A radio frequency comb generator, method of manufacture and signal generation method
By constructing a resonant cavity structure and a two-dimensional material diaphragm on a silicon substrate, and combining electrical parameter excitation and direct optical drive, the problems of high power consumption and low integration of existing RF frequency comb solutions are solved, realizing low power consumption and large comb tooth pitch RF frequency comb output, which is suitable for a variety of on-chip applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SICHUAN UNIV
- Filing Date
- 2026-04-13
- Publication Date
- 2026-07-14
AI Technical Summary
Existing RF frequency comb solutions suffer from problems such as large device size, high driving voltage, high power consumption, complex systems, and insufficient compatibility with on-chip processes, making it difficult to meet the application requirements of low power consumption, large comb tooth spacing, and high integration.
A resonant cavity structure built on a silicon substrate is adopted, combined with a two-dimensional material diaphragm and an electrical parameter excitation circuit. The parameter excitation is provided by electrical drive, and the direct optical drive unit provides direct drive. The mechanical resonance of the two-dimensional material diaphragm is used to generate an RF frequency comb signal, and the signal is analyzed by a readout circuit.
It achieves low power consumption, large comb tooth spacing, and high integration of RF frequency comb output, and is suitable for applications such as on-chip frequency synthesis, on-chip multi-frequency local oscillator source, microwave signal source and radar front-end frequency scale.
Smart Images
Figure CN122380290A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of radio frequency microwave signal source technology, specifically a radio frequency comb generator, its preparation method, and its signal generation method. Background Technology
[0002] A radio frequency (RF) frequency comb is a signal source that appears as a set of equally spaced spectral lines in the frequency domain. It can simultaneously provide multiple coherent frequency components and has significant application value in scenarios such as on-chip frequency synthesis, microwave communication, radar front-end, time and frequency references, and multi-tone testing. Compared with traditional single-frequency oscillators, RF frequency combs can provide multiple frequency components in a single device, which helps to improve the system's spectrum utilization efficiency, reduce the hardware complexity of multi-channel systems, and enhance functional integration.
[0003] In current practical applications, RF frequency combs can serve as multi-frequency local oscillator sources, providing multiple coherent reference signals for multi-channel transceivers, parallel frequency conversion systems, and broadband test platforms. They can also function as frequency scales or calibration sources in radar systems for local oscillator calibration, frequency linearity monitoring, intermediate frequency link calibration, and multi-frequency echo testing. Furthermore, they can be used for multi-tone response testing of integrated communication chips and RF front-end modules, in-band and out-of-band characteristic measurement of filters, mixer intermodulation testing, and amplifier linearity characterization. Therefore, developing RF frequency comb generators with low power consumption, small size, large comb tooth pitch, and easy integration has clear engineering application value.
[0004] Existing RF frequency comb solutions mostly rely on mode-locked lasers, microring resonators, strongly nonlinear electronic oscillation circuits, or bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices. These solutions generally suffer from large device size, high driving voltage, high power consumption, complex system structure, or insufficient compatibility with on-chip fabrication processes, making it difficult to simultaneously meet the application requirements of low power consumption, large comb tooth spacing, and high integration. These shortcomings are particularly pronounced in applications such as on-chip microwave signal sources, edge sensing nodes, portable test equipment, and high-density integrated radar front-ends.
[0005] Generating mechanical or electrical frequency combs using micro / nano electromechanical resonators is an important direction for realizing miniaturized on-chip frequency combs. However, when using direct electrostatic drive alone, the device typically requires a high drive amplitude to enter the significantly nonlinear operating region, which easily introduces coupling, additional losses, and extra power consumption, making it difficult to stably obtain tunable frequency comb output. If relying solely on optical drive, problems such as insufficient frequency tunability, inconvenient electrical interfaces, and difficulties in connecting with conventional on-chip readout circuits arise. Furthermore, existing solutions are often unclear in terms of the division of driving mechanisms, parameter adjustment paths, and practical testing implementation, which is not conducive to the rapid determination of the device's operating point and the promotion of engineering applications.
[0006] Therefore, there is an urgent need to propose a driving scheme that is logically clear, physically self-consistent, and practically feasible, so that the electric drive mainly undertakes the parameter excitation function, the optical drive mainly undertakes the direct driving function, and the parameter excitation amplitude can be adjusted by the voltage parameter, thereby achieving a stable, adjustable, easy-to-read, and suitable-for-on-chip RF frequency comb output under low power consumption conditions. Summary of the Invention
[0007] To address the shortcomings of the prior art, the technical problem to be solved by the embodiments of the present invention is to provide an RF frequency comb generator, a preparation method, and a signal generation method.
