Cavity system, tunable laser, and method for controlling a cavity system

Abstract

The present invention provides a resonator system including N-stage cascaded resonators, where N is an integer greater than 1, each resonator stage including a resonant cavity and a thermal phase shifter. In each resonator stage, the thermal phase shifter is integrated on the resonant cavity. The thermal phase shifters in the N-stage cascaded resonators are sequentially connected in series, with a first end of the thermal phase shifter in the first resonator connected to a predetermined voltage and a second end of the thermal phase shifter in the N-stage resonator grounded. A connection node between the thermal phase shifters in two adjacent resonators is connected to a variable voltage, and the resistances of the thermal phase shifters in the N-stage resonators are all equal. The resonator system of the present invention ensures that the change in the phase difference between two adjacent resonant cavities is linearly related to a control voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators. This simplifies the control method for the Vernier microring resonator and reduces the number of required control voltages. The present invention also provides a control method for a tunable laser and a resonator system.

Description

[Technical Field]

[0001] The present invention relates to the technical field of resonators, and in particular to a resonator system, a tunable laser, and a method for controlling a resonator system. [Background technology]

[0002] A Vernier-based microring resonator is composed of two or more sub-microring resonators with different free spectral ranges, where the free spectral range is the least common multiple of the free spectral ranges of the two or more sub-microring resonators. Microring resonators can expand the free spectral range and be used in a number of applications requiring broad spectrum and high sensitivity, such as tunable lasers, variable filters, and highly sensitive sensors.

[0003] FIG. 1 is a schematic diagram of a prior art tunable microring resonator based on the Vernier effect. The first-stage microring resonator and the second-stage microring resonator are cascaded to form a Vernier microring resonator, and the first-stage microring resonator and the second-stage microring resonator have different sizes. The first-stage microring resonator includes a first optical waveguide 11, a first microring resonant cavity 12, and a first thermal phase shifter 13. The second-stage microring resonator includes a second optical waveguide 21, a second microring resonant cavity 22, and a second thermal phase shifter 23. The first microring resonant cavity 12 is coupled to the first optical waveguide 11 and the second optical waveguide 21, respectively. The second microring resonant cavity 22 is coupled to the second optical waveguide 21 and the output optical waveguide 24, respectively. The optical propagation direction in the first optical waveguide 11 is a, and the optical propagation direction in the output optical waveguide is b. The first and second thermal phase shifters have one end connected to a control voltage V1 or V2, and the other end grounded, respectively, and the control voltages V1 and V2 control the two micro-ring resonators, respectively. The thermal phase shifter is based on the working principle of a heating resistor, and when a voltage V1 (or V2) is applied to the thermal phase shifter of resistor R1 (or R2), the generated heat is V1 2 / R1 (or V2 2 / R2), which changes the refractive index of the optical waveguide where it is located. Because the phase change is proportional to the refractive index change, i.e., Δφ ∝ dn, the microring resonator's optical phase is further altered and the spectrum is translated. By adjusting the two voltages V1 and V2, the final spectral shape of the vernier microring resonator can be controlled, for example, the center wavelength can be altered. Figure 2 shows the output spectrum of a prior art vernier microring resonator at different voltages V1 and V2. The vernier microring resonator requires simultaneous control of the two voltages V1 and V2 to adjust the spectrum of the two microrings to the desired center wavelength through the vernier effect. Because the two voltages must be controlled simultaneously, and the phase change of each microring is proportional to the square of the voltage, the control algorithm becomes complex.

