A ring modulator

Abstract

A microring modulator device, method and optical device, the microring modulator device comprising: a ring-shaped waveguide associated with N+ doping and P+ doping, wherein the N+ doping and P+ doping have two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections, wherein the modulation segment and the calibration segment are electrically isolated from each other; a second waveguide, optically coupled to the ring-shaped waveguide, and to a light source; a first driver circuit for driving an input signal to be modulated to the modulation segment; a second driver circuit for driving a calibration signal to the calibration segment, thereby affecting a refraction index of the ring-shaped waveguide and a resonance frequency of the ring-shaped waveguide; and a non-invasive device for measuring light intensity on the second waveguide without reducing light transmitted through the waveguide.

Description

A RING MODULATORCROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application No. 63 / 710,231 filed October 22, 2024, titled "A Ring Modulator", hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0001] The present disclosure relates to photonic systems in general, and to optical modulators, in particular.BACKGROUND

[0002] Photonic systems are gaining more and more popularity in all areas , such as but not limited to light detection, telecommunications, information processing, photonic computing, lighting, metrology, spectroscopy, holography, medicine (surgery, vision correction, endoscopy, health monitoring), biophotonics, military technology, laser material processing, art diagnostics, material processing, art diagnostics involving InfraRed Reflectography Xrays, UltraViolet fluorescence, XRF), agriculture, robotics, and others.

[0003] Some important uses of photonic systems include transmitting and receiving information, multiplexing and demultiplexing information, or the like. Photonic devices may include but are not limited to photodetectors including photo diodes or photo transistors, laser diodes, optical modulators, passive optical components, light-emitting diodes, solar and photovoltaic cells, displays and optical amplifiers. Other examples include devices for modulating a beam of light and for combining and separating beams of light of different wavelength.

[0004] A crucial component of any photonic system is its optical modulators, used for modulating a beam of light to reflect the electric input signal.

[0005] There are multiple types of optical modulator, the more common ones are listed below.

[0006] A first type of an optical modulator is a Silicon Mach-Zehnder modulator. The Mach-Zehnder modulator is an interferometric structure made of a material with strong electro-optic effect, such as LiNbO3, GaAs or InP. The modulator features am input segment that divides into two arms before rejoining. The constructive / destructive interference in each arm results in phase modulation, and combining the signal from the two arms with different phases converts the phase modulation into intensity modulation.

[0007] The Mach-Zehnder modulator is optically broadband and is thermally robust. However, it is a relatively large device, for example a typical length is about 1mm, which provides for a smaller number of devices than other modulator types that can be placed on a chip, and thus significantly reduces the amount of data levels. Another disadvantage of the Mach-Zehnder modulator is its high dynamic power.

[0008] A second type is a GeSi electro-absorption modulator. The principle of operation of the GeSi electro-absorption modulator is based on the Franz-Keldysh effect, i.e., a change in the absorption spectrum caused by an applied electric field, which changes the bandgap energy, and thus the photon energy of an absorption edge, but usually does not involve the excitation of carriers by the electric field.

[0009] Its advantages include smaller size than the Mach-Zehnder modulator, for example about 60 micron, and low dynamic power. Its disadvantages include mediocre optical bandwidth, for example smaller than 30 nano meter, and mediocre thermal sensitivity, for example under 3 OK.

[0010] A third type of optical modulator is a Silicon Ring modulator, comprised of a ring optically coupled to the waveguide carrying the light from the light source. Its advantages include compact dimensions, for example about 5 micron, and low dynamic power. However, it is optically narrowband, e.g., under 1 nanometer, and has high thermal sensitivity, for example under IK.BRIEF SUMMARY

