that the graphene exhibits particularly strong or effective saturable absorption. On the one hand, the relaxation time of the saturable absorption of the graphene can be small enough to enable fast switching. On the other hand, the relaxation time of the saturable absorption of the graphene can also be large enough to provide the pump signal, the first further pump signal and / or the second further pump signal with a sufficiently long time window so that, for example, they can pass through or propagate through the optically nonlinear element, the first further optically nonlinear element and / or the second further optically nonlinear element largely independently of a pulse shape of the first and second logic input signal (or the first and second optical signal) as soon as they are optically saturated.This also makes it possible to effectively restore the phase, pulse shape and / or intensity of the first optical signal, the second optical signal and / or the logic output signal or the logic level, thus further contributing to effective scalability.

[0061] The relaxation time of the saturable absorption of graphene can be less than one picosecond. Accordingly, the clock rate of the optical logic gate can be greater than 1 THz.

[0062] The use of graphene or a graphene layer also enables an integrated and / or CMOS-based construction of the optical logic gate or the optically nonlinear element, the first further optically nonlinear element and / or the second further optically nonlinear element.

[0063] The graphene layer of the first further optically nonlinear element may also be referred to below as the first or first further graphene layer. The graphene layer of the second further optically nonlinear element may also be referred to below as the second or second further graphene layer.

[0064] The length(s) of the graphene layer, the first additional graphene layer, and / or the second additional graphene layer can be different and can be flexibly adjusted so that the respective threshold and / or propagation loss of the saturable absorption corresponds to target specifications regarding the intensity of the signals coupled out from the respective graphene layer, thus allowing for flexible adjustment of various logic functions of the optical logic gate. The length(s) can also be selected to avoid critical points, such as bistable phases.

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

[0066] 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 shifted in phase and interfered by the interference means.

[0067] The at least one waveguide can pass through the optically nonlinear element and / or couple to the optically nonlinear element.

[0068] The at least one waveguide may also be connected or coupled at one end to a pump or light supply and / or a pump signal coupling element for providing the pump signal and at another end to a logic output for providing the logic output signal.

[0069] Preferably, the pump signal can propagate in a first direction and the first and second optical signals, which are phase-shifted by means of the phase modulation means and interfered by means of the interference means, can propagate in a second direction opposite to the first in the at least one waveguide through the optically non-linear element or can thus be coupled to the optically non-linear element in a propagating manner.

[0070] The at least one waveguide can be configured to receive the pump signal (e.g. coming from the pump supply) propagating in a first direction and to couple it completely or at least partially into / to the optically nonlinear element or its optically saturable absorber or its Kerr medium.

[0071] The at least one waveguide may further be configured to receive the phase-shifted and interfering / interfered first and second optical signals propagating in a second direction opposite to the first and to couple them completely or at least partially into / to the optically nonlinear element or its optically saturable absorber or its Kerr medium.

[0072] The at least one waveguide can further be configured to receive the optical output signal from the optically nonlinear element or its optically saturable absorber or its Kerr medium and to propagate it in the first direction and / or to forward it to the logic output.

[0073] Other waveguides a) Connecting waveguides

[0074] The optical logic gate may further comprise a first and / or second connecting waveguide.

[0075] The first connecting waveguide can pass through the first further optically non-linear element and connect it to the phase modulation means, the interference means, the optically non-linear element and / or the at least one waveguide, wherein the first connecting waveguide can be configured to receive the first further pump signal and to couple it into or to the first further optically non-linear element or its optically saturable absorber and / or to receive the first optical signal and to transmit it into or to the phase modulation means, the interference means, the optically non-linear element and / or the at least one waveguide.

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

[0077] The second connecting waveguide can extend through the second further optically nonlinear element and connect it to the phase modulation means, the interference means, the optically nonlinear element and / or the at least one waveguide, wherein the second connecting waveguide can be configured to receive the second further pump signal and couple it into or to the second further optically nonlinear element or its optically saturable absorber and / or to receive the second optical signal and forward it to or into the phase modulation means, the interference means, the optically nonlinear element and / or the at least one waveguide. The second connecting waveguide can be configured to receive the second further pump signal and / or the second optical signal propagating in a first direction.

[0078] The phase modulation means and / or the interference means can also be arranged on or in the first and / or second connecting waveguide or connected / coupled thereto. b) Input waveguide

[0079] The optical logic gate may further comprise a first logic input for providing the first (optical) logic input signal. The first logic input may be connected or coupled to the first further optically 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 couple the first logic input signal into the first further optically nonlinear element.

[0080] The first input waveguide can be coupled to the first connecting waveguide via a first waveguide coupling element. The first waveguide coupling element can be arranged between the first further optically nonlinear element, the phase modulation means, or the first heating element, and the interference means or the optically nonlinear element.

[0081] The first waveguide coupling element may be configured to propagate the first logic input signal or at least a portion of a signal present at the first logic input in the first input waveguide from the first logic input into the first connecting waveguide to the first further non-linear element.

[0082] If the first waveguide coupling element only transmits a portion of the signal present at the first logic input into the first connecting waveguide, only this portion can be understood as the first logic input signal within the meaning of this application. The first waveguide coupling element can also be configured such that it propagates the first optical signal or a portion of a signal coupled out by the first further optically nonlinear element as a result of the nonlinear interaction in the first connecting waveguide from the first further optically nonlinear element and / or the phase modulation means and / or the first heating element back into the first connecting waveguide to the interference means and / or the optically nonlinear element.

[0083] If the first waveguide coupling element only transmits a part of the signal coupled out from the first further optically non-linear element as a result of the non-linear interaction into the first connecting waveguide in the direction of the optically non-linear element, only this part can be understood as the first optical signal within the meaning of this application.

[0084] The first input waveguide can pass through the first further optically non-linear element and / or couple into / to the first further optically non-linear element or its optically saturable absorber or can run there at a distance from the first connecting waveguide and / or the first further pump waveguide.

[0085] The first logic input signal can couple into or to the first further optically nonlinear element in a second direction opposite to the first, for example in the first input waveguide or the first connecting waveguide, propagating.

[0086] The first input waveguide can additionally couple into / to the phase modulation means or pass through it, 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 the second (optical) logic input signal. The second logic input may be connected or coupled to the second further optically 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 into the second optically nonlinear element.

[0088] The second input waveguide can be coupled to the second connecting waveguide via a second waveguide coupling element. The second waveguide coupling element can be arranged between the second further optically nonlinear element, the phase modulation means, or the second heating element, and the interference means or the optically nonlinear element.