[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: An RF frequency comb generator includes: Silicon substrate; An insulating layer is disposed on the silicon substrate; A resonant cavity is formed in the insulating layer; A gate electrode is disposed at the bottom of the resonant cavity; The source electrode and the drain electrode are disposed on both sides of the resonant cavity; A two-dimensional material diaphragm is connected between the source electrode and the drain electrode and suspended above the resonant cavity; An electrical parameter excitation circuit, connected to the gate electrode, is used to apply a DC bias voltage and an AC pump voltage between the gate electrode and the two-dimensional material diaphragm. A direct optical drive unit is used to apply intensity-modulated laser light to the two-dimensional material diaphragm.
[0009] The two-dimensional material diaphragm is a suspended membrane structure with fixed supports at both ends.
[0010] The two-dimensional material diaphragm is a molybdenum disulfide diaphragm.
[0011] The driving signal applied to the gate electrode by the electrical parameter excitation circuit is: ; Among them, V dc V is the DC bias voltage. ac AC pump voltage, t represents the AC pump angular frequency, and t represents time.
[0012] As a further improvement, a readout circuit is also included, which includes a transimpedance amplifier and a spectrum analysis module for converting the current signal output from the drain electrode into a voltage signal and performing spectrum transformation.
[0013] A method for fabricating an RF frequency comb generator, the method comprising the following steps: The silicon substrate is cleaned, and an insulating layer is formed by thermal oxidation. A resonant cavity is formed in the insulating layer by photolithography and etching. A source electrode and a drain electrode are fabricated on the surface of the insulating layer, such that the source electrode and the drain electrode are located on both sides of the resonant cavity. A gate electrode is fabricated on the surface of an insulating layer within the resonant cavity; A two-dimensional material thin film is transferred onto the source electrode and the drain electrode, and the two-dimensional material thin film is patterned to form a two-dimensional material diaphragm. Release the two-dimensional material diaphragm, suspend it above the resonant cavity, and then encapsulate it.
[0014] As a further improvement: the gate electrode, source electrode, and drain electrode are prepared by electron beam evaporation or magnetron sputtering, and the electrode pattern is formed by a stripping process.
[0015] As a further improvement, the resonant cavity is formed by photolithography and reactive ion etching.
[0016] A signal generation method for an RF frequency comb generator includes the following steps: A DC bias voltage is applied to the gate electrode, and the fundamental mode angular frequency of the two-dimensional material diaphragm is measured. An AC pump voltage is superimposed on the DC bias voltage, and the modulation angular frequency of the AC pump voltage satisfies the following equation: ,and , to form parametric excitation, where ω0 is the fundamental mode angular frequency of the two-dimensional material diaphragm; The modulation angular frequency of the AC pump voltage; The frequency detuning of the parameter excitation is small; An intensity-modulated laser is applied to the two-dimensional material diaphragm using a direct optical drive unit, and the modulation angular frequency of the intensity-modulated laser satisfies the following equation: , , where ω s The modulation angular frequency of the intensity-modulated laser; To minimize frequency detuning of the optical drive; Adjust the DC bias voltage, the AC pump voltage, and the corresponding modulation angular frequency to make the two-dimensional material diaphragm output an RF frequency comb signal; The signal output from the drain electrode is collected and analyzed to obtain the parameters of the radio frequency comb.
[0017] As a further improvement: the number of teeth of the radio frequency comb is controlled by adjusting the excitation amplitude of the parameter, and the tooth spacing of the radio frequency comb is controlled by adjusting the detuning amount.