[0011] One exemplary embodiment of the disclosed subject matter is a microring modulator device comprising: a ring-shaped waveguide, the ring-shaped waveguide associated with N+ doping and P+ doping, wherein the N+ doping and P+ doping have two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections, the two gap sections electrically isolating the modulation segment and the calibration segment from each other; a second waveguide, optically coupled to the ring-shaped waveguide, and to a light source; a first driver circuit for driving an input signal to be modulated to the modulation segment; a second driver circuit for driving a calibration signal to the calibration segment, thereby affecting a refraction index of the ring-shaped waveguide and a resonance frequency of the ringshaped waveguide; and a non-invasive device for measuring a light intensity on the second waveguide without reducing light transmitted through the waveguide. The microring modulator can further comprise a temperature monitor for measuring the temperature of the ring-shaped waveguide, and wherein the temperature is used in calculating the calibration signal. The microring modulator can further comprise a processing module for determining the calibration signal. Within the microring modulator, the ring-shaped waveguide optionally comprises a silicon ridge core wrapped by a silicon layer. Within the microring modulator, the microring modulator of Claim 1, wherein the N+ doping and the P+ doping are doped into the ring-shaped waveguide in the modulation segment thereby creating a first PN junction, and in the calibration segment, thereby creating a second PN junction. The microring modulator can further comprise N++ doping and P++ doping doped into the ring-shaped waveguide in the modulation segment and in the calibration segment. Within the microring modulator, the N+ doping and the P+ doping are optionally doped into the ring shaped waveguide in the modulation segment, thereby creating a PN junction in the modulation segment, and wherein the N+ doping and P+ doping are added as an N+ layer and a P+ layer, respectively, around the calibration segment of the ring-shaped waveguide, thereby creating a PIN junction in the calibration segment. The microring modulator can further comprise N++ doping and P++ doping doped into the ring-shaped waveguide in the modulation segment; and N++ layer and P++ layer added externally to the N+ layerand P+ layer, respectively. The microring modulator can further comprise a second non-invasive device for measuring a second light intensity on the ring-shaped waveguide without reducing light transmitted through the ring-shaped waveguide. Within the microring modulator, an output light intensity of the microring resonator device is optionally determined in accordance with the light intensity measured on the second waveguide and the light intensity on the ring-shaped waveguide. Within the microring modulator, the modulation segment is optionally larger than the calibration segment. Within the microring modulator, the signal driven to the modulation segment is optionally comprised of a data signal and an offset signal.

[0012] Another exemplary embodiment of the disclosed subj ect matter is a method for calibrating a microring modulator device, the method comprising: in the microring modulator device comprising: a ring-shaped waveguide, the ring-shaped waveguide associated with N+ doping and P+ doping, wherein the N+ doping and P+ doping have two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections, the two gap sections electrically isolating the modulation segment and the calibration segment from each other; a second waveguide, optically coupled to the ring-shaped waveguide, and to a light source; a first driver circuit for driving an input signal to be modulated to the modulation segment; a second driver circuit for driving a calibration signal to the calibration segment, thereby affecting a refraction index of the ring-shaped waveguide and a resonance frequency of the ringshaped waveguide; and a non-invasive device for measuring a light intensity on the second waveguide without reducing light transmitted through the waveguide: setting the calibration signal applied to the modulation segment while monitoring a resonance frequency of the ring modulator device with respect to a selected wavelength; non-invasively monitoring current output by the ring modulator device; and repeatedly: adjusting the calibration voltage; and monitoring calibration result, until required performance is achieved.

[0013] Another exemplary embodiment of the disclosed subject matter is an optical device comprising: a first ring-shaped waveguide, and a second ring-shaped waveguide, wherein each of the first ring-shaped waveguide and the second ring-shaped waveguide is associated with N+ doping and P+ doping, wherein the N+ doping and P+ dopinghave two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections electrically isolating the modulation segment and the calibration segment from each other; a second waveguide, optically coupled to the first ring-shaped waveguide, to the second ring-shaped waveguide, and to a light source; a first driver circuit for driving a signal to be modulated to the modulation segment of the first ring-shaped waveguide, and a second driver circuit for driving a signal to be modulated to the modulation segment of the second ring-shaped waveguide; a third driver circuit for driving to the calibration segment of the first ring-shaped modulator a calibration signal, thereby affecting a refraction index of the first ring-shaped waveguide and a resonance frequency of the first ring-shaped waveguide; a fourth driver circuit for driving to the calibration segment of the second ring-shaped modulator a calibration signal, thereby affecting a refraction index of the second ring-shaped waveguide and a resonance frequency of the second ring-shaped waveguide; and a non-invasive device for measuring a light intensity on the second waveguide after passing the second ringshaped modulator, without reducing light transmitted through the second waveguide.

