Electrically adjustable cascade micro-ring resonator

Abstract

The invention discloses an electrically adjustable cascade micro-ring resonator, and relates to the technical field of electro-optical modulation, a signal transmission waveguide comprises a first bidirectional transmission waveguide and a second bidirectional transmission waveguide, and a cascade ring resonant cavity comprises a first cascade ring resonant cavity and a second cascade ring resonant cavity; the independent electrodes are arranged on the modulation area of the resonant cavity, and in the independent electrodes, the electrode spacing of the first modulation electrode group is smaller than the electrode spacing of the second modulation electrode group; the signal transmission waveguide and the cascaded annular resonant cavity are communicated through the micro-ring coupling area, and the two annular resonant cavities are communicated through the micro-ring coupling area, so that optical coupling channels are formed between the signal transmission waveguide and the annular resonant cavities, and between the annular resonant cavities. Through the technical scheme of the invention, the electric tuning of the resonance characteristic of the cascaded annular resonant cavity is realized, the full width at half maximum of an output spectrum resonance curve is narrowed, the intrinsic Q value of the resonator is improved, and the control precision and tuning flexibility of the resonant wavelength are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electro-optical modulation, and particularly relates to an electrically adjustable cascaded micro-ring resonator. BACKGROUND

[0002] Thin film lithium niobate on insulator (LNOI) has excellent electro-optical, acousto-optical and nonlinear optical properties, and plays an important role in active and passive integrated optical devices. Micro-ring resonators are widely used in filtering, modulation and resonant fiber optic gyroscope (R-FOG) sensing units due to their compact structure and easy integration. By setting electrodes near the resonant cavity to apply voltage, the effective refractive index of the waveguide can be changed and the resonant peak can be electrically tuned.

[0003] The prior art has common pain points in engineering applications: (1) The tuning "range-resolution" is difficult to balance. The electrode layout of a single pitch or a single region makes the modulation efficiency fixed, and when electro-optically tuning, either a larger frequency sweeping range is obtained but the step is difficult to be small, or a smaller step is obtained but the global coverage is insufficient. The electro-thermal tuning scheme has high power consumption, slow response and large temperature drift, which is not conducive to high-precision and fast closed-loop control.

[0004] (2) The half-width of the single-ring resonant structure is large, and the intrinsic Q value is restricted by the cavity loss and coupling setting, which is difficult to meet the requirements of narrow linewidth and high Q value of R-FOG, and the scale factor and demodulation accuracy are limited.

[0005] (3) The system often relies on tunable lasers to complete peak searching and frequency locking, which is complex and costly, and puts higher requirements on packaging and control, which is not conducive to miniaturization and high-stability integration. SUMMARY

[0006] To address the aforementioned problems, this invention provides an electrically tunable cascaded microring resonator. Through the signal transmission waveguide, the cascaded ring resonator structure, and the microring coupling region between them, narrowband resonant filtering of the input optical signal is achieved, further narrowing the full width at half maximum (FWHM) of the output spectral resonance curve and improving the intrinsic Q value of the resonator. Compared to a single ring resonator structure, this improves the resonant extinction ratio and spectral selectivity, thereby increasing the scaling factor of the resonant micro-optical gyroscope. By setting modulation electrode groups on the modulation region corresponding to the cascaded ring resonator and designing the electrode spacing, when using waveguide materials with electro-optic effects, modulation electric fields of different intensities can be generated in the same device, achieving electrically tunable resonant characteristics of the cascaded ring resonator. This improves the control accuracy and tuning flexibility of the resonant wavelength. Simultaneously, since the signal transmission waveguide is connected to the cascaded ring resonator through the microring coupling region, the input and output optical paths are led out on different waveguides, reducing the risk of optical crosstalk while maintaining the resonant filtering function.

[0007] To achieve the above objectives, the present invention provides an electrically tunable cascaded microring resonator, comprising: a signal transmission waveguide, a cascaded ring resonant cavity, and independent electrodes; The signal transmission waveguide includes a first bidirectional transmission waveguide and a second bidirectional transmission waveguide, and the cascaded ring resonant cavity includes a first ring resonant cavity and a second ring resonant cavity that form a cascaded structure. The independent electrode is disposed on the modulation region corresponding to the cascaded ring resonant cavity. The independent electrode includes a first modulation electrode group and a second modulation electrode group. The first modulation electrode group includes a first positive electrode and a first ground electrode. The second modulation electrode group includes a second positive electrode and a second ground electrode. The electrode spacing between the first positive electrode and the first ground electrode is smaller than the electrode spacing between the second positive electrode and the second ground electrode. The signal transmission waveguide and the cascaded ring resonator, as well as the first ring resonator and the second ring resonator, are all connected through a micro-ring coupling region.