[0018] Compared with the prior art, the beneficial effects of the present invention are: the electric drive is mainly responsible for parameter excitation, and the optical drive is mainly responsible for direct drive, with clear drive logic; the parameter excitation amplitude can be adjusted by voltage parameters, which facilitates quick finding of the operating point; the device has low power consumption, large comb tooth pitch, high integration and strong adjustability, and is suitable for applications such as on-chip frequency synthesis, on-chip multi-frequency local oscillator source, microwave signal source, radar front-end frequency scale and multi-tone testing. Attached Figure Description
[0019] Figure 1 An isometric view of a radio frequency comb generator; Figure 2 A plan view of a radio frequency comb generator; Figure 3 Figure (a) shows the parameter excitation amplitude F in an embodiment of the present invention. p With V dc and V ac (b) is a diagram showing the recommended operating points in an embodiment of the present invention. Figure 4 These are schematic diagrams of the time-domain and frequency-domain outputs of the frequency comb obtained under different driving conditions in embodiments of the present invention. All four figures are generated at α=0.028, γ=0.01, and F... s Given that ω = 0.041 and ω = 1.04395, (a) shows F. p =0.072, ω s The spectrum of F when = 0.0625, (b) is the time spectrum of F. p =0.06, ω s The spectral time spectrum when = 0.0625, Figure (c) shows the F-time spectrum. p =0.06, ω s The spectral time spectrum when F = 0.0495, (d) shows the F spectrum. p =0.06, ω s Spectral time plot at 1.0435; Figure 5 This is the photoelectric signal acquisition and spectrum analysis system in this embodiment of the invention; Figure 6 This is a plan view of the closed diaphragm resonator type radio frequency comb generator in an embodiment of the present invention; Figure 7 This is a plan view of the open tympanic membrane resonator type radio frequency comb generator in an embodiment of the present invention; In the figure: 1. Silicon substrate; 2. Insulating layer; 3. Resonant cavity; 4. Gate electrode; 5. Source electrode; 6. Drain electrode; 7. Two-dimensional material diaphragm; 8. Electrical parameter excitation circuit; 9. Direct optical drive unit. Detailed Implementation
[0020] The technical solution of this application will be further described in detail below with reference to specific embodiments.
[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0022] Please see Figure 1 , Figure 2 In one embodiment, a radio frequency comb generator includes: Silicon substrate 1; Insulating layer 2 is disposed on the silicon substrate 1; The resonant cavity 3 is formed in the insulating layer 2; The gate electrode 4 is disposed at the bottom of the resonant cavity 3; The source electrode 5 and the drain electrode 6 are disposed on both sides of the resonant cavity 3; A two-dimensional material diaphragm 7 is connected between the source electrode 5 and the drain electrode 6 and suspended above the resonant cavity 3; The electrical parameter excitation circuit 8 is connected to the gate electrode 4 and is used to apply a DC bias voltage and an AC pump voltage between the gate electrode 4 and the two-dimensional material diaphragm 7. The direct optical drive unit 9 is used to apply intensity-modulated laser light to the two-dimensional material diaphragm 7.
[0023] In this embodiment, the silicon substrate 1 serves as the supporting substrate for the device; the insulating layer 2 is disposed on the silicon substrate 1; the resonant cavity 3 is formed in the insulating layer 2; the gate electrode 4 is disposed at the bottom of the resonant cavity 3; the source electrode 5 and the drain electrode 6 are respectively disposed on the upper sides of the resonant cavity 3 and serve as the anchoring electrodes at both ends of the two-dimensional material diaphragm 7. The electrical parameter excitation circuit 8 is used to modulate the equivalent stiffness of the two-dimensional material diaphragm 7, thereby forming a parametric excitation. The optical direct drive unit 9 is used to apply intensity-modulated laser light to the two-dimensional material diaphragm 7, causing the two-dimensional material diaphragm 7 to generate direct drive.
[0024] Compared to traditional silicon-based resonators, two-dimensional materials such as MoS2 possess advantages such as low areal density, high Young's modulus, fast mechanical response, ease of obtaining high-frequency resonance characteristics, and significant photothermal coupling effects, making them more suitable for constructing high-frequency, low-power, and easily tunable nanoelectromechanical resonators. Furthermore, two-dimensional material devices can typically be fabricated using silicon substrates, metal electrodes, insulating layers, and conventional micro / nano fabrication processes, providing a solid foundation for device miniaturization, arraying, and on-chip integration. Therefore, they hold promising application prospects in RF signal sources, tunable micro / nano devices, and on-chip test modules.
[0025] The silicon substrate 1 is preferably a 4-inch single-crystal silicon wafer; the insulating layer 2 is preferably a silicon dioxide layer formed by thermal oxidation, and the thickness is preferably 300 nm.
[0026] Please see Figure 1 , Figure 2 In one embodiment, the two-dimensional material diaphragm 7 is a suspended membrane structure with fixed supports at both ends.
[0027] In this embodiment, the two-dimensional material diaphragm 7 is connected between the source electrode 5 and the drain electrode 6, and the part of it that spans the resonant cavity 3 constitutes the effective vibration zone, thereby forming a double-ended fixed-support suspension membrane structure.
[0028] Please see Figure 1 , Figure 2 In one embodiment, the two-dimensional material diaphragm 7 is a molybdenum disulfide diaphragm.
[0029] In this embodiment, the two-dimensional material diaphragm 7 is a multilayer MoS2 diaphragm; preferably, it is a 10-layer MoS2 diaphragm; the overall length of the MoS2 diaphragm is 3 μm, the width is 2 μm, the thickness is 6.5 nm, the density is 5060 kg / m³, the Young's modulus is 270 GPa, and the initial pretension is 0.1 GPa.