[0014] The optical device of Claim 14, further comprising a second non-invasive device for measuring a light intensity on the second waveguide between the first ringshaped modulator and the second ring-shaped modulator, without reducing light transmitted through the second waveguide.

[0015] The optical device of Claim 14, further comprising a temperature monitor for measuring the temperature of the first ring-shaped waveguide, and wherein the temperature is used in calculating the calibration signal.THE BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] The present disclosed subject matter will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which corresponding or like numerals or characters indicate corresponding or like components. Unless indicated otherwise, the drawings provide exemplary embodiments or aspects of the disclosure and do not limit the scope of the disclosure. In the drawings:

[0017] Fig. 1 is a schematic illustration of a ring modulator with a heater;

[0018] Fig. 2 is a schematic top-view illustration of a ring modulator, in accordance with some exemplary embodiments of the disclosure;

[0019] Fig. 3 is a schematic top- view illustration of another implementation of a ring modulator, in accordance with some exemplary embodiments of the disclosure;

[0020] Fig. 4A is a schematic illustration of cross-section A-A of Fig. 2, in accordance with some exemplary embodiments of the disclosure;

[0021] Fig. 4B is a schematic illustration of cross-section B-B of Fig. 3, in accordance with some exemplary embodiments of the disclosure;

[0022] Fig. 5 is a block diagram of the roles and influences within a modulator, in accordance with some exemplary embodiments of the disclosure;

[0023] Fig. 6 shows a schematic illustration of a cascade of two ring modulators, in accordance with some exemplary embodiments of the disclosure; and

[0024] Fig. 7, showing a flowchart of steps in a method for operating a ring modulator, in accordance with some exemplary embodiments of the disclosure.DETAILED DESCRIPTION

[0025] Any photonic system makes use of a plurality of optical modulators.

[0026] Each of the common types of optical modulators has a number of disadvantages. For example, a Mach-Zehnder modulator is too large in size thereby limiting the number of devices that can be placed on a chip, and has high dynamic power; the GeSi electro-absorption modulator has insufficient optical bandwidth, and thermal sensitivity; and the silicon ring modulator is optically narrowband.

[0027] Due to the narrow band, stabilization is required for maintaining the resonance frequency, which may be done by thermally coupling the ring with a heater, such that changing the temperature changes the resonance wavelength of the modulator. However, heating the ring is subject to environmental temperature, is time consuming, and cannot have an immediate effect on the resonance frequency. Heating may also result in overshooting, which in turn may take a long time to cool back.

[0028] In some situations, the modulator may have attached thereto a photodiode for measuring the current inside the ring. In order to enable measurement, some doping is introduced to the ring to increase its otherwise low absorption which is due to its small dimensions.

[0029] There is thus a need for a modulator that maintains as many as possible of the advantages of currently available modulators, and in particular is of a small size, while reducing the disadvantages, and in particular the heat sensitivity.

[0030] One technical solution provided by the disclosure comprises an improved silicon ring modulator.

[0031] The modulator comprises a ring waveguide, doped with N and P doping. However, the doping is not continuous. Rather, the waveguide is left undoped at two gaps, including a first gap where the ring couples to the waveguide that receives the light from the light source (hereinafter “the second waveguide”), and another gap. These gaps creates two separate doped segments of the waveguide. In some embodiments, the first doped segment may be significantly larger than the second doped segment, for example 1.2 times larger, 1.5 times larger, 2 times larger, 10 times larger, or the like.

[0032] The first, larger doped segment, may be connected to the input voltage upon which the light is to be modulated. A DC bias signal may be added to the input signal, for affecting the resonance frequency of the ring modulator.