[0008] In the above technical solution, preferably, one of the first bidirectional transmission waveguide and the second bidirectional transmission waveguide serves as the input end of the optical signal, and the other serves as the output end of the optical signal. The optical signal is sequentially coupled into the first ring resonant cavity and the second ring resonant cavity through the micro-ring coupling region and then output from the output end. The cascaded ring resonant cavity is configured to perform resonant filtering on a specific wavelength component of the optical signal from the input end that meets a preset resonance condition, so as to suppress the transmission of the specific wavelength component at the output end, and the optical signal that does not meet the preset resonance condition is directly output from the output end along the signal transmission waveguide.

[0009] In the above technical solution, preferably, the modulation region corresponding to the cascaded ring resonant cavity includes a first modulation region and a second modulation region. The first modulation region is located in the region corresponding to the first modulation electrode group, and the second modulation region is located in the region corresponding to the second modulation electrode group. When the optical signal is transmitted in the cascaded ring resonant cavity, it passes through the first modulation region and the second modulation region in sequence.

[0010] In the above technical solution, preferably, the cavity lengths of the first annular resonant cavity and the second annular resonant cavity are designed so that the cascaded annular resonant cavity has a preset free spectral range in the target operating band.

[0011] In the above technical solution, preferably, the cavity lengths of the first ring resonator and the second ring resonator are both 1108 μm, so that the free spectral range of the cascaded ring resonator in the target operating band is greater than 1 nm.

[0012] In the above technical solution, preferably, the main body of the signal transmission waveguide and the first and second annular resonant cavities are made of a material with electro-optic effect, and the material is selected from at least one of lithium niobate, gallium arsenide, indium phosphide and electro-optic polymer.

[0013] In the above technical solution, preferably, the signal transmission waveguide and the main body of the first ring resonant cavity and the second ring resonant cavity are made of thin-film lithium niobate, and the effective refractive index of the thin-film lithium niobate changes with the voltage applied to the first modulation electrode group and the second modulation electrode group.

[0014] In the above technical solution, preferably, the first positive electrode, the first ground electrode, the second positive electrode and the second ground electrode are made of gold material, and a silicon dioxide buffer layer is provided between the gold electrode and the waveguide body of thin-film lithium niobate.

[0015] In the above technical solution, preferably, the first modulation electrode group and / or the second modulation electrode group are used to apply a control voltage to the waveguide segment corresponding to the annular resonant cavity to form a modulation electric field in the region, and use the electro-optic effect to change the effective refractive index of the corresponding annular resonant cavity, thereby realizing the electrical tunability of the resonant wavelength of the corresponding annular resonant cavity.

[0016] In the above technical solution, preferably, the electrically tunable cascaded micro-ring resonator is integrated into a resonant micro-optical gyroscope. The resonant micro-optical gyroscope includes a laser and a detector coupled to the electrically tunable cascaded micro-ring resonator. The input terminal is connected to the laser, and the detector is connected to the output terminal. The electrically tunable cascaded micro-ring resonator is used to lock the output center frequency of the laser by electrically tuning its resonant wavelength.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By adopting a signal transmission waveguide and a cascaded ring resonator structure consisting of a first ring resonator and a second ring resonator, and setting micro-ring coupling regions between the signal transmission waveguide and the cascaded ring resonator and between the first ring resonator and the second ring resonator, narrowband resonant filtering of the input optical signal is realized, and a deeper resonance valley is formed at the target resonant wavelength, which improves the resonant extinction ratio and spectral selectivity compared to a single ring resonator structure.

[0018] By cascading the second ring resonant cavity, the full width at half maximum (FWHM) of the output spectrum resonance curve is further narrowed, and the intrinsic Q value of the resonator is improved, thereby increasing the scaling factor of the resonant micro-optical gyroscope, which is beneficial for meeting the requirements of high-precision measurement.

