Resonator system, tunable laser and method of controlling a resonator system

Abstract

The application provides a resonator system, comprising N-stage cascaded resonators, N being an integer greater than 1, each resonator comprising a resonant cavity and a thermal phase shifter, in each resonator, the thermal phase shifter is integrated on the resonant cavity, the thermal phase shifters in the N-stage cascaded resonators are connected in series, 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 N-stage resonator is grounded, a connecting node between the thermal phase shifters in two adjacent resonators is connected to an adjustable voltage, and the resistances of the thermal phase shifters in the N-stage resonators are equal. The resonator system can make the phase difference change of two adjacent resonant cavities linearly related to the control voltage connected to the connecting node between the thermal phase shifters in two adjacent resonators, simplifies the control method of the vernier micro-ring resonator, and reduces the number of required control voltages. The application also provides an adjustable laser and a control method of the resonator system.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and more particularly to a resonator system, a tunable laser, and a control method for the resonator system. Background Technology

[0002] A microring resonator based on the vernier effect consists of two or more sub-microring resonators with different free spectral ranges. The free spectral range of the microring resonator is the least common multiple of the free spectral ranges of the two or more sub-microring resonators. Microring resonators expand the free spectral range, making them suitable for applications requiring wide spectral density and high sensitivity, such as tunable lasers, tunable filters, and high-sensitivity sensors.

[0003] Figure 1 This is a schematic diagram of an adjustable microring resonator based on the vernier effect in the prior art. A first-stage microring resonator and a second-stage microring resonator are cascaded together to form a vernier microring resonator. The first-stage and second-stage microring resonators have different dimensions. 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. One end of the first and second thermal phase shifters are respectively connected to a control voltage V1 or V2, and the other end is grounded. The control voltages V1 and V2 control the two microring resonators respectively. The thermal phase shifter operates on the principle of a heating resistor. When a voltage V1 (or V2) is applied to the thermal phase shifter with a resistance of R1 (or R2), heat V1 is generated. 2 / R1 (or V2) 2 By changing the refractive index of the optical waveguide containing the microring resonator ( / R2), and since the phase change is proportional to the refractive index change (Δφ∝dn), the optical phase of the microring resonator is altered, resulting in a spectral shift. By adjusting voltages V1 and V2, the final spectral morphology of the vernier microring resonator can be controlled, for example, by changing the center wavelength. Figure 2 The output spectrum of a conventional vernier microring resonator is shown under voltages V1 and V2. In this vernier microring resonator, both voltages V1 and V2 need to be controlled simultaneously to appropriate values ​​so that the wavelengths of the two microrings are controlled at the desired center wavelength through the vernier effect. Both voltages need to be controlled simultaneously, and the phase change of each microring is proportional to the square of the voltage, which complicates the control algorithm.

[0004] Therefore, it is necessary to provide a novel resonator system, a tunable laser, and a control method for the resonator system to solve the aforementioned problems existing in the prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a resonator system, a tunable laser, and a control method for the resonator system, which enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonator stages, thereby simplifying the control method of the resonator system and reducing the number of control voltages required.

[0006] To achieve the above objectives, the resonator system of the present invention includes N 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 cascaded resonators are connected in series. The first terminal of the thermal phase shifter in the first stage resonator is connected to a preset voltage, and the second terminal of the thermal phase shifter in the Nth stage resonator is grounded. The connection node between the thermal phase shifters in adjacent stages of the resonator is connected to an adjustable voltage. The resistances of the thermal phase shifters in the N stages of the resonator are all equal.

[0007] The beneficial effect of the resonator system of the present invention is that it enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators, which simplifies the control method of the resonator system and reduces the number of control voltages required.

[0008] Optionally, the resonator includes any one of a microring resonator, a fiber optic ring resonator, a Bragg grating, a photonic crystal nanobow, a Fabry-Perot cavity, or a Mach-Zehnder interferometer.

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

[0010] Optionally, the Nth-stage microring resonator further includes an output waveguide coupled to the microring resonator cavity in the Nth-stage microring 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 multimode interferometer, and a splitting ratio adjustable coupler.

[0012] Optionally, the resonator is a micro-ring resonator, which can be ring-shaped, racetrack-shaped, tai chi-shaped, or figure-eight-shaped.

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

[0014] Optionally, the tunable laser further includes a total internal reflection loop, one end of the first-stage resonator of the resonator system is connected to the total internal reflection loop, and one end of the 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 it enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonators, which simplifies the control method of the resonator system and reduces the number of control voltages required.