[0089] The second waveguide coupling element may be configured to propagate the second logic input signal or at least a portion of a signal present at the second logic input in the second input waveguide from the second logic input into the second connecting waveguide to the second further non-linear element.

[0090] If the second waveguide coupling element only transmits a part of the signal present at the second logic input into the second connecting waveguide, only this part can be understood as a second logic input signal within the meaning of this application.

[0091] The second waveguide coupling element can also be configured to propagate the second optical signal or a portion of a signal coupled out from the second further optically non-linear element as a result of the non-linear interaction in the second connecting waveguide from the second further optically non-linear element and / or the phase modulation means and / or the second heating element back into the second connecting waveguide to the interference means and / or the optically non-linear element.

[0092] If the second waveguide coupling element only transmits a part of the signal coupled out from the second further optically non-linear element as a result of the non-linear interaction into the second connecting waveguide in the direction of the optically non-linear element, only this part can be understood as a second optical signal within the meaning of this application.

[0093] The second input waveguide can pass through the second further optically non-linear element and / or couple into / to the second further optically non-linear element or its optically saturable absorber or run there at a distance from the second connecting waveguide and / or the second further pump waveguide.

[0094] The second logic input signal can couple into or to the second further optically nonlinear element in a second direction opposite to the first, for example in the second input waveguide or the second connecting waveguide.

[0095] The second input waveguide can also couple to the phase modulation means or pass through it, for example, to shift the phase of the second logic output signal. c) Output waveguide

[0096] The optical logic gate may further comprise an output waveguide for coupling out and receiving the logic output signal from the optically nonlinear element and for propagating or forwarding the logic output signal to the logic output.

[0097] The output waveguide can connect the optically nonlinear element directly to the logic output. The output waveguide can also connect or couple the optically nonlinear element to the interference device and / or the interference device to the logic output.

[0098] The output waveguide may also correspond to a part or section of the at least one waveguide or may merge continuously into it. d) Pump supply

[0099] The optical logic gate may further comprise a pump waveguide for receiving the pump signal and coupling the pump signal into the optically nonlinear element. The pump waveguide may be a part or section of the at least one waveguide or may merge continuously into it.

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

[0101] The optical logic gate may further comprise a first additional pump waveguide for receiving the first additional pump signal and coupling the first additional pump signal into the first additional optically nonlinear element. The first additional pump waveguide may be a part or section of the first connecting waveguide or may continuously merge into it (e.g., in / on the first additional optically nonlinear element).

[0102] The optical logic gate may further comprise a second pump waveguide for receiving the second pump signal and coupling the second pump signal into the second optically nonlinear element. The second pump waveguide may be a part or section of the second connecting waveguide or may continuously merge into it (e.g., in / on the second optically nonlinear element).

[0103] The optical logic gate may also comprise an (optical) pump signal supply or light supply for providing the pump signal, the first further pump signal, the second further pump signal and / or an overall pump signal.

[0104] The optical logic gate may also comprise a pump coupling element configured to split a total pump signal provided by the pump signal supply into the pump signal, the first additional pump signal, and the second additional pump signal, and to forward or couple the pump signal into the pump waveguide, the first additional pump signal into the first additional pump waveguide, and the second additional pump signal into the second additional pump waveguide. For example, the pump coupling element may be configured as a multi-mode interferometer with one input and three outputs.

[0105] The length of the pump waveguide or the optical path that the pump signal travels from the pump coupling element to the optically non-linear element can be longer than the length of the first further pump waveguide or the optical path that the first further pump signal travels from the pump coupling element to the first further optically non-linear element, and can also be longer than the length of the second further pump waveguide or the optical path that the second further pump signal travels from the pump coupling element to the second further optically non-linear element.

[0106] A waveguide within the meaning of the present application can be a bidirectional waveguide. Accordingly, a direction or propagation direction in the waveguide can be defined by the sign of the respective occupied Fourier mode (k-mode).

[0107] CMOS

[0108] The optical logic gate may have a CMOS-based layer structure or be integrated in such a structure.

[0109] The graphene layer of the optically nonlinear element and the at least one waveguide can be integrated in a CMOS-based layer structure in an overlapping or stacked manner so that electromagnetic coupling can be ensured.

[0110] The graphene layer can be arranged in a first layer of the CMOS-based layered structure or correspond to it. The at least one waveguide can be arranged in a second layer above or below the graphene layer. The first and second layers can also be arranged on top of one another such that the graphene layer and the at least one waveguide touch each other.

[0111] The graphene layer can be formed as a strip, wherein the longitudinal axes of the graphene strip and the at least one waveguide in the optically nonlinear element can run parallel. The graphene or the graphene strip can cover the at least one waveguide in the optically nonlinear element along the longitudinal axis.

[0112] The length of the graphene strip can be selected such that the threshold of the optically nonlinear element, the propagation loss, and / or the intensity of the optical output signal correspond to a target value. This allows the threshold or the point of saturable absorption and / or the propagation loss to be flexibly adapted to the further structure or design of the optical logic gate. For example, the target value can be selected such that the optical logic gate is not operated at a critical point, such as a bistable region, of the graphene or the optically nonlinear element.

[0113] The features or design variants mentioned with regard to the design of the optically non-linear element can also be transferred or applied analogously to the first and second further optically non-linear element.

[0114] The first further graphene layer and the first connecting waveguide and / or the first input waveguide can be integrated in a CMOS-based layer structure so as to overlap or be arranged one above the other.

[0115] The first further graphene layer of the first further optically nonlinear element can cover the first connecting waveguide and / or the first input waveguide or electromagnetically couple them to them.

[0116] Preferably, the optically saturable absorber, the Kerr medium and / or the first further graphene layer of the first further optically nonlinear element covers the first input waveguide, the first further pump waveguide and / or the first connecting waveguide.

[0117] The second further graphene layer and the second connecting waveguide and / or the second input waveguide can be integrated in a CMOS-based layer structure in an overlapping or stacked manner.

[0118] The second further graphene layer of the second further optically nonlinear element can cover the second connecting waveguide and / or the second input waveguide or electromagnetically couple it to these / these.

[0119] Preferably, the optically saturable absorber, the Kerr medium and / or the second further graphene layer of the second further optically nonlinear element covers the second input waveguide, the second further pump waveguide and / or the second connecting waveguide.

[0120] Interference agents

[0121] The interference means can be a multi-mode interferometer. The multi-mode interferometer as interference means can be connected or arranged outside and / or between the optically nonlinear element and the phase modulation means.

