Semiconductor device and method of operating a silicon ring modulator

Abstract

Embodiments of the present invention provide a semiconductor device and a method for operating a silicon ring modulator. The semiconductor device includes: a first bus waveguide; a first silicon ring optically coupled to the first bus waveguide; a spare silicon ring optically coupled to the first bus waveguide; a first heater and a second heater configured to heat the first silicon ring and the spare silicon ring, respectively; and a first switch, wherein the first switch is configured to electrically couple the first silicon ring to a first radio frequency (RF) circuit when the first switch is in a first switch position, and is configured to electrically couple the spare silicon ring to the first RF circuit when the first switch is in a second switch position.

Description

Technical Field

[0001] Embodiments of the present invention relate to semiconductor devices and methods of operating silicon ring modulators. Background Art

[0002] Optical communications have long been used in telecommunications applications. For example, fiber optic cables serve as backbone networks for high-speed data transmission. Over the past decade, optical communications have made inroads into data communications, such as rack-to-rack communication in data centers. Currently, optical communications for rack-to-rack communication can be used, for example, over distances between approximately 10 meters and approximately 2,000 meters.

[0003] With the rapid increase in data rates within or between semiconductor chips, optical communications can be employed for chip-to-chip communication in high-performance semiconductor devices. Photonic integrated circuits (ICs) (also known as silicon photonics, photonic devices, photonic dies, photonic chips, or optical integrated dies) provide the ability to transmit, receive, and / or process optical signals in the same way that traditional integrated devices transmit, receive, and / or process electrical signals, but at significantly higher data rates.

[0004] Conventional optical modulators are large in size, consume a lot of power during operation, and are expensive to manufacture. There is a need in the art for silicon photonic devices with integrated optical modulators that are small in size, low in power consumption, and highly reliable. Summary of the Invention

[0005] According to one aspect of an embodiment of the present invention, a semiconductor device is provided, including: a first silicon ring modulator, wherein the first silicon ring modulator includes: a first bus waveguide; a first silicon ring optically coupled to the first bus waveguide; a second silicon ring optically coupled to the first bus waveguide; a first heater configured to heat the first silicon ring; a second heater configured to heat the second silicon ring; and a first switch having a first switch position and a second switch position, wherein the first switch is configured to: electrically couple the first silicon ring to a first radio frequency (RF) circuit in the first switch position; and electrically couple the second silicon ring to the first RF circuit in the second switch position.

[0006] According to another aspect of an embodiment of the present invention, a semiconductor device is provided, including: a first bus waveguide; a first silicon ring optically coupled to the first bus waveguide; a spare silicon ring optically coupled to the first bus waveguide; a first heater and a second heater configured to heat the first silicon ring and the spare silicon ring, respectively; and a first switch, wherein the first switch is configured to electrically couple the first silicon ring to a first radio frequency (RF) circuit when the first switch is in a first switch position, and is configured to electrically couple the spare silicon ring to the first radio frequency (RF) circuit when the first switch is in a second switch position.

[0007] According to another aspect of an embodiment of the present invention, a method for operating a silicon ring modulator is provided. The silicon ring modulator has a first ring, a second ring, and a bus waveguide optically coupled to the first ring and the second ring. The method includes: injecting an optical signal having a first wavelength into the bus waveguide; heating the first ring to a first temperature, wherein a first resonant wavelength of the first ring at the first temperature matches the first wavelength of the optical signal; heating the second ring to a second temperature different from the first temperature; and modulating the optical signal coupled to the first ring by applying a radio frequency (RF) signal to the first ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various aspects of the present invention are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with standard practice in the industry, various components are not drawn to scale and are used for illustrative purposes only. In fact, the dimensions of various components may be arbitrarily increased or decreased for clarity of discussion.

[0009] Figure 1 A block diagram of an optical communication system in an embodiment is shown.

[0010] Figure 2A A block diagram of a silicon photonics device in an embodiment is illustrated.

[0011] Figure 2B In the embodiment shown Figure 2A Operation of switching in silicon photonic devices.

[0012] Figure 3 A flow chart illustrating a method of operating a silicon photonics device in an embodiment is shown.

[0013] Figure 4 The graph shows the spectrum of the ring modulator in the embodiment at different temperatures.

[0014] Figure 5A and Figure 5B The diagram illustrates the adjustment of the resonant wavelength of a ring in a ring modulator in an embodiment.

[0015] Figure 6A 、 Figure 6B and Figure 6C Various power monitors for silicon photonic devices are illustrated in some embodiments.

[0016] Figure 7A 、 Figure 7B and Figure 7C Various views of a ring modulator in an embodiment are shown.

[0017] Figure 8 A block diagram of a silicon photonics device in another embodiment is illustrated.

[0018] Figure 9A block diagram of a silicon photonics device in another embodiment is illustrated.

[0019] Figure 10 A block diagram of a silicon photonics device in another embodiment is illustrated.

[0020] Figure 11 A block diagram of a silicon photonic device in yet another embodiment is illustrated.

[0021] Figure 12 A flow chart illustrating a method of operating a ring modulator according to some embodiments is illustrated. DETAILED DESCRIPTION

[0022] The following disclosure provides many different embodiments or examples for implementing the different features of the present invention. Specific embodiments or examples of components and arrangements are described below to simplify the present invention. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly in contact with each other, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the present invention may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0023] Furthermore, for ease of description, spatial relational terms such as "below," "beneath," "lower," "above," and "upper" may be used herein to describe the relationship of one element or component to another element or component as illustrated in the figures. These spatial relational terms are intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relational descriptors used herein should be interpreted accordingly.

[0024] According to an embodiment, a ring modulator includes a primary ring and a backup ring optically coupled to a bus waveguide. Each of the primary and backup rings has its own heater. The heaters can be controlled to heat the respective ring (e.g., primary or backup ring) to a target temperature. The resonant wavelengths of the primary and backup rings can be tuned by adjusting their temperatures. During operation of the ring modulator, the primary ring is heated to a first temperature to match the resonant wavelength of the primary ring with the operating wavelength of the ring modulator, and the backup ring is heated to a different second temperature to differ from the operating wavelength of the ring modulator. If a primary ring failure is detected, the primary ring is deactivated by heating it to a second temperature, and the backup ring is activated to replace the primary ring by heating it to a third temperature to match the resonant wavelength of the ring modulator. The third temperature can be the same as the first temperature. During device testing during manufacturing, if a defect is detected in the primary ring, the backup ring of the device can be tuned (e.g., by adjusting its temperature) to replace the primary ring, and the device can still be used. Therefore, by using the backup ring as redundancy, the device's production yield is improved. In addition, after the device is deployed in the field, if the primary ring fails, the backup ring can be activated to replace the primary ring. This reduces product failure rate and saves the cost of replacing devices.

[0025] Figure 1 The diagram illustrates a block diagram of an optical communication system 50 in an embodiment. In this embodiment, the optical communication system 50 includes a modulator 13 (e.g., an optical modulator), a light source 11, a signal source 15, an optical communication link 12, a detector 17, and a signal receiver 19. The light source 11 generates a light signal (e.g., a laser beam) having a predetermined wavelength, which is then transmitted to the modulator 13. The modulator 13 modulates the optical signal using an electrical signal from the signal source 15. The signal source 15 may include a device that generates an electrical signal carrying digital information (e.g., a radio frequency (RF) signal), which is then used to modulate the optical signal. For example, the signal source 15 may include functional blocks such as error correction coding, modulation, filtering, upsampling, analog-to-digital conversion (ADC), and RF processing. The optical signal may be modulated by the modulator 13 using, for example, amplitude modulation (AM), phase modulation (PM), polarization modulation, and the like. The modulated optical signal is transmitted via the optical communication link 12 (e.g., a fiber optic cable) and converted into an electrical signal by the detector 17 (e.g., a photodetector) at the receiver end. The output of the detector 17 is then sent to a signal receiver 19, which recovers the transmitted digital information using the electrical signal from the detector 17. As an example, the signal receiver 19 may include functional blocks such as demodulation, decoding, and error correction.