[0016] The present invention also provides a control method for a resonator system, wherein when N>=3, the control method includes the following steps:

[0017] S0: Fix the preset voltage to V0;

[0018] S1: Control the adjustable voltage connected to the second connection node until the adjustable voltage connected to the (N-1)th connection node is 0;

[0019] S2: Control the adjustable voltage connected to the first connection node to be greater than or equal to 0 and less than or equal to V0, and fix the adjustable voltage connected to the first connection node;

[0020] S3: Set the adjustable voltage of all connection nodes after the Mth connection node to 0, control the adjustable voltage of the Mth connection node to be greater than or equal to 0 and less than or equal to the adjustable voltage of the (M-1)th connection node, and fix the adjustable voltage of the Mth connection node.

[0021] S4: Repeat step S3 by taking integers from 2 to N-1 for M.

[0022] The beneficial effect of the control method for the resonator system of the present invention is that when the number of resonator cascades in the resonator system is greater than or equal to 3, the phase difference change between two adjacent resonant cavities is linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonator stages, thus simplifying the control method of the resonator system.

[0023] Optionally, the adjustable voltage connected to the connection node between the thermal phase shifters of adjacent resonators decreases from the first stage to the Nth stage, and the preset voltage is greater than the adjustable 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 adjustable 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 greater than 0.

[0024] The present invention also provides a control method for the resonator system, wherein when N=2, the control method includes the following steps:

[0025] The preset voltage is fixed at V0;

[0026] The adjustable voltage connected to the connection node is controlled to be greater than or equal to 0 and less than or equal to V0, and the adjustable voltage connected to the connection node is fixed.

[0027] The beneficial effect of the control method for the resonator system of the present invention is that when the number of resonator cascades in the resonator system is 2, the phase difference change between two adjacent resonant cavities is linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonator stages, which simplifies the control method of the resonator system and reduces the number of control voltages required. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an tunable microring resonator based on the vernier effect in the prior art;

[0029] Figure 2 The output spectrum of a prior art vernier microring resonator under voltages V1 and V2;

[0030] Figure 3 This is a schematic diagram of a micro-ring resonator system in some embodiments of the present invention;

[0031] Figure 4 This is a graph showing the relationship between the center wavelength of the output spectrum of the microring resonator and the waveguide refractive index generated by the control voltage in some embodiments of the present invention.

[0032] Figure 5 This is a schematic diagram of the cascaded configuration of microring resonators in some embodiments of the present invention;

[0033] Figure 6 This is a schematic diagram of the cascading method of the micro-ring resonator in some other embodiments of the present invention;

[0034] Figure 7 This is a schematic diagram of the cascading method of the micro-ring resonator in some embodiments of the present invention;

[0035] Figure 8This is a schematic diagram of the cascaded configuration of microring resonators in some embodiments of the present invention;

[0036] Figure 9 This is a schematic diagram of a microring resonator system with a 4-stage microring resonator in some embodiments of the present invention;

[0037] Figure 10 This is a schematic diagram of a tunable laser in some embodiments of the present invention;

[0038] Figure 11 This is a schematic diagram of a tunable laser in some other embodiments of the present invention;

[0039] Figure 12 This is a schematic diagram of a tunable laser in some other embodiments of the present invention;

[0040] Figure 13 This is a schematic diagram illustrating the change in laser output wavelength under different control voltages in some embodiments of the present invention.

[0041] Figure 14 This is a flowchart of the control method for the resonator system in some embodiments of the present invention;

[0042] Figure 15 This is a flowchart of the control method for the resonator system in other embodiments of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, but do not exclude other elements or objects.

[0044] To address the problems existing in the prior art, embodiments of the present invention provide a resonator system comprising N cascaded resonators, where N is an integer greater than 1. Each resonator stage includes a resonant cavity and a thermal phase shifter. In each resonator stage, the thermal phase shifter is integrated onto the resonant cavity. The thermal phase shifters in the N cascaded resonators are connected in series sequentially. The first terminal of the thermal phase shifter in the first stage resonator is connected to a preset voltage, and the second terminal of the thermal phase shifter in the Nth stage resonator is grounded. The connection node between the thermal phase shifters in adjacent resonator stages is connected to an adjustable voltage. The resistances of the thermal phase shifters in the N stages are all equal.

