A method for generating narrow-linewidth microwave signals based on all-optical mutual injection of semiconductor lasers

Abstract

This invention discloses a method for generating narrow-linewidth microwave signals based on all-optical mutual-injection semiconductor lasers, comprising the following steps: two distributed feedback lasers are mutually injected and coupled through free space; wherein the distributed feedback lasers do not have isolators; by adjusting the driving current and temperature of the two distributed feedback lasers, a frequency difference is generated between them, thereby generating a narrow-linewidth microwave signal; the coupling strength and coupling phase are controlled according to the narrow-linewidth microwave signal to make the distributed feedback lasers operate in the P1 state, thereby generating a stable narrow-linewidth microwave signal. This invention improves signal quality while reducing system cost and solves the problem of phase and polarization mismatch during optical fiber transmission.

Description

Technical Field

[0001] This invention belongs to the field of microwave signal technology, and particularly relates to a method for generating narrow linewidth microwave signals based on an all-optical inter-injection semiconductor laser. Background Technology

[0002] In recent years, high-frequency millimeter-wave signals have gradually become one of the key technologies in various fields such as communications, networking, military, and medicine due to their broad application prospects. Especially in 5G communications, radar detection, high-precision positioning, and imaging technologies, millimeter-wave signals have attracted widespread attention because they offer greater bandwidth and stronger penetration capabilities. However, traditional millimeter-wave signal generation methods, such as gyroscopes, electronic oscillators, and crystal oscillators, while meeting technical requirements to some extent, still have significant shortcomings in terms of high frequency, high power output, and signal stability. Specifically, the operating frequency of these electrical methods is limited by the bandwidth of the electronic devices, and they also suffer from significant power loss and poor system stability.

[0003] To overcome these limitations, methods for generating microwave signals using optical technology have been widely researched and applied in recent years. These technologies include optical heterodyne methods, external modulation methods, and photoelectric oscillators. These methods, through optical modulation and photoelectric conversion principles, can generate high-frequency signals and effectively avoid the limitations of traditional electrical methods. For example, the optical heterodyne method generates microwave signals with significant frequency differences by mixing two optical signals, overcoming the bandwidth limitations of traditional electronic devices and achieving advantages in frequency and power. Photoelectric oscillators, on the other hand, utilize frequency modulation of optical signals or external excitation to generate highly stable, low-noise microwave signals, and are widely used in high-precision measurement and high-speed communication.

[0004] While optoelectronic oscillator technology excels in generating high-quality microwave signals, its implementation inevitably relies on electro-optic modulation and photoelectric conversion. These processes are often limited by the performance of electronic components, thus affecting the system's stability and reliability. For example, during electro-optic modulation, the amplitude, phase, and frequency of the optical signal can be affected by fluctuations in modulator performance, leading to unstable signal quality. Therefore, despite the significant advantages of optoelectronic oscillators in terms of low noise and high frequency stability, they remain constrained by electronic limitations.

[0005] To effectively address the aforementioned issues, all-optical microwave signal generation technology has emerged as a crucial approach to overcoming traditional technological bottlenecks. This technology generates microwave signals entirely through optical means, eliminating the need for traditional electronic devices or photoelectric conversion processes, thus fundamentally avoiding the performance limitations imposed by electronic components. All-optical microwave signal generation technology not only overcomes the limitations of high-frequency microwave signal generation but also offers significant advantages in low power consumption, low noise, and high stability. Therefore, as a significant innovation in purely electrical or optoelectronic hybrid technologies, all-optical microwave signal generation technology provides an effective solution to the performance bottlenecks of electronic devices.

[0006] In technologies for generating all-optical microwave signals, DFB (distributed feedback) semiconductor lasers are widely used as the core light source. DFB lasers feature tunable wavelength, stable single-mode output, high power output, and strong anti-interference capabilities, making them ideal light sources for injection locking and all-optical microwave signal generation. Compared to traditional lasers, DFB lasers provide a more stable output signal, significantly improving the stability and anti-interference capabilities of microwave signals.

[0007] Currently, most common all-optical microwave signal generation methods employ a master laser injected into another laser via a unidirectional fiber optic path. However, this method has several significant drawbacks. First, unidirectional fiber injection easily leads to microwave signal instability, and its relatively large frequency linewidth cannot meet the requirements for high precision and stability. Second, the fiber optic structure is prone to introducing phase and polarization jitter, resulting in phase and polarization mismatch in the laser signal, thus affecting the quality of the final microwave signal. Furthermore, this fiber optic injection scheme typically requires the use of complex optical components such as circulators, leading to a complex system structure and high cost.