[0026] Figure 1Also shown is a feedback path 21 (e.g., one or more conductive paths) that can be used to transmit control information and / or measurement information from the signal receiver 19 to the modulator 13 to control (e.g., fine-tune or close-loop control) the operation of the modulator 13. For example, the signal receiver 19 can provide an indicator of the quality of the received signal, such as a bit error rate (BER) measurement, a signal-to-noise ratio (SNR) measurement, or a measurement of the eye opening in an eye diagram of the demodulated signal at the signal receiver 19. The modulator 13 can adjust its parameters (e.g., resonant wavelength or heating power) to optimize or improve the quality of the signal received at the signal receiver 19.

[0027] In some embodiments, the modulator 13 and signal source 15 can be formed in a first silicon photonics chip for modulating optical signals, and the detector 17 and signal receiver 19 can be formed in a second silicon photonics chip for demodulating / decoding the modulated optical signals. In some embodiments, a silicon photonics chip can include the modulator 13 and signal source 15 for modulating / transmitting optical signals, and can also include the detector 17 and signal receiver 19 for receiving / decoding optical signals. This disclosure discloses various embodiments of the modulator 13 (e.g., various silicon ring modulators) suitable for integration into silicon photonics circuits (e.g., semiconductor devices such as integrated circuits). While the disclosed embodiments are for optical modulation, as readily understood by those skilled in the art, the principles disclosed herein can also be applied to optical demodulation.

[0028] Silicon photonics devices are widely used in high-speed transceivers and other photonic systems. Typically, Mach-Zehnder modulators (MZMs), arrayed waveguide gratings (AWGs), and other optical devices with large dimensions are used in silicon photonics devices. The use of MZMs and AWGs results in large chip sizes and high manufacturing costs. For example, an MZM can have a diameter of approximately 2 mm. 2 Typical dimensions. The use of MZMs predates the advent of silicon photonics. As such, the characteristics of MZMs may not be optimal for integration into silicon photonics. The large size of MZMs can be attributed to the relatively weak electro-optical (EO) effect in silicon. To compensate for the weakness of the EO effect in silicon, MZMs tend to be larger. Due to the large size and high cost of MZMs, traditional optical devices are typically constructed without any redundant components (e.g., redundant MZMs) as backup. However, without redundancy, the failure of a single critical optical component could cause the entire optical device to fail, potentially reducing production yields and increasing average product costs. Furthermore, without any redundant components, adding or removing optical components from a photonic link is difficult.

[0029] Silicon photonic circuits are becoming increasingly complex with higher integration densities, more performance constraints, and tighter power budgets. These factors can lead to significant yield reductions in production and increased product failure rates after deployment for a number of reasons, some of which are discussed below.

[0030] One reason is that photonic devices are process sensitive. Small process variations can result in large performance deviations from design targets, which means potentially higher failure rates. "Process variation" typically manifests itself as deviations in the dimensions (e.g., physical dimensions) of the layout elements it manufactures from the expected / designed values. For example, the operating wavelength of a waveguide may depend on the width of the waveguide. If the width of the waveguide changes by 1 nm, the operating wavelength of the waveguide may shift by 1 nm. In some optical applications, a 1 nm shift may be enough to degrade the performance of an optical modulator or even cause the modulator to fail. A possible source of dimensional deviations is non-ideal etching. Non-idealities in photolithography are another example. In general, photonic devices may be more process sensitive than logic devices, in part because optical signals are more sensitive than electrical signals.

[0031] Another reason for yield degradation and / or product failure rates is that, in typical optical devices, system-level performance depends on the performance of each component in the photonic link. A single faulty component in the photonic link can directly lead to failure of the entire system. Yet another reason is that, over extended periods of deployment, device performance may degrade or even be damaged due to, for example, component aging and / or environmental factors such as moisture infiltration and oxidation.

[0032] Various embodiment optical devices are discussed herein that overcome or mitigate the yield degradation and product failure rate issues discussed above and are well suited for implementation in silicon photonics. The disclosed embodiment optical devices have redundant optical modulators (e.g., silicon ring modulators) and multiple optical signal paths, which allow for easy addition / removal of photonic elements in a photonic link and easy activation of redundant optical modulators as replacements if a primary optical modulator fails. The operating wavelength of the optical device is easily tunable. Additionally, optical devices having a small footprint (e.g., approximately 100 μm) can be fabricated. 2 Furthermore, due to its compact size and power-efficient structure, multiple instances of the disclosed optical modulator can be formed in silicon photonic circuits without significantly increasing power consumption.

[0033] Figure 2A FIG2 shows a block diagram of a silicon photonic device 100 in an embodiment. Note that for simplicity, not all components of the silicon photonic device 100 are shown. Figure 2AIn the example of FIG. 1 , the silicon photonic device 100 includes two silicon ring modulators 120 (e.g., 120A and 120B). The silicon ring modulators 120 (e.g., optical modulators) may also be referred to herein as ring modulators 120. The silicon ring modulators 120 (e.g., 120A and 120B) have the same structure but are controlled differently to have different resonant wavelengths and are modulated by different modulation signals, as discussed in more detail below.

[0034] like Figure 2A As shown, each ring modulator 120 (e.g., 120A or 120B) includes a bus waveguide 102, a silicon ring 107A, and a silicon ring 107B. Silicon rings 107 (e.g., 107A and 107B) are optically coupled to bus waveguide 102 and are also referred to as rings 107 in this discussion. In the illustrated embodiment, rings 107 (e.g., 107A and 107B) have identical structures, and ring 107B serves as a redundant ring (also referred to as a backup ring) for ring 107A (also referred to as a primary ring). For example, if ring 107A fails (e.g., malfunctions or is damaged), ring 107B can be activated to replace the functionality of ring 107A, as discussed in detail below.

[0035] The ring modulator 120 further includes a plurality of heaters 103 configured to heat the rings 107. Specifically, each ring 107 has a corresponding heater 103. Figure 2A Further shown is a heating element 105 (e.g., a resistor) for each heater 103. In addition to the heating element 105, each heater 103 may include other components, such as a temperature sensor that monitors (e.g., measures) the temperature of the corresponding ring 107, or a voltage control circuit and / or a current control circuit that controls (e.g., adjusts) the voltage across the heating element 105 and / or the current flowing through the heating element 105. In some embodiments, the voltage control circuit and / or the current control circuit of each heater 103 is used to regulate the heating power of the heating element 105 and is controlled by the heater control unit 101 (e.g., a microcontroller or digital logic) of the ring modulator 120 so that a target temperature of each ring 107 is maintained during operation of the silicon photonics device 100. For example, closed-loop control may be performed in which the heater control unit 101 (also referred to as a heater control circuit) monitors the measured temperature of each ring 107 and individually issues different control instructions to each heater 103 so that the voltage control circuit and / or the current control circuit of each heater 103 adjusts the heating power of the heating element 105 accordingly to maintain the target temperature of each ring 107.

[0036] Still refer to Figure 2AEach ring 107 has two contacts 109 and 111. One of the contacts 109 / 111 is electrically coupled to a P-doped region of the ring 107, and the other of the contacts 109 / 111 is electrically coupled to an N-doped region of the ring 107. The contacts 109 and 111 are configured to couple to a modulation signal (e.g., an RF signal generated by the RF circuit 115) to modulate the optical signal in the ring 107. Details of the ring 107 and its electrical connections are described below with reference to 7A to 7C discuss.