[0045] In the resonator system of the present invention, the first terminal of the thermal phase shifter in the first stage resonator is connected to a preset voltage, the second terminal of the thermal phase shifter in the Nth stage resonator is grounded, the connection node between the thermal phase shifters in adjacent resonators is connected to an adjustable voltage, and the resistance of the thermal phase shifters in the Nth stage resonator is equal. This enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in adjacent resonators, simplifying the control method of the resonator system and reducing the number of control voltages required.

[0046] In some embodiments, the resonator includes any one of a microring resonator, a fiber optic ring resonator, a Bragg grating, a photonic crystal nanobeam, a Fabry-Perot cavity, or a Mach-Zehnder interferometer.

[0047] In some embodiments, the resonator is a microring resonator, and each stage of the microring resonator further includes an optical waveguide. In each stage of the microring resonator, the microring resonant cavity is coupled to the optical waveguide, and the microring resonant cavity in the previous stage of the microring resonator is coupled to the optical waveguide in the next stage of the microring resonator.

[0048] In some embodiments, the Nth-stage microring resonator further includes an output waveguide coupled to the microring resonator cavity in the Nth-stage microring resonator.

[0049] Figure 3 This is a schematic diagram of a microring resonator system in some embodiments of the present invention. (Refer to...) Figure 3The microring resonator system includes a cascaded first-stage microring resonator and a second-stage microring resonator. 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, a second thermal phase shifter 23, and an output optical waveguide 24. The first thermal phase shifter 13 is integrated on the first microring resonant cavity 12, and the second thermal phase shifter 23 is integrated on the second microring resonant cavity 22. 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. a is the propagation direction of the input optical path in the first optical waveguide 11, and b is the propagation direction of the output optical path in the output optical waveguide 24. The resistance of the first thermal phase shifter 13 is the first resistor R1, and the resistance of the second thermal phase shifter 23 is the second resistor R2. The first resistor R1 and the second resistor R2 are the same. The first thermal phase shifter 13 and the second thermal phase shifter 23 are connected in series. One end of the first thermal phase shifter 13 is connected to a preset voltage V0, and one end of the second thermal phase shifter 23 is connected to the 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 an adjustable voltage, and the preset voltage V0 is a fixed voltage.

[0050] In some specific embodiments, the propagation direction a of the input optical path in the first optical waveguide 11 and the propagation direction b of the output optical path in the output optical waveguide 24 are the same.

[0051] The working principle of the resonator system of the present invention is explained using this embodiment as an example. The relationship between the phase difference Δφ between the first micro-ring resonator and the second micro-ring resonator and the first voltage V1 connected at the connection node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is shown by Equation 1.

[0052] Formula 1:

[0053] Where A is the first coefficient, which is determined by the properties of the waveguide itself, such as the waveguide material and waveguide structure.

[0054] As can be seen from Formula 1, since The phase difference Δφ between two adjacent microring resonators cancels each other out, and is proportional to the adjustable voltage V1 applied to the connection node between the thermal phase shifters of the two adjacent microring resonators, namely the first thermal phase shifter 13 and the second thermal phase shifter 23. Its advantage is that only one control voltage is needed, and the phase difference Δφ to be achieved is proportional to the required control voltage V1 (instead of V1). 2 The linear relationship facilitates control. Figure 4This is a graph showing the relationship between the center wavelength of the output spectrum of the microring resonator in some embodiments of the present invention and the waveguide refractive index generated by the control voltage. (Refer to...) Figure 4 Taking the simulation results as an example, the center wavelength of the output spectrum of the microring resonator is proportional to the change in waveguide refractive index generated by the control voltage.

[0055] Where A is the first coefficient, which is determined by the properties of the waveguide material and structure and can be obtained through measurement. This coefficient is well known in the industry and will not be elaborated here.

[0056] In some embodiments, the microring resonator is ring-shaped, racetrack-shaped, tai chi-shaped, or figure-eight-shaped.

[0057] In some embodiments, the coupling region of the microring resonator is any one of a directional coupler, a bent directional coupler, an adiabatic coupler, a multimode interferometer, or a split-ratio adjustable coupler.

[0058] In some embodiments, the heating resistor material of the heat phase shifter includes titanium nitride, doped silicon, or tungsten.

[0059] In some embodiments, the integrated material platform on which the microring resonator is located includes bulk silicon, silicon-on-insulator, silicon-on-sapphire, silicon dioxide, aluminum nitride, indium phosphide, lithium niobate, or polymers.

