Integrated variable optical attenuator

Abstract

The invention relates to an integrated variable optical attenuator. In some implementations, an electro-optical device includes a multimode interferometer (MMI) variable optical attenuator (VOA) and a control component, the MMI VOA including: an input for receiving an optical beam; an output section for outputting the light beam; and an optical waveguide for coupling the input to the output, wherein the optical waveguide is configured to self-image the light beam within the optical waveguide; the control assembly is used for applying forward voltage to the two ends of the MMI VOA so as to control attenuation of the MMI VOA.

Description

[0001] Cross - reference to related applications

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 607,962, filed on December 8, 2023, entitled "INTEGRATED VARIABLE OPTICAL ATTENUATOR". The disclosure of the prior application is hereby incorporated by reference in its entirety and made a part of this patent application. FIELD OF THE INVENTION

[0003] The present disclosure generally relates to an optical device and an integrated variable optical attenuator using current injection on a multimode interferometer. BACKGROUND OF THE INVENTION

[0004] An optical attenuator is an electro-optical device that can be used to reduce the power level of an optical signal in an optical system. For example, an optical attenuator can be provided in an optical signal to equalize the power in different channels, prevent photodetector saturation, or equalize the gain from different amplification sources, etc. The optical attenuator can be polarization-independent and wavelength-independent within a configured operating wavelength range and a configured operating temperature range to avoid introducing incorrect attenuation levels or altering another characteristic of the light beam, such as the polarization state or wavelength. SUMMARY OF THE INVENTION

[0005] In some implementations, a variable optical attenuator (VOA) includes a multimode interferometer (MMI) and a control component. The MMI includes: an optical waveguide, where a set of parameters of the optical waveguide is configured to cause a set of light beam modes to interfere and self-image the light beam; the control component is configured to apply a forward voltage across the VOA to control the attenuation of the VOA, and where a change in a portion of the refractive index of the optical waveguide is associated with carrier injection, and the carrier injection is associated with the forward voltage.

[0006] In some implementations, an electro-optical device includes at least one MMI VOA and a control component. The MMI VOA in the at least one MMI VOA includes: an input for receiving a light beam; an output for outputting the light beam; and a multimode optical waveguide located between the input and the output for coupling the input to the output. The control component is configured to apply a forward voltage across the MMI VOA to control the attenuation of the MMI VOA.

[0007] In some implementations, an electro-optic device includes an MMI VOA and a control component. The MMI VOA includes: an input section for receiving a light beam; an output section for outputting the light beam; and a multimode optical waveguide for coupling the input section to the output section, where the optical waveguide is configured to self-image the light beam within the optical waveguide; the control component is configured to apply a forward voltage across the MMI VOA to control the attenuation of the MMI VOA. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figures 1A - 1C FIG. is a diagram of an example electro-optic device associated with an integrated variable optical attenuator (VOA).

[0009] Figures 2A - 2C FIG. is a diagram of an example associated with self-imaging in an integrated multimode interferometer (MMI) VOA under different forward bias conditions.

[0010] Figure 3 FIG. is a flowchart of an example process associated with the fabrication of an integrated VOA.

[0011] Figure 4A and Figure 4B FIG. is a diagram of an example associated with an integrated MMI VOA. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0012] The following detailed description of example implementations refers to the accompanying drawings. The same reference numerals in different drawings may identify the same or similar elements.

[0013] Optical systems such as optical communication systems, optical measurement systems, or optical test systems may include an optical attenuator to apply attenuation to a light beam. For example, an optical communication system may include an electro-optic device to apply attenuation to a light beam to equalize the optical power between different channels, avoid saturation of a photodetector, or equalize the gain from different amplification sources, etc.