[0037] Ring modulator 120 also includes RF circuitry 115 and switch 113. In some embodiments, RF circuitry 115 includes functional blocks for generating an RF signal modulated by digital information (e.g., digital data such as 0s and 1s). In other words, RF circuitry 115 outputs a modulated RF signal carrying the digital information. The modulated RF signal from RF circuitry 115 is then connected to contacts 109 / 111 of each ring 107 via switch 113. In some embodiments, RF circuitry 115 includes multiple functional blocks, such as error correction coding, digital modulation (e.g., digital constellation mapping), digital filtering, upsampling, analog-to-digital conversion (ADC), analog modulation (e.g., mixing with a carrier), and / or an analog amplifier (e.g., a low-noise RF amplifier). In some embodiments, RF circuitry 115 includes only analog signal processing blocks, such as analog modulation and analog amplifiers. In some embodiments, RF circuitry 115 includes only electrical contacts (e.g., contact pads) for connecting to an external RF source, so that RF signals generated by the external RF device are transmitted to switch 113 via the electrical contacts of RF circuitry 115.

[0038] In the illustrated embodiment, the switch 113 is used as a double-pole double-throw switch. Specifically, when the switch 113 is in the first switch position (e.g., Figure 2A When the switch 113 is in the second switch position (e.g., the left-hand position in FIG), the RF signal from the RF circuit 115 is electrically coupled to the contacts 109 / 111 of the ring 107A. Figure 2A (right-hand position in the figure), the RF signal from the RF circuit 115 is electrically coupled to the contacts 109 / 111 of the ring 107B. Note that Figure 2A The switch arm 114 of the switch 113 is shown in the figure to schematically indicate the switching between the two switch positions of the switch 113. Those skilled in the art will readily understand that the switch 113 may not have a mechanical switch arm 114, and that the switch 113 may be any suitable type of switch, such as a plurality of transistors interconnected together and controlled by a control voltage to implement a double-pole double-throw switch function. For simplicity, Figure 2A The switch arm 114 in FIG. 1 (and subsequent figures) is shown by a single line. Figure 2B Shows Figure 2AFIG. 1 is a more detailed view of the switching of the switch 113 in FIG. 1 , wherein the switch arm 114 is shown having two conductive paths 114A and 114B connected to the contacts 109 and 111 in each switch position.

[0039] Although not in Figure 2A , but a power monitor that can measure the optical power of an optical signal at certain locations of the ring modulator 120 (eg, in the ring 107 or in the bus waveguide 102) can be formed in the silicon photonic device 100. Figures 6A to 6C The various types of power monitors and various locations of power monitors are discussed, and the details are beyond the scope of this article.

[0040] Figure 2A The number of ring modulators 120 in the silicon photonics device 100 (and subsequent figures) is merely a non-limiting example. Those skilled in the art will readily appreciate that any number of ring modulators 120 may be formed in the silicon photonics device 100. Furthermore, the use of the term "silicon photonics device," "silicon ring modulator," and "silicon ring" simply indicates that the device / structure (e.g., photonic device, ring modulator, or ring) in question is a semiconductor device or portion thereof formed using semiconductor manufacturing techniques, and does not limit the material of the device / structure in question to silicon (e.g., Si). Silicon photonics devices, silicon ring modulators, and silicon rings may be formed using any suitable material.

[0041] Figure 3 A flow chart of a method 300 for operating a silicon photonic device in an embodiment is illustrated. The method 300 can be used to operate various embodiment silicon photonic devices disclosed herein (e.g., 100, 100A, 100B, 100C, and 100D). The method 300 can be performed each time the device is powered on and / or when a real-time check is requested during device operation. Note that the method 300 describes operations associated with one of the ring modulators 120 in the silicon photonic device. As will be readily understood by those skilled in the art, if the silicon photonic device has more than one ring modulator 120, the method 300 can be applied to each ring modulator 120. As an example, the following reference Figure 2A and Figure 3 The operation of the silicon photonic device 100 is described. Note that in the discussion herein, without loss of generality, it is assumed that the ring modulator 120A is configured to modulate a wavelength λ 1 optical signal 131 (eg, a laser beam), and the ring modulator 120B is configured to modulate the optical signal 131 having a wavelength λ 2. Optical signal 133 (eg, laser beam). Wavelength λ 1 is referred to as the operating wavelength of the ring modulator 120A, and the wavelength λ 2 is referred to as the operating wavelength of the ring modulator 120B.

[0042] refer to Figure 3 and Figure 2A At block 310, the system (eg, silicon photonic device 100) is turned on. λ 1 optical signal 131 and having a wavelength λ The optical signal 133 of 2 is injected into the bus waveguide 102 at the input port of the bus waveguide 102.

[0043] At block 320, the main ring 107A of each ring modulator 120 (e.g., 120A or 120B) is turned on and the optical power in the main ring 107A is monitored, for example, by a power monitor. The main ring 107A is turned on by turning on the corresponding heater 103 (e.g., under the control of the heater control unit 101) and heating the main ring 107A. Details on monitoring (e.g., measuring) the optical power of the main ring 107A are described below. Figures 6A to 6C discussion, so it will not be discussed here.

[0044] exist Figure 3 At block 330, the output power (e.g., heating power) of the heater 103 of the primary ring 107A of each ring modulator 120 (e.g., 120A or 120B) is adjusted (e.g., by control of the heater control unit 101) to heat the primary ring 107A to a target temperature so that the resonant wavelength of the primary ring 107A of each ring modulator 120 (e.g., 120A or 120B) at its respective target temperature is aligned with the operating wavelength (e.g., wavelength) of the ring modulator 120. λ 1 or λ 2) Matching. The backup ring 107B of each ring modulator 120 is heated by its corresponding heater 103 to a temperature different from the target temperature of the main ring 107A of the ring modulator 120, so that the resonant wavelength of the backup ring 107B is tuned to a temperature different from the target temperature of the main ring 107A of the ring modulator 120. λ 1 and λ Predetermined value of 2 λ 0.

[0045] In the illustrated embodiment, when the resonant wavelength of the ring 107 (e.g., 107A or 107B) matches the wavelength of the optical signal propagating in the bus waveguide 102, optical coupling of the optical signal between the bus waveguide 102 and the ring 107 is maximized, and the optical signal is said to be coupled (e.g., optically coupled) into the ring 107. Conversely, if there is a mismatch between the resonant wavelength of the ring 107 and the wavelength of the optical signal in the bus waveguide 102, there is little or no optical coupling of the optical signal between the bus waveguide 102 and the ring 107, and the optical signal is said to be uncoupled into the ring 107. Figure 2A In the example, due to the processing of block 330, the wavelength λThe optical signal 131 of 1 is coupled into the main ring 107A of the ring modulator 120A and has a wavelength of λ The optical signal 133 of 2 is coupled into the main ring 107A of the ring modulator 120B.

[0046] In some embodiments, the heater control unit 101 of each ring modulator 120 can sweep the heater power within a range so that the resonant wavelength of the main ring 107A is aligned with the operating wavelength of the ring modulator 120 (eg, λ 1 or λ 2) Matching (e.g., alignment). For example, while adjusting the heater power, the optical power of the optical signal 131 coupled into the primary ring 107A of the ring modulator 120A is continuously monitored (e.g., measured), and the heater power setting (or the temperature of the primary ring 107A) that results in the maximum measured optical power in the primary ring 107A of the ring modulator 120A is used as the setting for aligning the resonant frequency of the primary ring 107A with the operating wavelength of the ring modulator 120A. λ 1. Alignment to the optimal setting.

[0047] As described above, the resonant wavelength of a ring 107 (eg, 107A or 107B) varies with the temperature of the ring 107 and, therefore, can be tuned (eg, adjusted) by adjusting the temperature of the ring 107 (eg, via the corresponding heater 103 ). Figure 4 The effect of temperature on the resonant wavelength of the ring 107 is shown.

