An electrical-optical modulator may include a first section configured for a first electrical-optical interaction between one or more optical waveguides and one or more signal electrodes. The electrical-optical modulator may include a second section configured to increase or decrease a relative velocity of signals of the one or more signal electrodes to optical signals of the one or more optical waveguides relative to the first section. The electrical-optical modulator may include a third section configured for a second electrical-optical interaction between the one or more optical waveguides and the one or more signal electrodes according to an opposite modulation polarity relative to the first section.

TECHNICAL FIELD

The present disclosure relates to electrical-optical modulators and, more particularly, to electrical-optical modulators utilizing a velocity-changed electrode signal.

BACKGROUND

Optical modulators, such as electrical-optical modulators, impress or modulate electrical signals, such as radio frequency (RF) signals or microwave signals, onto an optical beam in order to generate a modulated optical beam that carries data. A typical electrical-optical modulator may be a voltage-controlled device that includes a traveling-wave electrode structure positioned in close proximity to an optical waveguide. The electrode structure produces an electric field that overlaps the optical waveguide over a predetermined distance (the interaction length) and causes an electromagnetic interaction that modulates the optical signal. For example, an electrical-optical modulator may include a set of RF signal electrodes, a set of ground electrodes, and a set of coplanar optical waveguides. The set of coplanar waveguides can be part of a Mach-Zehnder (MZ) interferometer.

SUMMARY

According to some implementations, an electrical-optical modulator may include one or more optical waveguides to propagate optical signals in a direction of propagation, and one or more signal electrodes to propagate signals in the direction of propagation in order to modulate the optical signals through electrical-optical interaction. The one or more signal electrodes may include a velocity change section, a first modulation section preceding the velocity change section in the direction of propagation, and a second modulation section following the velocity change section in the direction of propagation. An optical waveguide, of the one or more optical waveguides, may include a first section and a second section configured to be associated with opposite modulation polarities based on an association with the first modulation section and the second modulation section of the one or more signal electrodes. The velocity change section may be configured to increase or decrease a relative velocity of the signals to the optical signals relative to the first modulation section.

According to some implementations, an electrical-optical modulator may include a first section configured for a first electrical-optical interaction between one or more optical waveguides and one or more signal electrodes, a second section configured to increase or decrease a relative velocity of signals of the one or more signal electrodes to optical signals of the one or more optical waveguides relative to the first modulation section, and a third section configured for a second electrical-optical interaction between the one or more optical waveguides and the one or more signal electrodes according to an opposite modulation polarity relative to the first section.

According to some implementations, an electrical-optical modulator may include one or more velocity change sections, and one or more modulation polarity reversal sections. The electrical-optical modulator may have a frequency response characterized by a modulation bandwidth above a threshold value.

DETAILED DESCRIPTION

An electrical-optical modulator may modulate an optical signal over a bandwidth. Typically, the bandwidth may be increased by reducing electrical (e.g., RF) signal loss, such as by reducing an interaction length of an electrode and an optical waveguide of the electrical-optical modulator (e.g., by reducing a length of the electrode). However, reducing the interaction length may require an increase in a drive voltage of the electrical-optical modulator. Other approaches may use an equalization technique to increase bandwidth and reduce drive voltage. According to the equalization technique, the electrical-optical modulator may include an electrode path delay (e.g., a circuitous path of the electrode) to provide a time delay of the electrical signal, and may include a modulation polarity reversal, for example, to adapt to a phase shift caused by the time delay. However, the electrode path delay also may increase electrical signal loss (e.g., by increasing the length of the electrode). Moreover, the electrode path delay increases a footprint of the electrical-optical modulator, which may cause interference (e.g., crosstalk) between electrodes of multiple nested electrical-optical modulators.

Some implementations described herein provide an electrical-optical modulator that includes one or more modulation sections, a velocity change section associated with one or more signal electrodes of the electrical-optical modulator, and a modulation polarity reversal of one or more optical waveguides of the electrical-optical modulator in one or more of the modulation sections. In this way, the electrical-optical modulator is equalized to provide a frequency response with increased modulation bandwidth. Moreover, the velocity change section enables a length of an electrode of the electrical-optical modulator to be minimized, thereby reducing electrical (e.g., RF) signal loss that may decrease bandwidth. Furthermore, the velocity change section enables compact geometries for the electrical-optical modulator that can reduce or eliminate interference with other nearby (e.g., nested) electrical-optical modulators.

FIGS. 1-4, 6A, 8A, and 9are diagrams of example electrical-optical modulators described herein. An electrical-optical modulator may be a modulator that uses a Pockels effect, an electro-optic effect, a quantum-confined Stark effect, a plasma dispersion effect, and/or the like, to change a phase of light under an applied voltage. In some implementations, an electrical-optical modulator may be an MZ modulator. For example, an electrical-optical modulator may be an indium phosphide (InP) MZ modulator. Alternatively, an electrical-optical modulator may employ silicon photonics, polymer, lithium niobate, thin lithium niobate, or gallium arsenide technologies.

In some implementations, an electrical-optical modulator may include one or more optical waveguides and one or more signal electrodes (e.g., one or more traveling-wave electrodes). A waveguide may propagate an optical signal in a direction of propagation of an electrical-optical modulator. An electrode may propagate an electrical signal (e.g., an RF signal, a microwave signal, and/or the like) in the direction of propagation. The electrical signal may modulate the optical signal through an electrical-optical interaction.

In some implementations, an electrical-optical modulator may include a set of waveguides (e.g., two waveguides). For example, an optical splitter may split an input optical signal to a first waveguide and a second waveguide of the electrical-optical modulator, and an optical combiner may combine an output of the first waveguide and the second waveguide. In some implementations, an electrical-optical modulator may include a set of electrodes (e.g., two electrodes). That is, the electrical-optical modulator may have a differential drive voltage. In such a case, a first electrode may propagate a positive polarity signal and a second electrode may propagate a negative polarity signal. Alternatively, an electrical-optical modulator may include a single electrode. That is, the electrical-optical modulator may have a single drive voltage.

As shown inFIGS. 1-4, 6A, 8A, and 9an electrical-optical modulator may have a first section of length S1, a second section of length S2, and a third section of length S3. In some implementations, S1may be greater than S2or S3. Additionally, or alternatively, S2may be greater than S3. The first section, the second section, and the third section may be referred to herein as S1, S2, and S3, respectively. The first section S1and the third section S3may provide modulation for the electrical-optical modulator. That is, in the first section S1and the third section S3, a waveguide and an electrode may interact (e.g., via electrical-optical interaction, via a quantum-confined Stark effect, via a plasma effect, and/or the like). Moreover, an electrical-optical interaction in the first section S1between one or more waveguides and one or more electrodes, and an electrical-optical interaction in the third section S3between the waveguides and the electrodes, may be according to opposite modulation polarities. In other words, a waveguide may be associated with opposite modulation polarities in the first section S1and the third section S3.

In the second section S2, an electrode may be configured to change (e.g., increase or decrease) a velocity of signals propagated by the electrode relative to a velocity of the signals when passing through the first section S1and/or the third section S3. For example, for an InP MZ modulator, the electrode may be configured to increase a velocity of signals in the second section S2. Moreover, in the second section S2, a velocity of optical signals propagated by a waveguide may remain constant (e.g., relative to sections S1and S3). In some aspects, in the second section S2, a relative velocity of electrical signals of the electrode to optical signals of the waveguide may be different than in the first section S1and/or the third section S3. Accordingly, signal velocities of the electrode and the waveguide may not be matched in the second section S2. In this way, the electrical-optical modulator may be equalized and may have a frequency response characterized by a modulation bandwidth that satisfies (e.g., is greater than) a threshold value (e.g., 60 gigahertz (GHz), 75 GHz, 80 GHz, or 85 GHz). Moreover, electrodes and waveguides of the electrical-optical modulator may be in a straight line (e.g., configured to provide a direct path for a signal). In this way, the electrical-optical modulator has a compact geometry that can reduce or eliminate interference with other nearby (e.g., nested) electrical-optical modulators.