[0004] Therefore, it is necessary to provide a new type of resonator system, a tunable laser, and a control method for the resonator system to solve the above problems existing in the prior art. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a resonator system, a tunable laser, and a control method for a resonator system, which can simplify the control method for the resonator system and reduce the number of required control voltages by making a linear relationship between the change in phase difference between two adjacent resonator cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent stages of the resonator. [Means for solving the problem]

[0006] In order to achieve the above object, the resonator system of the present invention includes at least N-stage cascaded resonators, where N is an integer greater than 1, each stage of the resonator includes a resonant cavity and a thermal phase shifter, in each stage of the resonator, the thermal phase shifter is integrated on the resonant cavity, the thermal phase shifters in the N-stage cascaded resonators are sequentially connected in series, a first end of the thermal phase shifter in the first stage resonator is connected to a predetermined voltage, a second end of the thermal phase shifter in the N-stage resonator is grounded, a connection node between the thermal phase shifters in two adjacent stages of the resonators is connected to a variable voltage, and the resistances of the thermal phase shifters in the N-stage resonators are all equal.

[0007] The beneficial effect of the resonator system of the present invention is that the phase difference change between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent stages of the resonators have a linear relationship, which simplifies the control method of the resonator system and reduces the number of required control voltages.

[0008] Optionally, the resonator comprises any one of a micro-ring resonator, a fiber ring resonator, a Bragg grating, a photonic crystal nanobeam, a Fabry-Perot cavity, or a Mach-Zehnder interferometer.

[0009] Optionally, the resonator is a micro-ring resonator, and the micro-ring resonator of each stage further includes an optical waveguide, and in the micro-ring resonator of each stage, the micro-ring resonant cavity is coupled to the optical waveguide, and the micro-ring resonant cavity in the micro-ring resonator of the previous stage is coupled to the optical waveguide in the micro-ring resonator of the next stage.

[0010] Optionally, the Nth stage micro-ring resonator further includes an output waveguide, the output waveguide being coupled to the micro-ring resonant cavity in the Nth stage micro-ring resonator.

[0011] Optionally, the resonator is a micro-ring resonator, and the coupling region of the micro-ring resonator includes any one of a directional coupler, a bent directional coupler, an adiabatic coupler, a multi-mode interferometer, and a variable optical ratio coupler.

[0012] Optionally, the resonator is a micro-ring resonator, and the micro-ring resonator is ring-shaped, track-shaped, taichi-shaped or octagon-shaped.

[0013] The present invention further provides a tunable laser including the above resonator system and a gain chip, wherein one end of the Nth resonator of the resonator system is connected to the gain chip.

[0014] Optionally, the tunable laser further includes a total reflection loopback, one end of a first stage resonator of the resonator system is connected to the total reflection loopback, and one end of an Nth stage resonator of the resonator system is connected to the gain chip.

[0015] The beneficial effect of the tunable laser chip of the present invention is that the phase difference change between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent stages of the resonators are linearly related, which simplifies the control method of the resonator system and reduces the number of required control voltages.

[0016] The present invention further provides a method for controlling a resonator system, wherein when N>=3, the control method comprises: Step S0 of fixing the preset voltage at V0; Step S1 of controlling the variable voltages connected to the second connection node to the (N-1)th connection node so that they are all 0; Step S2: controlling the variable voltage connected to the first connection node to be equal to or greater than 0 and equal to or less than V0, and fixing the variable voltage connected to the first connection node; Step S3: setting all variable voltages connected to the M-th connection node and subsequent connection nodes to 0, controlling the variable voltage connected to the M-th connection node to be equal to or greater than 0 and equal to or less than the variable voltage connected to the (M-1)-th connection node, and fixing the variable voltage connected to the M-th connection node; Step S4 of repeatedly executing step S3, where M is an integer from 2 to N-1.

[0017] The beneficial effect of the control method for a resonator system of the present invention is that when the number of cascaded resonators in the resonator system is three or more, the change in the phase difference between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators can be made to have a linear relationship, thereby simplifying the control method for the resonator system.

[0018] Selectively, the variable voltage connected to the connection node between the thermal phase shifters of adjacent resonators is controlled to change from large to small from the first stage to the Nth stage, and the preset voltage is controlled to be larger than the variable voltage connected to the connection node between the thermal phase shifter of the first stage resonator and the thermal phase shifter of the second stage resonator, and the variable voltage connected to the connection node between the thermal phase shifter of the (N-1)th stage resonator and the thermal phase shifter of the Nth stage resonator is controlled to be larger than 0.