[0030] The depth of the resonant cavity 3 is 200–500 nm, preferably 300 nm.
[0031] Due to the low surface density and excellent mechanical properties of the MoS2 diaphragm, it can achieve a high fundamental mode frequency with low drive power consumption, providing a structural basis for the generation of large-pitch RF frequency combs.
[0032] The direct optical drive unit 9 includes a laser, a microscope objective, and an electro-optic modulator. The laser emits a circular laser beam directly above the MoS2 diaphragm. The electro-optic modulator modulates the laser intensity to produce an output intensity-modulated light signal. Where P(t) represents the instantaneous optical power applied by the laser to the MoS2 diaphragm, P0 represents the DC component of the optical power, P1 represents the amplitude of the AC optical power, and ω sThe intensity-modulated laser is set to its modulation angular frequency, and t is the time for applying the optical drive. The modulated laser spot is then focused onto the central region of the MoS2 diaphragm using a microscope objective, forming an intensity-modulated optical signal drive. The optical signal generates photothermal and thermal tension changes in the MoS2 diaphragm, thus forming a direct drive.
[0033] The wavelength of the laser output by the laser is 405–1064 nm, preferably 532 nm.
[0034] In one embodiment, the driving signal applied by the electrical parameter excitation circuit 8 to the gate electrode 4 through the bias circuit is: ; Among them, V dc V is the DC bias voltage. ac Ω represents the AC pump voltage, t represents the AC pump angular frequency, and t represents time. The equivalent stiffness of the MoS2 diaphragm is used to periodically modulate the parametric excitation term.
[0035] In this embodiment, the dynamics of the generator can be described by the parametric excitation Duffing equation. When electrical parametric excitation and direct optical drive work together, the equivalent vibration equation of the system can be written as: ; In the formula, x is the displacement of the MoS2 diaphragm, m is the equivalent mass of the MoS2 diaphragm, c is the damping coefficient, k is the linear stiffness coefficient, k3 is the nonlinear stiffness coefficient, and K p For the parameter pump intensity, K is the pump angular frequency. s For the direct driving force amplitude, To directly drive the angular frequency, Let be the initial phase. After frequency and amplitude normalization, the above equation can be written as: ; In the formula, γ is the normalized damping ratio, α is the normalized nonlinear coefficient, and F p F is the normalized excitation amplitude parameter. s ω is the normalized direct driving force amplitude, and ω is the normalized pump frequency. s The normalized direct drive frequency is defined by the above model. It can be seen that the parameter pump term is responsible for injecting energy into the system and triggering parameter resonance, while the optical direct drive term determines the response and frequency tuning near the center frequency during comb formation.
[0036] The electrostatic force corresponding to the electrical parameter excitation can be expressed as: ; ; in, The vacuum permittivity, Let S be the relative permittivity, S be the effective overlap area, g be the depth of the resonant cavity 3 between the etched insulating layer 2 and the MoS2 diaphragm, denoted as the cavity gap, and x be the displacement of the MoS2 diaphragm. Under the condition that x is much smaller than g, for... Expanding Taylor's equations, we get: ; As can be seen from the formula, C is related to the vacuum permittivity. Relative permittivity The effective overlapping area S and cavity depth g are related, and F is related to C and V. ac V dc F is related to the stiffness modulation term F in electrostatic force. p cos(2ωt) are equal, thus the parameter excitation amplitude F is obtained. p By DC bias voltage V dc AC pump voltage V ac The resonant cavity gap g, the effective overlap area S, and the relative permittivity A joint decision.
[0037] By adjusting V dc and V ac It can achieve rapid electrical control of the amplitude of parameter excitation.
[0038] In one embodiment, a readout circuit is further included, which includes a transimpedance amplifier and a spectrum analysis module for converting the current signal output by the drain electrode 6 into a voltage signal and performing spectrum transformation.
[0039] In this embodiment, the readout circuit includes a transimpedance amplifier and a spectrum analysis module, which are used to acquire the current signal or voltage signal output by the drain electrode 6, and obtain the center frequency, tooth spacing, number of teeth and output amplitude of the radio frequency comb through fast Fourier transform.