[0122] The multi-mode interferometer or interference means may further be configured to interfere with the first and second optical signals shifted with respect to their relative phase coming from the phase modulation means and then to propagate the correspondingly interfering or interfered or interfering superimposed signal or superposition signal into the at least one waveguide in the direction of the optically non-linear element.

[0123] The interference means may further be configured to propagate the optical output signal in the at least one waveguide and to forward it from the optically non-linear element to a logic output.

[0124] The interference means can also be a part or region of the optically nonlinear element. For example, the interference means can also be designed as a waveguide coupling element. For example, the at least one waveguide can 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.

[0125] The first, second, and / or third waveguides can each extend through the optically nonlinear element at a distance from one another or can extend past it at a distance from one another. The third waveguide can be arranged in or on the optically nonlinear element between the first and second waveguides.

[0126] In this case, the interference means can be formed as a waveguide coupling element by a region in or on the optically nonlinear element in which the first and second waveguides each couple to the third waveguide or are arranged close to the third waveguide in such a way that the first and second optical signals, shifted with respect to their relative phase, interfere with each other or are superimposed in the third waveguide. The superposition signal thus formed can then couple to or into the optically nonlinear element or its optically saturable absorber or its Kerr medium.

[0127] The graphene layer of the optically nonlinear element can completely cover at least the third waveguide to ensure simultaneous interaction of the pump signal and the phase-shifted first and second optical signals, which are caused to interfere with each other by the interference agent, with the graphene layer. The graphene layer of the optically nonlinear element can additionally cover the first and second waveguides.

[0128] The first waveguide can, for example, correspond to the first connecting waveguide or be a part / section thereof or continuously merge into it.

[0129] The second waveguide can, for example, correspond to the second connecting waveguide, be a part / section thereof, or continuously transition into it. The pump waveguide and / or the output waveguide can each correspond to a part or section of the third waveguide, or continuously transition into it.

[0130] Phase modulating agent

[0131] The phase modulation means may comprise at least one heating element that may be suitable for shifting or changing the phase of the first and / or second optical signal such that the relative phase between the first and second optical signals corresponds to the predetermined phase difference. For this purpose, the at least one heating element may be arranged in / on the first and / or second connecting waveguide or thermally coupled to them.

[0132] The phase modulation means can be arranged or connected between the signal-providing means or the first and / or second further optically nonlinear element and the interference means and / or the optically nonlinear element. The phase modulation means can also be part of the signal-providing means.

[0133] In addition, the at least one heating element can also be arranged on the first or second input waveguide or thermally coupled to it.

[0134] It may be advantageous if the at least one heating element comprises a first heating element for changing the phase of the first optical signal and a second heating element for changing the phase of the second optical signal. The first heating element can then be arranged on / in the first connecting waveguide or thermally coupled to it. The second heating element can be arranged on / in the second connecting waveguide or thermally coupled to it. This allows the phase difference between the first and second optical signals to be adjusted particularly precisely, or corresponding fine-tuning can be performed.

[0135] Preferably, the phase modulation means, the at least one heating element and / or the first heating element are integrated together with the first further optically non-linear element, the first connecting waveguide and / or the first input waveguide in a CMOS-based layer structure.

[0136] The phase modulation means, the at least one heating element and / or the second heating element can also be integrated together with the second further optically non-linear element, the second connecting waveguide and / or the second input waveguide in a CMOS-based layer structure.

[0137] Instead of a heating element, at least one electro-optical modulator can be used as a phase modulation means.

[0138] Proceedings

[0139] The invention also relates to a method for operating the optical logic gate described above. The method comprises the following steps:

[0140] Providing a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal by means of the signal providing means, wherein the respective phases of the first and second optical signals are the same.

[0141] Shifting the relative phase of the first and second optical signals by a predetermined phase difference by means of the phase modulation means.

[0142] After shifting the relative phase, interfering the first and second optical signals by means of the interference means.

[0143] Interaction of a pump signal and the first and second optical signals interfered by the interference means with the optically non-linear element and, as a result of this non-linear interaction, coupling out an optical output signal as a logic output signal from the optically non-linear element.

[0144] The method may further comprise, e.g. as an initial step: operating the optical logic gate in a digital operating mode with amplitude or intensity modulation, wherein the predetermined phase difference is TT.

[0145] Operating in digital mode may include:

[0146] Associating a first logic state with a first intensity of each of the first logic input signal, the second logic input signal, and the logic output signal.

[0147] Associating a second logic state with a second intensity of each of the first logic input signal, the second logic input signal, and the logic output signal that is different from the first.

[0148] The association can be carried out in such a way that the logic output signal as a function of the first and second logic input signal is the result of a logical XOR function.

[0149] The logical state of the first logic input signal can be transferred to the first optical signal by means of the signal providing means. The logical state of the second logic input signal can be transferred to the second optical signal by means of the signal providing means.

[0150] In particular, if the first and second logic input signals have different intensities or are associated with different logic states, the phase of the logic output signal may always be the same regardless of which logic state the first and second logic input signals are associated with.

[0151] The intensity of the pump signal can be selected such that the optically nonlinear element or its optically saturable absorber is optically saturated during the simultaneous interaction when the first logic input signal or optical signal and the second logic input signal or optical signal are associated with different logic states, and is not optically saturated when the first logic input signal or optical signal and the second logic input signal or optical signal are associated with the same logic states. Before shifting the relative phase of the first and second optical signals, the method can further comprise:

[0152] Interaction of a first further pump signal and the first logic input signal with a first further optically nonlinear element, and as a result of this nonlinear interaction, coupling the first optical signal out of the first further optically nonlinear element. The interaction can occur simultaneously.

[0153] Interaction of a second further pump signal and the second logic input signal with a second further optically nonlinear element, and as a result of this interaction, coupling the second optical signal out of the second further optically nonlinear element. The interaction can occur simultaneously.

[0154] In the method, the intensity of the pump signal can be selected such that the optically nonlinear element or its optically saturable absorber is optically saturated during the 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 states.

[0155] The intensity of the first further pump signal and / or the first intensity of the first logic input signal can be selected such that the first further optically non-linear element or its optically saturable absorber is optically saturated during 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.

[0156] The intensity of the second further pump signal and / or the first intensity of the second logic input signal can be selected such that the second further optically nonlinear element or its optically saturable absorber optically saturates during the interaction when the second logic input signal is associated with the second logic state and does not optically saturate when the second logic input signal is associated with the first logic state. Additional remarks

[0157] The invention provides an optical logic gate and a method for its operation, with which optical or electro-optical processors can be operated efficiently and scalably or corresponding computing operations can be carried out.