[0033] Due to the discontinuities in the doping, the second, smaller doped segment may be disconnected from the first area and therefore from the input signal. However, this second area may be connected to another signal, being a calibration signal. The applied calibration signal changes the refraction index at the segment and hence the average refraction index over the ring, and therefore the resonance frequency. Thus, rather than heating the ring with a heater, the resonance frequency is changed by providing calibration voltage to a segment of the ring. The calibration voltage can be changed accurately and instantly, thus accurately controlling the resonance frequency, and avoiding the heating and cooling times and the overshooting effect.

[0034] In some embodiments, the output light may be measured by a non-invasive component coupled to the second waveguide, such that the measurement does not reduce the output amount of light. Some implementation details of a non-invasive measurement device may be found in WO / 2022 / 168074 filed Dec. 19, 2021, titled “Device and Method for Calibration, Monitoring and Control of the Integrated Photonic Systems”.

[0035] Another technical solution of the disclosure relates to the doping being applied to the waveguide itself in the first and in the second segments, wherein the P carriers may be applied to the internal part of the ring waveguide and the N carriers applied to the external part, or vice versa, thereby creating a PN junction from each doped segment.

[0036] Yet another technical solution of the disclosure relates to the waveguide being doped as above by N and P carriers in the first segment, thereby creating one PN junction. Additionally, P and N doping layers may be applied externally to the ring in contact with the second segment of the waveguide, thereby creating a PIN junction. For example, an N layer may be attached to the ring on its external side, and the P layer may be attached to the ring on its internal side or vice versa. The PIN junction, beyond serving for changing the refraction index of the ring, may also serve as a non-invasive device for measuring the current through the ring, which may be used for assessing the proximity of the ring frequency to the resonance frequency, and thus the amount of light.The amount of light calculation may use the measurement as performed by the non-invasive device coupled to the second waveguide, with or without a measurement taken over the second segment.

[0037] Yet another technical solution of the disclosure relates to two degrees of doping of each type being used. For example, in the first embodiment, the core of the waveguide may be doped over the two segments to a certain degree (both for the N and for the P doping), and its external part may be doped to a higher degree, thus creating an N+ N P P+ junction (also referred to as N++ N+ P+ P++ junction), on the first and the second segments.

[0038] In other embodiments, the first doped segment may be doped as described above, while the second segment may be doped by attaching to the waveguide two layers on its external side and two layers on its internal side, for example two N layers on its external side and two P layers on its internal side, such that the resulting segment is a PIN junction arranged as follows: N+ N I P P+ (also referred to as N++ N+ I P+ P++).

[0039] In some embodiments, the waveguide may be comprised of a silicon ridge core having silicon layers on either side, wherein the ring modulator may be embedded on a silicon oxide substrate.

[0040] One technical effect of the disclosure relates to providing a ring modulator having small dimensions similar to prior art ring modulators, for example about 5 microns, which enables to place a larger number of modulators on each single chip.

[0041] Another technical effect of the disclosure relates to the ring modulator in accordance with the disclosure having low dynamic power, for example Vpp.

[0042] Yet another technical effect of the disclosure relates to the elimination of the heater used for changing the resonance frequency of the ring modulator, and replacing it with an input calibration signal applied to a part of the ring modulator. The calibration signal provides for accurate and immediate change of the resonance frequency of the ring modulator as required, thereby compensating for the optical band being narrow, while avoiding the thermal sensitivity associated with a heater.

[0043] Yet another technical effect of the disclosure relates to non-invasively assessing the amount of light within the ring, and combining it with the amount of light measured non-invasively on the second waveguide, thereby providing for a more accurate measurement.

[0044] Referring now to Fig. 1, showing a schematic illustration of a ring modulator with a heater.

[0045] Fig. 1 shows a microring modulator 100, having a microring resonator 104 and a second waveguide 108 optically coupled with a light source (not shown). Microring resonator 104 and second waveguide 108 are optically coupled and light is transferred therebetween at region 116.

[0046] Photodiode 120 is provided surrounding a part of microring resonator 104, wherein microring resonator 104 has dopings 124 at the area of Photodiode 120. Thermo-optic tuner, also referred to as heater 112 is employed to stabilize microring resonator 104 with respect to thermal fluctuations via control system.