FIG. 1is a diagram of an example electrical-optical modulator100described herein. As shown inFIG. 1, electrical-optical modulator100may include a first signal electrode102a, a second signal electrode102b, a first optical waveguide104a, and a second optical waveguide104b. Electrical signals of the electrodes102may interact with optical signals of the waveguides104via a plurality of segmented loading lines108. For example, the loading lines108may cover (e.g., abut, attach to, be in proximity of, cause electrical-optical interaction with, or otherwise be in association with) portions of the waveguides104. The electrodes102may be configured to propagate an electrical signal in a direction of propagation110of the electrical-optical modulator100, and the waveguides104may be configured to propagate an optical signal in the direction of propagation110.

As shown inFIG. 1, the first electrode102amay include a first modulation section (spanning S1), a velocity change section106a(spanning S2), and a second modulation section (spanning S3). Similarly, the second electrode102bmay include a first modulation section (spanning S1), a velocity change section106b(spanning S2), and a second modulation section (spanning S3). In a velocity change section106, signals of an electrode102may have a different (e.g., increased) velocity relative to a first modulation section and/or a second modulation section of the electrode102. Additionally, or alternatively, in a velocity change section106, a relative velocity of signals of an electrode102to optical signals of a waveguide104may be different relative to a first modulation section and/or a second modulation section of the electrode102. In this way, the electrical signals may change phase (e.g., a phase shift of 180 degrees) relative to the imparted modulation on the optical signals of a waveguide104in the first modulation section (spanning S1).

In some implementations, the velocity change section106of the electrode102may be configured to have an RF mode index that is different (e.g., less) than an RF mode index of the first modulation section or the second modulation section of the electrode102, to thereby cause a signal velocity change. For example, the RF mode index may be less than 3 in the velocity change section106, and the RF mode index may be greater than 3 in the first modulation section or the second modulation section. Additionally, or alternatively, the velocity change section106of the electrode102may be configured to have an RF mode index that is different (e.g., less) than an optical mode index of a corresponding section of a waveguide104(e.g., a corresponding section of the waveguide104in section S2). For example, the RF mode index of the electrode102may be less than 3, and the optical mode index of the waveguide104may be greater than 3. As an example, the RF mode index may be 2.6, and the optical mode index may be 3.7.

In some implementations, the velocity change section106of the electrode102may have an electrode width (e.g., transverse to the direction of propagation110) that is different (e.g., greater) than an electrode width of the first modulation section or the second modulation section of the electrode102, to thereby cause a signal velocity change. For example, the electrode width in the velocity change section106may be at least 10%, at least 25%, at least 50%, at least 75%, or at least 100% greater than the electrode width in the first modulation section or the second modulation section.

In some implementations, as shown inFIG. 1, the velocity change section106of the electrode102may not include a loading line108, and the first modulation section or the second modulation section of the electrode102may include one or more loading lines108, to thereby cause a signal velocity change. Alternatively, the velocity change section106of the electrode102may include a quantity of loading lines108that is different (e.g., less) than a quantity of loading lines108included in the first modulation section or the second modulation section of the electrode102. For example, the velocity change section106may include one or two loading lines108, and the first modulation section or the second modulation section may include greater than one or two loading lines108, respectively.

As shown inFIG. 1, a first section (associated with section S1) and a second section (associated with section S3) of a waveguide104may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the electrodes102. In some implementations, the opposite modulation polarities are based on a crossing of the first waveguide104aand the second waveguide104b. For example, in the first section S1, the first electrode102a(+ signal) may modulate an optical signal of the first waveguide104a, and the second electrode102b(− signal) may modulate an optical signal of the second waveguide104b. Continuing with the previous example, in the third section S3, the first electrode102a(+ signal) may modulate an optical signal of the second waveguide104b, and the second electrode102b(− signal) may modulate an optical signal of the first waveguide104a, thereby reversing modulation polarity experienced by the second waveguide104brelative to the first waveguide104a. In particular, in the second section S2, the first waveguide104aand the second waveguide104bmay cross, to thereby redirect the first waveguide104ato the second electrode102band the second waveguide104bto the first electrode102a. In this way, modulation polarity may be reversed while a relative position of the loading lines108in the first section S1and the third section S3remains consistent.

In some implementations, the first waveguide104aand the second waveguide104bmay cross substantially orthogonally in the second section S2. For example, the first waveguide104aand the second waveguide104bmay cross at an angle of about 90 degrees (e.g., within ±10%, ±5%, or ±1%). In some implementations, the first waveguide104aand the second waveguide104bmay cross at an angle greater than 75 degrees. In this way, optical loss and/or crosstalk due to the crossing may be reduced. In some implementations, the width, or one or more other geometrical features, of the waveguides104may be different at a point of the crossing (or in the second section S2) relative to other portions of the waveguides104.

As indicated above,FIG. 1is provided merely as an example. Other examples may differ from what is described with regard toFIG. 1.

FIG. 2is a diagram of an example electrical-optical modulator200described herein. As shown inFIG. 2, electrical-optical modulator200may include a first signal electrode202a, a second signal electrode202b, a first optical waveguide204a, and a second optical waveguide204b. Electrical signals of the electrodes202may interact with optical signals of the waveguides204via a plurality of segmented loading lines208, as described above in connection withFIG. 1. The electrodes202may be configured to propagate an electrical signal in a direction of propagation210of the electrical-optical modulator200, and the waveguides204may be configured to propagate an optical signal in the direction of propagation210.

As shown inFIG. 2, the first electrode202amay include a first modulation section (spanning S1), a velocity change section206a(spanning S2), and a second modulation section (spanning S3), and the second electrode202bmay include a first modulation section (spanning S1), a velocity change section206b(spanning S2), and a second modulation section (spanning S3), as described above in connection withFIG. 1. In a velocity change section206, signals of an electrode202may have a different velocity relative to a first modulation section and/or a second modulation section of the electrode202, as described above in connection withFIG. 1.

As shown inFIG. 2, a first section (associated with section S1) and a second section (associated with section S3) of a waveguide204may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the electrodes202. In some implementations, the opposite modulation polarities are based on a crossing of the first electrode202aand the second electrode202b. For example, in the first section S1, the first electrode202a(+ signal) may modulate an optical signal of the first waveguide204a, and the second electrode202b(− signal) may modulate an optical signal of the second waveguide204b. Continuing with the previous example, in the third section S3, the first electrode202a(+ signal) may modulate an optical signal of the second waveguide204b, and the second electrode202b(− signal) may modulate an optical signal of the first waveguide204a, thereby reversing modulation polarity experienced by the second waveguide204brelative to the first waveguide204a. In particular, in the second section S2, the velocity change section206aand the velocity change section206bmay cross, to thereby redirect the second electrode202bto the first waveguide204aand the first electrode202ato the second waveguide204b. In this way, modulation polarity may be reversed while a relative position of the loading lines208in the first section S1and the third section S3remains consistent.

In some implementations, the velocity change section206aand the velocity change section206bmay cross substantially orthogonally. For example, the velocity change section206aand the velocity change section206bmay cross at an angle of about 90 degrees (e.g., within ±10%, ±5%, or ±1%). In some implementations, the velocity change section206aand the velocity change section206bmay cross at an angle greater than 75 degrees. In this way, signal loss and/or crosstalk due to the crossing may be reduced.