[0158] In particular, efficient input / output isolation is ensured, as no light or optical signals need to flow directly from a logic input to a logic output. Furthermore, the relative modulation depth of the optical logic gate is largely independent of the (absolute) intensity of the signals provided at the first and second logic inputs.

[0159] The optical logic gate according to the invention and the method for its operation can also be used in various optical or electro-optical circuits in the field of network technology and metrology or sensor technology.

[0160] Furthermore, the invention is applicable to various optical logic input signals. The logic input signals or the logic output signal can correspond to classical or quasi-classical states of light or electromagnetic radiation, up to quantum states, i.e., individual photons or coherent signals with very weak intensity (e.g., corresponding microwave signals).

[0161] It should be noted that the term "optical" in the context of this invention refers to electromagnetic radiation in general and is not necessarily to be understood as limiting the frequency range of the electromagnetic radiation used. For example, input and output signals of the optical logic gate or its components, e.g., the signal-providing means and / or the optically nonlinear element, can also be microwave radiation or electromagnetic radiation in the THz range. For example, the optically nonlinear element can also be formed with a superconducting circuit comprising at least one Josephson contact (emitting microwave radiation), or a terahertz resonator or terahertz metamaterial. The invention is therefore applicable and feasible in a broad range of the electromagnetic spectrum.

[0162] The optical logic gate and the method for its operation will be explained in more detail below using examples.

[0163] This shows

[0164] Figure 1 shows a schematic representation of an embodiment of the optical logic gate;

[0165] Figure 2 shows a schematic representation of another embodiment of the optical logic gate;

[0166] Figure 3 shows a logic truth table of the optical logic gate;

[0167] Figures 4a, 4b and 4c each show a schematic representation of a cross-section of a CMOS layer structure with graphene and a waveguide;

[0168] Figures 5a, 5b and 5c each show a schematic representation of a cross-section of a CMOS layer structure with graphene and two waveguides;

[0169] Figures 6a, 6b and 6c each show a schematic representation of a cross-section of a CMOS layer structure with graphene and three waveguides;

[0170] Figure 7a is a schematic representation of a cross-section of a CMOS layer structure with the phase modulation means and a waveguide;

[0171] Figure 7b is a schematic representation of a cross-section of a CMOS layer structure with the phase modulation means and two waveguides;

[0172] Figure 8a shows a nonlinear input / output characteristic of the optically nonlinear element; Figure 8b shows a transmittance of the optically nonlinear element.

[0173] The optical logic gate shown in Figure 1 comprises a signal providing means 1.1, 1.2 for providing a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal. The respective phases of the first and second optical signals are equal or identical (modulo 2TT).

[0174] The optical logic gate further comprises phase modulation means 2.1, 2.2 for shifting the phase of the first optical signal with respect to the phase of the second optical signal by a predetermined phase difference.

[0175] The optical logic gate further comprises an interference means 3 which is configured to cause the first and second optical signals, which are phase-shifted by means of the phase modulation means 2.1, 2.2, to interfere with each other.

[0176] The optical logic gate also comprises an optically non-linear element 1.3, which is configured to interact with a pump signal and with the first and second optical signals, which are phase-shifted by means of the phase modulation means 2.1, 2.2 and interfered by means of the interference means 3, and to couple out an optical output signal as a logic output signal as a result of this non-linear interaction.

[0177] The signal providing means 1.1, 1.2 comprises a first further optically non-linear element 1.1 and a second further optically non-linear element 1.2.

[0178] The phase modulation means 2.1, 2.2 comprises a first heating element 2.1 and a second heating element 2.2.

[0179] The interference means 3 is designed as a multi-mode interferometer and is connected between the first and second heating elements 2.1, 2.2 on the one hand and the optically non-linear element 1.3 on the other hand.

[0180] The first connecting waveguide CI connects or couples the first further optically nonlinear element 1.1 to the first heating element 2.1 and the interference means 3. The second connecting waveguide C2 connects or couples the second further optically nonlinear element 1.2 to the second heating element 2.2 and the interference means 3.

[0181] The first input waveguide E1 connects or couples the first logic input INI to the first connecting waveguide C1 via the first waveguide coupling element 5.1. The second input waveguide E2 connects or couples the second logic input IN2 to the second connecting waveguide C2 via the second waveguide coupling element 5.2.

[0182] The at least one waveguide W connects or couples the interference means 3 to the optically nonlinear element 1.3 and extends through it. In this example, the at least one waveguide W consists of a single waveguide, hereinafter referred to as the through waveguide W.

[0183] The output waveguide Wa connects or couples the interference means 3 to the logic output OUT.

[0184] The 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 the pump coupling element 4. The pump coupling element 4 is also designed as a multi-mode interferometer.

[0185] The pump signal supply provides a total pump signal, which is split by the pump coupling element 4 into the pump signal, the first additional pump signal, and the second additional pump signal. The pump signal is received by the pump waveguide P3 and propagates into the through-waveguide W and into the optically nonlinear element 1.3 or couples thereto. The first additional pump signal is received by the pump waveguide P1 and propagates into the first additional optically nonlinear element 1.1 or couples thereto. The second additional pump signal is received by the second additional pump waveguide P2 and propagates into the second additional optically nonlinear element 1.2 or couples thereto.

[0186] The first additional pump waveguide PI continuously transitions into the first connecting waveguide CI. The second pump waveguide continuously transitions into the second connecting waveguide C2. The first logic input INI provides the first logic input signal. This is received by the first input waveguide E1 and propagates via the first waveguide coupling element 5.1 into the first connecting waveguide CI, through the first heating element 2.1 into the first additional optically nonlinear element 1.1, or it couples to it.

[0187] The second logic input IN2 provides the second logic input signal. This is received by the second input waveguide E2 and propagates via the second waveguide coupling element 5.2 into the second connecting waveguide C2, through the second heating element 2.2 into the second further optically nonlinear element 1.2, or couples to it.

[0188] The first logic input signal and the first additional pump signal thus propagate in the first connecting waveguide CI and the first additional optically nonlinear element 1.1 in opposite directions (in positive and negative k-modes, respectively). The second logic input signal and the second additional pump signal also propagate in the second connecting waveguide C2 and the second additional optically nonlinear element 1.2 in opposite directions (in positive and negative k-modes, respectively).