[0008] To address these issues, researchers have recently proposed novel mutual injection schemes, in which multiple lasers are mutually injected through sophisticated optical structures to stably generate all-optical microwave signals. While this scheme offers theoretical advantages, it still faces challenges in practical application, particularly in optical phase control, where phase and polarization mismatches remain unresolved during fiber optic transmission. Summary of the Invention

[0009] This invention proposes a method for generating narrow-linewidth microwave signals based on an all-optical inter-injection semiconductor laser to solve the problems existing in the prior art.

[0010] To achieve the above objectives, the present invention provides a method for generating narrow linewidth microwave signals based on an all-optical inter-injection semiconductor laser, comprising the following steps:

[0011] Two distributed feedback lasers are mutually injected and coupled through free space; the distributed feedback lasers do not have isolators.

[0012] By adjusting the driving current and temperature of two distributed feedback lasers, a frequency difference is generated between the two distributed feedback lasers, thereby producing a narrow linewidth microwave signal.

[0013] By controlling the coupling strength and coupling phase according to the narrow linewidth microwave signal, the distributed feedback laser operates in the P1 state, thereby generating a stable narrow linewidth microwave signal.

[0014] Preferably, controlling the coupling strength and coupling phase based on the narrow linewidth microwave signal includes:

[0015] The spectral and electrical spectrum data of narrow linewidth microwave signals are collected by a real-time monitoring and analysis system, and the coupling strength and coupling phase are controlled by the spectral and electrical spectrum data.

[0016] Preferably, the real-time monitoring and analysis system includes a spectrometer, an electric spectrometer, a frequency counter, a photodetector, and an electric amplifier.

[0017] Preferably, controlling the coupling strength includes adjusting the laser power using a gradient neutral density filter.

[0018] Preferably, controlling the coupling phase includes changing the phase of the standing wave injection by moving the distributed feedback laser at the nanoscale via a micro / nano platform.

[0019] Preferably, the spectra of the two distributed feedback semiconductor lasers are consistent within the 0.18 nm range.

[0020] Preferably, the wavelength of the distributed feedback semiconductor laser is 1550nm.

[0021] This invention also proposes a narrow-linewidth microwave signal generation device based on an all-optical inter-injection semiconductor laser, comprising:

[0022] Two distributed feedback semiconductor lasers with the same wavelength;

[0023] A laser beam splitter is used to split the output light of each distributed feedback semiconductor laser into two paths.

[0024] A gradient neutral density filter is used to adjust the optical power injected into another distributed feedback semiconductor laser, thereby controlling the coupling strength;

[0025] Micro-nano platforms are used to move distributed feedback semiconductor lasers at the nanoscale and change the phase of standing wave injection.

[0026] A collimator is used to receive and collimate the output light of a laser.

[0027] Optical fiber is used to transmit collimated optical signals.

[0028] A photodetector is used to convert optical signals into electrical signals;

[0029] An electrical amplifier is used to amplify electrical signals.

[0030] An electric spectrum analyzer is used to analyze the frequency characteristics of electrical signals.

[0031] A spectrometer is used to analyze the spectral characteristics of optical signals;

[0032] A laser driver platform used to control the current and temperature of the laser.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] This invention discloses a method for generating narrow-linewidth microwave signals based on all-optical mutual-injection semiconductor lasers, comprising the following steps: two distributed feedback lasers are mutually injected and coupled through free space; wherein the distributed feedback lasers do not have isolators; by adjusting the driving current and temperature of the two distributed feedback lasers, a frequency difference is generated between them, thereby generating a narrow-linewidth microwave signal; the coupling strength and coupling phase are controlled according to the narrow-linewidth microwave signal to make the distributed feedback lasers operate in the P1 state, thereby generating a stable narrow-linewidth microwave signal. This invention improves signal quality while reducing system cost and solves the problem of phase and polarization mismatch during optical fiber transmission. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of mutual injection of a distributed feedback semiconductor laser according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the principle of mutual injection for generating microwave signals according to an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the device according to an embodiment of the present invention;

[0039] Figure 4 The probability density diagram of microwave signals generated by different coupling phase matching degrees in embodiments of the present invention. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0042] Example 1

[0043] like Figure 1-2 As shown, this embodiment provides a method for generating narrow linewidth microwave signals based on an all-optical inter-injection semiconductor laser, including the following steps:

[0044] Two distributed feedback lasers are mutually injected and coupled through free space; the distributed feedback lasers do not have isolators.