As shown inFIG. 2, the first electrode202amay be segmented to enable the crossing of the first electrode202aand the second electrode202b. For example, the velocity change section206amay include a gap. The velocity change section206amay include a wire bond212that bridges the gap. Additionally, or alternatively, the second electrode202bmay include a gap and corresponding wire bond212. In some implementations, velocity change section206amay include a first via, an electrode on another electrode layer (e.g., below velocity change section206a), and a second via. The vias may connect velocity change section206ato the electrode on the other electrode layer, to thereby bridge the gap in the velocity change section206a. In this case, the crossing may be below velocity change section206b, rather than above, as in the case of a wire bond. Moreover, the velocity change sections206and the electrode on the other layer may be separated vertically by silicon dioxide or other insulator layers (e.g., in a manner used for silicon photonic Photonic Integrated Circuits (PICs)).

As indicated above,FIG. 2is provided merely as an example. Other examples may differ from what is described with regard toFIG. 2.

FIG. 3is a diagram of an example electrical-optical modulator300described herein. As shown inFIG. 3, electrical-optical modulator300may include a first signal electrode302a, a second signal electrode302b, a first optical waveguide304a, and a second optical waveguide304b. Electrical signals of the electrodes302may interact with optical signals of the waveguides304via a plurality of segmented loading lines308, as described above in connection withFIG. 1. The electrodes302may be configured to propagate an electrical signal in a direction of propagation310of the electrical-optical modulator300, and the waveguides304may be configured to propagate an optical signal in the direction of propagation310.

As shown inFIG. 3, the first electrode302amay include a first modulation section (spanning S1), a velocity change section306a(spanning S2), and a second modulation section (spanning S3), and the second electrode302bmay include a first modulation section (spanning S1), a velocity change section306b(spanning S2), and a second modulation section (spanning S3), as described above in connection withFIG. 1. In a velocity change section306, signals of an electrode302may have a different velocity relative to a first modulation section and/or a second modulation section of the electrode302, as described above in connection withFIG. 1.

As shown inFIG. 3, a first section (associated with section S1) and a second section (associated with section S3) of a waveguide304may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the electrodes302. In some implementations, the opposite modulation polarities are based on loading lines308of the first electrode302ahaving an association with a first section of the first waveguide304aand a second section of the second waveguide304b, and loading lines308of the second electrode302bhaving an association with a first section of the second waveguide304band a second section of the first waveguide304a.

For example, in the first section S1, the first electrode302a(+ signal) may modulate an optical signal of the first waveguide304a, and the second electrode302b(− signal) may modulate an optical signal of the second waveguide304b. In particular, in the first section S1, loading lines308of the first electrode302amay cover the first waveguide304a, and loading lines308of the second electrode302bmay cover the second waveguide304b. Continuing with the previous example, in the third section S3, the first electrode302a(+ signal) may modulate an optical signal of the second waveguide304b, and the second electrode302b(− signal) may modulate an optical signal of the first waveguide304a, thereby reversing modulation polarity experienced by the second waveguide304brelative to the first waveguide304a. In particular, in the third section S3, loading lines308of the first electrode302amay cover the second waveguide304b, and loading lines308of the second electrode302bmay cover the first waveguide304a.

As indicated above,FIG. 3is provided merely as an example. Other examples may differ from what is described with regard toFIG. 3.

FIG. 4is a diagram of an example electrical-optical modulator400described herein. As shown inFIG. 4, electrical-optical modulator400may include a first signal electrode402a, a second signal electrode402b, a first optical waveguide404a, and a second optical waveguide404b. Electrical signals of the electrodes402may interact with optical signals of the waveguides404via a plurality of segmented loading lines408, as described above in connection withFIG. 1. The electrodes402may be configured to propagate an electrical signal in a direction of propagation410of the electrical-optical modulator400, and the waveguides404may be configured to propagate an optical signal in the direction of propagation410.

As shown inFIG. 4, the first electrode402amay include a first modulation section (spanning S1), a velocity change section406a(spanning S2), and a second modulation section (spanning S3), and the second electrode402bmay include a first modulation section (spanning S1), a velocity change section406b(spanning S2), and a second modulation section (spanning S3), as described above in connection withFIG. 1. In a velocity change section406, signals of an electrode402may have a different velocity relative to a first modulation section and/or a second modulation section of the electrode402, as described above in connection withFIG. 1.

As shown inFIG. 4, a first section (associated with section S1) and a second section (associated with section S3) of a waveguide404may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the electrodes402. In some implementations, the opposite modulation polarities may be based on the first section and the second section being disposed between semiconductor structures of different material structures.

For example, in the first section S1, a first section of the first waveguide404amay be disposed in a first semiconductor structure502(as shown inFIG. 5) configured for a first modulation polarity, and in the third section S3, a second section of the first waveguide404amay be disposed in a second semiconductor structure504(as shown inFIG. 5) configured for a second modulation polarity that is opposite to the first modulation polarity. Similarly, in the first section S1, a first section of the second waveguide404bmay be disposed in a first semiconductor structure, and in the third section S3, a second section of the second waveguide404bmay be disposed in a second semiconductor structure.

As indicated above,FIG. 4is provided merely as an example. Other examples may differ from what is described with regard toFIG. 4.

In this way, lengths and/or modulation polarities of the modulation sections and/or the velocity change sections may be tailored (e.g., using a model of frequency response) to target a particular frequency response. Furthermore, using multiple modulation sections and/or velocity change sections enables tailoring of a shape of an electrical-optical frequency response to further target a particular frequency response bandwidth and/or shape. For example, the frequency response shape may be tailored to be complementary to a shape of a particular electrical driver.

FIG. 5is a diagram of an example500of semiconductor structures. In particular, as shown inFIG. 5, a first semiconductor structure502may be different (e.g., have a different material structure, such as different layers) than a second semiconductor structure504. For example, the first semiconductor structure502may have a p-i-n semiconductor structure, and the second semiconductor structure504may have an n-i-p semiconductor structure. In this way, the first semiconductor structure502and the second semiconductor structure504may provide opposite modulation polarities to sections of an optical waveguide, as described above.

As shown inFIG. 5, the semiconductor structure502and the semiconductor structure504may be disposed between a ground electrode506and a loading line508of a signal electrode, as described above. The semiconductor structure502may include, from the ground electrode506, an n+ type semiconductor layer (e.g., n+ type InP layer), an n-type semiconductor region (e.g., n-type InP region), an intrinsic homogeneous or layered multiple quantum well (i-MQW) region, a p-type semiconductor region (e.g., p-type InP region), a p+ type semiconductor region (e.g., p+ type indium gallium arsenide (InGaAs) region), and a p-type semiconductor contact.

As shown inFIG. 5, the semiconductor structure504may include, from the ground electrode506, an n+ type semiconductor layer (e.g., n+ type InP layer), a p-type semiconductor region (e.g., p-type InP region), a homogeneous or layered i-MQW region, an n-type semiconductor region (e.g., n-type InP region), an n+ type semiconductor region (e.g., n+ type InGaAs region), and an n-type semiconductor contact.

Ground electrodes506in semiconductor structures502and504may be direct current (DC)-isolated from each other, yet have low RF impedance to RF ground, using capacitive and inductor circuits, to allow for independent reverse biasing of the PN junctions in502and504. In some implementations, if the frequency response is dependent on a magnitude of reverse bias, the overall equalized frequency response may be tuned by statically or dynamically tuning the magnitudes of reverse bias voltages.

As indicated above,FIG. 5is provided merely as an example. Other examples may differ from what is described with regard toFIG. 5.

FIG. 6Ais a diagram of an example electrical-optical modulator600described herein. In some implementations, the electrical-optical modulator600may employ silicon photonics. As shown inFIG. 6A, electrical-optical modulator600may include a first signal electrode602a(+ signal), a second signal electrode602b(− signal), a first optical waveguide604a, and a second optical waveguide604b. Electrical signals of the signal electrodes602may interact with optical signals of the waveguides604based on a proximity between the signal electrodes602and the waveguides604. For example, electrical signals of the first signal electrode602amay interact with optical signals of the first waveguide604a, and electrical signals of the second signal electrode602bmay interact with optical signals of the second waveguide604b. The signal electrodes602may be configured to propagate an electrical signal in a direction of propagation610of the electrical-optical modulator600, and the waveguides604may be configured to propagate an optical signal in the direction of propagation610.