[0189] The first further optically nonlinear element 1.1 has a first further graphene layer 1.1.1 as an optically saturable absorber. The first further graphene layer 1.1.1 is formed as a strip that runs along its longitudinal axis parallel to and above the first connecting waveguide CI and covers it. The first further pump signal and the first logic input signal couple to the first further graphene layer 1.1.1 via the first connecting waveguide CI in the first further optically nonlinear element 1.1 and simultaneously interact with it.

[0190] As a result of this nonlinear interaction, the first additional optically nonlinear element 1.1 couples out the first optical signal and also makes it available in the first connecting waveguide CI. The first optical signal corresponds to the portion of the first additional pump signal not absorbed by the first additional graphene layer 1.1.1 or the portion of the first additional pump signal transmitted through the first additional optically nonlinear element 1.1. The phase of the first optical signal corresponds to the phase of the first additional pump signal.

[0191] The second further optically nonlinear element 1.2 has a second further graphene layer 1.2.1 as an optically saturable absorber. The second further graphene layer 1.2.1 is formed as a strip that runs parallel to the second connecting waveguide C2 along its longitudinal axis and covers it. The second further pump signal and the second logic input signal couple to the second further graphene layer 1.2.1 via the second connecting waveguide C2 in the second further optically nonlinear element 1.2 and simultaneously interact with it.

[0192] As a result of this nonlinear interaction, the second additional optically nonlinear element 1.2 couples out the second optical signal and also makes it available in the second connecting waveguide C2. The second optical signal corresponds to the portion of the second additional pump signal not absorbed by the second additional graphene layer 1.2.1 or the portion of the second additional pump signal transmitted through the second additional optically nonlinear element 1.2. The phase of the second optical signal corresponds to the phase of the second additional pump signal.

[0193] The first optical signal propagates in the first connecting waveguide CI into / to the first heating element 2.1, and the second optical signal propagates into / to the second heating element 2.2. The first 2.1 and second 2.2 heating elements are configured to set a predetermined phase difference or relative phase between the first and second optical signals. The predetermined phase difference or relative phase is n. The first and second optical signals, shifted with respect to their relative phases, propagate via the first 5.1 and second 5.2 waveguide coupling elements into the interference element 3.

[0194] The interference element 3 superimposes or interferes with the first and second optical signals and guides the corresponding superimposed signal into the through-waveguide W. There, it propagates further into the optically nonlinear element 1.3. The superimposed signal, or the first and second optical signals, which are phase-shifted and interfered with by the interference means 3, and the pump signal propagate in the through-waveguide W and in / on the optically nonlinear element 1.3 in opposite directions (in positive and negative k-modes, respectively).

[0195] The optically nonlinear element 1.3 has a graphene layer 1.3.1 as an optically saturable absorber. The graphene layer 1.3.1 is formed as a strip that runs parallel to and overlaps the through-waveguide W along its longitudinal axis. The pump signal and the heterodyne signal couple to the graphene layer 1.3.1 via the through-waveguide W in the optically nonlinear element 1.3 and simultaneously interact with it.

[0196] As a result of this nonlinear interaction, the graphene layer 1.3.1 or the optically nonlinear element 1.3 couples the optical output signal into the through-waveguide W. There, it propagates in the direction of the interference means 3 and is further guided by it into the output waveguide Wa and to the logic output OUT.

[0197] The optical output signal is essentially identical to the logic output signal (except for propagation losses in the waveguides, etc.) and corresponds to the portion of the pump signal not absorbed by the graphene layer 1.3.1 or the portion of the pump signal transmitted through the optically nonlinear element 1.3. The phase of the logic output signal corresponds to the phase of the pump signal.

[0198] The waveguides shown in Figure 1 are made of silicon nitride.

[0199] The reference numerals introduced in Figure 1 are used identically in the figures described below.

[0200] 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 runs at a distance from the first connecting waveguide CI through the first further optically nonlinear element 1.1 and the first heating element 2.1. In the first further optically nonlinear element 1.1, the first further graphene layer 1.1.1 covers both the first input waveguide E1 and the first connecting waveguide CI. The second input waveguide E2 runs at a distance from the second connecting waveguide C2 through the second further optically nonlinear element 1.2 and the second heating element 2.2. In the second further optically nonlinear element 1.2, the second further graphene layer 1.2.1 covers both the second input waveguide E2 and the second connecting waveguide C2.

[0201] In Figure 2, the at least one waveguide W comprises a first waveguide W1, a second waveguide W2, and a third waveguide W3. The first connecting waveguide C1 continuously transitions into the first waveguide W1. The second connecting waveguide C2 continuously transitions into the second waveguide W2. The pump waveguide P3 continuously transitions into the third waveguide W3. The third waveguide W3 continuously transitions into the output waveguide Wa.

[0202] The first W1, second W2, and third W3 waveguides extend through the optically nonlinear element 1.3 at a distance from each other. The third waveguide W3 is arranged in the optically nonlinear element 1.3 between the first W1 and the second W2 waveguides.

[0203] The interference means 3 is a waveguide coupling element and is a part or region of the optically non-linear element 1.3.

[0204] In this region, the first W1 and second W2 waveguides are each coupled to the third waveguide W3 or run close to the third waveguide W3 in such a way that the first and second optical signals, which are shifted with respect to their relative phase, interfere with each other or are superimposed in the third waveguide W3.

[0205] The graphene layer 1.3.1 of the optically nonlinear element 1.3 also covers the first W1, second W2, and third W3 waveguides in this area to enable interaction of the pump signal and the first and second optical signals, which are phase-shifted and interfered with by the interference means 3, with the graphene layer 1.3.1. The optical logic gate shown in the examples in Figures 1 and 2 is operated in a digital mode. The first and second logic states are encoded using amplitude and intensity modulation, respectively.

[0206] A first logic state with bit value 0 is associated with the first and second logic input signals and the logic output signal when they each have a first intensity, and a second logic state with bit value 1 is associated with the first and second logic input signals and the logic output signal when they each have a second intensity, wherein the second intensity of a signal is higher than the first intensity of that signal.

[0207] The signal providing means 1.1, 1.2, together with the optically non-linear element 1.3, is configured to link the intensity of the logic output signal at the logic output OUT with the respective intensities of the first and second logic input signals at the first and second logic inputs INI, IN2 such that the logic output signal, as a function of the first and second logic input signals, is the result of a logical XOR function.