[0014] A variable optical attenuator (VOA) can be used to apply different degrees of attenuation to a light beam at different times. For example, a Mach-Zehnder (MZ) interferometer (MZI) can be used for an MZ-VOA. For an integrated MZ-VOA, the light beam is coupled into a chip (e.g., an indium phosphide (InP) receiver chip), and is split into two arms of the MZI using a Y-branch beam splitter or a 1×2 multimode interferometer (MMI). When the split light beams pass through the respective parts of the corresponding arms of the MZI, a phase shift is applied, and when the split light beams are recombined, destructive interference between the two arms results in attenuation of the light beam. In this example, the phase shift of one arm of the MZI (e.g., in a single-ended drive scenario) or both arms of the MZI (e.g., in a differential drive scenario) can be controlled by changing the dispersion characteristics of the corresponding waveguides forming the arms of the MZI. The dispersion characteristics of the corresponding waveguides can be adjusted by applying heat to the corresponding waveguides (e.g., using a thermal phase electrode (TPE)) or by reverse biasing the MZI. However, using an MZ-VOA to attenuate a light beam may result in excessive optical loss due to the presence of couplers (e.g., at the input of the MZI) and combiners (e.g., at the output of the MZI). In addition, the MZI may have a relatively strong dependence on the operating wavelength and chip temperature, which may lead to poor optical loss and calibration performance. In addition, physical asymmetries in the arms of the MZI (e.g., due to manufacturing tolerances) may result in further optical losses or poor calibration performance.

[0015] Another type of VOA that can be used is an electro-absorption (EA) VOA. The EA-VOA uses the anisotropic electro-optic effect to achieve a change in the refractive index (e.g., and thus a change in the resulting attenuation), which includes the linear electro-optic effect (e.g., the Pockels effect) and / or the nonlinear electro-optic effect (e.g., the Kerr effect). The linear electro-optic effect occurs under an applied electric field of relatively low magnitude and in a crystal structure without inversion symmetry. Therefore, the EA-VOA is limited in terms of waveguide material selection and orientation, as well as the applied electric field strength. The nonlinear electro-optic effect has a strong nonlinear dependence on the electric field, which may result in distortion of the output optical signal. Therefore, the strong dependence on the applied bias voltage, large power consumption, and large temperature and wavelength dependence in the EA-VOA may make it difficult to configure a feedback control loop.

[0016] Accordingly, there is a desire to provide an integrated VOA, such as for 100 Gigabit (Gb) or higher C or L band receiver chips. For example, it is desirable for the VOA to have relatively strong temperature and wavelength independence, so that the VOA can be stably controlled. Additionally or alternatively, it is desirable for the VOA to use a relatively small control signal range (e.g., a range of 0 volts (V) to 3 volts) to control the attenuation of the VOA, where a linear increase in the control signal current provides a linear increase in optical attenuation (e.g., rather than a cosine-squared transfer function relationship between current and optical attenuation in an MZI). Additionally or alternatively, it is desirable for the drive current of the VOA to be relatively small (e.g., less than 30 milliamperes (mA)) to avoid excessive power consumption requirements.

[0017] Some implementations described herein provide an efficient VOA using a multimode interferometer (MMI) with carrier injection. For example, the VOA can use carrier injection to cause a refractive index change within the MMI waveguide, thereby disrupting the self-imaging phenomenon within the MMI waveguide. This results in a reduction in the optical power coupled to the output waveguide. By controlling the refractive index change in the multimode waveguide, the degradation of the self-imaging phenomenon can be controlled to achieve the desired optical attenuation of the light beam in the output waveguide. Based on using carrier injection to cause a refractive index change in the MMI waveguide, the VOA achieves efficient attenuation over a wide optical wavelength and chip temperature range and enables stable operation using a relatively small control signal range and a relatively small drive current.

[0018] Figures 1A - 1C is a diagram of an exemplary electro-optic device 100 associated with a top view (1A / 1C) and a cross-section (1B) of an integrated MMI VOA. As Figures 1A - 1C shown, the electro-optic device 100 includes an MMI waveguide 110, an input waveguide 120, and an output waveguide 130. In this case, the MMI 110 forms a 1×1 MMI VOA.