As shown inFIG. 6A, the electrical-optical modulator600may include a first bias electrode608ain section S1, and a second bias electrode608bin section S3. The first bias electrode608amay be between the first waveguide604aand the second waveguide604bin section S1, and the second bias electrode608bmay be between the first waveguide604aand the second waveguide604bin section S3. The first waveguide604aand the second waveguide604bmay be between the first signal electrode602aand the second signal electrode602b.

The first bias electrode608aand the second bias electrode608bmay be isolated (e.g., electrically isolated) from each other. For example, the first bias electrode608amay provide a first bias voltage (e.g., a first direct current (DC) voltage), and the second bias electrode608bmay provide a second bias voltage (e.g., a second DC voltage). In some implementations, the first bias voltage and the second bias voltage may have opposite polarities. In some implementations, the first bias voltage and the second bias voltage may have the same magnitude (e.g., with opposite polarities) or may be different (e.g., the first bias voltage and the second bias voltage may be tuned). The first bias electrode608amay provide reverse biasing for one or more first semiconductor junctions in section S1, as described below, and the second bias electrode608bmay provide reverse biasing for one or more second semiconductor junctions in section S2, as described below.

As shown inFIG. 6A, the first signal electrode602amay include a first modulation section (spanning S1), a velocity change section606a(spanning S2), and a second modulation section (spanning S3). Similarly, the second signal electrode602bmay include a first modulation section (spanning S1), a velocity change section606b(spanning S2), and a second modulation section (spanning S3). In a velocity change section606, signals of a signal electrode602may have a different velocity relative to a first modulation section and/or a second modulation section of the signal electrode602, as described above in connection withFIG. 1.

A first section (associated with section S1) and a second section (associated with section S3) of a waveguide604may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the signal electrodes602. That is, section S1and section S3of the electrical-optical modulator600may have opposite modulation polarities. In some implementations, the opposite modulation polarities are based on a semiconductor structure associated with section S1having a reversed orientation relative to a semiconductor structure associated with section S3, as described below.

In some implementations, portions of the waveguides604in section S1and section S3of the electrical-optical modulator600may be rib-type waveguides (shown inFIGS. 6C, 6E, 6F, 6I, 6K, and 6L). Additionally, or alternatively, portions of the waveguides604in section S2of the electrical-optical modulator600may be strip-type waveguides (shown inFIG. 6G). In other words, the waveguides604may be tapered waveguides that transition from a rib waveguide (e.g., a ridge waveguide) to a strip waveguide at a first portion (e.g., at a transition from section S1to section S2), and transition from a strip waveguide to a rib waveguide at a second portion (e.g., at a transition from section S2to section S3).

In this way, the electrical-optical modulator600may include a first section configured for a first electrical-optical interaction between at least one optical waveguide and at least one signal electrode, a second section configured to increase or decrease a velocity of signals of the at least one signal electrode or the at least one optical waveguide relative to the first section, and a third section configured for a second electrical-optical interaction between the at least one optical waveguide and the at least one signal electrode according to an opposite modulation polarity relative to the first section. The first section may include a first semiconductor junction in the at least one optical waveguide according to a first semiconductor-type ordering, and a first bias electrode to provide reverse biasing to the first semiconductor junction. The third section may include a second semiconductor junction in the at least one optical waveguide according to a second semiconductor-type ordering that is opposite to the first semiconductor-type ordering, and a second bias electrode to provide reverse biasing to the second semiconductor junction. The first semiconductor junction and the second semiconductor junction may be planar (e.g., the semiconductor junctions are lateral, rather than stacked, as described in connection withFIG. 5). In addition, in some aspects, the at least one optical waveguide does not include a semiconductor junction in the second section.

As indicated above,FIG. 6Ais provided as an example. Other examples may differ from what is described with regard toFIG. 6A.

FIG. 6Bis a diagram of an enlarged detail view of the electrical-optical modulator600ofFIG. 6A. In particular,FIG. 6Bshows one embodiment of an enlarged detail view of a portion612in section S1of the electrical-optical modulator600. Section S1of the electrical-optical modulator600may include a layer of semiconductor material. For example, the semiconductor material may be silicon. The semiconductor layer may include segmented semiconductor portions, shown as multiple semiconductor bridges614, that connect sections of the semiconductor layer. In some implementations, the semiconductor layer may include continuous connecting portions rather than bridges614.

In some implementations, the semiconductor layer may include one or more first semiconductor junctions616in section S1of the electrical-optical modulator600. For example, a semiconductor junction616may be in the first waveguide604a, and a semiconductor junction616may be in the second waveguide604b. A semiconductor junction may refer to a region of a first semiconductor type (e.g., n-type) that is adjacent to a region of a second semiconductor type (e.g., p-type). The first bias voltage of the first bias electrode608amay provide reverse biasing to the semiconductor junctions616in section S1.

As indicated above,FIG. 6Bis provided as an example. Other examples may differ from what is described with regard toFIG. 6B.

FIG. 6Cis a cross-sectional view taken along line A-A of the enlarged detail view of the electrical-optical modulator600ofFIG. 6B. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6C, the first signal electrode602amay connect (e.g., electrically connect) to the semiconductor layer by a connector618(e.g., a metal via), and the second signal electrode602bmay connect to the semiconductor layer by a connector618. In section S1, the first signal electrode602aand the second signal electrode602bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the first semiconductor type (e.g., n++), and the first bias electrode608amay be connected (e.g., electrically connected) to a connection region of the semiconductor layer having the second semiconductor type (e.g., p++).

The semiconductor layer may extend laterally across a width of the electrical-optical modulator600(e.g., orthogonal to the direction of propagation610). For example, the semiconductor layer may extend laterally (e.g., horizontally) from the first signal electrode602ato the second signal electrode602b. In section S1, the semiconductor layer may have a first semiconductor-type ordering. The first semiconductor-type ordering may include one or more regions of the second type of semiconductor (e.g., p-type) between regions of the first type of semiconductor (e.g., n-type).

For example, in section S1, a portion of the semiconductor layer, between the connections of the first signal electrode602aand the first bias electrode608a, may have an n-type semiconductor region adjacent to a p-type semiconductor region, and a portion of the semiconductor layer, between the connections of the first bias electrode608aand the second signal electrode602b, may have a p-type semiconductor region adjacent to an n-type semiconductor region (e.g., sequentially from the first signal electrode602ato the second signal electrode602b). Accordingly, in section S1, the semiconductor junction616in the first waveguide604amay be an NP junction, and the semiconductor junction616in the second waveguide may be a PN junction. In other words, a lateral NP-PN series push-pull junction region may be between the first signal electrode602aand the second signal electrode602b. The semiconductor junctions616in the first waveguide604aand the second waveguide604bmay extend parallel to the direction of propagation610.

As indicated above,FIG. 6Cis provided as an example. Other examples may differ from what is described with regard toFIG. 6C.

FIG. 6Dis a diagram of an enlarged detail view of the electrical-optical modulator600ofFIG. 6A. In particular,FIG. 6Dshows another embodiment of an enlarged detail view of the portion612in section S1of the electrical-optical modulator600(e.g., additionally, or alternatively, to the embodiment shown inFIG. 6B). Section S1of the electrical-optical modulator600may include a layer of semiconductor material, as described above in connection withFIG. 6B.