[0208] The intensity of the first further pump signal and the first further graphene layer 1.1.1 are configured such that the first further graphene layer 1.1.1 or the first further optically nonlinear element 1.1 is not optically saturated when the first logic input signal has the first intensity of the first logic input signal or corresponds to the first logical state (bit value 0). In particular, the total intensity, i.e. the addition of the intensities of the first further pump signal and the first logic input signal, is less than the threshold value of the first further graphene layer 1.1.1 when the first logic input signal corresponds to the first logical state. In this case, the intensity of the coupled-out or provided first optical signal is also low or even corresponds to a zero signal. The first optical signal then has the first intensity of the first optical signal or is associated with the first logical state (bit value 0).

[0209] The intensity of the first further pump signal and the first further graphene layer 1.1.1 are further configured such that the first further graphene layer 1.1.1 or the first further optically nonlinear element 1.1 is optically saturated when the first logic input signal has the second intensity of the first logic input signal or corresponds to the second logic state (bit value 1). In particular, the total intensity, i.e. the addition of the intensities of the first further pump signal and the first logic input signal, is greater than the threshold value of the first further 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 or provided first optical signal is high and does not correspond to a zero signal. The first optical signal then has the second intensity of the first optical signal or is associated with the second logic state (bit value 1).

[0210] The intensity of the second further pump signal and the second further graphene layer 1.2.1 are configured such that the second further graphene layer 1.2.1 or the second further optically nonlinear element 1.2 is not optically saturated when the second logic input signal has the first intensity of the second logic input signal or corresponds to the first logical state (bit value 0). In particular, the total intensity, i.e. the addition of the intensities of the second further pump signal and the second logic input signal, is smaller than the threshold value of the second further graphene layer 1.2.1 when the second logic input signal corresponds to the first logical state. In this case, the intensity of the coupled-out or provided second optical signal is also low or even corresponds to a zero signal. The second optical signal then has the first intensity of the second optical signal oris associated with the first logical state (bit value 0).

[0211] The intensity of the second further pump signal and the second further graphene layer 1.2.1 are further configured such that the second further graphene layer 1.2.1 or the second further optically nonlinear element 1.2 is optically saturated when the second logic input signal has the second intensity of the second logic input signal or corresponds to the second logic state (bit value 1). The total intensity, i.e. the addition of the intensities of the second further pump signal and the second logic input signal, is greater than the threshold value of the second further graphene layer 1.2.1 when the second logic input signal corresponds to the second logic state. In this case, the intensity of the coupled-out or provided second optical signal is high and does not correspond to a zero signal. The second optical signal then has the second intensity of the second optical signal or is associated with the second logic state (bit value 1).

[0212] The nonlinear interactions mediated by the first 1.1.1 and second 1.2.1 graphene layers are phase-insensitive. Thus, while the logical states of the first and second logic input signals are transferred to the first and second optical signals by the signal provision means 1.1, 1.2, the phases of the first and second optical signals are identical, regardless of the phases of the first and second logic input signals. This enables a precise and efficient relative phase shift by the first 2.1 and second 2.2 heating elements.

[0213] After the relative phase of the first and second optical signals is fixed or shifted by the first and second heating elements 2.1, 2.2, the first and second optical signals arrive at the interference device 3 at the same time. This device causes the first and second optical signals to interfere or superimpose such that the superimposed signal corresponds to a zero signal (fully destructive interference) when the first optical signal and the second optical signal are associated with the same logical states. The superimposed signal itself is then associated with the first logical state (low intensity or zero signal) (bit value 0).

[0214] The overlay signal does not correspond to a zero signal if the first optical signal and the second optical signal are associated with different logical states. In one embodiment, the signal providing means 1.1, 1.2 is configured such that the first intensity of the first and second optical signals each corresponds to a zero signal (first logical state). The overlay signal then corresponds precisely to the first or second optical signal that corresponds to the second logical state with high intensity. The overlay signal itself is then associated with the second logical state (high intensity) (bit value 1).

[0215] The beat signal then couples simultaneously with the pump signal to the optically nonlinear element 1.3 or its graphene layer 1.3.1. The intensity of the pump signal and the graphene layer 1.3.1 are configured such that the graphene layer 1.3.1 or the optically nonlinear element 1.3 is not optically saturated when the beat signal corresponds to the first logical state (bit value 0). In particular, the total intensity, i.e., the addition of the intensities of the pump signal and the beat signal, is smaller than the threshold value of the graphene layer 1.3.1 or the optically nonlinear element 1.3 when the beat signal corresponds to the first logical state. In this case, the intensity of the coupled-out optical output signal is also low or even corresponds to a zero signal. The optical output signal then has the first intensity of the optical output signal or is associated with the first logical state (bit value 0).

[0216] The intensity of the pump signal and the graphene layer 1.3.1 are further configured such that the graphene layer 1.3.1 or the optically nonlinear element 1.3 is optically saturated when the superposition signal corresponds to the second logical state (bit value 1). The total intensity, i.e., the sum of the intensities of the pump signal and the superposition signal, is greater than the threshold value of the graphene layer 1.3.1 or the optically nonlinear element 1.3 when the superposition signal corresponds to the second logical state. In this case, the intensity of the coupled-out optical output signal is high and does not correspond to a zero signal. The optical output signal then has the second intensity of the optical output signal or is associated with the second logical state (bit value 1).

[0217] Figure 3 shows a logical truth table corresponding to the logical XOR function described above.

[0218] The first column corresponds to the logical state or bit value of the first logic input signal at the first logic input INI. The second column corresponds to the logical state or bit value of the second logic input signal at the second logic input IN2. The third column corresponds to the logical state or bit value of the optical output signal or logic output signal at the logic output OUT. The fourth column corresponds to the phase of the logic output signal.

[0219] The phase 4> of the logic output signal is always the same, regardless of the logical state associated with the first and second logic input signals. The phase 4> corresponds to the phase of the pump signal.

[0220] This significantly improves the modularity and scalability of the optical logic gate.

[0221] Figures 4, 5 and 6 show schematic representations of cross sections through the optical logic gate with a CMOS layer structure in which a graphene layer (hatched area) covers one, two or three waveguides (black area).

[0222] The graphene layer 1.3.1 as part of the optically nonlinear element 1.3, the first additional graphene layer 1.1.1 as part of the first additional optically nonlinear element 1.1, and the second additional graphene layer 1.2.1 as part of the second additional optically nonlinear element 1.2 are each formed as strips. The cross-sections shown correspond to normal planes with respect to the layer plane of the graphene or the longitudinal axis of the graphene strips and waveguides shown.

[0223] Figures 4a, 4b and 4c correspond to the embodiment shown in Figure 1.