[0060] In some embodiments, the waveguide type of the microring resonator includes channel waveguide, ridge waveguide, slot waveguide, diffused waveguide, and photonic crystal waveguide.

[0061] In some embodiments, the operating wavelength range of the microring resonator includes the visible light band, O band, E band, S band, C band, L band, U band, and mid-infrared band.

[0062] In some embodiments, the microring resonator is in the form of an optical resonant system composed of an integrated chip, optical fiber, or free optical components.

[0063] Figure 5 This is a schematic diagram illustrating the cascaded configuration of microring resonators in some embodiments of the present invention. (Refer to...) Figure 5 The light propagation direction of the second optical waveguide 21 is turned 180 degrees, a is the propagation direction of the input optical path in the first optical waveguide 11, and c is the propagation direction of the output optical path in the output optical waveguide 24.

[0064] In some specific embodiments, the propagation direction a of the input optical path in the first optical waveguide 11 and the propagation direction c of the output optical path in the output optical waveguide 24 are opposite or at any angle.

[0065] Figure 6 This is a schematic diagram illustrating the cascaded configuration of microring resonators in other embodiments of the present invention. (Refer to...) Figure 6The first optical waveguide 11 and the output optical waveguide 24 are bent, e is the propagation direction of the input optical path in the first optical waveguide 11, and f is the propagation direction of the output optical path in the output optical waveguide 24.

[0066] Figure 7 This is a schematic diagram illustrating the cascading configuration of micro-ring resonators in some embodiments of the present invention. (Refer to...) Figure 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 propagation direction of the input optical path in the first optical waveguide 11 and a is the propagation direction of the output optical path in the output optical waveguide 24.

[0067] Figure 8 This is a schematic diagram illustrating the cascaded configuration of microring resonators in some embodiments of the present invention. (Refer to...) Figure 8 The first micro-ring resonator 12 and the second micro-ring resonator 22 are both coupled to the first optical waveguide 11, and the two micro-ring resonators are also coupled to each other. c is the propagation direction of the input optical path in the first optical waveguide 11, and a is the propagation direction of the output optical path in the first optical waveguide 11.

[0068] Figure 9 This is a schematic diagram of a microring resonator system with a 4-stage microring resonator in some embodiments of the present invention. (Refer to...) Figure 9 The microring resonator system includes four cascaded microring resonators. In each microring resonator, the thermal phase shifter is integrated into the microring resonant cavity. 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 cascaded microring resonators are connected in series. The first terminal of the first thermal phase shifter 13 in the first-stage microring resonator is connected to a preset voltage V0, and the second terminal of the fourth thermal phase shifter 43 in the fourth-stage microring resonator is connected to the ground pin GND (voltage is 0V). The node between the first thermal phase shifter 13 and the second thermal phase shifter 23 is connected to a first voltage V1. The node between the second thermal phase shifter 23 and the third thermal phase shifter 33 is connected to a second voltage V2. The 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 adjustable voltages. The resistances of 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 are the same. 'a' represents the propagation direction of the input optical path in the first optical waveguide 11, and 'b' represents the propagation direction of the output optical path in the output optical waveguide 24.

[0069] The present invention also provides a tunable laser, including the resonator system and a gain chip, wherein one end of the Nth stage resonator of the resonator system is connected to the gain chip.

[0070] In some embodiments, the gain chip is a III-V family chip.

[0071] Figure 10 This is a schematic diagram of a tunable laser in some embodiments of the present invention. (Refer to...) Figure 10 The tunable laser chip includes the resonator system and the gain chip 6. The left side 61 of the gain chip 6 is a total internal reflection surface, allowing light to be emitted from the other end of the resonator system, with the optical path output direction as shown in c. The resonator system is used to adjust the laser output wavelength.

[0072] Figure 11 This is a schematic diagram of a tunable laser chip in other embodiments of the present invention. (Refer to...) Figure 11 The tunable laser chip includes the resonator system, a total internal reflection loop 5, and a gain chip 6. One end of the first-stage resonator of the resonator system is connected to the total internal reflection loop 5, and one end of the Nth-stage resonator of the resonator system is connected to the gain chip 6. The optical output direction 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.

[0073] In some embodiments, the tunable laser further includes a thermal phase shifter integrated between the total internal reflection loop and the resonator system for phase control outside the resonator system.