[0019] (2) By setting up independent first modulation electrode groups and second modulation electrode groups on the modulation region corresponding to the cascaded ring resonator, and designing the electrode spacing between the first positive electrode and the first ground electrode to be smaller than the electrode spacing between the second positive electrode and the second ground electrode, when using waveguide materials with electro-optic effect, modulation electric fields of different intensities can be generated in the same device, realizing the electrical tunability of the resonance characteristics of the cascaded ring resonator, and obtaining different tuning sensitivities or tuning ranges, thereby improving the control accuracy and tuning flexibility of the resonance wavelength.

[0020] (3) By setting the signal transmission waveguide to include a first bidirectional transmission waveguide and a second bidirectional transmission waveguide, and connecting them to the cascaded ring resonant cavity through the micro-ring coupling region respectively, the input optical path and the output optical path are led out on different waveguides. While maintaining the resonant filtering function, the risk of optical path crosstalk is reduced, which is beneficial to the integration and packaging of the device with external optical fibers and other photonic chips. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an electrically adjustable cascaded microring resonator disclosed in one embodiment of the present invention; Figure 2 This is a schematic diagram of resonance curves for two different tuning levels disclosed in one embodiment of the present invention.

[0022] In the diagram, the correspondence between the components and the reference numerals is as follows: 1. First bidirectional transmission waveguide, 2. Second bidirectional transmission waveguide, 3. First ring resonant cavity, 4. Second ring resonant cavity, 5. First positive electrode, 6. First ground electrode, 7. Second ground electrode, 8. Second positive electrode. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 As shown, an electrically tunable cascaded microring resonator according to the present invention includes: a signal transmission waveguide, a cascaded ring resonant cavity, and independent electrodes; The signal transmission waveguide includes a first bidirectional transmission waveguide 1 and a second bidirectional transmission waveguide 2, and the cascaded ring resonator includes a first ring resonator 3 and a second ring resonator 4 constituting a cascaded structure. Independent electrodes are disposed on the modulation region corresponding to the cascaded ring resonant cavity. The independent electrodes include a first modulation electrode group and a second modulation electrode group. The first modulation electrode group includes a first positive electrode 5 and a first ground electrode 6. The second modulation electrode group includes a second ground electrode 7 and a second positive electrode 8. The electrode spacing between the first positive electrode 5 and the first ground electrode 6 is smaller than the electrode spacing between the second ground electrode 7 and the second positive electrode 8. The signal transmission waveguide and the cascaded ring resonator, as well as the first ring resonator 3 and the second ring resonator 4, are connected through a micro-ring coupling region, so that optical coupling channels are formed between the signal transmission waveguide and the ring resonator, as well as between the ring resonators.

[0025] Specifically, two electrode groups are arranged sequentially along the waveguide modulation region of the cascaded ring resonator, covering the corresponding waveguide segments of the ring resonator to form a first modulation region and a second modulation region. The spacing between the first positive electrode 5 and the first ground electrode 6 is designed to be smaller than the spacing between the second ground electrode 7 and the second positive electrode 8, so as to form two modulation electric fields of different intensities when a voltage is subsequently applied. The smaller spacing of the first modulation electrode group enables a wide range of wavelength tuning, with a large ratio of tuning wavelength to tuning voltage; the larger spacing of the second modulation electrode group enables a narrower range of wavelength tuning, with a small ratio of tuning wavelength to tuning voltage.

[0026] In this embodiment, narrowband resonant filtering of the input optical signal is achieved through the signal transmission waveguide, the cascaded ring resonant cavity structure, and the micro-ring coupling region between them. The cascading of the second ring resonant cavity 4 further narrows the full width at half maximum (FWHM) of the output spectral resonance curve, thereby improving the intrinsic Q value of the resonator. Compared with a single ring resonant cavity structure, the resonant extinction ratio and spectral selectivity are improved, thus increasing the scaling factor of the resonant micro-optical gyroscope. By setting a modulation electrode group on the modulation region corresponding to the cascaded ring resonant cavity and designing the electrode spacing, when using waveguide materials with electro-optic effects, modulation electric fields of different intensities can be generated in the same device, realizing the electrical tunability of the resonant characteristics of the cascaded ring resonant cavity, improving the control accuracy and tuning flexibility of the resonant wavelength. At the same time, since the signal transmission waveguide is connected to the cascaded ring resonant cavity through the micro-ring coupling region, the input optical path and the output optical path are led out on different waveguides, reducing the risk of optical path crosstalk while maintaining the resonant filtering function.