The semiconductor layer may include multiple semiconductor bridges614that connect sections of the semiconductor layer, as described in connection withFIG. 6B. As shown inFIG. 6D, a bridge614may extend partially between sections of the semiconductor layer, as described below in connection withFIGS. 6E and 6F. However, the bridges614may be interdigitated to connect the sections of the semiconductor layer. For example, between the first signal electrode602aand the first bias electrode608a, a first set of bridges614may be interdigitated, and between the first bias electrode608aand the second signal electrode602b, a second set of bridges614may be interdigitated.

Moreover, in section S1, interdigitation of the bridges614may alternate between semiconductor types according to a first semiconductor-type ordering. For example, in section S1, the first semiconductor-type ordering may begin with, and end with, the first semiconductor type (e.g., n-type). For example, a first bridge614may be an n-type semiconductor, a second bridge614may be a p-type semiconductor, a third bridge614may be an n-type semiconductor, a fourth bridge614may be a p-type semiconductor, and so forth, and a last bridge may be an n-type semiconductor.

In some implementations, the semiconductor layer may include one or more first semiconductor junctions616in section S1of the electrical-optical modulator600. For example, one or more semiconductor junctions616may be in the first waveguide604a, and one or more semiconductor junctions616may be in the second waveguide604b. As shown inFIG. 6D, a semiconductor junction616may occur at a region of adjacency between alternating bridges614of the first semiconductor type and the second semiconductor type. Accordingly, the semiconductor junctions616may be orthogonal to the direction of propagation610. The first bias voltage of the first bias electrode608amay provide reverse biasing to the semiconductor junctions616in section S1.

As indicated above,FIG. 6Dis provided as an example. Other examples may differ from what is described with regard toFIG. 6D.

FIG. 6Eis a cross-sectional view taken along line B-B of the enlarged detail view of the electrical-optical modulator600ofFIG. 6D. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6E, the first signal electrode602amay connect to the semiconductor layer by a connector618, and the second signal electrode602bmay connect to the semiconductor layer by a connector618, as described above. In section S1, the first signal electrode602aand the second signal electrode602bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the first semiconductor type (e.g., n++), and the first bias electrode608amay be connected (e.g., electrically connected) to a connection region of the semiconductor layer having the second semiconductor type (e.g., p++). As shown inFIG. 6E, a bridge614of the first semiconductor type may extend from a connection region of the first semiconductor type (e.g., associated with a signal electrode602), and partially toward a connection region of the second semiconductor type (e.g., associated with the first bias electrode608a). For example, a bridge614that is an n-type semiconductor may extend from an n++ connection region, and partially toward a p++ connection region.

As indicated above,FIG. 6Eis provided as an example. Other examples may differ from what is described with regard toFIG. 6E.

FIG. 6Fis a cross-sectional view taken along line C-C of the enlarged detail view of the electrical-optical modulator600ofFIG. 6D. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6F, a bridge614of the second semiconductor type may extend from a connection region of the second semiconductor type, and partially toward a connection region of the first semiconductor type. For example, a bridge614that is a p-type semiconductor may extend from a p++ connection region (e.g., associated with the first bias electrode608a), and partially toward an n++ connection region (e.g., associated with a signal electrode602).

As indicated above,FIG. 6Fis provided as an example. Other examples may differ from what is described with regard toFIG. 6F.

FIG. 6Gis a cross-sectional view taken along line D-D of the electrical-optical modulator600ofFIG. 6A. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6G, in section S2, the signal electrode602amay include the velocity change section606a, and the signal electrode602bmay include the velocity change section606b. For example, in section S2, the signal electrodes602may be wider relative to section S1and section S3and/or the signal electrodes602may be separated by a narrower gap relative to section S1and section S3. Moreover, in section S2, the semiconductor layer may be etched to include the waveguides604without surrounding semiconductor material. In addition, in section S2, the waveguides604do not include a semiconductor junction. For example, in section S2, the first waveguide604amay include a first continuous undoped semiconductor region (e.g., a silicon-on-insulator region), and the second waveguide604bmay include a second continuous undoped semiconductor region.

In section S2, an RF impedance of the signal electrodes602may correspond to (e.g., be the same as, be within a particular range as, and/or the like) an RF impedance of the signal electrodes602in section S1(e.g., based on the signal electrodes602having a different width and/or gap in section S2relative to section S1). Moreover, removal of the semiconductor junctions in section S2may reduce a microwave index in section S2relative to section S1(similar to the removal of loading lines, as described above). In addition, RF and optical indices may correspond (e.g., be the same, be within a particular range, and/or the like) in section S1and section S3in order to increase intrinsic bandwidth in section S1and section S3, thereby requiring less electrical-optical equalization (e.g., compared to when RF and optical indices do not correspond) in order to achieve a target bandwidth of the electrical-optical modulator600. Thus, the electrode geometry (e.g., electrode widths, gaps between electrodes, electrode thicknesses, and/or the like) may be configured to provide microwave and optical indices that differ by a threshold value.

In some implementations, section S2may include an optical delay (e.g., in addition to, or instead of, wider signal electrodes606). For example, the waveguides604may include path-length delays in section S2(e.g., as shown in sections S1and S3ofFIG. 9, or another path-length delay configuration). In other words, path lengths of the waveguides604in section S2may be greater than path lengths of the signal electrodes606in section S2. Accordingly, the waveguides604may take a circuitous path, such that respective path lengths of the waveguides604in section S2are greater than a length of S2.

As indicated above,FIG. 6Gis provided as an example. Other examples may differ from what is described with regard toFIG. 6G.

FIG. 6His a diagram of an enlarged detail view of the electrical-optical modulator600ofFIG. 6A. In particular,FIG. 6Hshows one embodiment of an enlarged detail view of a portion620in section S3of the electrical-optical modulator600. Section S3of the electrical-optical modulator600may include the layer of semiconductor material, and multiple semiconductor bridges614may connect sections of the semiconductor layer, as described in connection withFIG. 6B.

In some implementations, the semiconductor layer may include one or more second semiconductor junctions616in section S3of the electrical-optical modulator600. For example, a semiconductor junction616may be in the first waveguide604a, and a semiconductor junction616may be in the second waveguide604b. The second semiconductor junctions616in section S3may be reversed (e.g., reversed polarity) relative to the first semiconductor junctions616in section S1(described inFIGS. 6B and 6C). That is, a second semiconductor-type ordering in section S3may be reversed relative to the first semiconductor-type ordering in section S1(described inFIG. 6C). The second bias voltage of the second bias electrode608bmay provide reverse biasing to the semiconductor junctions616in section S3.

As indicated above,FIG. 6His provided as an example. Other examples may differ from what is described with regard toFIG. 6H.

FIG. 6Iis a cross-sectional view taken along line E-E of the enlarged detail view of the electrical-optical modulator600ofFIG. 6H. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6I, the first signal electrode602amay connect to the semiconductor layer by a connector618, and the second signal electrode602bmay connect to the semiconductor layer by a connector618, as described above. In section S3, the first signal electrode602aand the second signal electrode602bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the second semiconductor type (e.g., p++), and the second bias electrode608bmay be connected (e.g., electrically connected) to a connection region of the semiconductor layer having the first semiconductor type (e.g., n++).

In section S3, the semiconductor layer may have a second semiconductor-type ordering. The second semiconductor-type ordering may include one or more regions of the first type of semiconductor (e.g., n-type) between regions of the second type of semiconductor (e.g., p-type). That is, second semiconductor-type ordering may be reversed to the first semiconductor-type ordering in section S1(described inFIG. 6C).

For example, in section S3, a portion of the semiconductor layer, between the connections of the first signal electrode602aand the second bias electrode608b, may have a p-type semiconductor region adjacent to an n-type semiconductor region, and a portion of the semiconductor layer, between the connections of the second bias electrode608band the second signal electrode602b, may have an n-type semiconductor region adjacent to a p-type semiconductor region (e.g., sequentially from the first signal electrode602ato the second signal electrode602b). Accordingly, in section S3, the semiconductor junction616in the first waveguide604amay be a PN junction, and the semiconductor junction616in the second waveguide may be an NP junction. In other words, a lateral PN-NP series push-pull junction region may be between the first signal electrode602aand the second signal electrode602b.