[0048] Temporary reference Figure 4 , which shows the spectrum of the ring modulator at different temperatures in the embodiment. Figure 4 The optical power on the bus waveguide 102 measured after a broad spectrum optical signal (eg, an optical component having wavelengths spanning a wide range, such as a white light signal) injected into the bus waveguide 102 is coupled to the ring 107 is shown. Figure 4 The four curves 401, 402, 403 and 404 shown in FIG correspond to the temperatures of the ring 107 at 10°C, 20°C, 30°C and 40°C, respectively. Figure 4 As shown, when the wavelength of an optical component matches the resonant wavelength of ring 107 at a specific temperature, the specific optical component is coupled into ring 107 and undergoes modulation, which may reduce the power of the optical component. As a result, the power of the remaining optical signal on bus waveguide 102 shows a notch at the resonant wavelength of ring 107. Figure 4 It is shown that different temperatures of the ring result in different resonance wavelengths of the ring. In addition, for a specific temperature, there are multiple resonance wavelengths, such as Figure 4 Indicated by the number of notches in each curve.

[0049] Still refer to Figure 4The distance between two consecutive (e.g., adjacent) notches of a particular curve (e.g., 401, 402, 403, 404) is called the free spectral range (FSR). The FSR is a design parameter for the ring 107. A common range for the FSR is between approximately 5 nm and approximately 30 nm. If multiple ring modulators are employed in a wavelength division multiplexing (WDM) system with multiple operating wavelengths, the FSR is often designed to be wider. In some embodiments, the resonant wavelength range adjustable (e.g., covered) by the heater 103 is designed to span at least one FSR. This provides flexibility in selecting the resonant wavelength of the ring 107 and in ensuring sufficient separation in resonant wavelength between the primary ring 107A and the backup ring 107B.

[0050] Research has shown that silicon has a strong thermo-optical effect, meaning that its optical properties can be significantly altered by changing its temperature. The resonant wavelength of the silicon ring 107 can be tuned substantially linearly with respect to temperature. For example, for each degree of temperature change (e.g., 1°C), the resonant wavelength of the silicon ring may shift by approximately 0.08 nm. Therefore, by changing the temperature of the ring 107 to alter its resonant wavelength, the ring 107 can be enabled or disabled, depending on whether the resonant wavelength matches the operating wavelength of the ring modulator 120.

[0051] return Figure 3 and Figure 2A At block 340, for each ring modulator 120 (e.g., 120A or 120B), the RF circuit 115 is turned on, and the RF signal generated by the RF circuit 115 is applied (e.g., connected) to the main ring 107A via switch 113. In other words, switch 113 is in the left-hand position to connect the RF circuit 115 to the main ring 107A. In the illustrated embodiment, the RF signal applied to the contacts 109 / 111 of the main ring 107A in each ring modulator 120 (e.g., 120A or 120B) modulates the optical signal (e.g., 131 or 133) coupled into the main ring 107A. Modulation of the optical signal is accomplished through physical processes such as plasmon dispersion and free-carrier absorption, which alter the refractive index and absorption coefficient of the ring 107 to modulate the optical signal. The modulated optical signal 131 in the ring modulator 120A is coupled back into the bus waveguide 102 and propagates toward the through port of the bus waveguide 102. Similarly, the modulated optical signal 133 in the ring modulator 120B is coupled back to the bus waveguide 102 and propagates toward the through port of the bus waveguide 102. The through port may be connected to one or more receivers to demodulate / decode the modulated optical signal 131 / 133.

[0052] Next, at block 350, each of the modulated optical signals 131 and 133 is processed at the receiver end by a corresponding receiver, which may be a receiver comprising, for example, Figure 1In some embodiments, the receiver detects, analyzes, optimizes and monitors the optical signal at the receiver end and provides a feedback signal to the ring modulator 120 (e.g., via Figure 1 The feedback path 21 shown in FIG. 21 is used to further fine-tune the ring modulator 120. For example, as described above with reference to FIG. Figure 1 As discussed, the receiver can provide an indicator of received signal quality, such as a bit error rate (BER) measurement, a signal-to-noise ratio (SNR) measurement, or an eye opening measurement of an eye diagram of the demodulated signal at the receiver. Based on the indicator of received signal quality, the ring modulator 120 can adjust its parameters (e.g., by adjusting the resonant wavelength by adjusting the heater power) to optimize or improve the received signal quality at the receiver. In some embodiments, the feedback path from the receiver to the ring modulator 120 is omitted. In other words, the ring modulator 120 operates without feedback from the receiver.

[0053] Next, at block 360 , the status of the primary ring 107A of each ring modulator 120 is monitored to detect a failure in the primary ring 107A. Any suitable method can be used to detect a failure in the primary ring 107A. For example, if the optical power measured in the normally operating primary ring 107A suddenly drops below a predetermined threshold, this may indicate a failure in the primary ring. To confirm this, the heater control unit 101 may sweep the heater power within a predetermined range around the last known good setting (e.g., the last heater power setting that aligned the resonant wavelength with the operating wavelength) to adjust the resonant wavelength of the primary ring 107A. If the measured optical power in the primary ring 107A remains below the predetermined threshold regardless of the heater power setting during the sweep, it can be determined that the primary ring 107A has failed (e.g., is damaged). As another example, the measured optical powers in the primary ring 107A and the backup ring 107B may be compared to detect a failure in the primary ring 107A. If primary ring 107A is functioning properly, the measured optical power in primary ring 107A should be higher (e.g., by a predetermined percentage or amount) than the measured optical power in backup ring 107B during modulation. However, if primary ring 107A fails, the measured optical power in primary ring 107A may be substantially the same as the measured optical power in backup ring 107B (e.g., within a small predetermined range).

[0054] If no failure of the primary ring 107A is detected, the process returns to block 350. Otherwise, the process proceeds to block 370, where the backup ring 107B is activated to replace the failed primary ring 107A. Specifically, at block 370, the heater control unit 101 controls the heater 103 of the primary ring 107A so that the primary ring 107A is heated to a temperature corresponding to the resonant wavelength. λ 0 temperature, where λ0 is different from the operating wavelength of the ring modulator 120 (eg, λ 1 or λ 2). This ensures that the main ring 107A is cut off and the optical signal 131 or 133 is not coupled into the main ring 107A. In addition, the heater control unit 101 controls the heater 103 of the backup ring 107B so that the backup ring 107B is heated to a wavelength corresponding to the operating wavelength of the ring modulator 120 (e.g., λ 1 or λ 2) Temperature of the matched resonant wavelength. In other words, the spare ring 107B is now enabled so that the optical signal 131 or 133 is coupled into the spare ring 107B.

[0055] Next, at block 380, the switch 113 is switched to the Figure 2A Changing the left-hand switch position of 107A to the right-hand switch position routes the RF signal from the RF circuit 115 from the (failed) primary ring 107A to the backup ring 107B. As a result, the optical signal in the backup ring 107B is now modulated by the RF signal.

[0056] Next, at block 390, each of the modulated optical signals 131 and 133 is processed at the receiver end by a corresponding receiver. The receiver detects, analyzes, optimizes, and monitors the optical signal at the receiver end and provides a feedback signal to the ring modulator 120 (e.g., via Figure 1 21) to further fine-tune the ring modulator 120. The processing is the same or similar to that of block 350, so the details are not repeated. In some embodiments, the processing of block 390 is omitted so that the ring modulator 120 operates without feedback from the receiver side.