[0019] The present invention further provides a method for controlling the resonator system, wherein when N=2, the control method comprises: Fixing the preset voltage at V0; controlling the variable voltage connected to the connection node to be greater than or equal to 0 and less than or equal to V0, and fixing the variable voltage connected to the connection node.

[0020] The beneficial effect of the control method for a resonator system of the present invention is that, when the number of cascaded resonators in the resonator system is two, the change in the phase difference between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators can be linearly related, thereby simplifying the control method for the resonator system and reducing the number of required control voltages. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a prior art tunable micro-ring resonator based on the Vernier effect. [Figure 2] The output spectrum of a conventional Vernier microring resonator at V1 and V2 voltages. [Figure 3] 1 is a schematic diagram of a microring resonator system according to some embodiments of the present invention. [Figure 4] FIG. 10 is a diagram illustrating the relationship between the control voltage for the center wavelength of the output spectrum of a microring resonator and the change in the refractive index of the waveguide in some embodiments of the present invention. [Figure 5]FIG. 2 is a schematic diagram of a cascaded microring resonator scheme in accordance with some embodiments of the present invention. [Figure 6] 10A and 10B are schematic diagrams of cascaded microring resonators according to some other embodiments of the present invention. [Figure 7] FIG. 10 is a schematic diagram of a cascade connection scheme of microring resonators in accordance with still other embodiments of the present invention. [Figure 8] FIG. 10 is a schematic diagram of a cascade connection scheme of microring resonators in accordance with further embodiments of the present invention. [Figure 9] FIG. 1 is a schematic diagram of a microring resonator system having four stages of microring resonators according to some embodiments of the present invention. [Figure 10] FIG. 1 is a schematic diagram of a tunable laser according to some embodiments of the present invention. [Figure 11] FIG. 2 is a schematic diagram of a tunable laser according to some alternative embodiments of the present invention. [Figure 12] FIG. 2 is a schematic diagram of a tunable laser according to some further embodiments of the present invention. [Figure 13] 3 is a schematic diagram of laser output wavelength variation under different control voltages of a tunable laser in some embodiments of the present invention. FIG. [Figure 14] 1 is a flowchart of a method for controlling a resonator system in accordance with some embodiments of the present invention. [Figure 15] 10 is a flowchart illustrating a method for controlling a resonator system according to some other embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to clarify the objectives, technical solutions, and advantages of the present invention, the following clearly and completely describes the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. It is clear that the described embodiments are only a part of the embodiments of the present invention, and do not include all the embodiments. All other embodiments obtained based on the embodiments of the present invention without the need for creative efforts by those skilled in the art are within the scope of protection of the present invention. Unless otherwise defined, technical or scientific terms used herein have the ordinary meanings understood by those skilled in the art. As used in this specification, similar words such as "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0023] In order to solve the problems in the prior art, an embodiment of the present invention provides a resonator system including N-stage cascaded resonators, where N is an integer greater than 1, and each stage of the resonator includes a resonant cavity and a thermal phase shifter. In each stage of the resonator, the thermal phase shifter is integrated on the resonant cavity. The thermal phase shifters in the N-stage cascaded resonators are sequentially connected in series, a first end of the thermal phase shifter in the first stage resonator is connected to a predetermined voltage, a second end of the thermal phase shifter in the N-stage resonator is grounded, a connection node between the thermal phase shifters in two adjacent stages of the resonators is connected to a variable voltage, and the resistances of the thermal phase shifters in the N-stage resonators are all equal.

[0024] In the resonator system of the present invention, a first end of the thermal phase shifter in the first stage resonator is connected to a preset voltage, a second end of the thermal phase shifter in the Nth stage resonator is grounded, a connection node between the thermal phase shifters in two adjacent stages of the resonators is connected to a variable voltage, the resistances of the thermal phase shifters in the Nth stage resonators are all equal, and a change in the phase difference between the two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent stages of the resonators are linearly related, thereby simplifying the control method of the resonator system and reducing the number of required control voltages.