[0019] As Figure 1A further shown, in the absence of electrical control, the MMI waveguide 110 couples the input waveguide 120 to the output waveguide 130. For example, the input section 120 can receive an input light beam, which can propagate through the MMI waveguide 110 and self-image, thereby producing the same shape of the input light beam at the output waveguide 130. In this case, the output section 130 can provide an output light beam similar to the input light beam, with almost the same power, as Figure 2A more detailedly described, without any attenuation.

[0020] Self-imaging is a characteristic of electromagnetic field propagation in a multimode waveguide that has a constant transverse refractive index along the propagation direction, such as an MMI 110 for an MMI VOA. In self-imaging, an input light beam is laterally replicated at certain positions along the propagation direction. This replication can be a single image, a double image, a triple image, or even more images, depending on the design parameters of the MMI waveguide and the optical signal wavelength. For example, as Figure 2A described in more detail, in one example of self-imaging, 1, 2, and 3 lateral replicas can be self-imaged along the propagation. The output waveguide 130 can be located at a propagation distance where there is only one image, which results in a 1×1 MMI for an MMI VOA. Alternatively, if 2 output waveguides are located at the lateral positions of 2 images, a 1×2 MMI can be implemented and used as a beam splitter or coupler, where the input field (e.g., the input light beam) is split between the two outputs in a 50:50 ratio.

[0021] In some implementations, the MMI waveguide 110 can be coupled to a control component (not shown). For example, the MMI waveguide 110 can be associated with a bias source (e.g., an electrode or a set of electrodes) and a controller that is associated with the control of the bias source. In this case, the controller can generate and provide a control signal to cause the bias source to apply a bias voltage that controls the attenuation of the MMI waveguide 110. As described in more detail below, applying the bias voltage can inject current into some regions of the MMI waveguide 110, which results in an asymmetric change in the refractive index of the multimode MMI waveguide 110. Based on the asymmetric change in the refractive index of the MMI waveguide 110, the self-imaging phenomenon of the MMI waveguide 110 is disturbed, resulting in the degradation of the power coupled to each image along the propagation, and thus the attenuation of the optical power of the single image of the 1×1 MMI, as described in more detail below.

[0022] In some implementations, the MMI waveguide 110 can include a first part and a second part. For example, as Figure 1A shown, in a top view, the MMI waveguide 110 can include a non-conductive region 140 and a conductive region 142. Similarly, as Figure 1BAs shown, in the cross-sectional view, the MMI waveguide 110 may include a p-metal region 150, an n-metal region 152, an optical core 154, an n-doped lower cladding 156, and a substrate 158. For example, the p-metal region 150 may be paired with the n-metal region 152 to provide current injection through the conductive region 142 and the optical core 154 (and the n-doped lower cladding 156). In this case, one or more parameters of the MMI waveguide 110 are associated with the refractive index of the optical core 154. For example, geometric parameters (such as the geometry of the non-conductive region 140 and the conductive region 142) may affect the refractive index of the optical core 154. Additionally or alternatively, material parameters (such as the material selection of the non-conductive region 140 and the conductive region 142) may affect the refractive index of the optical core 154. For example, the optical core 154 may be a bulk semiconductor material forming an epitaxial structure. In some implementations, the non-conductive region 140 may include an implanted region that is ion-implanted to affect the flow of current through the non-conductive region 140. In some implementations, the non-conductive region 140 is an insulating region. For example, the conductivity of the non-conductive region 140 may be lower than that of the conductive region 142.

[0023] In some implementations, the p-metal region 150 and the n-metal region 152 are a pair of ohmic contacts (e.g., aligned at the top and bottom of the MMI), which results in a forward voltage being applied across the MMI and current flowing through the MMI. In some implementations, the pair of ohmic contacts only covers a portion of the MMI (e.g., less than the entire optical core 154). In this case, when current flows through the MMI (e.g., the optical core 154), carriers (e.g., electrons and holes) flow through the MMI and interact with the electromagnetic field propagating through it. The carriers cause a perturbation in the refractive index of the optical core 154 by changing its absorption characteristics. The change in absorption characteristics and the associated refractive index may be the result of free carrier absorption (FCA) effects, bandgap shrinkage effects, and / or band filling effects. Based on the changed refractive index, the propagation of the electromagnetic field through the optical core 154 is perturbed, resulting in a change in the output beam relative to the input beam. For example, the output beam may be attenuated, split (split into multiple beams), or combined (combined with another beam) relative to the input beam.