[0057] Note that method 300 can be used during product testing to replace a failed primary ring 107A with a spare ring 107B. For example, after the silicon photonic device 100 is manufactured in a fabrication facility, the manufactured silicon photonic device 100 can be tested (e.g., by feeding an optical signal into the ring modulator 120), modulating the optical signal with an RF signal using the ring modulator 120, and demodulating / decoding the output of the ring modulator 120. If, during product testing, one of the primary rings 107A is found to be damaged, the spare ring 107B can be activated to replace the primary ring 107A, and the silicon photonic device 100 remains functional and usable. This improves product yield. As another example, after the silicon photonic device 100 has been deployed in the field, if a primary ring 107A fails, the corresponding spare ring 107B can be activated to replace the failed primary ring 107A without having to replace the silicon photonic device. This reduces product failure rates and saves the cost of replacing silicon photonic chips.

[0058] Figure 5A and Figure 5B The diagram shows the adjustment of the resonant wavelength of the ring in the ring modulator in an embodiment. Figure 5A In FIG, two curves 501 and 502 are plotted in two separate subgraphs, wherein the x-axes of the two subgraphs are aligned, and wherein the curves 501 and 502 show the spectra of the primary ring 107A and the backup ring 107B, respectively. Figure 4 , the notches in curves 501 and 502 correspond to the resonant wavelengths of the corresponding rings. Figure 5A The positions of the resonant wavelengths of the main ring 107A and the backup ring 107B are shown when the main ring 107A is operating normally. Figure 3 As discussed, the resonant wavelength of the main ring 107A is tuned to the operating wavelength of the ring modulator 120. λ , the operating wavelength λ Can be Figure 2A Example λ 1 or λ 2, and the resonant wavelength of the backup ring 107B is tuned to λ 0, so that the optical signal in the bus waveguide 102 is not coupled to the spare ring 107B.

[0059] Figure 5B Similar to Figure 5A , but corresponds to the case where the main ring 107A fails. Figure 3 As discussed, when the main ring 107A fails, the resonant wavelength of the main ring 107A is tuned to λ 0, so that the optical signal in the bus waveguide 102 is not coupled into the main ring 107A, and the resonant wavelength of the backup ring 107B is tuned to the operating wavelength of the ring modulator λ , so that the backup ring 107B replaces the function of the primary ring 107A.

[0060] Figure 6A 、 Figure 6B and Figure 6C FIGURE 1 shows various power monitors for use with silicon photonic devices in some embodiments. Figure 6A 、 Figure 6B and Figure 6C In the figure, only Figure 2A The same or similar optical monitors can be formed for the rings 107A and 107B of the ring modulator 120A and the corresponding optical monitors.

[0061] refer to Figure 6A, two power monitors 137A and 137B are connected to optical power taps 135A and 135B, respectively. Optical power tap 135A is optically coupled to bus waveguide 102 at a location between rings 107A and 107B. Optical power tap 135B is optically coupled to bus waveguide 102 at a location after optical signal 131 is coupled to ring 107B. Therefore, power monitor 137A measures the optical power in bus waveguide 102 at a location between rings 107A and 107B, and power monitor 137B measures the optical power in bus waveguide 102 at a location after ring 107B. The optical power monitors can be designed to detect the optical power of a single wavelength or the optical power in a frequency band. Optical power taps 135A / 135B and power monitors 137A / 137B can be any suitable devices known and used in the art, and the details will not be discussed here.

[0062] for Figure 6A If the corresponding ring 107 (e.g., 107A or 107B) is enabled (e.g., its resonant wavelength matches the operating wavelength), the optical power measured during modulation will decrease because the optical signal is coupled to the ring 107 for modulation, which can reduce the optical power on the bus waveguide 102. By monitoring the measured optical power value (e.g., by the heater control unit 101), it can be determined whether a particular ring 107 is enabled, disabled, or damaged. For example, if the optical power measured by power monitor 137A decreases by a predetermined percentage after ring 107A is heated to a target temperature (which aligns the resonant wavelength of ring 107A with the operating wavelength), it can be determined that ring 107A is enabled. If ring 107A, which has been enabled, is heated to a different temperature and the optical power measured by power monitor 137A increases by a predetermined percentage, it can be determined that ring 107A is now disabled. As another example, if the optical power measured by power monitor 137A remains high (eg, above a predetermined threshold) regardless of the temperature of ring 107A during the temperature sweep, then ring 107A may be determined to be damaged.

[0063] refer to Figure 6B , two power monitors 137A and 137B are connected to optical power taps 135A and 135B, respectively. Optical power tap 135A is optically coupled to ring 107A, and optical power tap 135B is optically coupled to ring 107B. Figure 6BPower monitors 137A and 137B measure the optical power within rings 107A and 107B, respectively. If ring 107 is enabled (e.g., its resonant wavelength matches the operating wavelength), the measured optical power increases; if ring 107 is disabled or damaged, the measured optical power decreases. Therefore, by monitoring the measured optical power values, it is possible to determine whether a particular ring 107 is enabled, disabled, or damaged. For example, if the optical power measured by power monitor 137A increases by a predetermined percentage after ring 107A is heated to a target temperature that aligns the resonant wavelength of ring 107A with the operating wavelength, it can be determined that ring 107A is enabled. If ring 107A, which had been enabled, is heated to a different temperature and the optical power measured by power monitor 137A decreases by a predetermined percentage, it can be determined that ring 107A is now disabled. As another example, if the optical power measured by power monitor 137A remains low (e.g., below a predetermined threshold) regardless of the temperature of ring 107A during a temperature scan, it can be determined that ring 107A is damaged.

[0064] refer to Figure 6C , photocurrent monitors 139A and 139B are optically coupled to rings 107A and 107B, respectively, and measure the optical power in the corresponding ring 107. If the optical signal 131 is coupled into the ring 107, it will cause a photocurrent in the photocurrent monitor 139 (e.g., 139A or 139B) coupled to the ring. Therefore, by monitoring the current flowing through the photocurrent monitors 139A and 139B, it can be determined whether a particular ring 107 is enabled, disabled, or damaged. For example, the same method as above can be used. Figure 6B The methods discussed are the same or similar methods.

[0065] Figure 7A 、 Figure 7B and Figure 7C Various views (eg, plan view, cross-sectional view) of a ring modulator 700 in an embodiment are shown. Figure 7A 、 Figure 7B and Figure 7C The ring modulator 700 can be used as the ring modulator 120 in various embodiments disclosed herein. Note that for simplicity, not all components of the ring modulator 700 are shown. Figure 7A 、 Figure 7B and Figure 7C Only portions of the ring modulator 700 may be shown.

[0066] Figure 7A A plan view of a ring modulator 700 is shown. For simplicity, Figure 7A The ring modulator 700 corresponds to Figure 2A A portion of a ring 107 is provided. Figure 7B Shown with Figure 7AThe same plan view, but with additional elements of the ring modulator 700 shown (eg, heating element, electrical contacts). Figure 7C The ring modulator 700 is shown along Figure 7B The cross-sectional view of section AA in FIG. Note that Figure 7C , two identical structures on opposite sides of dashed line 750 are shown, each of which corresponds to Figure 2A (part of) one of the rings 107 and its corresponding heating element 105 .

[0067] like Figure 7A As shown, the ring modulator 700 includes a bus waveguide 702, a first doped region 705, a second doped region 707, a ring 709, a first contact region 713, and a second contact region 711. The bus waveguide 702 may be formed of a semiconductor material such as silicon and corresponds to Figure 2A The bus waveguide 102 of FIG. 1 is a bus waveguide 102. The first doped region 705 and the second doped region 707 are two ring-shaped regions (or portions of ring-shaped regions) formed of a suitable semiconductor material (e.g., silicon) and doped with opposite types of dopants (e.g., N-type or P-type). For example, the first doped region 705 can be an N-type doped region (e.g., a silicon region doped with N-type dopants), and the second doped region 707 can be a P-type doped region (e.g., a silicon region doped with P-type dopants); or vice versa. The ring 709 is the interface region between the first doped region 705 and the second doped region 707, which forms a ring waveguide. The ring 709 corresponds to Figure 2A Ring 107.