[0047] In some exemplary non-limiting embodiments, microring 104 is about 10-15 micron in radius, and segment 116 where microring 104 couples to the second waveguide 108 is about 210 nano meter.

[0048] Microring modulator 100 thus has the disadvantages detailed above including the thermal sensitivity and optical narrowband.

[0049] Referring now to Fig. 2, showing a schematic illustration of a ring modulator, in accordance with some exemplary embodiments of the disclosure.

[0050] The ring modulator, generally referenced 200, may comprise a ring waveguide 204 and a second, substantially straight waveguide 208. Ring waveguide 204 and straight waveguide 208 may be embedded over a silicon oxide substrate 219.

[0051] Ring waveguide 204 and straight waveguide 208 may have a core of silicon ridge 212, having attached thereto internal and external silicon layers 216.

[0052] Core 214 of second waveguide 208 may be in contact on both sides with silicon layers 219.

[0053] In some embodiments of the disclosure, ring waveguide 204 may be doped, for example by two layers of each doping type. Thus, core 212 may be doped withN carriers on its external part to create layer 224 and P carriers on its internal part to create layer 228, further N+ carriers on the further external side of core 212 to create layer 220, and further P+ carriers on the further internal side of core 212 to create layer 232.

[0054] In some embodiments, the doping and therefore layers 220, 224, 228 and 232 may not be continuous, and gaps 236 and 238 may not be doped. Gap 238 may be in the coupling area between waveguide 204 and second waveguide 208, and gap 236 may be anywhere else. The gap size may be, for example between 50 and 500 nm, betweenl50 and 250nm, or the like. Gap 238 may serve for coupling light from second waveguide 208 and Ring waveguide 204, and affects factors related to the ring quality factor Q.

[0055] Gaps 236 and 238 may thus create two doped segments of ring waveguide 204, such as calibration segments 245 and modulation segment 247.

[0056] Referring now to Fig. 4A, showing cross section A-A through calibration segment 245, in accordance with some exemplary embodiments of the disclosure.

[0057] It is appreciated that the same cross section is also applicable to modulation segment 248.

[0058] The cross section shows silicon oxide substrate 219, and above that, from the external part of the ring modulator inward: N+ layer 220, N layer 224, P layer 228 and P+ layer 232, wherein layers 224 and 228 consist of silicon ridge layer 212 doped with N and P doping, respectively, and wherein layers 220 and 232 consist of silicon layer 216 which is further doped with N+ and P+ doping, respectively. The meaning of the layers is detailed in legend 264.

[0059] Referring now back to Fig. 2, segment 245 may be a calibration segment and Vcaiibration 260 may be applied thereto, while segment 247 may be a modulation region, and Vdata, which is the signal upon which the light needs to be modulated, may be applied thereto. In some embodiments, a bias voltage may also be applied, such that the signal applied to segment 247 may be equal to Vdata +Vbias.

[0060] By applying a DC signal, Vcaiibration, to calibration segment 245, the refraction index of ring waveguide 204 may be changed and hence its resonance frequency.

[0061] The proportion between the sizes of segments 245 and 247, and gaps 236, 238 may be determined in accordance with the different considerations. For example, longer segment 245 requires lower calibration voltage, but shorter segment 247 reduces the modulation effectivity. The lengths of gaps 236 and 238 need to enable electrical disconnection between segments 245 and 247, and the length of gap 238 should enable efficient light coupling and light propagation in the ring.

[0062] Second waveguide 208 may also have an N layer 244 on one side and a P layer 248 on the other, and may also have an N+ layer 240 and a P+ layer 252 externally to N layer 244 and P layer 248, respectively. Layers 244-219-214-248, or layers 240-244-219-214-248-252 create a PIN junction that may serve as a non-invasive device 256 for measuring the amount of light on second waveguide 208. In some embodiments, N+ layer 240 is referred to as N++ layer, N layer 244 is referred to as N+ layer, P layer 248 is referred to as P+ layer, and P+ layer 252 is referred to as P++ layer.