[0025] In some embodiments, the resonator comprises any one of a microring resonator, a fiber ring resonator, a Bragg grating, a photonic crystal nanobeam, a Fabry-Perot cavity, or a Mach-Zehnder interferometer.

[0026] In some embodiments, the resonator is a micro-ring resonator, and the micro-ring resonator of each stage further includes an optical waveguide, and in the micro-ring resonator of each stage, the micro-ring resonant cavity is coupled to the optical waveguide, and the micro-ring resonant cavity in the micro-ring resonator of the previous stage is coupled to the optical waveguide in the micro-ring resonator of the next stage.

[0027] In some embodiments, the Nth stage of the micro-ring resonator further includes an output waveguide, the output waveguide being coupled to the micro-ring resonant cavity in the Nth stage of the micro-ring resonator.

[0028] 3 is a schematic diagram of a micro-ring resonator system according to some embodiments of the present invention. Referring to FIG. 3, the micro-ring resonator system includes at least a first stage micro-ring resonator and a second stage micro-ring resonator that are cascaded together. The first stage micro-ring resonator includes a first optical waveguide 11, a first micro-ring resonant cavity 12, and a first thermal phase shifter 13. The second stage micro-ring resonator includes a second optical waveguide 21, a second micro-ring resonant cavity 22, a second thermal phase shifter 23, and an output optical waveguide 24. The first thermal phase shifter 13 is connected to the first micro-ring resonator. the first micro-ring resonant cavity 12 is integrated on top of the first thermal phase shifter 23, the second micro-ring resonant cavity 12 is coupled to the first optical waveguide 11 and the second optical waveguide 21, respectively, the second micro-ring resonant cavity 22 is coupled to the second optical waveguide 21 and the output optical waveguide 24, respectively, a is the input optical path propagation direction in the first optical waveguide 11, and b is the output optical path propagation direction in the output optical waveguide 24. The resistance value of the first thermal phase shifter 13 is a first resistor R1, the resistance value of the second thermal phase shifter 23 is a second resistor R2, the first resistor R1 and the second resistor R2 are the same, the first thermal phase shifter 13 is connected in series to the second thermal phase shifter 23, one end of the first thermal phase shifter 13 is connected to a preset voltage V0, one end of the second thermal phase shifter 23 is connected to a ground pin GND (voltage is 0V), the connection node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is connected to a first voltage V1, the first voltage V1 is a variable voltage, and the preset voltage V0 is a fixed voltage.In some embodiments of the present invention, the resonator system includes at least a first-stage resonator and a second-stage resonator that are cascaded together, each of the resonators including a resonant cavity and a thermal phase shifter, the thermal phase shifter being integrated on the resonant cavity in each of the resonators, the thermal phase shifters of the cascaded first-stage resonator and the second-stage resonator being sequentially connected in series, a first end of the thermal phase shifter in the first-stage resonator being connected to a predetermined voltage, a second end of the thermal phase shifter in the second-stage resonator being grounded, a connection node between the thermal phase shifters of the cascaded first-stage resonator and the second-stage resonator being connected to a variable voltage, and the resistances of the thermal phase shifters of the first-stage resonator and the second-stage resonator being equal to each other. That is, in the above embodiment, a part of the resonator system includes thermal phase shifters having the same resistance value on two resonant cavities, one common end of the two thermal phase shifters is connected to a variable voltage V1, and the other ends of the two thermal phase shifters are each connected to a fixed voltage V0 and grounded, and the remaining part of the resonator system is not limited to this.

[0029] In some specific embodiments, the input optical path propagation direction a in the first optical waveguide 11 and the output optical path propagation direction b in the output optical waveguide 24 are the same.

[0030] The working principle of the resonator system of the present invention will be described using this embodiment as an example. The relationship between the phase difference Δφ between the first micro-ring resonant cavity and the second micro-ring resonant cavity and the first voltage V1 connected to the connection node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is expressed by Equation 1. JPEG2025539902000002.jpg14170Here, A is a first coefficient, which is determined by the properties of the waveguide itself, such as the waveguide material and waveguide structure.