[0045] By adjusting the driving current and temperature of two distributed feedback lasers, a frequency difference is generated between the two distributed feedback lasers, thereby producing a narrow linewidth microwave signal.

[0046] By controlling the coupling strength and coupling phase according to the narrow linewidth microwave signal, the distributed feedback laser operates in the P1 state, thereby generating a stable narrow linewidth microwave signal.

[0047] Furthermore, controlling the coupling strength and coupling phase based on the narrow linewidth microwave signal includes:

[0048] The spectral and electrical spectrum data of narrow linewidth microwave signals are collected by a real-time monitoring and analysis system, and the coupling strength and coupling phase are controlled by the spectral and electrical spectrum data.

[0049] Furthermore, the real-time monitoring and analysis system includes a spectrometer, an electric spectrometer, a frequency counter, a photodetector, and an electric amplifier.

[0050] Furthermore, controlling the coupling strength includes adjusting the laser power using a gradient neutral density filter.

[0051] Furthermore, controlling the coupling phase includes changing the phase of the standing wave injection by moving the distributed feedback laser at the nanoscale via a micro / nano platform.

[0052] Furthermore, the spectra of the two distributed feedback semiconductor lasers are consistent within the 0.18 nm range.

[0053] Furthermore, the wavelength of the distributed feedback semiconductor laser is 1550nm.

[0054] The principle of this invention is as follows:

[0055] Figure 1 A general model of mutual injection between two distributed feedback semiconductor lasers is presented. In this model, neither laser has an isolator and mutual injection coupling can be achieved through an optical fiber link, free space, or an integrated chip optical path. The dynamic characteristics of the mutually coupled lasers are studied by controlling the coupling strength κ, coupling phase ψ, and delay τ. A large number of nonlinear dynamic states can occur from the two unrelated main peaks, including mutual injection lock-in, P1 state, multi-period oscillation, four-wave mixing, and chaotic states involving photon-electron and photon-photon interactions. The advantage of using a free space mutual injection coupling system is that, compared to an optical fiber link, the laser output phase is stable and does not change due to fiber jitter, and compared to an integrated chip, its coupling parameters can be controlled by a single variable.

[0056] In this embodiment, the principle of generating microwave signals through mutual injection is mainly based on P1 oscillation and sideband modulation.

[0057] When LD1 is injected into LD2, by controlling the laser's drive current and temperature, and adjusting the appropriate frequency difference, a beat frequency signal will be generated. At this time, the mutually injected lasers operate in the P1 state, such as... Figure 2 As shown in (a), the beat frequency signal modulates the output light of the LD2, which manifests as a spectral shift in the frequency domain; the power gradually decreases as the sideband order increases. For example... Figure 2 (b). Similarly, the mutual injection structure is completely symmetrical, and the output light of LD1 is also frequency modulated, such as... Figure 2 (c) In this case, due to the change in damping factor at the relaxation resonance frequency enhancement caused by the photon-photon resonance effect, the oscillation is completely undamped. A gain region exists around the cavity mode, represented by the black curve. Any weak external optical modulation sideband, if it happens to be located in this region, will receive a significant power boost. Therefore, the first-order sideband of LD2 falling within the cavity mode gain region of LD1 will result in power boost; the first-order sideband of LD1 falling within the cavity mode gain region of LD2 will also result in power boost.

[0058] The specific implementation is as follows:

[0059] Two identical 1550nm distributed feedback semiconductor lasers without isolators, manufactured in the same batch, were selected to ensure parameter matching, as their spectra are consistent within the 0.18nm range. The output light from DFB-LD1 was split into two paths by a laser beam splitter (BS). One path, after a 3dBm attenuation due to transmission, was injected into DFB-LD2. The other path, after a similar 3dBm attenuation due to reflection, was received by a collimator and coupled into a single-mode fiber. Spectral and electrical spectrum data were then collected by a real-time monitoring and analysis system. Similarly, due to the symmetry of the mutual injection structure, the output light from DFB-LD2 was split into two paths by the laser beam splitter (BS). One path, after a 3dBm attenuation due to transmission, was injected into DFB-LD1. The other path, after a 3dBm attenuation due to reflection, was received by a collimator and coupled into a single-mode fiber. Data from these two paths were also observed and collected by a real-time monitoring and analysis system. The devices and instruments used in the real-time monitoring and analysis system of the experiment included: an OSA spectrometer (Anritsu MS9710C) with a resolution of 0.05 nm, an ESA spectrometer with a bandwidth of 40 GHz (Agilent 8564EC), a frequency counter (Keysight 53230A), a photodetector (PD), and an amplifier (EA). During the experiment, the laser's current and temperature were controlled by a laser driving platform (Gooch & Housego, EM595) to change the laser's free oscillation frequency and output power, with an accuracy of ±0.01 mA and ±0.01 °C. The coupling strength was adjusted by changing the laser power through a neutral density filter (NDF). A micro-nano platform (P66.X60S, repeatability: 0.05%) was controlled by a host computer to move the laser at the nanometer scale, thereby changing the phase of the standing wave injection. Since the distance between DFB-LD1 and DFB-LD2 is much larger than the movement range of the micro-nano platform, and the optical path length is 15 cm, the coupling time between the two lasers can be considered to be 0.5 ns.