[0024] In some implementations, the p-metal region 150 and the n-metal region 152 may apply a forward voltage only through a portion of the optical core 154. For example, the geometry of the non-conductive region 140 and / or the positions of the p-metal region 150 and the n-metal region 152 along the length of the MMI waveguide 110 may result in some portions of the optical core 154 being subject to a different forward voltage (or a complete lack of forward voltage) than other portions. In this way, the refractive index of the optical core 154 can be selectively perturbed to control the attenuation (or other effects) of the light beam passing through the MMI waveguide 110. In some implementations, an etching process, a cladding process, a masking process, or another type of layer formation or fabrication process can be used to control the geometric parameters (e.g., the geometric parameters of the p-metal region 150, the n-metal region 152, or the non-conductive region 140, etc.).

[0025] As Figure 1C shown, the exemplary optical system 180 may include at least one electro-optic device 100. For example, the optical system 180 may include a first electro-optic device 100-1 and a second electro-optic device 100-2. In this case, the first electro-optic device 100-1 and the second electro-optic device 100-2 form a cascaded 1×1 MMI VOA set, where the 1×1 mode filter 185 is connected to the second electro-optic device 100-2. In some implementations, the first electro-optic device 100-1 and the second electro-optic device 100-2 are connected in series. In some implementations, the current injected into the first electro-optic device 100-1 is the same as the current injected into the second electro-optic device 100-2. Additionally or alternatively, the currents injected into the electro-optic devices 100 may be different to achieve, for example, different levels of attenuation in each electro-optic device 100 or another adjustment of the characteristics of the electro-optic devices 100.

[0026] By injecting current into a plurality of electro-optic devices 100 connected in series, the optical system 180 can achieve a higher level of attenuation relative to what can be achieved when driving a single MMI VOA with the same total current. For example, compared to the attenuation achieved by a single electro-optic device 100 driven with the same 10 mA, the optical system 180 can achieve a higher level of attenuation (e.g., approximately twice the attenuation) at, for example, 10 mA. This may be because the attenuation slope of the electro-optic device 100 is maximum at lower currents. A filter 185 may be included in the optical system 180 to filter out higher-order modes that may be generated by the disturbed self-imaging of the light beam within each electro-optic device 100 caused by current injection. For example, the filter 185 may be a passive 1×1 MMI (e.g., the first electro-optic device 100 and the second electro-optic device 100 may be active MMIs), and the passive 1×1 MMI is configured to filter out higher-order modes (e.g., modes higher than the first fundamental mode). In this way, the filter 185 ensures that only the fundamental mode is coupled into the output single-mode waveguide of the optical system 180. Additionally or alternatively, the filter 185 can improve the attenuation efficiency.

[0027] As described above, Figures 1A - 1C is provided as an example. Other examples may be different from those Figures 1A - 1C described. Figures 1A - 1C The number and arrangement of the devices shown are provided as an example.