[0031] JPEG2025539902000003.jpg58170

[0032] where A is a first coefficient, which is determined by the properties of the waveguide material, structure, and can be obtained by measurement, and this coefficient is well known in the industry and will not be further described here.

[0033] In some embodiments, the microring resonator is ring-shaped, track-shaped, taichi-shaped, or octagon-shaped.

[0034] In some embodiments, the coupling region of the micro-ring resonator is any one of a directional coupler, a flexural directional coupler, an adiabatic coupler, a multimode interferometer, or a variable optical ratio coupler.

[0035] In some embodiments, the heating resistance material of the thermal phase shifter comprises titanium nitride, doped silicon, or tungsten.

[0036] In some embodiments, the integrated material platform on which the micro-ring resonator is located comprises bulk silicon, silicon-on-insulator, silicon-on-sapphire, silica, aluminum nitride, indium phosphide, lithium niobate, or a polymer.

[0037] In some embodiments, the waveguide type of the microring resonator includes a channel waveguide, a ridge waveguide, a slot waveguide, a diffused waveguide, and a photonic crystal waveguide.

[0038] In some embodiments, the operating wavelength range of the micro-ring resonator includes the visible band, O-band, E-band, S-band, C-band, L-band, U-band, and mid-infrared band.

[0039] In some embodiments, the micro-ring resonator is in the form of an optically resonant system made of an integrated chip, optical fiber, or free-standing optics.

[0040] 5 is a schematic diagram of a cascade connection scheme of micro-ring resonators in some embodiments of the present invention. Referring to FIG. 5, the light propagation direction of the second optical waveguide 21 is rotated by 180 degrees, and a is the input light path propagation direction in the first optical waveguide 11, and c is the output light path propagation direction in the output optical waveguide 24.

[0041] In some specific embodiments, the input optical path propagation direction a in the first optical waveguide 11 and the output optical path propagation direction c in the output optical waveguide 24 are opposite or form an arbitrary angle.

[0042] 6 is a schematic diagram of a cascade connection scheme of microring resonators in some other embodiments of the present invention. Referring to FIG. 6, the first optical waveguide 11 and the output optical waveguide 24 are refractive, e is the input optical path propagation direction in the first optical waveguide 11, and f is the output optical path propagation direction in the output optical waveguide 24.

[0043] 7 is a schematic diagram of a cascade connection scheme of micro-ring resonators in some other embodiments of the present invention. Referring to FIG. 7, the first micro-ring resonant cavity 12 and the second micro-ring resonant cavity 22 are located between the first optical waveguide 11 and the output optical waveguide 24, where c is the input optical path propagation direction in the first optical waveguide 11 and a is the output optical path propagation direction in the output optical waveguide 24.

[0044] 8 is a schematic diagram of a cascade connection scheme of micro-ring resonators in some other embodiments of the present invention. Referring to FIG. 8, the first micro-ring resonant cavity 12 and the second micro-ring resonant cavity 22 are both coupled to the first optical waveguide 11, and the two micro-ring resonant cavities are mutually coupled, where c is the input optical path propagation direction in the first optical waveguide 11, and a is the output optical path propagation direction in the first optical waveguide 11.