[0060] The following experiments were conducted:

[0061] By adjusting the mounting frames housing the lasers, beam splitters, and collimators, all spatial optical paths are aligned to the same horizontal plane to achieve good coupling. Since the DFB laser's output light is linearly polarized, rotating the lasers on the mounting frames ensures consistent polarization. The current of LD1 is set to 50.7 mA, temperature to 24.97°C, and output power to 11.20 dBm; the current of LD2 is set to 40.0 mA, temperature to 24°C, and output power to 9.70 dBm. The filters are rotated to adjust the appropriate coupling strength, and the spectra and electrical spectra are observed in the real-time monitoring system. Keeping the spectral detuning Δf between the lasers constant, the coupling phase between the lasers is altered by moving LD2 within a wavelength range of 1550 nm.

[0062] The host computer controls the micro / nano platform to step at a distance of 155nm. For standing waves, the phase change is π / 5. Frequency values ​​are collected for 20 seconds at different coupling phases within one phase period. Since the beat frequency signal is a high-frequency signal, the frequency counter sampling principle is integration. The frequency counter gate value is adjusted to 10ms to make the collected data more accurate. Ten sets of frequency data under different coupling phase conditions are obtained, and the probability density distribution plots of the ten sets of data are obtained, as shown below. Figure 4 As shown, within the period, due to the influence of the coupling phase matching degree, the minimum 3dB linewidth of the beat frequency signal is 3.43MHz, which generates a narrow linewidth high-frequency microwave signal.

[0063] like Figure 3 As shown, this embodiment also proposes a narrow-linewidth microwave signal generation device based on an all-optical inter-injection semiconductor laser, comprising:

[0064] Two distributed feedback semiconductor lasers with the same wavelength;

[0065] A laser beam splitter is used to split the output light of each distributed feedback semiconductor laser into two paths.

[0066] A gradient neutral density filter is used to adjust the optical power injected into another distributed feedback semiconductor laser, thereby controlling the coupling strength;

[0067] Micro-nano platforms are used to move distributed feedback semiconductor lasers at the nanoscale and change the phase of standing wave injection.

[0068] A collimator is used to receive and collimate the output light of a laser.

[0069] Optical fiber is used to transmit collimated optical signals.

[0070] A photodetector is used to convert optical signals into electrical signals;

[0071] An electrical amplifier is used to amplify electrical signals.

[0072] An electric spectrum analyzer is used to analyze the frequency characteristics of electrical signals.

[0073] A spectrometer is used to analyze the spectral characteristics of optical signals;

[0074] A laser driver platform used to control the current and temperature of the laser.

[0075] Figure 3In the diagram, DFB-LD stands for Distributed Feedback Semiconductor Laser, Bias stands for Bias Current, TEC stands for Temperature Control, BS stands for Laser Beam Splitter, NDF stands for Gradient Neutral Density Filter, Micro Nano stands for Micro / Nano Platform, collimator stands for Collimator, optical fiber stands for Optical Fiber, PD stands for Photodetector, AMP stands for Electrical Amplifier, ESA stands for Electro-Spectrometer, and OSA stands for Spectrometer.