[0028] Figures 2A - 2C is a diagram of an example 200 associated with self-imaging in an integrated MMI VOA. For example, Figures 2A - 2C shows an example of self-imaging increasing with a current control signal in a 1×1 MMI. As Figure 2A shown, in an undisturbed state (e.g., with a current injection of 0 milliamperes (mA)), the undisturbed refractive index within the 1×1 MMI results in the correct self-imaging of the light beam from the input 210 to the output 220 via the multimode waveguide 230. In this case, the light beam has no attenuation. In Figure 2B , with a certain amount of current injection (such as 5 mA), the change in refractive index in the active portion of the 1×1 MMI (corresponding to the conductive region 142 in the MMI waveguide 110) disturbs the self-imaging of the light beam within the waveguide 230. This causes characteristics such as the shape, position, or power of the light beam image at the end of the waveguide region 230 not to match correctly with the output waveguide 220, resulting in an attenuated light beam coupled to 220. Similarly, in Figure 2C , as the amount of current injection is higher (such as 20 mA), the further change in refractive index in the active region of the 1×1 MMI causes the self-imaging phenomenon of the light beam within the waveguide 230 to be more disrupted, and thus results in a further reduction in the amount of power coupled to the output waveguide 220, and therefore a higher attenuation.

[0029] As indicated above, Figures 2A - 2C is provided as an example. Other examples may differ with respect to Figures 2A - 2C those described.

[0030] Figure 3 is a flow chart of an example process 300 associated with the fabrication of an integrated VOA. In some implementations, Figure 3 one or more process blocks of are performed by a fabrication device (e.g., a process control device, a controller, a server device, or a deposition device).

[0031] As Figure 3 shown, process 300 may include identifying a set of operating parameters (block 310). For example, a fabrication device may identify an operating wavelength range, an operating temperature range, a range of possible control signal current values, a range of possible voltages, or another operating parameter of the integrated VOA. In some implementations, the range of possible voltages may be a range from about 0V to 3V. In some implementations, the possible operating wavelength range may include the L-band. In some implementations, the range of possible control signal current values may be from about 0 mA to 30 mA. In such a case, the integrated VOA may be configured to have a total current for driving the integrated VOA that is less than a threshold current value. Meeting one or more of the above ranges may enable use with, for example, a 130G L-band receiver chip that may be deployed in an optical communication system. Other parameter ranges may enable use with other optical devices or optical systems.

[0032] As Figure 3 further shown, process 300 may include identifying a set of fabrication parameters corresponding to the set of operating parameters (block 320). For example, a fabrication device may identify geometric parameters (e.g., the geometry of a conductive or non-conductive region) or material parameters (e.g., the material selected for a conductive or non-conductive region), etc. In some implementations, the fabrication device may perform an optimization process to determine the set of fabrication parameters. For example, the fabrication device may generate a carrier distribution based on an injection current (e.g., using a simulation package), generate a corresponding refractive index change based on the injection current, and generate an interpolation lookup table that maps the refractive index change to any amount of electrical current. In such a case, the fabrication device may use a set of dimensions of the VOA to generate a model of the integrated VOA and use the lookup table to determine the refractive index distribution of the VOA for a configured current range. Based on the model of the integrated VOA, the fabrication device may simulate the VOA loss as a function of the injection current and identify a set of optimized parameters to achieve a desired amount of attenuation loss within a possible injection current range.

[0033] As Figure 3As further shown, process 300 may include fabricating a waveguide (block 330) using a set of fabrication parameters corresponding to a set of operating parameters. For example, a fabrication device may deposit a set of material layers to form a waveguide having a particular set of material profiles or geometric parameters.

[0034] As Figure 3 As further shown, process 300 may include configuring control functions to implement a set of operating parameters using the waveguide (block 340). For example, a fabrication device may provide information identifying control signals to a control component (e.g., a controller that controls voltage and current injection) to achieve a desired current injection level, associated refractive index change, and associated attenuation.

[0035] Process 300 may include additional implementations, such as any single implementation or any combination of implementations described herein.

[0036] Although Figure 3 example blocks of process 300 are shown, in some implementations, process 300 includes more blocks, fewer blocks, different blocks, or differently arranged blocks than Figure 3 shown. Additionally or alternatively, two or more blocks of process 300 may be executed in parallel.