[0045] 9 is a schematic diagram of a microring resonator system having four stages of microring resonators in some embodiments of the present invention. Referring to FIG. 9, the microring resonator system includes four stages of cascaded microring resonators, in which the thermal phase shifter is integrated on the microring resonator cavity in each stage of the microring resonator, and the first thermal phase shifter 13, the second thermal phase shifter 23, the third thermal phase shifter 33 and the fourth thermal phase shifter 43 in the four-stage cascaded microring resonators are sequentially connected in series, and a first end of the first thermal phase shifter 13 in the first stage of the microring resonator is connected to a predetermined voltage V0, and a fourth thermal phase shifter 43 in the fourth stage of the microring resonator is connected to a predetermined voltage V1. A second end of the phase shifter 43 is connected to a ground pin GND (voltage is 0V), a node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is connected to a first voltage V1, a node between the second thermal phase shifter 23 and the third thermal phase shifter 33 is connected to a second voltage V2, a node between the third thermal phase shifter 23 and the fourth thermal phase shifter 33 is connected to a third voltage V3, the first voltage V1, the second voltage V2, and the third voltage V3 are all variable voltages, and the first thermal phase shifter 13, the second thermal phase shifter 23, the third thermal phase shifter 33, and the fourth thermal phase shifter 43 have the same resistance. a is the input optical path propagation direction in the first optical waveguide 11, and b is the output optical path propagation direction in the output optical waveguide 24.

[0046] The present invention further provides a tunable laser including the above resonator system and a gain chip, wherein one end of the Nth resonator of the resonator system is connected to the gain chip.

[0047] In some embodiments, the gain chip is a III-V chip.

[0048] 10 is a schematic diagram of a tunable laser according to some embodiments of the present invention. Referring to FIG. 10, the tunable laser chip includes the resonator system and a gain chip 6. The left side surface 61 of the gain chip 6 is a total internal reflection surface, so that light is emitted from the other end of the resonator system, and the optical output direction is shown in c. The resonator system is used to adjust the laser output wavelength.

[0049] 11 is a schematic diagram of a tunable laser chip according to some other embodiments of the present invention. Referring to FIG. 11, the tunable laser chip includes the resonator system, a total internal reflection loopback 5, and a gain chip 6. One end of the first resonator of the resonator system is connected to the total internal reflection loopback 5, and one end of the Nth resonator of the resonator system is connected to the gain chip 6. The optical output direction is shown in FIG. 11. In this embodiment, neither end of the gain chip 6 is a total internal reflection surface. The resonator system is used to adjust the laser output wavelength.

[0050] In some embodiments, the tunable laser further comprises a thermal phase shifter, the thermal phase shifter being integrated between the total internal reflection loopback and a resonator system for providing phase control outside of the resonator system.

[0051] Specifically, referring to FIG. 11, the total reflection loopback 5 is connected to the right end of the first optical waveguide 11, and an initial thermal phase shifter 51 is integrated on the first optical waveguide 11.

[0052] FIG. 12 is a schematic diagram of a tunable laser according to some other embodiments of the present invention. Referring to Figure 12, the resonator system is a Vernier resonator consisting of two photonic crystal nanobeams, and a first thermal phase shifter and a second thermal phase shifter are integrated on the two photonic crystal nanobeams, respectively. The first thermal phase shifter 13 is a first resistor R1, the second thermal phase shifter 23 is a second resistor R2, the first resistor R1 and the second resistor R2 are the same, the first thermal phase shifter 13 is connected in series to the second thermal phase shifter 23, one end of the first thermal phase shifter 13 is connected to a predetermined voltage V0, one end of the second thermal phase shifter 23 is connected to a ground pin GND (voltage is 0V), and the connection node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is connected to a first voltage V1, the first voltage V1 is a variable voltage, and the predetermined voltage V0 is a fixed voltage. One end of the resonator system is connected to the gain chip 6, and the output optical path propagation direction of the tunable laser is shown in b. Note that in this embodiment, neither end of the gain chip 6 is a total internal reflection surface. The resonator system is used to adjust the laser output wavelength.

[0053] 13 is a schematic diagram of the laser output wavelength change under different control voltages of a tunable laser in some embodiments of the present invention. Referring to FIG. 13, with the same step change in voltage, the laser outputs four different spectrums from left to right, and the wavelength change of the four spectrums is the same. The control method of the tunable laser chip of the present invention ensures that the phase difference change between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators are linearly related, and further ensures that the output wavelength change and the control voltage are linearly related, thereby simplifying the resonator control method and reducing the number of required control voltages.