[0068] Figure 7A Also shown is a first contact region 713 surrounded by and contacting the first doped region 705. Figure 7A A second contact region 711 is shown surrounding and contacting the second doping region 707. The first contact region 713 is a heavily doped semiconductor region having the same doping type as the first doping region 705, and the second contact region 711 is a heavily doped semiconductor region having the same doping type as the second doping region 707. In an example embodiment, the first doping region 705 is an N-doping region and the second doping region 707 is a P-doping region, and the first contact region 713 and the second contact region 711 are an N++ region and a P++ region, respectively.

[0069] Figure 7B Additional layers of the ring modulator 700 are shown. Specifically, Figure 7B A heating element 719 (metal pattern) is shown, which corresponds to Figure 2A The heating element 105. In addition, Figure 7B Metal contacts 721 and 723 are shown, which are electrically coupled to the first contact area 713 and the second contact area 711 below. The metal contacts 721 and 723 correspond to Figure 2A Contact members 111 and 109.

[0070] Figure 7C The substrate 701 of the ring modulator 700 is shown. Substrate 701 can be a doped or undoped semiconductor substrate, such as silicon, or the active layer of a semiconductor-on-insulator (SOI) substrate. The semiconductor substrate can include other semiconductor materials, such as germanium; compound semiconductors, including silicon carbide, gallium arsenide, gallium phosphide, gallium nitride, indium phosphide, indium arsenide, and / or indium antimonide; alloy semiconductors, including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and / or GaInAsP; or combinations thereof. Other substrates, such as multilayer or gradient substrates, may also be used.

[0071] like Figure 7C As shown, a plurality of dielectric layers 703 are formed over a substrate 701. The dielectric layers 703 may be made of one or more suitable dielectric materials, such as silicon oxide, silicon nitride, low-k dielectric materials (such as carbon-doped oxides), ultra-low-k dielectrics (such as porous carbon-doped silicon dioxide), combinations thereof, etc. The dielectric layers 703 may be formed by a process such as chemical vapor deposition (CVD), but any suitable process may be utilized.

[0072] exist Figure 7C In the example of , each of the first doped region 705, the second doped region 707, the first contact region 713, and the second contact region 711 is a silicon region doped with an N-type or P-type dopant. The silicon region can be formed by forming a silicon layer (e.g., Si) above the underlying dielectric layer 703, doping the silicon layer with an N-type or P-type dopant, and patterning the silicon layer to form the designed shape of the respective region. Figure 7C , the first doped region 705 , the second doped region 707 , the first contact region 713 , and the second contact region 711 are formed at the same vertical level (eg, the same vertical distance from the substrate 701 ), such as over the same upper surface of the dielectric layer 703 .

[0073] exist Figure 7C In the embodiment of the present invention, the first doped region 705 and the second doped region 707 have an L-shaped cross-section. For example, the first doped region 705 and the second doped region 707 are thicker in the interface region (e.g., 709) and thinner in other regions. In other words, the upper surface 709U of the interface region is higher (e.g., farther from the substrate 701) than the upper surface 705U of the portion of the first doped region 705 away from the interface region, and is higher than the upper surface 707U of the portion of the second doped region 707 away from the interface region. As discussed above, the interface region 709 between the first doped region 705 and the second doped region 707 (e.g., the area within the dashed circle) forms a waveguide and is referred to as the ring 709 (e.g., a silicon ring) of the ring modulator 700.

[0074] Figure 7C Further shown are conductive structures formed in the dielectric layer 703, such as vias 715 and conductive lines 716, which are electrically coupled to the first contact region 713 and the second contact region 711. The conductive features also include a heating element 719 (eg, a resistor) corresponding to Figure 2A The heating element 105. Figure 7C In FIG. 7 , the heating element 719 is formed in a metallization layer disposed above the ring 709 .

[0075] exist Figure 7C , metal contacts 721 and 723 (also referred to as contact pads) are formed above the uppermost dielectric layer 703 to electrically connect to other devices. Vias 715, conductive lines 716, heating elements 719, and metal contacts 712 / 723 may be formed of one or more suitable metal materials, such as copper, cobalt, tungsten, or the like, or combinations thereof, and may be formed using any suitable method. Although not shown, electronic devices such as transistors, diodes, capacitors, resistors, and the like may be formed in and / or above substrate 701 and may be interconnected to form functional circuits, for example, by interconnect structures formed by metallization patterns in dielectric layer 703. The functional circuits may be or include, for example Figure 2A The RF circuit 115 , heater control unit 101 and / or switch 113 are electrically coupled to the ring modulator 700 .

[0076] The ring modulator disclosed herein can be implemented in semiconductor devices with very small footprints. For example, the size (e.g., area) of the resonant structure (e.g., each ring and its corresponding heater and switch) can be approximately 100 μm. 2 For comparison, a typical electrical contact pad has a size of approximately 2500 μm. 2 Due to the compact size of the resonant structure, having redundant resonant structures in the ring modulator has little impact on the overall size and cost of the silicon photonics device. Furthermore, by using a compact and power-efficient resonant structure, adding redundant resonant structures does not significantly increase power consumption. In some embodiments, more than one spare ring can be added to each ring modulator without significantly increasing chip size and power consumption.

[0077] Figure 8 FIG. 1 is a block diagram of a silicon photonic device 100A in another embodiment. The silicon photonic device 100A is similar to Figure 2A 107B is used as a backup ring for rings 107A and 107C. In other words, the ring modulator 120 has two rings 107B and the ring 107B is used as a backup ring for rings 107A and 107C. Figure 2A different, Figure 8The silicon photonic device 100A uses three rings 107 (e.g., 107A, 107B, and 107C) to implement two ring modulators, wherein ring 107B is shared by rings 107A and 107C as a shared backup ring. Those skilled in the art will readily understand that if ring 107A fails, switch 113A switches to the right-hand switch position to couple RF circuit 115A to ring 107B, and ring 107B is heated to tune its resonant wavelength to align with the resonant wavelength of optical signal 131. Similarly, if ring 107C fails, switch 113B switches to the left-hand switch position to couple RF circuit 115B to ring 107B, and ring 107B is heated to tune its resonant wavelength to align with the resonant wavelength of optical signal 133. Due to Figure 8 The design has fewer resonant structures (e.g., the ring 107 and its corresponding heater 103), so Figure 8 Design ratio Figure 2A The design has greater area efficiency and energy efficiency.

[0078] Figure 9 FIG. 1 is a block diagram of a silicon photonic device 100B in another embodiment. The silicon photonic device 100B is similar to Figure 2A The silicon photonic device 100 is similar to the silicon photonic device 100 of FIG. 1 , but has a second bus waveguide 104 coupled to the ring 107 . The optical signals 131 and 133 are optically coupled to the second bus waveguide 104 after being modulated by the ring modulator 120 and are output at a drop port of the second bus waveguide 104 .

[0079] Figure 10 FIG. 1 is a block diagram of a silicon photonic device 100C in another embodiment. The silicon photonic device 100C is similar to Figure 8 1 , but with a second bus waveguide 104 coupled to a ring 107. Optical signals 131 and 133 are optically coupled to the second bus waveguide 104 after being modulated by the ring modulator 120 and output at a drop port of the second bus waveguide 104.