As indicated above,FIG. 6Iis provided as an example. Other examples may differ from what is described with regard toFIG. 6I.

FIG. 6Jis a diagram of an enlarged detail view of the electrical-optical modulator600ofFIG. 6A. In particular,FIG. 6Jshows another embodiment of an enlarged detail view of the portion620in section S3of the electrical-optical modulator600(e.g., additionally, or alternatively, to the embodiment shown inFIG. 6H). Section S3of the electrical-optical modulator600may include a layer of semiconductor material, as described above in connection withFIG. 6H.

The semiconductor layer may include multiple semiconductor bridges614that connect sections of the semiconductor layer, as described in connection withFIG. 6Dand below in connection withFIGS. 6K and 6L. For example, between the first signal electrode602aand the second bias electrode608b, a first set of bridges614may be interdigitated, and between the second bias electrode608band the second signal electrode602b, a second set of bridges614may be interdigitated.

Moreover, in section S3, interdigitation of the bridges614may alternate between semiconductor types according to a second semiconductor-type ordering. The second semiconductor-type ordering may be reversed to the first semiconductor-type ordering in section S1(described inFIG. 6D). For example, in section S3, the second semiconductor-type ordering may begin with, and end with, the second semiconductor type (e.g., p-type). For example, a first bridge614may be a p-type semiconductor, a second bridge614may be an n-type semiconductor, a third bridge614may be a p-type semiconductor, a fourth bridge614may be an n-type semiconductor, and so forth, and a last bridge may be a p-type semiconductor.

In some implementations, the semiconductor layer may include one or more second semiconductor junctions616in section S3of the electrical-optical modulator600, as described above in connection withFIG. 6H. For example, one or more semiconductor junctions616may be in the first waveguide604a, and one or more semiconductor junctions616may be in the second waveguide604b, as described in connection withFIG. 6D. The second bias voltage of the second bias electrode608bmay provide reverse biasing to the semiconductor junctions616in section S3.

As indicated above,FIG. 6Jis provided as an example. Other examples may differ from what is described with regard toFIG. 6J.

FIG. 6Kis a cross-sectional view taken along line F-F of the enlarged detail view of the electrical-optical modulator600ofFIG. 6J. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6K, the first signal electrode602amay connect to the semiconductor layer by a connector618, and the second signal electrode602bmay connect to the semiconductor layer by a connector618, as described above. In section S3, the first signal electrode602aand the second signal electrode602bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the second semiconductor type (e.g., p++), and the second bias electrode608bmay be connected (e.g., electrically connected) to a connection region of the semiconductor layer having the first semiconductor conductivity type (e.g., n++). As shown inFIG. 6K, a bridge614of the second semiconductor type may extend from a connection region of the second semiconductor type (e.g., associated with a signal electrode602), and partially toward a connection region of the first semiconductor type (e.g., associated with the second bias electrode608b). For example, a bridge614that is a p-type semiconductor may extend from a p++ connection region, and partially toward an n++ connection region.

As indicated above,FIG. 6Kis provided as an example. Other examples may differ from what is described with regard toFIG. 6K.

FIG. 6Lis a cross-sectional view taken along line G-G of the enlarged detail view of the electrical-optical modulator600ofFIG. 6J. In some implementations, the electrical-optical modulator600may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 6L, a bridge614of the first semiconductor type may extend from a connection region of the first semiconductor type, and partially toward a connection region of the second semiconductor type. For example, a bridge614that is an n-type semiconductor may extend from an n++ connection region (e.g., associated with the second bias electrode608b), and partially toward a p++ connection region (e.g., associated with a signal electrode602).

As indicated above,FIG. 6Lis provided as an example. Other examples may differ from what is described with regard toFIG. 6L. While section S1and section S3of the electrical-optical modulator600are described according to an example semiconductor-type configuration, other examples may use different semiconductor-type configurations in section S1and section S3, provided that the semiconductor-type configuration in section S1is reversed relative to the semiconductor-type configuration in section S3. For example, in some implementations, section S1of the electrical-optical modulator600may have the semiconductor-type configuration described above with respect to section S3(i.e., in one or more ofFIGS. 6H-6L), and section S3of the electrical-optical modulator600may have the semiconductor-type configuration described above with respect to section S1(i.e., in one or more ofFIGS. 6B-6F).

FIG. 7shows a diagram of example differential voltages used in connection with the electrical-optical modulator600ofFIG. 6Adescribed herein. In particular,FIG. 7shows a differential voltage graph705for section S1of the electrical-optical modulator600, and a differential voltage graph710for section S3of the electrical-optical modulator600. InFIG. 7, S+ refers to the RF voltage of the first signal electrode602a(+ signal), S− refers to the RF voltage of the second signal electrode602b(− signal), Vb1refers to the bias voltage of the first bias electrode608a, and Vb2refers to the bias voltage of the second bias electrode608b.

As shown by differential voltage graph705, a positive change in S+ in section S1increases a magnitude of the reverse bias in a semiconductor junction in the first waveguide604afrom AV1to AV2. As shown by differential voltage graph710, a positive change in S+ in section S3decreases a magnitude of the reverse bias in a semiconductor junction in the first waveguide604afrom AV3to AV4. Accordingly, an index change in the first waveguide604aof S1increases with an increase in magnitude of reverse bias voltage which occurs with a positive change in S+ while an index change in the first waveguide604aof S3decreases with a decrease in the magnitude of reverse bias voltage, which occurs with the same positive change in S+, thereby reversing modulation polarity in section S3relative to section S1.

As indicated above,FIG. 7is provided as an example. Other examples may differ from what is described with regard toFIG. 7.

FIG. 8Ais a diagram of an example electrical-optical modulator800described herein. In some implementations, the electrical-optical modulator800may employ silicon photonics. As shown inFIG. 8A, electrical-optical modulator800may include a first signal electrode802a(+ signal), a second signal electrode802b(− signal), a first optical waveguide804a, and a second optical waveguide804b. Electrical signals of the signal electrodes802may interact with optical signals of the waveguides804based on a proximity between the signal electrodes802and the waveguides804. The signal electrodes802may be configured to propagate an electrical signal in a direction of propagation810of the electrical-optical modulator800, and the waveguides804may be configured to propagate an optical signal in the direction of propagation810.

In addition, the first signal electrode802amay be included in a first pair of dual-drive electrodes with a first ground electrode808a,808c, and the second signal electrode802bmay be included in a second pair of dual-drive electrodes with a second ground electrode808b,808d. Accordingly, the first waveguide804amay be between the first pair of dual drive electrodes, and the second waveguide804bmay be between the second pair of dual drive electrodes. The first ground electrode808a,808cand the second ground electrode808b,808dmay provide a first bias voltage (e.g., a first DC voltage) in section S1, and a second bias voltage (e.g., a second DC voltage) in section S3. In some implementations, the first bias voltage and the second bias voltage may have opposite polarities. The first ground electrode808a,808cmay provide reverse biasing for a first semiconductor junction in the first waveguide804ain section S1, and reverse biasing for a second semiconductor junction in the first waveguide804ain section S3. The second ground electrode808b,808dmay provide reverse biasing for a first semiconductor junction in the second waveguide804bin section S1, and reverse biasing for a second semiconductor junction in the second waveguide804bin section S3.