[0054] 14 is a flowchart of a control method for a resonator system in some embodiments of the present invention, in which one end of the thermal phase shifter of the first resonator is connected to the preset voltage, the second end of the thermal phase shifter of the Nth resonator is grounded, there are N-1 connection nodes between the N thermal phase shifters, and the N-1 connection nodes are respectively connected to N-1 variable voltages, and when N>=3, referring to FIG. Step S0 of fixing the preset voltage at V0; Step S1 of controlling the variable voltages connected to the second connection node to the (N-1)th connection node so that they are all 0; Step S2: controlling the variable voltage connected to the first connection node to be equal to or greater than 0 and equal to or less than V0, and fixing the variable voltage connected to the first connection node; Step S3: setting all variable voltages connected to the M-th connection node and subsequent connection nodes to 0, controlling the variable voltage connected to the M-th connection node to be equal to or greater than 0 and equal to or less than the variable voltage connected to the (M-1)-th connection node, and fixing the variable voltage connected to the M-th connection node; Step S4 of repeatedly executing step S3, where M is an integer from 2 to N-1.

[0055] The control method for a resonator system of the present invention, when the number of cascaded resonators in the resonator system is three or more, makes the change in the phase difference between two adjacent resonant cavities linearly related to the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators, thereby simplifying the control method for the resonator system and reducing the number of required control voltages.

[0056] In some embodiments, in steps S2 and S3, the method of controlling and fixing the variable voltage includes scanning the voltage, observing the output spectrum of the resonator system, and controlling the variable voltage value so that the spectrum meets desired characteristics, for example, moving the center wavelength to a target wavelength.

[0057] In some embodiments, the variable voltage connected to the connection node between the thermal phase shifters of adjacent resonators is controlled so that it changes from large to small from the first stage to the Nth stage, and the preset voltage is controlled so that it is larger than the variable voltage connected to the connection node between the thermal phase shifter of the first stage resonator and the thermal phase shifter of the second stage resonator, and the variable voltage connected to the connection node between the thermal phase shifter of the N-1th stage resonator and the thermal phase shifter of the Nth stage resonator is controlled so that it is larger than 0.

[0058] In some specific embodiments, referring to FIG. 9 , the micro-ring resonator system includes four cascaded micro-ring resonators, a voltage connected to a first connection node is V1, a voltage connected to a second connection node is V2, and a voltage connected to a third connection node is V3, and the control method includes: Step S0 of fixing the preset voltage at V0; Step S10 of controlling the variable voltages connected to the second connection node to the fourth connection node so that they are all 0; Step S20: controlling V1 to be equal to or greater than 0 and equal to or less than V0, and fixing V1; Step S30 of controlling the variable voltages connected to the third connection node to the fourth connection node so that they are all 0; Step S40: controlling V2 so that V2 is equal to or greater than 0 and equal to or less than V1, and fixing V2; and step S50 of controlling V3 so that V3 is equal to or greater than 0 and equal to or less than V2, and fixing V3.

[0059] Referring to FIG. 9, the micro-ring resonator system includes four cascaded micro-ring resonators, and the magnitude relationship between the preset voltage V0, the first voltage V1, the second voltage V2, the third voltage V3 and the GND voltage (voltage is 0) is V0≧V1≧V2≧V3≧0.

[0060] 15 is a flowchart of a control method for a resonator system in some other embodiments of the present invention. When N=2, there is one connection node between two thermal phase shifters, and the one connection node is connected to one variable voltage. Referring to FIG. 15, the control method can be as follows: Fixing the preset voltage at V0; controlling the variable voltage connected to the connection node to be equal to or greater than 0 and equal to or less than V0, and fixing the variable voltage connected to the connection node.

[0061] The control method for a resonator system of the present invention, when the number of cascaded resonators in the resonator system is two, makes a linear relationship between the change in phase difference between two adjacent resonant cavities and the variable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators, thereby simplifying the control method for the resonator system.

[0062] Although the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as defined by the appended claims. Furthermore, the present invention described herein may have other embodiments and may be practiced or realized in multiple ways.