[0080] Figure 11 FIG. 1 is a block diagram of a silicon photonic device 100D in another embodiment. The silicon photonic device 100D is similar to Figure 9 The silicon photonic device 100D is similar to the silicon photonic device 100B, but has separate input bus waveguides 102A and 102B for the ring modulators 120A and 120B, respectively. Specifically, the optical signal 131 is injected into the bus waveguide 102A, and the optical signal 133 is injected into the bus waveguide 102B. After being modulated by the ring modulators 120A and 120B, the optical signals 131 and 133 are optically coupled to the second bus waveguide 104 and output at the drop port of the second bus waveguide 104. Note that the silicon photonic device 100D functions not only as an optical modulator but also as an optical multiplexer. Figure 11 As shown, optical signals 131 and 133 initially transmitted in separate bus waveguides 102A and 102B are combined after modulation into a second bus waveguide 104. Thus, the silicon photonics device 100D can be used to combine optical signals of different wavelengths.

[0081] Figure 12 A flow chart of a method 1000 of operating a ring modulator having a first ring, a second ring, and a bus waveguide optically coupled to the first ring and the second ring is illustrated. Figure 12 The embodiment methods shown are only examples of many possible embodiment methods. Those skilled in the art will recognize many variations, substitutions, and modifications. For example, the following may be added, removed, replaced, rearranged, or repeated: Figure 12 The various steps shown.

[0082] refer to Figure 12 At block 1010, an optical signal having a first wavelength is injected into a bus waveguide. At block 1020, the first ring is heated to a first temperature, wherein a first resonant wavelength of the first ring at the first temperature matches the first wavelength of the optical signal. At block 1030, the second ring is heated to a second temperature different from the first temperature. At block 1040, the optical signal coupled to the first ring is modulated by applying a radio frequency (RF) signal to the first ring.

[0083] The disclosed embodiments achieve several advantageous features. For example, by including a spare ring in the ring modulator 120, the redundancy provided by the spare ring improves product yield during device manufacturing. After the product is deployed in the field, a damaged ring can be replaced with a spare ring, reducing product failure rates and saving the cost of replacing silicon photonic components. The spare ring also allows for the flexible addition or removal of optical components in an optical communication link. The disclosed embodiments can be easily integrated into semiconductor devices using existing semiconductor manufacturing processes. Other advantages include small footprint and low power consumption.

[0084] According to an embodiment of the present disclosure, a semiconductor device includes a first silicon ring modulator, wherein the first silicon ring modulator includes: a first bus waveguide; a first silicon ring optically coupled to the first bus waveguide; a second silicon ring optically coupled to the first bus waveguide; a first heater for heating the first silicon ring; a second heater for heating the second silicon ring; and a first switch having a first switch position and a second switch position, wherein the first switch is configured to: in the first switch position, electrically couple the first silicon ring to a first radio frequency (RF) circuit; and in the second switch position, electrically couple the second silicon ring to the first RF circuit. In an embodiment, the semiconductor device further includes a first heater control circuit, wherein the first heater control circuit is configured to control the first heater and the second heater such that, during operation of the first silicon ring modulator, the first silicon ring and the second silicon ring are heated to a first temperature and a second temperature, respectively, wherein the first temperature is different from the second temperature. In an embodiment, a first resonant wavelength of the first silicon ring is determined by the first temperature, and a second resonant wavelength of the second silicon ring is determined by the second temperature. In an embodiment, during operation of the first silicon ring modulator, the first resonant wavelength of the first silicon ring at the first temperature matches the operating wavelength of the first silicon ring modulator. In one embodiment, during operation of the first silicon ring modulator, the second resonant wavelength of the second silicon ring at the second temperature is different from the operating wavelength of the first silicon ring modulator. In one embodiment, during operation of the first silicon ring modulator, the first switch is configured to be in a first switch position when the first resonant wavelength of the first silicon ring at the first temperature matches the operating wavelength of the first silicon ring modulator, or to be in a second switch position when the second resonant wavelength of the second silicon ring at the second temperature matches the operating wavelength of the first silicon ring modulator. In one embodiment, the semiconductor device further includes a first RF circuit. In one embodiment, the semiconductor device further includes: a first optical power monitor configured to measure optical power in the first silicon ring; and a second optical power monitor configured to measure optical power in the second silicon ring. In one embodiment, the semiconductor device further includes a second bus waveguide optically coupled to the first silicon ring and the second silicon ring. In one embodiment, during operation of the first silicon ring modulator, the first bus waveguide is configured to receive an input optical signal, and the second bus waveguide is configured to output a modulated optical signal, wherein the modulated optical signal is the input optical signal modulated by the RF signal from the first RF circuit.In an embodiment, the semiconductor device further comprises: a second silicon ring modulator, wherein the second silicon ring modulator comprises: a first bus waveguide; a third silicon ring optically coupled to the first bus waveguide; a fourth silicon ring optically coupled to the first bus waveguide; a third heater configured to heat the third silicon ring; a fourth heater configured to heat the fourth silicon ring; a second switch having a third switch position and a fourth switch position, wherein the second switch is configured to: electrically couple the third silicon ring to the second RF circuit in the third switch position; and electrically couple the fourth silicon ring to the second RF circuit in the fourth switch position; and a second heater control circuit configured to control the third heater and the fourth heater such that, during operation of the second silicon ring modulator, the third silicon ring and the fourth silicon ring are heated to a third temperature and a fourth temperature, respectively, wherein the third temperature is different from the fourth temperature. In an embodiment, the first heater control circuit and the second heater control circuit are configured to set the first temperature and the third temperature such that a first resonant wavelength of the first silicon ring at the first temperature matches a first operating wavelength of the first silicon ring modulator, and a second resonant wavelength of the third silicon ring at the third temperature matches a second operating wavelength of the second silicon ring modulator. In an embodiment, the semiconductor device further comprises: a second silicon ring modulator, wherein the second silicon ring modulator comprises: a first bus waveguide; a third silicon ring optically coupled to the first bus waveguide; a third heater configured to heat the third silicon ring; and a second switch having a third switch position and a fourth switch position, wherein the second switch is configured to: electrically couple the third silicon ring to the second RF circuit in the third switch position; and electrically couple the second silicon ring to the second RF circuit in the fourth switch position.

[0085] According to an embodiment of the present disclosure, a semiconductor device includes: a first bus waveguide; a first silicon ring optically coupled to the first bus waveguide; a spare silicon ring optically coupled to the first bus waveguide; a first heater and a second heater configured to heat the first silicon ring and the spare silicon ring, respectively; and a first switch, wherein the first switch is configured to electrically couple the first silicon ring to a first radio frequency (RF) circuit when the first switch is in a first switch position, and to electrically couple the spare silicon ring to the first radio frequency (RF) circuit when the first switch is in a second switch position. In an embodiment, the semiconductor device further includes a heater control circuit, wherein the heater control circuit is configured to, during operation of the semiconductor device, heat the first silicon ring to a first temperature using the first heater; and heat the spare silicon ring to a second temperature different from the first temperature using the second heater. In an embodiment, a first resonant wavelength of the first silicon ring at the first temperature matches an operating wavelength of the semiconductor device, wherein a second resonant wavelength of the spare silicon ring at the second temperature is different from the operating wavelength of the semiconductor device. In an embodiment, the heater control circuit is further configured to, in response to detecting a failure of the first silicon ring, heat the first silicon ring to the second temperature using the first heater and heat the spare silicon ring to the first temperature using the second heater.

[0086] According to an embodiment of the present disclosure, a method for operating a silicon ring modulator having a first ring, a second ring, and a bus waveguide optically coupled to the first and second rings includes: injecting an optical signal having a first wavelength into the bus waveguide; heating the first ring to a first temperature, wherein a first resonant wavelength of the first ring at the first temperature matches the first wavelength of the optical signal; heating the second ring to a second temperature different from the first temperature; and modulating the optical signal coupled to the first ring by applying a radio frequency (RF) signal to the first ring. In an embodiment, the method also includes: monitoring a first optical power in the first ring; monitoring a second optical power in the second ring; and detecting a fault in the first ring. In an embodiment, the method also includes: in response to detecting a fault in the first ring: heating the first ring to a second temperature; heating the second ring to the first temperature; and modulating the optical signal coupled to the second ring by applying an RF signal to the second ring.