[0037] Figure 4A and Figure 4B are diagrams of example 400 / 410 associated with an integrated VOA. Figure 4A Shows a comparison between the simulated attenuation and the observed attenuation of an integrated VOA configured as a 1×1 MMI VOA with respect to the total input current. As shown, for current values in the range of 0 mA to 30 mA, as described herein, the observed integrated VOA can achieve an attenuation amount between 0 decibels (dB) and -25 dB. Additionally, within the input current range between 0 mA and 30 mA, the deviation between the simulated attenuation and the observed attenuation does not exceed 5 dB. Thus, as described herein, the use of an integrated VOA can achieve relatively high stability with respect to the theoretical configuration of such a VOA. Additionally or alternatively, for example, the use of a closed-loop feedback controller for the integrated VOA can compensate for the deviation between the theoretical configuration and the observed performance of the integrated VOA.

[0038] Figure 4B Shows an example 410 of refractive index distribution perturbation of the core of an MMI (e.g., the optical core of a waveguide of a 1×1 MMI VOA as described herein). As Figure 4B shown, at different lateral positions of a 1×1 MMI VOA, the refractive index change can vary in the range of -0.0125 to -0.0345 with respect to the nominal value at an operating wavelength of 1600 nm. Different electrode positions, widths, and lengths may result in different refractive index value changes with current injection.

[0039] As described above, Figure 4A and Figure 4B are provided as examples. Other examples may vary with respect to Figure 4A and Figure 4B as described.

[0040] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementation to the exact forms disclosed. Modifications and variations can be made in light of the foregoing disclosure, or can be obtained from the practice of the implementation. Additionally, any implementations described herein can be combined, unless the foregoing disclosure expressly provides a reason why one or more implementations cannot be combined.

[0041] As used herein, depending on the context, meeting a threshold can mean that a value is greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and so forth.

[0042] Although specific combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of the various implementations. In fact, many of these features can be combined in ways not specifically recited in the claims and / or not expressly disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of the various implementations includes the combination of each dependent claim with every other claim in the claim set. As used herein, the phrase "at least one" in reference to a list of items means any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to cover a, b, c, a - b, a - c, b - c, and a - b - c, as well as combinations of multiple occurrences of the same item.

[0043] When one or more components (e.g., an MMI or one or more MMIs) are described or claimed (within a single claim or across multiple claims) as performing multiple operations or being configured to perform multiple operations, such language is intended to broadly cover a variety of architectures and environments. For example, unless otherwise expressly claimed (e.g., by using "a first component" and "a second component" in a claim or other language that differentiates components), such language is intended to cover a single component performing or being configured to perform all operations, a group of components jointly performing or being configured to perform all operations, a first component performing or being configured to perform a first operation and a second component performing or being configured to perform a second operation, or any combination of components performing or being configured to perform the operations. For example, when a claim is in the form "one or more components are configured to: perform X; perform Y; and perform Z", the claim should be interpreted as "one or more components are configured to perform X; one or more (possibly different) components are configured to perform Y; and one or more (also possibly different) components are configured to perform Z."

[0044] Unless expressly stated otherwise, any element, act, or instruction used herein should not be construed as critical or essential. Additionally, as used herein, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more". Additionally, as used herein, the article "the" is intended to include one or more items referenced in conjunction with the article "the" and may be used interchangeably with "one or more". Additionally, the term "set" as used herein is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items) and may be used interchangeably with "one or more". If only one item is intended, the phrase "only one" or similar language is used. Additionally, as used herein, the terms "having", "have", "containing", etc. are intended to be open-ended terms. Additionally, unless expressly stated otherwise, the term "based on" is intended to mean "at least partially based on". Additionally, as used herein, the term "or" is inclusive when used in series and may be used interchangeably with "and / or", unless expressly stated otherwise (e.g., if used in combination with "any one of... " or "only one of... "). Additionally, for ease of description, spatial relative terms (such as "below", "lower", "above", "upper", etc.) may be used herein to describe the relationship of one element or feature to other elements or features shown in the figures. Except for the orientation shown in the figures, spatial relative terms are intended to cover different orientations of the device, apparatus, and / or element in use or operation. The device may be oriented otherwise (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

Claims

1. A variable optical attenuator (VOA), comprising: Multimode interferometer MMI, including: Optical waveguides, wherein the set of parameters of the optical waveguide is configured to: cause a set of light beam modes to interfere and self-image the light beams; and A control component for applying a forward voltage across the VOA to control the attenuation of the VOA, The change in a portion of the refractive index of the optical waveguide is associated with carrier injection, which is associated with the forward voltage.