[0063] Referring now to Fig. 3, showing a schematic top-view illustration of another implementation of a ring modulator, in accordance with some exemplary embodiments of the disclosure.

[0064] Ring modulator 300 may comprise ring waveguide 304 having doped segment 247, gaps 236 and 238, and second waveguide 208 as in Fig. 2.

[0065] However, instead of segment 245 of Fig. 2, ring modulator 300 may comprise segment 345.

[0066] On segment 345, core 212 and layers 216 are undoped. Rather, doping layers are provided externally to layers 216. Thus, on the external side of segment 345, N layer 312 and optionally external to that N+ layer 316 may be provided, and on the internal side of calibration segment 345, P layer 320 and optionally further internal to that P+ layer 324 may be provided. As above, in some cases, the layers may be annotated N+ layer 312, N++ layer 316, P+ layer 320 and P++ layer 324.

[0067] Referring now to Fig. 4B, showing a cross-section B-B through calibration segment 345, in accordance with some exemplary embodiments of the disclosure.

[0068] The cross section shows silicon oxide substrate 219, and above substrate 219, from the external part of the ring modulator inward: silicon ridge core 212, silicon layer316, and then on one side, being the external side of ring modulator 304, N layer 312 and N+ layer 316 and on the other side which is the internal side of ring modulator 304 P layer 320 and P+ layer 324, wherein layers 312 and 320 are doping layers, and wherein layers 316 and 324 are further doped layers.

[0069] As above, Vcaiibration may be applied to segment 345, for example to N+ layer 316 and P+ layer 324, for changing the refraction index of ring waveguide 304 and hence its resonance frequency.

[0070] Calibration segment 345 may provide for assessing the actual light intensity through non-invasive measurement of the photocurrent within ring waveguide 304. Thus, segment 345 may have dual capabilities provided by measurement and calibration device 356: calibrating the resonance wavelength of ring waveguide 304 by causing changes in the refractive index by applying Vcalibration, as well as measuring the light intensity within ring waveguide 304. The assessed light intensity may be used in combination with the light intensity as measured by the non-invasive device 256 formed by on second waveguide 208.

[0071] Referring now to Fig. 5, showing a block diagram of the roles and influences within a modulator, in accordance with some exemplary embodiments of the disclosure.

[0072] Ring modulator 500, such as ring modulator 200 of Fig. 2 or ring modulator 300 of Fig. 3 may comprise a ring waveguide having a tuning or calibration segment. The ring waveguide is subject to thermal effects, to a calibration signal, and to other factors.

[0073] For example, factors 504 may comprise thermal fluctuations and other ring resonance affecting factors that may influence the modulator, even in the absence of a heater, for example environmental temperature and pressure, the ring structure, wafer and / or process variations, adjustment between the wavelength radiated by the light source and the ring modulator resonance frequency, or the like,

[0074] The refraction index of ring modulator 500 is also affected by signals 508 driven to parts of ring modulator 500. Signals 508 may include a data signal, with or without a bias signal that may be applied to the modulation segment of ring modulator 500, such as modulation segment 247. Signals 508 may further include a calibrationsignal 260 applied to the calibration segment of ring modulator 500, such as calibration segment 245 of Fig. 2 or calibration segment 345 of Fig. 3.

[0075] The optical power output by the modulator may be monitored, for example by measuring the photocurrent through a non-invasive monitoring device 512, such as device 256 of Fig. 2, and optionally converting the photocurrent to voltage using a trans-impedance amplifier (TIA). In some embodiments, the calculation of the amount of light may also take into account the current measured by device 356 between layers 316 and 324 of Fig. 3.

[0076] The current measurement nay be provided to feedback calculation module 516 which may calculate the required signals for adjusting the resonance frequency of ring modulator 500. Thus, feedback calculation module 516 can calculate the calibration signal to be applied to the calibration segment, and optionally the bias signal applied to the modulation segment. Based on the resonance 516 can also be connected to the temperature monitor. Feedback calculation module 516 may also receive measurements from a temperature monitor, and may use the temperature in the calculations. Feedback calculation module 516 may be implemented as a processing module realized as hardware, firmware, or the like.