[0074] Specifically, refer to Figure 11 The total internal reflection loop 5 is connected to the right end of the first optical waveguide 11, and the first optical waveguide 11 is integrated with an initial thermal phase shifter 51.

[0075] Figure 12 This is a schematic diagram of a tunable laser in some embodiments of the present invention. (Refer to...) Figure 12The resonator system is a vernier resonator composed of two photonic crystal nanobeams. 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, and 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 and the second thermal phase shifter 23 are connected in series. One end of the first thermal phase shifter 13 is connected to a preset voltage V0, and 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, which is adjustable, while the preset voltage V0 is a fixed voltage. One end of the resonator system is connected to a gain chip 6. The propagation direction of the output optical path of the tunable laser is shown in b. Note that in this embodiment, neither end of the gain chip 6 is a total reflection surface. The resonator system is used to adjust the output wavelength of the laser.

[0076] Figure 13 This is a schematic diagram illustrating the variation of the laser output wavelength under different control voltages in some embodiments of the present invention. (Refer to...) Figure 13 Under a voltage with the same wavelength variation, the laser outputs four different spectra from left to right, with all four spectra exhibiting the same wavelength variation. The control method of the tunable laser chip of this invention enables the phase difference between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the junction of the thermal phase shifters in the two adjacent resonator stages. This, in turn, makes the output wavelength variation linearly related to the control voltage, simplifying the resonator control method and reducing the number of required control voltages.

[0077] Figure 14 This is a flowchart of a control method for a resonator system in some embodiments of the present invention. One end of the thermal phase shifter of the first-stage resonator is connected to the preset voltage, and the second end of the thermal phase shifter of the Nth-stage resonator is grounded. There are N-1 connection nodes between the N thermal phase shifters, and each of these N-1 connection nodes is connected to N-1 adjustable voltages. When N>=3, refer to... Figure 14 The control method includes the following steps:

[0078] S0: Fix the preset voltage to V0;

[0079] S1: Control the adjustable voltage connected to the second connection node until the adjustable voltage connected to the (N-1)th connection node is 0;

[0080] S2: Control the adjustable voltage connected to the first connection node to be greater than or equal to 0 and less than or equal to V0, and fix the adjustable voltage connected to the first connection node;

[0081] S3: Set the adjustable voltage of all connection nodes after the Mth connection node to 0, control the adjustable voltage of the Mth connection node to be greater than or equal to 0 and less than or equal to the adjustable voltage of the (M-1)th connection node, and fix the adjustable voltage of the Mth connection node.

[0082] S4: Repeat step S3 by taking integers from 2 to N-1 for M.

[0083] The control method of the resonator system of the present invention enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonator stages when the number of resonator cascades in the resonator system is greater than or equal to 3. This simplifies the control method of the resonator system and reduces the number of control voltages required.

[0084] In some embodiments, the method of controlling and fixing the adjustable voltage in steps S2 and S3 includes scanning the voltage, observing the output spectrum of the resonator system, and making the spectrum meet the desired characteristics, for example, controlling the adjustable voltage value to move the center wavelength to the target wavelength.

[0085] In some embodiments, the adjustable voltage connected to the connection node between the thermal phase shifters of adjacent resonators decreases from the first stage to the Nth stage, and the preset voltage is greater than the adjustable 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 adjustable 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 greater than 0.

[0086] In some specific embodiments, reference is made to Figure 9 The microring resonator system includes four cascaded microring resonators. The voltage connected to the first connection node is V1, the voltage connected to the second connection node is V2, and the voltage connected to the third connection node is V3. The control method includes the following steps.

[0087] S0: Fix the preset voltage to V0;

[0088] S10: Control the adjustable voltage connected to the second connection node to be 0 for all adjustable voltages connected to the fourth connection node;

[0089] S20: Control V1 to be greater than or equal to 0 and less than or equal to V0, and fix V1;

[0090] S30: Control the adjustable voltage connected to the 3rd connection node to be 0 for all adjustable voltages connected to the 4th connection node;

[0091] S40: Control V2 to be greater than or equal to 0 and less than or equal to V1, and fix V2;

[0092] S50: Control V3 to be greater than or equal to 0 and less than or equal to V2, and fix V3.

[0093] Reference Figure 9 The microring resonator system includes cascaded 4 microring resonators, and the 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.