[0224] In Figures 4a, 4b, and 4c, the graphene layer 1.3.1 is arranged on or connected to the at least one waveguide or through-waveguide W. Similarly, the first additional graphene layer 1.1.1 is arranged on or connected to the first connecting waveguide CI. The second additional graphene layer 1.2.1 is arranged on or connected to the second connecting waveguide C2.

[0225] In Figure 4a, the graphene layer 1.3.1 is arranged above the at least one waveguide or through waveguide W, the first further graphene layer 1.1.1 above the first connecting waveguide CI and the second further graphene layer 1.2.1 above the second connecting waveguide C2.

[0226] In Figure 4b, the at least one waveguide or through-waveguide W, the first connecting waveguide CI, and the second connecting waveguide C2 each consist of an upper sublayer and a lower sublayer. The respective graphene layer is arranged between the upper and lower sublayers and connected to the first and second sublayers.

[0227] In Figure 4c, the graphene layer 1.3.1, the first additional graphene layer

[0228] 1.1.1 and the second additional graphene layer 1.2.1 each consist of at least two sublayers or layers of graphene with a corresponding passivation GP between the two sublayers or layers. The passivation GP can be formed with or consist of silicon nitride or silicon oxide.

[0229] Figures 5a, 5b, and 5c each correspond to a schematic representation of a cross-section of a CMOS layer structure with graphene analogous to Figures 4a, 4b, and 4c, but each with two waveguides according to the embodiment shown in Figure 2. The first additional graphene layer 1.1.1 is arranged directly on the first connecting waveguide CI and the first input waveguide E1. The second additional graphene layer

[0230] 1.2.1 is arranged directly on the second connecting waveguide C2 and the second input waveguide E2.

[0231] Figures 6a, 6b, and 6c each correspond to a schematic representation of a cross-section of a CMOS layer structure with graphene analogous to Figures 4a, 4b, and 4c, but each with three waveguides according to the embodiment shown in Figure 2. The graphene layer 1.3.1 of the optically nonlinear element 1.3 is arranged directly on the first waveguide W1, the second waveguide W2, and the third waveguide W3.

[0232] Figures 7a and 7b show the schematic representation of cross sections through the phase modulation means 2.1, 2.2.

[0233] The first 2.1 and second 2.2 heating elements each have a metal layer (dotted areas) that is electrically connected and can thus be heated. The electrical resistance of the respective metal layer leads to heating and a change in the refractive index of the waveguides located underneath when an electrical power supply is applied.

[0234] The cross sections shown in Figure 7 correspond to normal planes with respect to the layer planes of the metal layers and the longitudinal axes of the waveguides shown.

[0235] Figure 7a shows a cross section of the CMOS-based layer structure of the phase modulation means 2.1, 2.2 according to the embodiment shown in Figure 1.

[0236] The first heating element 2.1, with its metal layer, is arranged above the first connecting waveguide CI and spaced apart from it. The first heating element 2.1 is integrated with the first connecting waveguide CI in a CMOS layer structure.

[0237] The second heating element 2.2 is arranged with its metal layer above the second connecting waveguide C2 and spaced apart from it. The second heating element 2.2 is integrated with the second connecting waveguide C2 in a CMOS layer structure.

[0238] Figure 7b shows a cross section of the CMOS-based layer structure of the phase modulation means 2.1, 2.2 according to the embodiment shown in Figure 2.

[0239] The first heating element 2.1, with its metal layer, is arranged above the first connecting waveguide CI and the first input waveguide E1 and spaced apart from them. The first heating element 2.1 is integrated with the first connecting waveguide CI and the first input waveguide E1 in a CMOS layer structure.

[0240] The second heating element 2.2 is arranged with its metal layer above the second connecting waveguide C2 and the second input waveguide E2 and spaced apart from them. The second heating element 2.2 is integrated with the second connecting waveguide C2 and the second input waveguide E2 in a CMOS layer structure.

[0241] Figures 8a and 8b show a nonlinear input / output characteristic and a transmittance of the optically nonlinear element 1.3. Figure 8a shows the intensity of the optical output signal l ou t as a function of the total intensity hn of the simultaneously coupled or interacting input signals (solid line). The total intensity hn corresponds to the sum of the intensity of the pump signal IP and the intensity of the superimposed signal. The vertical dotted line corresponds to the threshold value of the saturable absorption of the optically nonlinear element 1.3 or the graphene layer 1.3.1.

[0242] If the total intensity hn of the simultaneously coupled or interacting input signals is smaller than the threshold value, the intensity of the optical output signal l out is very low (e.g., zero signal). The optical output signal then has the first intensity of the optical output signal or corresponds to the first logical state. This is the case when the first and second logic input signals correspond to different logical states.

[0243] If the total intensity hn of the simultaneously coupled or interacting input signals is greater than the threshold value, the intensity of the optical output signal l ou t high (no zero signal). The optical output signal then has the second intensity of the optical output signal or corresponds to the second logical state. This is the case when the first and second logic input signals correspond to the same logical states.

[0244] Figure 8b shows the transmittance T of the optically nonlinear element 1.3 or the portion of the pump signal not absorbed by the graphene layer 1.3.1 and transmitted through the optically nonlinear element 1.3 as a function of the total intensity hn.

[0245] The permeability T results from the comparison of the intensity of the pump signal l p with the intensity of the optical output signal l ou t, where lout = T Ip. The permeability T is exponentially related to the length x of the graphene layer 1.3.1, where T = e' axwith an intensity-dependent propagation loss a = a(hn) (per micrometer). The transmittance T describes a sigmoid function with the threshold of optical saturation as the inflection point. Below the threshold, the transmittance T is low, and the pump signal is almost completely absorbed by the graphene layer 1.3.1 in the optically nonlinear element 1.3. The logic output signal has a correspondingly low intensity, corresponding to the first intensity of the optical output signal.

[0246] Above the threshold value, the transmittance T exhibits a plateau as a signature of the optical saturation of the optically nonlinear element 1.3 or the graphene layer 1.3.1. The pump signal can transmit through the optically nonlinear element 1.3 or pass through the graphene layer 1.3.1 without being completely absorbed. The logic output signal has a correspondingly high intensity, which corresponds to the second intensity of the optical output signal. Individual or multiple features of the embodiments shown in Figures 1 to 8 can also be combined with one another.