2. The VOA of claim 1, wherein the MMI is a 1×1 MMI.

3. The VOA of claim 1, wherein the optical waveguide is configured to support three or more electromagnetic field modes.

4. The VOA of claim 1, further comprising: A set of ohmic contacts is aligned with the MMI to apply the forward voltage across a portion of the MMI, the portion of the MMI being smaller than the entire MMI. 5 . The VOA of claim 4 , wherein the MMI comprises a conductive region and an insulating region, and wherein the conductive region is associated with the portion of the MMI across which the forward voltage is applied.

6. The VOA of claim 1, wherein the parameter set comprises at least one of: a geometric parameter set or a material parameter set.

7. The VOA of claim 1 , wherein the MMI is a first VOA MMI, and the VOA further comprises: A second VOA MMI is connected in series with the first MMI so that current combined with the forward voltage is equally or differently injected into the first MMI and the second MMI.

8. The VOA of claim 1 , wherein the MMI is an active MMI, and the VOA further comprises: A passive MMI is aligned with the output of the active MMI, and is configured to filter the higher order modes and pass the fundamental mode.

9. An electro-optical device comprising: at least one multimode interferometer MMI variable optical attenuator VOA, The MMIVOA in the at least one MMIVOA comprises: An input portion, for receiving a light beam; an output portion, configured to output the light beam; and a multimode waveguide for coupling the input portion to the output portion, wherein a set of parameters of the multimode waveguide is associated with self-imaging of the light beam within the multimode waveguide, the set of parameters comprising at least one of: a set of geometric parameters and / or a set of material parameters; and A control component for applying a forward voltage across the MMI VOA to control the attenuation of the MMIVOA, wherein the forward voltage causes a current to flow through the MMI, and The change in the real part and / or the imaginary part of the refractive index of the multimode waveguide is associated with carrier injection, which is associated with the current.

10. The electro-optic device of claim 9, wherein the multimode waveguide comprises a non-conductive region and a conductive region.

11. The electro-optical device of claim 9, wherein the at least one MMI VOA forms at least one of: a beam splitter, a coupler, or a filter.

12. The electro-optical device according to claim 9, further comprising: A mode filter is aligned with the output portion of the at least one MMIVOA.

13. The electro-optic device of claim 9, the control component being configured to perturb the refractive index of the core of the at least one MMIVOA by at least a threshold percentage.

14. The electro-optic device of claim 9, wherein the epitaxial structure of the multimode waveguide comprises a bulk semiconductor material.

15. The electro-optic device of claim 9, wherein carrier injection in the multimode waveguide is associated with at least one of the following: a free carrier absorption effect, a band gap shrinking effect, or a band filling effect.

16. An electro-optical device comprising: Multimode interferometer MMI variable optical attenuator VOA, including: An input portion, for receiving a light beam; an output portion, configured to output the light beam; and a waveguide for coupling the input portion to the output portion, wherein the waveguide is configured to self-image the light beam within the waveguide; and A control component is used to apply a forward voltage across the MMI VOA to control the attenuation of the MMI VOA.

17. The electro-optic device of claim 16, wherein a refractive index of the waveguide is correlated to the forward voltage applied across the MMIVOA.

18. The electro-optical device of claim 16, further comprising: A set of insulating regions aligned with the optical waveguide, wherein a refractive index of the optical waveguide is associated with: the set of insulating regions aligned with the waveguide.

19. The electro-optic device of claim 16, wherein the waveguide is a MMI waveguide.

20. The electro-optic device of claim 16, further comprising: An ohmic contact assembly is connected to the control component for applying the forward voltage.

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