[0027] The above structure constructs an electrically tunable cascaded micro-ring resonator consisting of two-stage ring resonators and two sets of modulation electrodes with different spacings, laying the hardware foundation for subsequent large-range coarse tuning and small-range fine tuning within the same device.

[0028] In the above embodiment, preferably, one of the first bidirectional transmission waveguide 1 and the second bidirectional transmission waveguide 2 serves as the input end of the optical signal, and the other serves as the output end of the optical signal. After the optical signal is coupled into the first ring resonant cavity 3 and the second ring resonant cavity 4 in sequence through the micro-ring coupling region, it is output from the output end. The cascaded ring resonant cavity is configured to perform resonant filtering on a specific wavelength component of the optical signal from the input end that meets the preset resonance condition, so as to suppress the transmission of the specific wavelength component at the output end, and the optical signal that does not meet the preset resonance condition is directly output from the output end along the signal transmission waveguide.

[0029] Based on the above embodiments, in a preferred embodiment, one end of the first bidirectional transmission waveguide 1 serves as the input end of the optical signal, and one end of the second bidirectional transmission waveguide 2 serves as the output end of the optical signal.

[0030] During operation, the optical signal to be processed is coupled into the first bidirectional transmission waveguide 1 from the input end. In the micro-ring coupling region between the first bidirectional transmission waveguide 1 and the first ring resonant cavity 3, part of the optical power is coupled into the first ring resonant cavity 3. The light circulates multiple times along the ring waveguide in the first ring resonant cavity 3 and is further coupled into the second ring resonant cavity 4 in the micro-ring coupling region between the first ring resonant cavity 3 and the second ring resonant cavity 4, thereby forming a cascaded system in the two-stage ring resonant cavities.

[0031] The optical signal filtered by the cascaded ring resonator is finally coupled back to the straight waveguide section through the micro-ring coupling region between the second ring resonator 4 and the second bidirectional transmission waveguide 2, and output from the output end of the second bidirectional transmission waveguide 2, thereby suppressing the narrowband wavelength components in the input optical signal that meet the preset resonance conditions and transmitting the non-resonant wavelength components.

[0032] Specifically, light of a specific wavelength resonates in both sets of resonant cavities, and the power in the second bidirectional transmission waveguide 2 is close to 0; while light of non-resonant wavelengths will be directly output from the second bidirectional transmission waveguide 2, with a power similar to that of the incident light signal, differing only from the loss of the straight waveguide; this process generally exhibits a resonance curve with a resonance valley; and the resonant cavity is extremely sensitive to changes in refractive index, so high-precision tuning can be achieved by changing the refractive index of the micro-ring waveguide.

[0033] In the above embodiments, preferably, the modulation region corresponding to the cascaded ring resonator includes a first modulation region and a second modulation region. The first modulation region is located in the region corresponding to the first modulation electrode group, and the second modulation region is located in the region corresponding to the second modulation electrode group. When the optical signal is transmitted in the cascaded ring resonator, it passes through the first modulation region and the second modulation region in sequence.

[0034] Based on the above embodiments, in a further embodiment, the waveguide modulation region of the cascaded ring resonator is sequentially formed into a first modulation region and a second modulation region along the direction of light propagation in the ring resonator. The first modulation region is located in the region corresponding to the ring waveguide segment covered by the first positive electrode 5 and the first ground electrode 6, and the second modulation region is located in the region corresponding to the ring waveguide segment covered by the second ground electrode 7 and the second positive electrode 8.

[0035] After the optical signal enters from the input end, it is transmitted in the first ring resonant cavity 3 and the second ring resonant cavity 4. When the light moves to the first modulation region in the ring resonant cavity, it is subjected to the electric field generated by the voltage applied by the first modulation electrode group, and the refractive index of the ring resonant cavity waveguide is modulated for the first time. When the light continues to be transmitted along the ring path to the second modulation region, it is subjected to the electric field generated by the voltage applied by the second modulation electrode group, and the refractive index of the ring resonant cavity waveguide is modulated for the second time.