In some implementations, the first ground electrode808a,808cand the second ground electrode808b,808dare floated relative to DC signals and continuous relative to RF signals. For example, the first ground electrode808a,808cmay include a discontinuity in section S2in order to de-couple the bias voltage between section S1and section S3(e.g., the first ground electrode has a first segment corresponding to808aand a second segment corresponding to808c). Section S2may include a first coupling capacitor822a(e.g., multiple differently sized capacitors in parallel) associated with the first ground electrode808a,808cin order to maintain continuity of RF signals. Similarly, the second ground electrode808b,808dmay include a discontinuity in section S2(e.g., the second ground electrode has a first segment corresponding to808band a second segment corresponding to808d), and section S2may include a second coupling capacitor822b(e.g., multiple differently sized capacitors in parallel) associated with the second ground electrode808b,808d. Moreover, first ends of the first ground electrode808aand the second ground electrode808bin section S1may be associated with respective coupling capacitors (not shown), and second ends of the first ground electrode808cand the second ground electrode808din section S3may be associated with respective coupling capacitors (not shown).

As shown inFIG. 8A, the first signal electrode802amay include a first modulation section (spanning S1), a velocity change section806a(spanning S2), and a second modulation section (spanning S3). Similarly, the second signal electrode802bmay include a first modulation section (spanning S1), a velocity change section806b(spanning S2), and a second modulation section (spanning S3). In a velocity change section806, signals of a signal electrode802may have a different velocity relative to a first modulation section and/or a second modulation section of the signal electrode802, as described above in connection withFIG. 1.

A first section (associated with section S1) and a second section (associated with section S3) of a waveguide804may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the signal electrodes802. That is, section S1and section S3of the electrical-optical modulator800may have opposite modulation polarities. In some implementations, the opposite modulation polarities are based on a semiconductor structure associated with section S1having a reversed orientation relative to a semiconductor structure associated with section S3, as described below.

In some implementations, portions of the waveguides804in section S1and section S3of the electrical-optical modulator800may be rib-type waveguides (shown inFIGS. 8B and 8F), as described above. Additionally, or alternatively, portions of the waveguides804in section S2of the electrical-optical modulator800may be strip-type waveguides (shown inFIGS. 8C-8E), as described above.

As indicated above,FIG. 8Ais provided as an example. Other examples may differ from what is described with regard toFIG. 8A.

FIG. 8Bis a cross-sectional view taken along line H-H of the electrical-optical modulator800ofFIG. 8A. Section S1of the electrical-optical modulator800may include a layer of semiconductor material. For example, the semiconductor material may be silicon. The semiconductor layer may include segmented semiconductor portions (e.g., bridges814) that connect sections of the semiconductor layer, or include continuous connecting portions, as described in connection withFIG. 6B. In some implementations, the electrical-optical modulator800may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 8B, in section S1, the first signal electrode802aand the first ground electrode808amay respectively connect to a first portion of the semiconductor layer by connectors818, and the second signal electrode802band the second ground electrode808bmay respectively connect to a second portion of the semiconductor layer by connectors818. In section S1, the first ground electrode808aand the second signal electrode802bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the second semiconductor type (e.g., p++). Additionally, the first signal electrode802aand the second ground electrode808bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the first semiconductor type (e.g., n++).

The first portion of the semiconductor layer may extend laterally (e.g., orthogonal to the direction of propagation810) between the first ground electrode808aand the first signal electrode802a. The second portion of the semiconductor layer may extend laterally between the second signal electrode802band the second ground electrode808b.

In some implementations, the first portion and the second portion of the semiconductor layer may include first semiconductor junctions816in section S1of the electrical-optical modulator800. For example, a semiconductor junction816may be in the first waveguide804a, and a semiconductor junction816may be in the second waveguide804b. The first bias voltage of the first ground electrode808amay provide reverse biasing to the semiconductor junction816in the first waveguide804a, and the second bias voltage of the second ground electrode808bmay provide reverse biasing to the semiconductor junction816in the second waveguide804b, in section S1.

In section S1, the first portion of the semiconductor layer and the second portion of the semiconductor layer may have a first semiconductor-type ordering. The first semiconductor-type ordering may include (e.g., sequentially from the first ground electrode808ato the first signal electrode802a, or from the second signal electrode802bto the second ground electrode808b) a region of the second type of semiconductor (e.g., p-type) adjacent to a region of the first type of semiconductor (e.g., n-type).

For example, in section S1, the first portion of the semiconductor layer may have a p-type semiconductor region adjacent to an n-type semiconductor region (e.g., sequentially from the first ground electrode808ato the first signal electrode802a), and the second portion of the semiconductor layer may have a p-type semiconductor region adjacent to an n-type semiconductor region (e.g., sequentially from the second signal electrode802bto the second ground electrode808b). Accordingly, in section S1, the semiconductor junction816in the first waveguide604amay be a PN junction, and the semiconductor junction816in the second waveguide may be a PN junction. The semiconductor junctions816in the first waveguide804aand the second waveguide804bmay extend parallel to the direction of propagation810. In some implementations, the semiconductor junctions816in the first waveguide804aand the second waveguide804bmay be orthogonal to the direction of propagation810. For example, the first portion and the second portion of the semiconductor layer may employ interdigitated bridges, as described above.

As indicated above,FIG. 8Bis provided as an example. Other examples may differ from what is described with regard toFIG. 8B.

FIG. 8Cis a cross-sectional view taken along line I-I of the electrical-optical modulator800ofFIG. 8A. In some implementations, the electrical-optical modulator800may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 8C, in section S2, the first signal electrode802amay include the velocity change section806a, and the second signal electrode802bmay include the velocity change section806b. For example, in section S2, the signal electrodes802may be wider relative to section S1and section S3, and/or the signal electrodes802may be separated by a narrower gap relative to section S1and section S3. Moreover, in section S2, the semiconductor layer may be etched to include the waveguides804without surrounding semiconductor material. In addition, in section S2, the waveguides804do not include a semiconductor junction. For example, in section S2, the first waveguide804amay include a first continuous undoped semiconductor region, and the second waveguide804bmay include a second continuous undoped semiconductor region. In some implementations, section S2may include an optical delay (e.g., in addition to, or instead of, wider signal electrodes802), as described above.

As indicated above,FIG. 8Cis provided as an example. Other examples may differ from what is described with regard toFIG. 8C.

FIG. 8Dis a cross-sectional view taken along line J-J of the electrical-optical modulator800ofFIG. 8A. In some implementations, the electrical-optical modulator800may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity. As shown inFIG. 8D, in section S2, the first coupling capacitor822a(e.g., a coupling capacitor plate) may be positioned below a portion of the first ground electrode808a,808c, and the second coupling capacitor822b(e.g., a coupling capacitor plate) may be positioned below a portion of the second ground electrode808b,808d.

As indicated above,FIG. 8Dis provided as an example. Other examples may differ from what is described with regard toFIG. 8D.

FIG. 8Eis a cross-sectional view taken along line K-K of the electrical-optical modulator800ofFIG. 8A. In some implementations, the electrical-optical modulator800may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity. As shown inFIG. 8E, in section S2, the first ground electrode may include a discontinuity, and the first coupling capacitor822amay overlap a gap between the first segment808aof the first ground electrode and the second segment808cof the first ground electrode. Similarly, the second ground electrode may include a discontinuity, and the second coupling capacitor822bmay overlap a gap between the first segment808bof the second ground electrode and the second segment808dof the second ground electrode.

As indicated above,FIG. 8Eis provided as an example. Other examples may differ from what is described with regard toFIG. 8E.

FIG. 8Fis a cross-sectional view taken along line L-L of the electrical-optical modulator800ofFIG. 8A. Section S3of the electrical-optical modulator800may include the layer of semiconductor material, and multiple semiconductor bridges814may connect sections of the semiconductor layer, as described in connection withFIG. 8B. In some implementations, the electrical-optical modulator800may include one or more additional layers (e.g., a substrate layer, oxide layers, metal layers, and/or the like) above and/or below the semiconductor layer, which are not shown in the cross-section for simplicity.