[0040] The present invention also provides a method for manufacturing an radio frequency comb generator, comprising the following steps: The silicon substrate 1 is cleaned, and an insulating layer 2 is formed by thermal oxidation. A source electrode 5 and a drain electrode 6 are prepared on the surface of the insulating layer 2. The source electrode 5 and the drain electrode 6 have the same shape, each including a long strip electrode and a square electrode located at its rear end. A resonant cavity 3 is formed in the insulating layer 2 using photolithography and etching processes, such that the source electrode 5 and the drain electrode 6 are located on both sides of the resonant cavity 3; the resonant cavity 3 includes an elongated cavity and a square cavity located at its front end; Then, a gate electrode 4 is fabricated on the surface of the insulating layer 2 inside the resonant cavity 3; A two-dimensional material thin film is transferred onto the long strip electrodes of the source electrode 5 and the drain electrode 6, and the two-dimensional material thin film is patterned to form a two-dimensional material diaphragm 7. Release the two-dimensional material diaphragm 7 and suspend it above the elongated cavity of the resonant cavity 3 for encapsulation.
[0041] The gate electrode 4, source electrode 5, and drain electrode 6 are prepared by electron beam evaporation or magnetron sputtering, and the electrode patterns are formed by a stripping process.
[0042] The resonant cavity 3 is formed by photolithography and reactive ion etching.
[0043] In this embodiment, the silicon substrate 1 is cleaned using the RCA process, and a 300 nm thick silicon dioxide insulating layer is formed by thermal oxidation at approximately 1000°C. Then, a resonant cavity 3 is formed in the silicon dioxide insulating layer by photolithography and reactive ion etching. The gate electrode 4, source electrode 5, and drain electrode 6 are fabricated at the desired positions on the surface of the insulating layer 2 by electron beam evaporation or magnetron sputtering. The electrode material is preferably Au, and the electrode pattern is formed by a lift-off process.
[0044] A multilayer MoS2 thin film was transferred to the device surface using a PMMA-assisted transfer process. The PMMA was then removed by immersion in acetone, followed by isopropanol cleaning and nitrogen drying. Next, the MoS2 diaphragm pattern was defined using electron beam lithography, and excess MoS2 was removed by oxygen plasma etching to form a precise double-ended support structure. The suspended MoS2 diaphragm was released using a critical point drying method. The diaphragm was then annealed at 200-300°C for 2-4 hours in an inert atmosphere to remove residues, improve contact, and stabilize pretension. Finally, wire bonding was completed, and a packaging structure with a transparent window was adopted to facilitate subsequent laser irradiation.
[0045] The present invention also provides a signal generation method for an RF frequency comb generator, the signal generation method specifically including the following steps: A small-signal sweeping AC signal and a DC bias voltage are applied together to the gate electrode 4, driving the two-dimensional material diaphragm 7 to vibrate under electrostatic force. Signal detection is performed through the source electrode 5-drain electrode 6 path of the two-dimensional material diaphragm 7. With a constant bias voltage applied to the source electrode 5 and the drain electrode 6 grounded, the frequency of the AC signal applied to the gate electrode 4 is scanned point by point (i.e., frequency point by frequency). When the angular frequency of the sweeping signal is equal to the fundamental mode angular frequency ω0 of the two-dimensional material diaphragm 7, the diaphragm undergoes mechanical resonance. Its vibration modulates the channel carrier concentration through the field effect, causing the current I between the source and drain electrodes to... DS The AC component exhibits a significant resonant peak. The frequency corresponding to this current peak is recorded, which is the fundamental mode angular frequency ω0 of the two-dimensional material diaphragm 7.
[0046] An AC pump voltage is superimposed on the DC bias voltage, and the angular frequency of the AC pump voltage satisfies the following equation: ,and This is used to generate parametric excitation, where ω0 is the fundamental mode angular frequency of the two-dimensional material diaphragm 7. The modulation angular frequency of the AC pump voltage. To minimize frequency detuning of the parameter excitation, an intensity-modulated laser is applied to the two-dimensional material diaphragm 7 using a direct optical drive unit 9. The modulation angular frequency of the intensity-modulated laser satisfies the following equation: , Where ω0 is the fundamental mode angular frequency of the two-dimensional material diaphragm 7, ω s The modulation angular frequency of the intensity-modulated laser. To minimize frequency detuning of the optical drive; Adjust the DC bias voltage, the AC pump voltage, and the modulation angular frequency to make the two-dimensional material diaphragm 7 enter the parameter instability region and output an RF frequency comb signal; The signal output from the drain electrode 6 is collected and analyzed to obtain the parameters of the radio frequency comb.
[0047] In this embodiment, the output signal of the drain electrode 6 is acquired and its spectrum is transformed using a readout circuit to obtain the center frequency of the frequency comb, the spacing between the comb teeth, the number of comb teeth, and the output amplitude.