Claims

1. a resonator system including at least resonators cascaded in N stages, N being an integer greater than 1, wherein the resonators in each stage include a resonant cavity and a thermal phase shifter, the thermal phase shifter in each resonator stage being integrated on the resonant cavity, the thermal phase shifters in the resonators cascaded in N stages being sequentially connected in series, a first end of the thermal phase shifter in a first resonator stage being connected to a predetermined voltage, a second end of the thermal phase shifter in an Nth resonator stage being grounded, a connection node between the thermal phase shifters in two adjacent resonators stages being connected to a variable voltage, and resistances of the thermal phase shifters in the Nth resonators being equal.

2. 10. The resonator system of claim 1, wherein the resonator comprises any one of a microring resonator, a fiber ring resonator, a Bragg grating, a photonic crystal nanobeam, a Fabry-Perot cavity, or a Mach-Zehnder interferometer.

3. 3. The resonator system of claim 2, wherein the resonators are micro-ring resonators, and the micro-ring resonators of each stage further include an optical waveguide, and in the micro-ring resonators of each stage, the micro-ring resonant cavity is coupled to the optical waveguide, and the micro-ring resonant cavity of the micro-ring resonator of the previous stage is coupled to the optical waveguide of the micro-ring resonator of the next stage.

4. 4. The resonator system of claim 3, wherein the Nth stage of the micro-ring resonator further includes an output waveguide, the output waveguide being coupled to a micro-ring resonant cavity in the Nth stage of the micro-ring resonator.

5. 3. The resonator system of claim 2, wherein the resonator is a micro-ring resonator, and a coupling region of the micro-ring resonator includes any one of a directional coupler, a bent directional coupler, an adiabatic coupler, a multi-mode interferometer, and a variable optical ratio coupler.

6. The resonator system according to claim 2 , wherein the resonator is a micro-ring resonator, and the micro-ring resonator is ring-shaped, track-shaped, Tai Chi-shaped, or Eight-shaped.

7. 2. A tunable laser including the resonator system according to claim 1 and a gain chip, wherein one end of an Nth stage resonator of the resonator system is connected to the gain chip.

8. 8. The tunable laser of claim 7, further comprising a total reflection loopback, wherein one end of a first stage resonator of the resonator system is connected to the total reflection loopback, and one end of an Nth stage resonator of the resonator system is connected to the gain chip.

9. 2. A control method for a resonator system according to claim 1, wherein when N>=3, the control method comprises: Step S0 of fixing the preset voltage to V0; Step S1: controlling the variable voltages connected to the second connection node to the (N-1)th connection node so that they are all 0; Step S2: controlling the variable voltage connected to the first connection node to be equal to or greater than 0 and equal to or less than V0, and fixing the variable voltage connected to the first connection node; Step S3: setting all variable voltages connected to the M-th connection node and subsequent connection nodes to 0, controlling the variable voltage connected to the M-th connection node to be equal to or greater than 0 and equal to or less than the variable voltage connected to the (M-1)-th connection node, and fixing the variable voltage connected to the M-th connection node; 2. The control method for a resonator system according to claim 1, further comprising: a step S4 of repeatedly executing step S3, where M is an integer from 2 to N-1 in succession.

10. 10. The control method according to claim 9, wherein the variable voltage connected to the connection node between the thermal phase shifters of adjacent resonators changes from large to small from the first stage to the Nth stage, the preset voltage is larger than the variable voltage connected to the connection node between the thermal phase shifter of the first stage resonator and the thermal phase shifter of the second stage resonator, and the variable voltage connected to the connection node between the thermal phase shifter of the (N-1)th stage resonator and the thermal phase shifter of the Nth stage resonator is larger than 0.

11. 2. A control method for a resonator system according to claim 1, wherein when N=2, the control method comprises: Fixing the preset voltage at V0; 2. The control method for a resonator system according to claim 1, further comprising the steps of: controlling a variable voltage connected to the connection node to be greater than or equal to 0 and less than or equal to V0; and fixing the variable voltage connected to the connection node.

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