Claims

Claims Optical logic gate comprising: Signal providing means (1.1, 1.2) for providing 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 respective phases of the first and second optical signals are the same; Phase modulation means (2.1, 2.2) for shifting the phase of the first optical signal with respect to the phase of the second optical signal by a predetermined phase difference; an interference means (3) configured to cause the first and second optical signals, whose phases have been shifted by the phase modulation means (2.1, 2.2), to interfere with each other; an optically non-linear element (1.3) configured to interact with a pump signal and 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 couple out an optical output signal as a logic output signal as a result of this non-linear interaction. Optical logic gate according to the preceding claim, wherein the predetermined phase difference is n and the signal providing means (1.1, 1.2) together with the optically non-linear element (1.3) are configured to link the intensity of the logic output signal with the respective intensities of the first and second logic input signals such that the logic output signal as a function of the first and second logic input signals is the result of a logical XOR function, wherein the respective logical states of the first and second logic input signals and the logic output signal are intensity modulated.

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

4. Optical logic gate according to claim 2 or 3, wherein the signal providing means (1.1, 1.2) together with the optically non-linear 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 which logic state the first and second logic input signals are respectively associated with.

5. Optical logic gate according to one of the preceding claims, wherein the optical output signal corresponds to the portion of the pump signal transmitted through the optically non-linear element (1.3) and / or the phase of the optical output signal corresponds to the phase of the pump signal.

6. Optical logic gate according to one of the preceding claims, wherein the optically non-linear element (1.3) has a graphene layer as an optically saturable absorber (1.3, 1.3.1) for mediating the non-linear interaction in the optically non-linear element (1.3).

7. Optical logic gate according to one of the preceding claims, further comprising at least one waveguide (W, W1, W2, W3) which passes through the optically non-linear element (1.3) and / or couples to the optically non-linear element (1.3), wherein the at least one waveguide (W, W1, W2, W3) is designed to couple the pump signal propagating in a first direction into or to the optically non-linear element (1.3); and Receiving the optical output signal propagating in the first direction from the optically nonlinear element (1.3); and receiving the first and second optical signals, whose phases are shifted by the phase modulation means (2.1, 2.2) and interfered with by the interference means (3), propagating in a second direction opposite to the first direction, and coupling them into or to the optically nonlinear element (1.3). The 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 in a CMOS-based layer structure and arranged one above the other in such a way that electromagnetic coupling between the graphene layer (1.3, 1.3.1) and the at least one waveguide (W, W1, W2, W3) is ensured. Optical logic gate according to one of the preceding claims, wherein the signal providing means (1.1, 1.2) comprises a first (1.1) and a second (1.2) further optically non-linear element, and wherein the first further optically non-linear element (1.1) is configured to interact with a first further pump signal and the first logic input signal and, as a result of this non-linear interaction, to couple out and provide the first optical signal, wherein the first optical signal corresponds to the portion of the first further pump signal transmitted through the first further optically non-linear element 1.1 and / or the phase of the first optical signal corresponds to the phase of the first further pump signal; the second further optically non-linear element (1.2) is configured to interact with a second further pump signal and the second logic input signal and, as a result of this non-linear interaction, to couple out and provide the second optical signal, wherein the second optical signal corresponds to the portion of the first further pump signal transmitted through the second further optically non-linear element (1.2) transmitted portion of the second further pump signal and / or the phase of the second. optical signal corresponds to the phase of the second further pump signal. Optical logic gate according to claim 9, further comprising: a first connecting waveguide (CI) which runs through the first further optically non-linear element (1.1) and connects it to the phase modulation means (2.1, 2.2), the interference means (3), the optically non-linear element (1.3) and / or the at least one waveguide (W, W1, W2, W3), wherein the first connecting waveguide (CI) is configured to receive the first further pump signal propagating in a first direction and to couple it into or to the first further optically non-linear element (1.1); and to receive the first optical signal propagating in the first direction and to couple it to or to the phase modulation means (2.1, 2.2), the interference means (3), the optically non-linear element (1.3)3) and / or the at least one waveguide (W, WI, W2, W3); and a second connecting waveguide (C2) which runs through the second further optically non-linear element (1.2) and connects it to the phase modulation means (2.1, 2.2), the interference means (3), the optically non-linear element (1.3) and / or the at least one waveguide (W, WI, W2, W3), wherein the second connecting waveguide (C2) is configured to receive the second further pump signal propagating in a first direction and to couple it into or to the second further optically non-linear element (1.2); and to receive the second optical signal propagating in the first direction and to transmit it to or into the phase modulation means (2.1, 2.2), the interference means (3), the optically non-linear element (1.3) and / or the at least one waveguide (W, WI, W2, W3). An optical logic gate according to claim 10, wherein the first logic input signal couples into or to the first further optically nonlinear element (1.1) in a second direction opposite to the first; and the second logic input signal couples into or to the second further optically nonlinear element (1.2) in a second direction opposite to the first. A method for operating an optical logic gate according to any one of claims 1 to 11, comprising the following steps: Providing a first optical signal based on a first logic input signal and a second optical signal based on a second logic input signal by means of the signal providing means (1.1, 1.2), wherein the respective phases of the first and second optical signals are the same; Shifting the relative phase of the first and second optical signals by a predetermined phase difference by means of the phase modulation means (2.1, 2.2); after shifting the relative phase, interfering the first and second optical signals by means of the interference means (3); Interaction of a pump signal and the first and second optical signals interfered by the interference means (3) with the optically nonlinear element (1.3) and, as a result of this nonlinear interaction, coupling out an optical output signal as a logic output signal from the optically nonlinear element (1-3). Method according to claim 12, further comprising Operating the optical logic gate in a digital operating mode with amplitude or intensity modulation, wherein the predetermined phase difference is n; and wherein operating in the digital operating mode comprises: Associating a first logic state with a first intensity of each of the first logic input signal, the second logic input signal, and the logic output signal; and Associating a second logical state with a second intensity of the first logic input signal, the second logic input signal, and the logic output signal, each different from the first, wherein the association is carried out such that the logic output signal as a function of the first and second logic input signals is the result of a logical XOR function. The method according to claim 13, wherein if the first and second logic input signals have different intensities or are associated with different logical states, the phase of the logic output signal is always the same, regardless of the logical state with which the first and second logic input signals are respectively associated. The method according to claim 12, 13, or 14, wherein the optically nonlinear element (1.3) comprises an optically saturable absorber (1.3, 1.3.1) for mediating the nonlinear interaction in the optically nonlinear element (1.3).3), and wherein the intensity of the pump signal is selected such that the optically saturable absorber (1.3, 1.3.1) is optically saturated during the 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 states; and / or wherein the optical output signal corresponds to the portion of the pump signal not absorbed by the optically saturable absorber (1.3, 1.3.1) and transmitted through the non-linear element (1.3).

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