[0048] In one embodiment, the number of teeth of the radio frequency comb is controlled by adjusting the excitation amplitude of the parameter, and the tooth spacing of the radio frequency comb is controlled by adjusting the detuning amount.
[0049] In this embodiment, when the parameter excitation amplitude F p When F is between 0.06 and 0.10, a identifiable frequency comb can be formed; when F... p When the value is close to 0.072, a larger and more stable comb output can be obtained. This can be achieved by increasing F... p It can increase the number of comb teeth, and the spacing between comb teeth can be changed by adjusting the detuning amount δ.
[0050] By adjusting the excitation amplitude F p and detuning It can adjust the number of comb teeth and the spacing between them, with the number of comb teeth mainly controlled by the excitation amplitude F. p The spacing between the comb teeth is mainly controlled by the detuning amount δ.
[0051] During operation, the signal input terminal of the lock-in amplifier is first connected to the source electrode 5-drain electrode 6 path to acquire the AC current signal generated by the diaphragm vibration modulation. The reference input terminal of the lock-in amplifier is connected to the drive signal source of the gate electrode 4 to provide a reference clock with the same frequency as the drive signal. A DC bias and a small-signal sweep frequency AC signal are applied to the gate electrode 4 to drive the two-dimensional material diaphragm 7 to vibrate. At the same time, a constant bias voltage is applied to the source electrode 5 and the drain electrode 6 is grounded. The source and drain AC current signals are acquired through the lock-in amplifier, and the resonant peak value is extracted to obtain the fundamental mode angular frequency ω0 of the diaphragm. Subsequently, the parameter pump angular frequency is... Adjust to around 2ω0 and gradually increase V. dc and V ac This causes the device to enter the parameter instability region; the direct optical drive unit 9 consists of a laser, a microscope objective, and an electro-optic modulator. It uses a continuous laser as the light source and utilizes the electro-optic modulator EOM to modulate the intensity and frequency of the output light. By adjusting the frequency of the radio frequency signal applied to the EOM, the direct optical drive angular frequency is precisely controlled. Regulation to Nearby, by controlling the detuning amount A stable, equally spaced frequency comb was obtained.
[0052] When the excitation amplitude F p As the voltage increases, the system's energy injection rate rises, and the number of visible teeth on the frequency comb increases; when the detuning factor δ changes, the tooth spacing changes accordingly. Therefore, it is possible to determine the frequency by increasing the voltage V. dc and V ac By controlling the number of comb teeth and controlling the spacing between the comb teeth via δ, the frequency comb output can be decoupled and adjusted.
[0053] Performance testing of the resulting frequency comb: During testing, the drain electrode 6 can be grounded on the microprobe stage, the source electrode 5 can be connected to the transimpedance amplifier and the spectrum analysis module, and the gate electrode 4 can be connected to the DC source and the function generator through the bias. At the same time, the 532 nm laser is modulated in intensity and frequency by an acousto-optic modulator and then focused onto the center of the MoS2 diaphragm through the microscope objective to achieve direct optical drive.
[0054] During the operation, a network analyzer or lock-in amplifier is first used to perform a small-signal frequency sweep on the device to obtain the fundamental mode angular frequency ω0, and then... Adjust to around 2ω0 and gradually increase V. dc and V ac This causes the device to enter the parameter instability region; finally, ω s By adjusting to near ω0, a stable equidistant frequency comb can be obtained by controlling the detuning amount.
[0055] like Figure 4As shown, in a set of normalized numerical simulations, the direct drive amplitude F can be taken as... s =0.041, normalized damping ratio γ=0.01, nonlinear coefficient α=0.028, normalized natural frequency ω0=1.04395, and the parameter excitation amplitude F is also examined. p and direct driving angular frequency ω s The effect on the spectrum. Simulation results show that when ω s =1.0625 and F p When ω = 0.072, approximately 23 stable visible comb teeth can be obtained; when ω is maintained... s =1.0625 and F p When the value is reduced to 0.06, the number of comb teeth decreases to approximately 5, indicating that F... p It mainly determines the number of comb teeth and the ability to resist interference.
[0056] In another set of simulations, when F p When fixed at 0.06, change ω s It will change the comb tooth spacing and spectral purity. When ω s When ω = 1.0495, the mistuning is 0.00555, corresponding to a comb tooth pitch of approximately 0.0111; when ω s When the amplitude is 1.0435, the detuning is -0.00045, and many stray frequencies will appear in the system, making it possible to identify only a single dominant frequency comb. The above results indicate that the pump amplitude F... p The number of comb teeth is determined by controlling the energy injection rate, while the detuning is determined by adjusting the phase matching conditions to determine the comb tooth spacing and spectral purity. The synergistic optimization of these two factors is key to achieving a frequency comb with large comb tooth spacing and high spectral purity.