[0077] The resonance frequency of ring modulator 500 may then be adjusted (520) by applying the signals as calculated by feedback calculation module 516, such as calibration signal being applied to the calibration segment, and optionally the bias signal being applied to the modulation segment in addition to the signal to be modulated.

[0078] Referring now to Fig. 6, showing schematic illustration of a cascade of two ring modulators, in accordance with some exemplary embodiments of the disclosure.

[0079] In the cascade, two or more ring modulators such as ring modulators 300 (or alternatively two ring modulators 200) may be cascaded such that the one farther from light source 600 receives the output of the one(s) closer to light source 600. The output of each ring modulator 300 may be calculated by the corresponding non-invasive (NI) light measurement device 256, 256’, optionally with the output of the corresponding measurement and calibration device 260. It is appreciated that the output as measured by NI light measurement device 256’ is the overall light output after passing the two modulation rings. However, intermediate results, such as the output of NI lightmeasurement device 256, may also be usefill for adjusting each ring modulator 300 for adjusting the overall resonance frequencies.

[0080] It is appreciated that the disclosure is not limited to a two-modulator cascade, rather any number of modulators may be cascaded as described.

[0081] Referring now to Fig. 7, showing a flowchart of steps in a method for operating a ring modulator, in accordance with some exemplary embodiments of the disclosure.

[0082] At step 704, a bias voltage to be applied to the modulation segment and a calibration voltage to be applied to the calibration segment may be set, while monitoring the ring waveguide resonance with respect to the selected wavelength and the actual temperature of the ring.

[0083] At step 708, electrical current representing the amount of light output by the ring modulator may be monitored, for example by a non-invasive device. The light intensity may be calculated in accordance with the measured current, and optionally with the actual temperature, as may be measured by one or more temperature sensors can be used to monitor the actual temperature of the ring.

[0084] At step 712, the calibration voltage and / or the modulation bias voltage may be adjusted in accordance with the current measured by the non-invasive device.

[0085] At step 716, the calibration result, e.g., the amount of light, may be monitored. Monitoring step 716 and adjusting step 712 may repeat until the calibration is successful. Once the calibration is successful, the monitoring step 716 and adjusting step 712 may also be repeated periodically, when changes are experienced, or the like.

[0100] The present invention may be a system, a method, and / or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

[0101] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0102] Computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0103] Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, such as "C", C#, C++, Java, Phyton, Smalltalk, or others. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local areanetwork (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

[0104] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer readable program instructions.

[0105] These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and / or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the fimction / act specified in the flowchart and / or block diagram block or blocks.

[0106] The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or otherdevice implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0107] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustration, and combinations of blocks in the block diagrams and / or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

[0108] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0109] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spiritof the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMSWhat is claimed is:

1. A microring modulator device comprising:a ring-shaped waveguide, the ring-shaped waveguide associated with N+ doping and P+ doping, wherein the N+ doping and P+ doping have two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections, the two gap sections electrically isolating the modulation segment and the calibration segment from each other;a second waveguide, optically coupled to the ring-shaped waveguide, and to a light source;a first driver circuit for driving an input signal to be modulated to the modulation segment;a second driver circuit for driving a calibration signal to the calibration segment, thereby affecting a refraction index of the ring-shaped waveguide and a resonance frequency of the ring-shaped waveguide; anda non-invasive device for measuring a light intensity on the second waveguide without reducing light transmitted through the waveguide.

2. The microring modulator of Claim 1, further comprising a temperature monitor for measuring the temperature of the ring-shaped waveguide, and wherein the temperature is used in calculating the calibration signal.

3. The microring modulator of Claim 1, further comprising a processing module for determining the calibration signal.

4. The microring modulator of Claim 1, wherein the ring-shaped waveguide comprises a silicon ridge core wrapped by a silicon layer.

5. The microring modulator of Claim 1, wherein the N+ doping and the P+ doping are doped into the ring-shaped waveguide in the modulation segment thereby creating a first PN junction, and in the calibration segment, thereby creating a second PN junction.