[0036] After two modulations, the output waveguide exhibits the following behavior: when different voltages are applied to the two sets of electrodes, the resonant peak wavelength observed at the output end shifts to different degrees relative to the position when no voltage is applied. The amount of shift is related to the voltage applied to the two sets of electrodes, thus achieving two-stage electrical tuning of the resonant wavelength.

[0037] The key feature of this electrically tunable cascaded microring resonator is that the tuning section is composed of two electrodes with different spacings. By designing the spacing of the modulation electrodes, two peak wavelengths with different modulation sensitivities can be tuned: one for large-amplitude tuning and the other for small-amplitude tuning, allowing for more precise adjustment to the required optical wavelength. In addition, the designed dual-electrode group structure is also beneficial for the separation and control of the disturbance voltage and the closed-loop control voltage during the peak search process.

[0038] In the above embodiments, preferably, the cavity lengths of the first annular resonant cavity 3 and the second annular resonant cavity 4 are designed so that the cascaded annular resonant cavity has a preset free spectral range in the target operating band.

[0039] In the implementation process, in order to meet the design requirements of the resonant micro-optical gyroscope for free spectral range (FSR), the cavity lengths of the first ring resonant cavity 3 and the second ring resonant cavity 4 are matched through structural design.

[0040] Specifically, based on the relationship between the free spectral range and the cavity length and effective refractive index, the radius of the ring resonator and the refractive index of the waveguide can be jointly designed to ensure that the cascaded ring resonator has a preset free spectral range in the target operating band. By reasonably selecting the length of the micro-ring, i.e., the cavity length, and the waveguide cross-sectional dimensions, the free spectral range required for resonant micro-optical gyroscope applications can be achieved while ensuring the compact size of the device, providing a foundation for subsequent multi-stage resonance, resonant peak selection, and locking.

[0041] The formula involved in designing the free spectral range is as follows: in, c The speed of light in a vacuum L The length of the ring resonant cavity is given. n eff The effective refractive index of the resonant ring optical waveguide. n g Let the group refractive index be the group refractive index of the optical waveguide. Lambda This is the operating wavelength of the resonant ring. FSR v For the free spectral region in wavelength form, FSR λ It is a free spectral region in frequency form.

[0042] In the above embodiments, preferably, the cavity lengths of the first annular resonant cavity 3 and the second annular resonant cavity 4 are both 1108 μm, so that the free spectral range of the cascaded annular resonant cavity in the target operating band is greater than 1 nm.

[0043] Based on the above embodiments, in a preferred embodiment, the cavity lengths of the first annular resonant cavity 3 and the second annular resonant cavity 4 are designed to be the same, both being 1108 μm. Based on the design formula for free spectral range, under this cavity length condition, the cascaded annular resonant cavities achieve a free spectral range greater than 1 nm in the target operating wavelength band.

[0044] By configuring the cavity length as described above, we can ensure the compact size of the ring resonant cavity when it is integrated on the chip, and make the mode spacing of the resonator large enough to facilitate the identification and locking of the resonance peaks and avoid mutual interference between adjacent resonance peaks, thereby meeting the device performance requirements of the resonant micro-optical gyroscope for a large free spectral range.

[0045] In the above embodiments, preferably, the main body of the signal transmission waveguide and the first ring resonant cavity 3 and the second ring resonant cavity 4 is made of a material with a significant strong electro-optic effect, and the material is selected from at least one of lithium niobate, gallium arsenide, indium phosphide and electro-optic polymers with a strong electro-optic effect.

[0046] During implementation, under the miniaturization design requirements based on integrated photonics, thin-film electro-optic materials can be used as waveguide layers to fabricate electro-optic waveguide structures on silicon or other substrates. The ring waveguides of the first ring resonant cavity 3 and the second ring resonant cavity 4, along with the signal transmission waveguides coupled to them, are formed through photolithography and etching. By placing independent electrodes above the aforementioned electro-optic material and applying a voltage, the effective refractive index of the ring resonant cavity can be modulated using the electro-optic effect of the material itself.

[0047] In the above embodiments, preferably, the main body of the signal transmission waveguide and the first annular resonant cavity 3 and the second annular resonant cavity 4 is made of thin-film lithium niobate, and the effective refractive index of the thin-film lithium niobate changes with the voltage applied to the first modulation electrode group and the second modulation electrode group.