[0057] like Figure 3 As shown, from the perspective of the electrical control relationship of the parameter excitation amplitude, in =8.85×10 -12 , Under the conditions of 4.5 g / nm and 300 nm, V can be adjusted in combination. dc and V ac Change F p When F p When the operating range is between 0.06 and 0.10, a identifiable frequency comb can be formed; when F p When the value approaches 0.072, the number of comb teeth reaches a relatively large value, making it suitable for use as a clock or multi-frequency reference signal output. Preferably, under the conditions of a MoS2 diaphragm size of 3 μm × 2 μm × 6.5 nm, a resonant cavity depth of 300 nm, and an initial pretension of 0.1 GPa, the DC bias voltage V... dc Set to 2.35 V, AC pump voltage V acSetting it to 500 mV yields a value close to F. p The recommended operating point is 0.072.
[0058] Theoretical estimation methods for device power consumption: The power consumption of this device mainly originates from the dynamic power consumption of the nanoparallel plate capacitor during the electrical parameter excitation stage, rather than the significant static Joule heat dissipation found in traditional devices. It can be approximated using the following formula: ; In the formula, f is the pump frequency, which is ω mentioned earlier, typically in the MHz range; V is the effective driving voltage; and C is the nanometer gap capacitance formed between the gate electrode 4 and the MoS2 diaphragm, which can be in the femtofarad range. dc =2.35 V, V ac With a voltage of 0.5 V and an effective driving voltage of approximately 2.85 V, the dynamic power consumption can be estimated to be in the microwatt range, based on device energy loss estimates. Since the direct optical drive section uses non-contact coupling, its core resonator experiences lower additional energy loss, thus the overall system is conducive to achieving low-power operation.
[0059] In actual debugging, you can first fix it. Then fine-tune ω s The laser power is used to obtain the desired comb center frequency, comb tooth spacing, and output amplitude. Therefore, this invention not only has a clear device fabrication path but also a clear operating point search method and an operable experimental procedure.
[0060] Figure 5 shows the system architecture for signal detection and spectrum analysis of a two-dimensional nanoelectromechanical resonator-type RF frequency comb generator driven by optoelectronic composite drive according to the present invention. In this embodiment, after determining the system constant k, a recommended operating point is set based on simulation data and experimental requirements, specifically selecting F... p =0.072 is used as the core control indicator. The system workflow is as follows: First, the electrical parameter excitation signal source provides a DC bias voltage V. dc With AC excitation voltage V ac The laser unit is used to perform photoelectric coordinated excitation of the MoS2 frequency comb generator, at V dc Approximately 2.15V-2.55V and V ac A high-quality frequency comb signal is generated within the recommended parameter range of approximately 300mV-900mV. Subsequently, the source-drain current Ids of the readout circuit is acquired. The signal is then pre-amplified by a transimpedance amplifier (TIA), filtered by a low-pass filter to remove high-frequency noise, and converted from analog to digital by an ADC module. Finally, the digitized signal is processed by an FFT spectrum analysis module, ultimately outputting a spectrum signal containing both visible and weak comb tooth characteristics, achieving a precise characterization of the frequency comb's performance.
[0061] Please see Figure 6 In one embodiment, the resonant cavity 3 can also be a closed tympanic membrane cavity, in which a conductive gate plate with the same shape as the tympanic membrane cavity is placed, forming the cavity structure of a closed tympanic membrane resonator type radio frequency comb generator. Its basic motion law is consistent with that of the above-mentioned double-ended fixed strip film, and both can be uniformly described by the thin film small deflection vibration equation. Under simple harmonic excitation, they have similar motion laws, modal distributions and frequency response characteristics.
[0062] In this embodiment, the tympanic membrane is a fully fixed and enclosed film, and both cavities are sealed structures, accompanied by gas compression and expansion effects during vibration. Theoretical calculations based on structural dimensions, membrane stiffness, and cavity volume show that its damping is mainly composed of structural damping and enclosed gas damping.
[0063] Please see Figure 7 In one embodiment, the resonant cavity 3 can also be an open tympanic cavity, in which a conductive gate plate with the same shape as the tympanic cavity is placed, forming the cavity structure of an open tympanic resonator type radio frequency comb generator. The tympanic membrane is vibrated by an electric drive and an optical drive, and the vibration is detected and converted into an electrical signal to analyze the frequency comb phenomenon. The basic vibration laws are basically the same and can be described by the same equation of motion. The thin film bending deformation and dynamic response are similar.