6. The microring modulator of Claim 5, further comprising N++ doping and P++ doping doped into the ring-shaped waveguide in the modulation segment and in the calibration segment.

7. The microring modulator of Claim 1, wherein the N+ doping and the P+ doping are doped into the ring shaped waveguide in the modulation segment, thereby creating a PN junction in the modulation segment, and wherein the N+ doping and P+ doping are added as an N+ layer and a P+ layer, respectively, around the calibration segment of the ring-shaped waveguide, thereby creating a PIN junction in the calibration segment.

8. The microring modulator of Claim 7, further comprising:N++ doping and P++ doping doped into the ring-shaped waveguide in the modulation segment; andN++ layer and P++ layer added externally to the N+ layer and P+ layer, respectively.

9. The microring modulator of Claim 1, further comprising a second non-invasive device for measuring a second light intensity on the ring-shaped waveguide without reducing light transmitted through the ring-shaped waveguide.

10. The microring modulator of Claim 9, wherein an output light intensity of the microring resonator device is determined in accordance with the light intensity measured on the second waveguide and the light intensity on the ring-shaped waveguide.

11. The microring modulator of Claim 1, wherein the modulation segment is larger than the calibration segment.

12. The microring modulator of Claim 1 , wherein the signal driven to the modulation segment is comprised of a data signal and an offset signal.

13. A method for calibrating a microring modulator device, the method comprising: in the microring modulator device comprising:a ring-shaped waveguide, the ring-shaped waveguide associated with N+ doping and P+ doping, wherein the N+ doping and P+ dopinghave two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibration segment of the ring-shaped waveguide, and two gap sections, the two gap sections electrically isolating the modulation segment and the calibration segment from each other;a second waveguide, optically coupled to the ring-shaped waveguide, and to a light source;a first driver circuit for driving an input signal to be modulated to the modulation segment;a second driver circuit for driving a calibration signal to the calibration segment, thereby affecting a refraction index of the ringshaped waveguide and a resonance frequency of the ring-shaped waveguide; anda non-invasive device for measuring a light intensity on the second waveguide without reducing light transmitted through the waveguide:setting the calibration signal applied to the modulation segment while monitoring a resonance frequency of the ring modulator device with respect to a selected wavelength;non-invasively monitoring current output by the ring modulator device; and repeatedly:adjusting the calibration voltage; andmonitoring calibration result,until required performance is achieved.

14. An optical device comprising:a first ring-shaped waveguide, and a second ring-shaped waveguide, wherein each of the first ring-shaped waveguide and the second ring-shaped waveguide is associated with N+ doping and P+ doping, wherein the N+ doping and P+ doping have two discontinuities over the ring-shaped waveguide, thereby creating a modulation segment of the ring-shaped waveguide, a calibrationsegment of the ring-shaped waveguide, and two gap sections electrically isolating the modulation segment and the calibration segment from each other;a second waveguide, optically coupled to the first ring-shaped waveguide, to the second ring-shaped waveguide, and to a light source;a first driver circuit for driving a signal to be modulated to the modulation segment of the first ring-shaped waveguide, and a second driver circuit for driving a signal to be modulated to the modulation segment of the second ring-shaped waveguide;a third driver circuit for driving to the calibration segment of the first ring-shaped modulator a calibration signal, thereby affecting a refraction index of the first ring-shaped waveguide and a resonance frequency of the first ringshaped waveguide;a fourth driver circuit for driving to the calibration segment of the second ring-shaped modulator a calibration signal, thereby affecting a refraction index of the second ring-shaped waveguide and a resonance frequency of the second ring-shaped waveguide; anda non-invasive device for measuring a light intensity on the second waveguide after passing the second ring-shaped modulator, without reducing light transmitted through the second waveguide.

15. The optical device of Claim 14, further comprising a second non-invasive device for measuring a light intensity on the second waveguide between the first ringshaped modulator and the second ring-shaped modulator, without reducing light transmitted through the second waveguide.

16. The optical device of Claim 14, further comprising a temperature monitor for measuring the temperature of the first ring-shaped waveguide, and wherein the temperature is used in calculating the calibration signal.

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