[0048] Specifically, thin-film lithium niobate materials possess excellent electro-optic, acousto-optic, and nonlinear optical properties, making them suitable for on-chip integration to realize compact active and passive photonic devices. Straight waveguides and ring waveguides are fabricated on a thin-film lithium niobate platform to form the main body of signal transmission waveguides and cascaded ring resonant cavities.

[0049] When a modulation voltage is applied to the first and second modulation electrode groups, an electric field is established in the thin-film lithium niobate waveguide region, and the effective refractive index of the material... n eff According to the electro-optic effect formula, the following changes occur, where n eff With respect to the intrinsic effective refractive index of the material n e-ray refractive index of the material n e and electro-optic coefficient r33 Electrode spacing g, light intensity value E , applied voltage value V Related to parameters such as...

[0050] Specifically, the formula relating the applied voltage to the effective refractive index of the material is as follows: The resonant frequency of the resonant ring is ,in f The resonant frequency, n eff The effective refractive index of the resonant ring optical waveguide. L The length of the ring resonant cavity is given. c The speed of light in a vacuum m The resonant order is... n e The e-ray refractive index of thin-film lithium niobate is... V To apply voltage, g The distance between the electrodes. E The applied electric field strength, r 33 This represents the electro-optic coefficient of the thin-film lithium niobate material. Therefore, the resonant frequency also changes when the effective refractive index of the waveguide material changes.

[0051] A ring resonator has a transfer function formula, the specific form of which is shown below: In the formula, α c For the coupler loss, α L k represents the unit loss within the cavity. c The coupling coefficient of the coupler. Δf=ff q Let f be the deviation between the laser output frequency and the resonant frequency of the q-th resonant point, and f be the center frequency. q Let q be the resonant frequency of the q-th resonant point, L be the cavity length of the ring resonant cavity, and c be the speed of light in a vacuum.

[0052] By adjusting the voltage applied to the two sets of electrodes, the effective refractive index of the thin-film lithium niobate waveguide can be varied to different degrees, thereby changing the inherent resonant wavelength of the resonant cavity and achieving electrical tunability of the resonant wavelength of the ring resonant cavity.

[0053] Specifically, when a voltage is applied to the electrodes, the transfer function changes, as shown in the following equation: In the formula, V1 and V2 are the voltages applied to the first modulation electrode group and the second modulation electrode group, respectively, and α c For the coupler loss, α L k represents the unit loss within the cavity. c The coupling coefficient of the coupler. Δf=ff q Let f be the deviation between the laser output frequency and the resonant frequency of the q-th resonant point, and f be the center frequency. q Let be the resonant frequency of the q-th resonant point, L be the cavity length of the ring resonant cavity, c be the speed of light in vacuum, and r be the resonant frequency of the q-th resonant point. 33 denoted as , where g is the electro-optic coefficient of the thin-film lithium niobate material, E is the electrode spacing, and n is the applied electric field strength. e Let be the e-optical refractive index of thin-film lithium niobate, H(Δf) be the power transfer function of the ring resonator at a frequency detuning of Δf, ρ be the interference contrast / resonance depth coefficient obtained by combining A, D, and W, A be the self-coupling amplitude transmission coefficient of the through waveguide in the coupling region, D be the out-coupling amplitude coefficient coupled from the ring cavity back to the through waveguide, and W be the single-loop equivalent field attenuation coefficient of the ring cavity. When performing wavelength tuning, such as... Figure 2 As shown, when no voltage is applied, the resonant wavelength of the resonant cavity is represented by a solid line. When a voltage is applied to the first positive electrode 5 and no voltage is applied to the second positive electrode 8, the resonant wavelength will shift to a certain extent, specifically as a dotted horizontal curve. Furthermore, when a voltage is applied to the second positive electrode 8, the resonant wavelength will shift a second time, specifically as a short horizontal curve. All three curves show... Figure 2 This is reflected in the process. The tuning process of the tunable ring resonator is now complete.

[0054] In the above embodiments, preferably, the first positive electrode 5, the first ground electrode 6, the second ground electrode 7, and the second positive electrode 8 are made of gold material, and a silicon dioxide buffer layer is disposed between the gold electrode and the waveguide body of thin-film lithium niobate.

[0055] In the above embodiments of the thin-film lithium niobate implementation scheme, the independent electrode part is made of a metal material containing gold to ensure good conductivity and process feasibility.