[0064] The key difference from a closed tympanic cavity is that the cavity in this embodiment is connected to the outside, allowing gas to flow freely without significant gas compression. Theoretical modeling and numerical calculations show that its damping is primarily fluid shear damping and flow damping, with completely different damping structures and mechanisms. Furthermore, due to differences in membrane configuration, boundary constraints, and cavity flow conditions, the calculated damping values and frequency domain attenuation characteristics also exhibit significant differences.
[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.
[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A radio frequency comb generator, characterized in that, include: Silicon substrate; An insulating layer is disposed on the silicon substrate; A resonant cavity is formed in the insulating layer; A gate electrode is disposed at the bottom of the resonant cavity; The source electrode and the drain electrode are disposed on both sides of the resonant cavity; A two-dimensional material diaphragm is connected between the source electrode and the drain electrode and suspended above the resonant cavity; An electrical parameter excitation circuit, connected to the gate electrode, is used to apply a DC bias voltage and an AC pump voltage between the gate electrode and the two-dimensional material diaphragm. A direct optical drive unit is used to apply intensity-modulated laser light to the two-dimensional material diaphragm.
2. The radio frequency comb generator according to claim 1, characterized in that, The two-dimensional material diaphragm is a suspended membrane structure with fixed supports at both ends.
3. The radio frequency comb generator according to claim 2, characterized in that, The two-dimensional material diaphragm is a molybdenum disulfide diaphragm.
4. The radio frequency comb generator according to claim 1, characterized in that, The driving signal applied to the gate electrode by the electrical parameter excitation circuit is: ； Among them, V dc V is the DC bias voltage. ac AC pump voltage, t represents the AC pump angular frequency, and t represents time.
5. The radio frequency comb generator according to claim 4, characterized in that, It also includes a readout circuit, which includes a transimpedance amplifier and a spectrum analysis module, used to convert the current signal output from the drain electrode into a voltage signal and perform spectrum transformation.
6. A method for manufacturing an radio frequency comb generator, characterized in that, The preparation method is used to prepare the radio frequency comb generator according to any one of claims 1-5, and includes the following steps: The silicon substrate is cleaned, and an insulating layer is formed by thermal oxidation. A resonant cavity is formed in the insulating layer by photolithography and etching. A source electrode and a drain electrode are fabricated on the surface of the insulating layer, such that the source electrode and the drain electrode are located on both sides of the resonant cavity. A gate electrode is fabricated on the surface of an insulating layer within the resonant cavity; A two-dimensional material thin film is transferred onto the source electrode and the drain electrode, and the two-dimensional material thin film is patterned to form a two-dimensional material diaphragm. Release the two-dimensional material diaphragm, suspend it above the resonant cavity, and then encapsulate it.
7. The method for preparing an RF frequency comb generator according to claim 6, characterized in that, The gate electrode, source electrode, and drain electrode are prepared by electron beam evaporation or magnetron sputtering, and the electrode patterns are formed by a stripping process.
8. The method for preparing an RF frequency comb generator according to claim 6, characterized in that, The resonant cavity is formed by photolithography and reactive ion etching.
9. A signal generation method for an radio frequency comb generator, characterized in that, The signal generation method is implemented based on the radio frequency comb generator according to any one of claims 1-5, and the signal generation method specifically includes the following steps: A DC bias voltage is applied to the gate electrode, and the fundamental mode angular frequency of the two-dimensional material diaphragm is measured. An AC pump voltage is superimposed on the DC bias voltage, and the modulation angular frequency of the AC pump voltage satisfies the following equation: ,and , to form parametric excitation, where ω0 is the fundamental mode angular frequency of the two-dimensional material diaphragm; The modulation angular frequency of the AC pump voltage; The frequency detuning of the parameter excitation is small; An intensity-modulated laser is applied to the two-dimensional material diaphragm using a direct optical drive unit, and the modulation angular frequency of the intensity-modulated laser satisfies the following equation: , , where ω s The modulation angular frequency of the intensity-modulated laser; To minimize frequency detuning of the optical drive; Adjust the DC bias voltage, the AC pump voltage, and the corresponding modulation angular frequency to make the two-dimensional material diaphragm output an RF frequency comb signal; The signal output from the drain electrode is collected and analyzed to obtain the parameters of the radio frequency comb.
10. The signal generation method of an RF frequency comb generator according to claim 9, characterized in that, The number of teeth in the radio frequency comb is controlled by adjusting the excitation amplitude, and the tooth spacing is controlled by adjusting the detuning.