As shown inFIG. 8F, in section S3, the first signal electrode802aand the first ground electrode808cmay respectively connect to a first portion of the semiconductor layer by connectors818, and the second signal electrode802band the second ground electrode808dmay respectively connect to a second portion of the semiconductor layer by connectors818, as described above. In section S3, the first ground electrode808cand the second signal electrode802bmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the first semiconductor type (e.g., n++). Additionally, the first signal electrode802aand the second ground electrode808dmay be connected (e.g., electrically connected) to respective connection regions of the semiconductor layer having the second semiconductor type (e.g., p++).

The first portion of the semiconductor layer may extend laterally (e.g., orthogonal to the direction of propagation810) between the first ground electrode808cand the first signal electrode802a. The second portion of the semiconductor layer may extend laterally between the second signal electrode802band the second ground electrode808d.

In some implementations, the first portion and the second portion of the semiconductor layer may include second semiconductor junctions816in section S3of the electrical-optical modulator800. For example, a semiconductor junction816may be in the first waveguide804a, and a semiconductor junction816may be in the second waveguide804b. The second semiconductor junctions816in section S3may be reversed (e.g., reversed polarity) relative to the first semiconductor junctions816in section S1(described inFIG. 8B). That is, a second semiconductor-type ordering in section S3may be reversed relative to the first semiconductor-type ordering in section S1(described inFIG. 8B).

For example, in section S3, the first portion of the semiconductor layer and the second portion of the semiconductor layer may have a second semiconductor-type ordering. The second semiconductor-type ordering may include (e.g., sequentially from the first ground electrode808cto the first signal electrode802a, or from the second signal electrode802bto the second ground electrode808d) a region of the first type of semiconductor (e.g., n-type) adjacent a region of the second type of semiconductor (e.g., p-type).

For example, in section S3, the first portion of the semiconductor layer may have an n-type semiconductor region adjacent to a p-type semiconductor region (e.g., sequentially from the first ground electrode808cto the first signal electrode802a), and the second portion of the semiconductor layer may have an n-type semiconductor region adjacent to an p-type semiconductor region (e.g., sequentially from the second signal electrode802bto the second ground electrode808d). Accordingly, in section S3, the semiconductor junction816in the first waveguide804amay be an NP junction, and the semiconductor junction816in the second waveguide804bmay be an NP junction. The semiconductor junctions816in the first waveguide804aand the second waveguide804bmay extend parallel to the direction of propagation810. In some implementations, the semiconductor junctions816in the first waveguide804aand the second waveguide804bmay be orthogonal to the direction of propagation810. For example, the first portion and the second portion of the semiconductor layer may employ interdigitated bridges, as described above.

As indicated above,FIG. 8Fis provided as an example. Other examples may differ from what is described with regard toFIG. 8F.

In some implementations, the bias voltages for the PN junctions are provided to signal electrodes802a,802b,808c, and808dwith “bias tee” electrical networks that sum in the DC bias voltages with the RF signals, thereby providing a path for RF to travel from RF input to RF electrodes in sections S1, S2, and S3, to the RF termination, with a DC bias voltage applied to each RF signal electrode. In silicon photonic PICs, the bias tee networks may be integrated on chip with the electrical-optical modulator. The bias tee networks may introduce RF insertion loss at high frequencies as well as low frequency cut-off below which RF cannot pass.

FIG. 9is a diagram of an example electrical-optical modulator900described herein. In some implementations, the electrical-optical modulator900may employ silicon photonics. As shown inFIG. 9, electrical-optical modulator900may include a first signal electrode902a(+ signal), a second signal electrode902b(− signal), a first optical waveguide904a, and a second optical waveguide904b. Electrical signals of the signal electrodes902may interact with optical signals of the waveguides904based on a proximity between the signal electrodes902and the waveguides904. The signal electrodes902may be configured to propagate an electrical signal in a direction of propagation910of the electrical-optical modulator900, and the waveguides904may be configured to propagate an optical signal generally (e.g. averaging over the circuitous path of the waveguides904aand904b) in the direction of propagation910.

As shown inFIG. 9, the electrical-optical modulator900may include a first bias electrode908ain section S1and section S2a, and a second bias electrode908bin section S2cand section S3. The first bias electrode908amay be between the first waveguide904aand the second waveguide904bin section S1and section S2a, and the second bias electrode908bmay be between the first waveguide904aand the second waveguide904bin section S2cand section S3.

The first bias electrode908aand the second bias electrode908bmay be isolated (e.g., electrically isolated) from each other, as described in connection withFIG. 6A. For example, the first bias electrode908amay provide reverse biasing for one or more first semiconductor junctions in section S1, and the second bias electrode908bmay provide reverse biasing for one or more second semiconductor junctions in section S3.

In some implementations, an RF signal of the signal electrodes902may have a lower velocity than an optical signal of the waveguides904. Accordingly, the waveguides904may include optical delays in section S1and section S3which are shown, for example, by the circuitous, or back and forth, path of the waveguides904aand904binFIG. 9, as described above.

As shown inFIG. 9, the first signal electrode902amay include a first modulation section (spanning S1), a velocity change section (spanning S2), and a second modulation section (spanning S3). Similarly, the second signal electrode902bmay include a first modulation section (spanning S1), a velocity change section (spanning S2), and a second modulation section (spanning S3). In a velocity change section, signals of a signal electrode902may have a different relative velocity to the average velocity of the optical signal in waveguide904, relative to a first modulation section and/or a second modulation section of the signal electrode902, as described above in connection withFIG. 1.

For example, in the first and second modulation sections, the optical delays produced by circuitous, or back and forth, paths of the waveguides904reduce the average velocity of the optical signals in waveguides904such that the average velocity of the optical signals and the average velocity of the RF signals in electrodes902have a first difference (e.g., no difference). In the velocity change section (spanning S2), the optical delays are removed, thereby increasing the average optical velocity, such that the average velocity of the optical signals in waveguides904and the average velocity of the RF signals in electrodes902have a second difference greater than the first difference. Hence in the velocity change section (spanning S2), the average velocity of the RF signals in electrodes902is lower than the average velocity of the optical signals in waveguides904.

A first section (associated with section S1) and a second section (associated with section S3) of a waveguide904may be configured to have opposite modulation polarities based on an association with a first modulation section and a second modulation section of the signal electrodes902. That is, sections S1, S2aand sections S2c, S3of the electrical-optical modulator900may have opposite modulation polarities. The electrical-optical modulator900may include a layer of semiconductor material. For example, the semiconductor material may be silicon. In some implementations, the opposite modulation polarities are based on a semiconductor structure associated with sections S1, S2ahaving a reversed orientation relative to a semiconductor structure associated with sections S2c, S3.

For example, in section S1and section S2a, the semiconductor layer may have a semiconductor structure as described for section S1of the electrical-optical modulator600(e.g., in one or more ofFIGS. 6B-6F). As an example, a cross-section of the electrical-optical modulator900taken along line M-M may correspond to what is shown inFIG. 6C. Similarly, in section S2cand section S3, the semiconductor layer may have a semiconductor structure as described for section S3of the electrical-optical modulator600(e.g., in one or more ofFIGS. 6H-6L). As an example, a cross-section of the electrical-optical modulator900taken along line N-N may correspond to what is shown inFIG. 6I. Section S2bof the electrical-optical modulator900may be as described for section S2of electrical-optical modulator600(e.g., inFIG. 6G). In some implementations, a length of section S2bis configured such that a width of signal electrodes902a,902bin section S2bis the same as in sections S1and S3.

Thus, the configuration of the electrical-optical modulator900may be the same as the configuration of the electrical-optical modulator600, as described above, except that the waveguides904of the electrical-optical modulator900may include optical delays, and a width of section S2bmay be narrower than a width of section S2of the electrical-optical modulator600.

As indicated above,FIG. 9is provided as an example. Other examples may differ from what is described with regard toFIG. 9.