[0056] Specifically, a silicon dioxide buffer layer can be deposited first on the thin-film lithium niobate waveguide layer. This buffer layer provides electrical insulation and refractive index transition between the metal electrode and the thin-film lithium niobate waveguide, reducing the absorption of optical signals by the electrode and preventing excessive loss of the optical guide mode field caused by direct metal-waveguide contact. A metal layer is then deposited on the silicon dioxide buffer layer using sputtering or evaporation. A first positive electrode 5, a first ground electrode 6, a second ground electrode 7, and a second positive electrode 8 are then formed through photolithography and etching. The metal layer can be a gold-containing metal stack structure, such as a chromium / gold stack, to improve adhesion and conductivity. By forming the aforementioned metal electrodes on the silicon dioxide buffer layer, electro-optic modulation structure integration with the thin-film lithium niobate waveguide is achieved.

[0057] In the above embodiments, preferably, the first modulation electrode group and / or the second modulation electrode group are used to apply a control voltage to the waveguide segment corresponding to the ring resonant cavity to form a modulation electric field in the region, and use the electro-optic effect to change the effective refractive index of the corresponding ring resonant cavity, thereby realizing the electrical tunability of the resonant wavelength of the corresponding ring resonant cavity.

[0058] Based on the above embodiments, in a further embodiment, the first modulation electrode group and / or the second modulation electrode group are configured to apply a control voltage on the annular waveguide segment corresponding to the first annular resonant cavity 3 and / or the second annular resonant cavity 4.

[0059] Specifically, a voltage V1 is applied between the first positive electrode 5 and the first ground electrode 6, forming a first modulation electric field in the annular waveguide segment they cover, causing a first change in the effective refractive index of the thin-film lithium niobate material in that waveguide segment. A voltage V2 is applied between the second ground electrode 7 and the second positive electrode 8, forming a second modulation electric field in the annular waveguide segment they cover, causing a second change in the effective refractive index of the thin-film lithium niobate material in that waveguide segment. Because the electrode spacing between the first and second electrode groups is different, the intensity of the modulation electric field formed under the same or different voltages varies, thereby achieving resonant wavelength tuning channels with different voltage sensitivities.

[0060] In the analysis of the transfer function, the change in the effective refractive index of the material after applying voltages V1 and V2 can be incorporated into the transfer function expression of the ring resonator, allowing the resonant frequency to shift controllably with the applied voltage. By adjusting V1 and V2 respectively, one can switch between a large tuning range and fine-tuning with small steps, achieving precise electrical tunability of the corresponding ring resonator wavelength.

[0061] In the above embodiments, preferably, the electrically tunable cascaded micro-ring resonator is integrated into the resonant micro-optical gyroscope. The resonant micro-optical gyroscope includes a laser and a detector coupled to the electrically tunable cascaded micro-ring resonator. The input terminal is connected to the laser, and the detector is connected to the output terminal. The electrically tunable cascaded micro-ring resonator is used to lock the output center frequency of the laser by electrically tuning its resonant wavelength.

[0062] In one specific implementation, electrically adjustable cascaded micro-ring resonators are integrated into a resonant micro-optical gyroscope system.

[0063] The resonant micro-optical gyroscope includes a laser and a detector. The output of the laser is connected to the input of a micro-ring resonator (one end of the first bidirectional transmission waveguide 1) via an optical fiber or an on-chip waveguide. The input of the detector is connected to the output of the micro-ring resonator (one end of the second bidirectional transmission waveguide 2). The micro-ring resonator and the laser can form a heterodyne structure. By adjusting the control voltage applied to the first and second modulation electrode groups, the resonant wavelength of the micro-ring resonator is matched with the output center frequency of the laser, thus achieving locking of the laser's output center frequency.