[0076] This device selects two identical 1550nm distributed feedback semiconductor lasers (DFB-LD1) without isolators, manufactured in the same batch, with consistent spectra within the 0.18nm range to ensure parameter matching. The output light from DFB-LD1 is split into two paths by a laser beam splitter (BS). One path undergoes a 3dBm attenuation after transmission and is injected into DFB-LD2. The other path undergoes a similar 3dBm attenuation after reflection and is then collimated and coupled into a single-mode fiber. Spectral and electrical spectrum data are collected by a real-time monitoring and analysis system. Similarly, due to the symmetry of the mutual injection structure, the output light from DFB-LD2 is split into two paths by the laser beam splitter (BS). One path undergoes a 3dBm attenuation after transmission and is injected into DFB-LD1. The other path undergoes a 3dBm attenuation after reflection and is coupled into a single-mode fiber by a collimator. Data is also observed and collected by the real-time monitoring and analysis system. The devices and instruments used in the real-time monitoring and analysis system of the experiment included: an OSA spectrometer (Anritsu MS9710C) with a resolution of 0.05 nm, an ESA spectrometer with a bandwidth of 40 GHz (Agilent 8564EC), a frequency counter (Keysight 53230A), a photodetector (PD), and an amplifier (EA). During the experiment, the laser's current and temperature were controlled by a laser driving platform (Gooch & Housego, EM595) to change the laser's free oscillation frequency and output power, with an accuracy of ±0.01 mA and ±0.01 °C. The coupling strength was adjusted by changing the laser power through a neutral density filter (NDF). A micro-nano platform (P66.X60S, repeatability: 0.05%) was controlled by a host computer to move the laser at the nanometer scale, thereby changing the phase of the standing wave injection. Since the distance between DFB-LD1 and DFB-LD2 is much larger than the movement range of the micro-nano platform, and the optical path length is 15 cm, the coupling time between the two lasers can be considered to be 0.5 ns.

[0077] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for generating narrow-linewidth microwave signals based on an all-optical inter-injection semiconductor laser, characterized in that, Includes the following steps: Two distributed feedback lasers are mutually injected and coupled through free space; The distributed feedback laser does not have an isolator; By adjusting the driving current and temperature of two distributed feedback lasers, a frequency difference is generated between the two distributed feedback lasers, thereby producing a narrow linewidth microwave signal. By controlling the coupling strength and coupling phase according to the narrow linewidth microwave signal, the distributed feedback laser is made to operate in the P1 state, thereby generating a stable narrow linewidth microwave signal. Controlling coupling strength and coupling phase based on narrow-linewidth microwave signals includes: The spectral and electrical spectrum data of narrow-linewidth microwave signals are acquired through a real-time monitoring and analysis system, and the coupling strength and coupling phase are controlled by the spectral and electrical spectrum data. Controlling the coupling strength includes adjusting the laser power using a gradient neutral density filter; Controlling the coupling phase includes changing the phase of the standing wave injection by moving the distributed feedback laser at the nanoscale via a micro / nano platform.

2. The method according to claim 1, characterized in that, The real-time monitoring and analysis system includes a spectrometer, an electric spectrometer, a frequency counter, a photodetector, and an electric amplifier.

3. The method according to claim 1, characterized in that, The spectra of the two distributed feedback lasers are consistent in the 0.18 nm range.

4. The method according to claim 1, characterized in that, The wavelength of the distributed feedback laser is 1550nm.

5. A narrow-linewidth microwave signal generation device based on an all-optical inter-injection semiconductor laser, characterized in that, include: Two distributed feedback semiconductor lasers with the same wavelength; A laser beam splitter is used to split the output light of each distributed feedback semiconductor laser into two paths. A gradient neutral density filter is used to adjust the optical power injected into another distributed feedback semiconductor laser, thereby controlling the coupling strength; Micro-nano platforms are used to move distributed feedback semiconductor lasers at the nanoscale and change the phase of standing wave injection. A collimator is used to receive and collimate the output light of a laser. Optical fiber is used to transmit collimated optical signals. A photodetector is used to convert optical signals into electrical signals; An electrical amplifier is used to amplify electrical signals. An electric spectrum analyzer is used to analyze the frequency characteristics of electrical signals. A spectrometer is used to analyze the spectral characteristics of optical signals; A laser driver platform used to control the current and temperature of the laser; Two distributed feedback lasers, DFB-LD1 and DFB-LD2, are driven and conditioned by a bias power supply and a temperature controller, respectively; the output beams of the lasers are split by a beam splitter to achieve mutual injection coupling between the two lasers. A gradient neutral density filter is located in the optical path of DFB-LD2 to adjust the optical power injected into DFB-LD1 and control the coupling strength; a micro-nano platform is used to move DFB-LD2 at the nanoscale to control the coupling phase; a collimator is located at the output end of the two lasers to receive and collimate the output light of the lasers. The collimated optical signal is transmitted through an optical fiber to a photodetector, where it is converted into an electrical signal. The electrical signal is then amplified by an electrical amplifier and transmitted to an electro-spectrum analyzer and a spectrometer for analysis.

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