[0087] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the present disclosure. Those skilled in the art will appreciate that they can easily use the present disclosure as a basis for designing or modifying other processes and structures for achieving the same purpose and / or achieving the same advantages of the embodiments introduced herein. Those skilled in the art will also appreciate that such equivalent structures do not depart from the spirit and scope of the present invention, and that they can make various changes, substitutions, and modifications in the present invention without departing from the spirit and scope of the present invention.

Claims

1. A semiconductor device comprising: A first silicon ring modulator, wherein the first silicon ring modulator comprises: a first bus waveguide configured to transmit a first optical signal having a first wavelength; a first silicon ring optically coupled to the first bus waveguide; a second silicon ring optically coupled to the first bus waveguide; a first heater configured to heat the first silicon ring; a second heater configured to heat the second silicon ring; and A first switch having a first switch position and a second switch position, wherein the first switch is configured to: electrically coupling the first silicon ring to a first radio frequency circuit at the first switch position, wherein the first silicon ring is configured to modulate the first optical signal having the first wavelength with a radio frequency signal from the first radio frequency circuit when the first switch is in the first switch position; and The second silicon ring is electrically coupled to the first radio frequency circuit at the second switch position, wherein the second silicon ring is configured to modulate the first optical signal having the first wavelength with a radio frequency signal from the first radio frequency circuit when the first switch is in the second switch position.

2. The semiconductor device according to claim 1, further comprising a first heater control circuit, wherein The first heater control circuit is configured to control the first heater and the second heater so that during operation of the first silicon ring modulator, the first silicon ring and the second silicon ring are heated to a first temperature and a second temperature, respectively, wherein the first temperature is different from the second temperature.

3. The semiconductor device according to claim 2, wherein A first resonant wavelength of the first silicon ring is determined by the first temperature, and a second resonant wavelength of the second silicon ring is determined by the second temperature.

4. The semiconductor device according to claim 3, wherein During operation of the first silicon ring modulator, the first resonant wavelength of the first silicon ring at the first temperature matches an operating wavelength of the first silicon ring modulator.

5. The semiconductor device according to claim 4, wherein During the operation of the first silicon ring modulator, a second resonant wavelength of the second silicon ring at the second temperature is different from the operating wavelength of the first silicon ring modulator. The semiconductor device according to claim 2 , wherein: The first silicon ring and the second silicon ring have the same structure. The semiconductor device according to claim 1 , further comprising the first radio frequency circuit.

8. The semiconductor device according to claim 1, further comprising: a first optical power monitor configured to measure optical power in the first silicon ring; and A second optical power monitor is configured to measure the optical power in the second silicon ring. 9 . The semiconductor device of claim 1 , further comprising a second bus waveguide optically coupled to the first silicon ring and the second silicon ring.

10. The semiconductor device according to claim 9, wherein During operation of the first silicon ring modulator, the first bus waveguide is configured to receive an input optical signal and the second bus waveguide is configured to output a modulated optical signal, wherein the modulated optical signal is the input optical signal modulated by a radio frequency signal from the first radio frequency circuit.

11. The semiconductor device according to claim 2, further comprising: A second silicon ring modulator, wherein the second silicon ring modulator comprises: said first bus waveguide; a third silicon ring optically coupled to the first bus waveguide; a fourth silicon ring optically coupled to the first bus waveguide; a third heater configured to heat the third silicon ring; a fourth heater configured to heat the fourth silicon ring; A second switch having a third switch position and a fourth switch position, wherein the second switch is configured to: At the third switch position, electrically coupling the third silicon ring to a second radio frequency circuit; and At the fourth switch position, electrically coupling the fourth silicon ring to the second radio frequency circuit; and A second heater control circuit is configured to control the third heater and the fourth heater so that the third silicon ring and the fourth silicon ring are heated to a third temperature and a fourth temperature, respectively, during operation of the second silicon ring modulator, wherein the third temperature is different from the fourth temperature.

12. The semiconductor device according to claim 11, wherein The first heater control circuit and the second heater control circuit are configured to set the first temperature and the third temperature so that a first resonant wavelength of the first silicon ring at the first temperature matches a first operating wavelength of the first silicon ring modulator, and a second resonant wavelength of the third silicon ring at the third temperature matches a second operating wavelength of the second silicon ring modulator.

13. The semiconductor device according to claim 2, further comprising: A second silicon ring modulator, wherein the second silicon ring modulator comprises: said first bus waveguide; a third silicon ring optically coupled to the first bus waveguide; a third heater configured to heat the third silicon ring; and A second switch having a third switch position and a fourth switch position, wherein the second switch is configured to: At the third switch position, electrically coupling the third silicon ring to a second radio frequency circuit; and In the fourth switch position, the second silicon ring is electrically coupled to the second radio frequency circuit.

14. A semiconductor device comprising: a first bus waveguide configured to transmit a first optical signal having a first wavelength; a first silicon ring optically coupled to the first bus waveguide; a spare silicon ring optically coupled to the first bus waveguide; a first heater and a second heater, configured to heat the first silicon ring and the backup silicon ring, respectively; as well as a first switch, wherein the first switch is configured to electrically couple the first silicon ring to a first RF circuit when the first switch is in a first switch position, and is configured to electrically couple the backup silicon ring to the first RF circuit when the first switch is in a second switch position, wherein the first switch is configured to modulate the first optical signal having the first wavelength with a RF signal from the first RF circuit when the first switch is in the first switch position, and the backup silicon ring is configured to modulate the first optical signal having the first wavelength with the RF signal from the first RF circuit when the first switch is in the second switch position.

15. The semiconductor device according to claim 14, further comprising a heater control circuit, wherein The heater control circuit is configured to, during operation of the semiconductor device: heating the first silicon ring to a first temperature using the first heater; and The backup silicon ring is heated to a second temperature different from the first temperature using the second heater.

16. The semiconductor device according to claim 15, wherein A first resonant wavelength of the first silicon ring at the first temperature matches an operating wavelength of the semiconductor device, wherein a second resonant wavelength of the backup silicon ring at the second temperature is different from the operating wavelength of the semiconductor device.

17. The semiconductor device according to claim 16, wherein The heater control circuit is further configured to: In response to detecting a failure of the first silicon ring, the first silicon ring is heated to the second temperature using the first heater, and the backup silicon ring is heated to the first temperature using the second heater.

18. A method of operating a silicon ring modulator having a first ring, a second ring, and a bus waveguide optically coupled to the first ring and the second ring, the method comprising: injecting an optical signal having a first wavelength into the bus waveguide; heating the first ring and the second ring to a first temperature and a second temperature, respectively, wherein a first resonant wavelength of the first ring at the first temperature matches the first wavelength of the optical signal, the first temperature being different from the second temperature; and modulating the optical signal coupled to the first loop by applying a radio frequency signal to the first loop; detecting a failure of the first ring; In response to detecting a failure of the first ring: heating the first ring and the second ring to the second temperature and the first temperature, respectively; and The optical signal coupled into the second loop is modulated by applying the radio frequency signal to the second loop.

19. The method according to claim 18, wherein Detecting a fault in the first ring includes: monitoring a first optical power in the first ring; A second optical power in the second ring is monitored.

20. The method of claim 18, further comprising: receiving a feedback signal from a receiver that receives the modulated optical signal, wherein the feedback signal indicates a quality of a signal received by the receiver; and The first temperature or the second temperature is adjusted according to the feedback signal.

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