[0064] During the operation of the gyroscope, the first modulation electrode group can be used in conjunction with the perturbation voltage to search for the resonance peak, and the second modulation electrode group can be used in conjunction with the closed-loop control voltage to lock the resonance point. This replaces the traditional scheme of using a tunable laser to adjust the output wavelength in the resonant micro-optical gyroscope, reduces system complexity, improves the stability and measurement accuracy of resonance peak locking, realizes high-precision sensing and signal demodulation of the gyroscope effect, and facilitates resonance peak search and closed-loop locking control.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrically adjustable cascaded microring resonator, characterized in that, include: Signal transmission waveguide, cascaded ring resonant cavity and independent electrodes; The signal transmission waveguide includes a first bidirectional transmission waveguide and a second bidirectional transmission waveguide, and the cascaded ring resonant cavity includes a first ring resonant cavity and a second ring resonant cavity that form a cascaded structure. The independent electrode is disposed on the modulation region corresponding to the cascaded ring resonant cavity. The independent electrode includes a first modulation electrode group and a second modulation electrode group. The first modulation electrode group includes a first positive electrode and a first ground electrode. The second modulation electrode group includes a second positive electrode and a second ground electrode. The electrode spacing between the first positive electrode and the first ground electrode is smaller than the electrode spacing between the second positive electrode and the second ground electrode. The signal transmission waveguide and the cascaded ring resonator, as well as the first ring resonator and the second ring resonator, are all connected through a micro-ring coupling region.

2. The electrically adjustable cascaded microring resonator according to claim 1, characterized in that, One of the first bidirectional transmission waveguide and the second bidirectional transmission waveguide serves as the input end of the optical signal, and the other serves as the output end of the optical signal. The optical signal is sequentially coupled into the first ring resonant cavity and the second ring resonant cavity through the micro-ring coupling region and then output from the output end. The cascaded ring resonant cavity is configured to perform resonant filtering on a specific wavelength component of the optical signal from the input end that meets a preset resonance condition, so as to suppress the transmission of the specific wavelength component at the output end, and the optical signal that does not meet the preset resonance condition is directly output from the output end along the signal transmission waveguide.

3. The electrically adjustable cascaded microring resonator according to claim 2, characterized in that, The modulation region corresponding to the cascaded ring resonant cavity includes a first modulation region and a second modulation region. The first modulation region is located in the region corresponding to the first modulation electrode group, and the second modulation region is located in the region corresponding to the second modulation electrode group. When the optical signal is transmitted in the cascaded ring resonant cavity, it passes through the first modulation region and the second modulation region in sequence.

4. The electrically adjustable cascaded microring resonator according to claim 1, characterized in that, The cavity lengths of the first and second annular resonant cavities are designed to ensure that the cascaded annular resonant cavities have a preset free spectral range in the target operating band.

5. The electrically adjustable cascaded microring resonator according to claim 4, characterized in that, The cavity lengths of the first and second ring resonant cavities are both 1108 μm, so that the free spectral range of the cascaded ring resonant cavities in the target operating band is greater than 1 nm.

6. The electrically adjustable cascaded microring resonator according to claim 1, characterized in that, The signal transmission waveguide and the main bodies of the first and second annular resonant cavities are made of a material with an electro-optic effect, wherein the material is selected from at least one of lithium niobate, gallium arsenide, indium phosphide and electro-optic polymers.

7. The electrically adjustable cascaded microring resonator according to claim 6, characterized in that, The signal transmission waveguide and the main bodies of the first and second annular resonant cavities are made of thin-film lithium niobate, and the effective refractive index of the thin-film lithium niobate changes with the voltage applied to the first and second modulation electrode groups.

8. The electrically adjustable cascaded microring resonator according to claim 7, characterized in that, The first positive electrode, the first ground electrode, the second positive electrode, and the second ground electrode are made of gold material, and a silicon dioxide buffer layer is disposed between the gold electrode and the waveguide body of thin-film lithium niobate.

9. The electrically adjustable cascaded microring resonator according to claim 7, characterized in that, The first modulation electrode group and / or the second modulation electrode group are used to apply a control voltage to the waveguide segment corresponding to the annular resonant cavity to form a modulation electric field in the region, thereby changing the effective refractive index of the corresponding annular resonant cavity by utilizing the electro-optic effect, thereby achieving electrical tunability of the resonant wavelength of the corresponding annular resonant cavity.

10. The electrically adjustable cascaded microring resonator according to claim 2, characterized in that, The electrically tunable cascaded micro-ring resonator is integrated into a resonant micro-optical gyroscope. The resonant micro-optical gyroscope includes a laser and a detector coupled to the electrically tunable cascaded micro-ring resonator. The input terminal is connected to the laser, and the detector is connected to the output terminal. The electrically tunable cascaded micro-ring resonator is used to lock the output center frequency of the laser by electrically tuning its resonant wavelength.

Images