[0094] Figure 15 This 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 the two thermal phase shifters, and this connection node is connected to an adjustable voltage, as shown in the figure. Figure 15 The control method comprises the following steps:

[0095] The preset voltage is fixed at V0;

[0096] The adjustable voltage connected to the connection node is controlled to be greater than or equal to 0 and less than or equal to V0, and the adjustable voltage connected to the connection node is fixed.

[0097] The control method of the resonator system of the present invention enables the phase difference change between two adjacent resonant cavities to be linearly related to the adjustable voltage connected to the connection node between the thermal phase shifters in the two adjacent resonator stages when the number of resonator cascades in the resonator system is 2, thereby simplifying the control method of the resonator system.

[0098] While 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 fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A resonator system, characterized by, The resonator includes N-stage cascaded resonators, N being an integer greater than 1, each stage of the resonators including a resonant cavity and a thermal phase shifter, in each stage of the resonators, the thermal phase shifter is integrated on the resonant cavity, the thermal phase shifters in the N-stage cascaded resonators are connected in series, 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 N-stage resonator is grounded, a connection node between the thermal phase shifters in adjacent two stages of the resonators is connected to an adjustable voltage, and the resistances of the thermal phase shifters in the N-stage resonators are equal.

2. The resonator system of claim 1, wherein, The resonator includes any one of a micro-ring resonator, a Bragg grating, a photonic crystal nanobeam, a Fabry-Perot cavity or a Mach-Zehnder interferometer.

3. The resonator system of claim 2, wherein, The micro-ring resonator is a fiber ring resonator.

4. The resonator system of claim 2, wherein, The resonator is a micro-ring resonator, and each stage of the micro-ring resonators further includes an optical waveguide, in each stage of the micro-ring resonators, a micro-ring resonant cavity in the micro-ring resonator is coupled with the optical waveguide, and a micro-ring resonant cavity in a previous-stage micro-ring resonator is coupled with an optical waveguide in a next-stage micro-ring resonator.

5. The resonator system of claim 4, wherein, The N-stage micro-ring resonator further includes an output waveguide, and the output waveguide is coupled with a micro-ring resonant cavity in the N-stage micro-ring resonator.

6. 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, an adiabatic coupler, a multimode interferometer or a split-ratio adjustable coupler.

7. The resonator system of claim 6, wherein, The directional coupler is a curved directional coupler.

8. The resonator system of claim 2, wherein, The resonator is a micro-ring resonator, and the micro-ring resonator is in a ring shape, a racetrack shape, a Tai Chi shape or an eight-character shape.

9. A tunable laser, characterized by The resonator system includes the resonator system and a gain chip according to any one of claims 1-8, and one end of an N-stage resonator of the resonator system is connected to the gain chip.

10. The tunable laser of claim 9, wherein, The resonator system further includes a total reflection back loop, and one end of a first-stage resonator of the resonator system is connected to the total reflection back loop.

11. A method of controlling a resonator system as claimed in any one of claims 1 to 8, characterized by When N≥3, the control method includes the following steps, S0: fixing the preset voltage as V0; S1: controlling the adjustable voltages connected to the 2nd connection node to the (N-1)th connection node to be all 0; S2: controlling the adjustable voltage connected to the 1st connection node to be greater than or equal to 0 and less than or equal to V0, and fixing the adjustable voltage connected to the 1st connection node; S3: setting the adjustable voltages connected to the connection nodes after the Mth connection node to be all 0, controlling the adjustable voltage connected to the Mth connection node to be greater than or equal to 0 and less than or equal to the adjustable voltage connected to the (M-1)th connection node, and fixing the adjustable voltage connected to the Mth connection node; S4: repeatedly executing step S3 with M being an integer from 2 to N-1 in sequence.

12. The control method according to claim 11, characterized by, The adjustable voltages connected to the connection nodes between the thermal phase shifters of adjacent resonators decrease from the first stage to the Nth stage, and the preset voltage is greater than the adjustable 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 adjustable 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 greater than 0.

13. A method of controlling a resonator system as claimed in any one of claims 1 to 8, characterized by When N=2, the control method includes the following steps, fixing the preset voltage as V0; Controlling the adjustable voltage connected to the connection node to be greater than or equal to 0 and less than or equal to V0, and fixing the adjustable voltage connected to the connection node. Controlling the adjustable voltage connected to the connection node to be greater than or equal to 0 and less than or equal to V0, and fixing the adjustable voltage connected to

Images