A photon microwave signal generator based on quantum dot laser and acquisition method

Abstract

The present invention discloses a quantum dot laser-based photon microwave signal generator and acquisition method. The generator includes a tunable semiconductor laser, a quantum dot laser, an aspheric lens, a beam splitter, a neutral density plate, a fiber Bragg grating, an isolator, a beam splitter, and a photodetector. The output light of the tunable semiconductor laser is injected into the quantum dot laser. The single-cycle oscillation light output by the quantum dot laser is focused by the aspheric lens and then split into two parts by the beam splitter. One part of the light is filtered by the fiber Bragg grating and fed back into the cavity of the quantum dot laser. The other part of the light is focused by the isolator and the aspheric lens in turn and then split into two parts by the beam splitter. One part is the output photon microwave signal, and the other part is converted into an electrical signal by the photodetector for microwave signal quality detection and adjustment. The present invention solves the problems of wide linewidth and high phase noise of light-injected semiconductor lasers, significantly improving the quality of photon microwaves.

Description

Technical Field

[0001] The present invention relates to the field of photon microwave technology, and in particular to a photon microwave signal generator based on quantum dot lasers and an acquisition method thereof. Background Art

[0002] Photonic microwave generation technology has attracted widespread attention due to its potential applications in fiber-optic radio communication networks, photonic radar systems, and satellite communication systems.

[0003] Traditional electronic methods of generating microwave signals have problems such as high cost and limited frequency adjustment range, while photonic methods of generating microwave signals have the advantages of high speed, wide frequency tunability, low power consumption and simple system structure.

[0004] Currently, there are several main methods for generating photonic microwaves: optical heterodyning based on two semiconductor lasers, mode-locked semiconductor lasers, optoelectronic oscillators, direct or externally modulated semiconductors, or single-cycle dynamics generation using light injection into semiconductors.

[0005] Among these technologies, the generation of photonic microwave signals by single-cycle dynamics induced by optical injection has some outstanding advantages, such as continuous and wide-range frequency tunability, low equipment cost due to the all-optical structure, no need for microwave seed source and approximate single-sideband spectral structure, which is conducive to improving its propagation efficiency in optical fibers.

[0006] However, the spontaneous emission noise of semiconductor lasers makes the single-cycle dynamics inherently include phase noise, which causes the generated photon microwave signal to have a large linewidth, hindering the practical application of photon microwave signals. Summary of the Invention

[0007] The present invention provides a photon microwave signal generator and acquisition method based on quantum dot lasers to solve the technical problems of wide line width and large phase noise of light-injected semiconductor lasers in the prior art.

[0008] To solve the above problems, the first object of the present invention is to provide a photon microwave signal generator based on a quantum dot laser, comprising a narrow linewidth laser, a quantum dot laser, a first aspheric lens, a second aspheric lens, a first beam splitter, a second beam splitter, a neutral density sheet, a fiber Bragg grating, an isolator, and a photodetector, wherein the output end of the fiber Bragg grating is connected to the first beam splitter, and the output ends of the isolator and the second beam splitter are both connected to the first beam splitter, wherein:

[0009] The output light of the narrow linewidth laser is injected into the quantum dot laser, and the single-cycle oscillation light output by the quantum dot laser is focused by the first aspheric lens and then split into two parts by the first beam splitter;

[0010] A portion of the light is fed back into the cavity of the quantum dot laser after being filtered by the neutral density sheet and the fiber Bragg grating. The neutral density sheet is used to adjust the intensity of the feedback light, and the fiber Bragg grating is used to reduce the line width and phase noise of the photon microwave signal.

[0011] The other part of the light is focused by the isolator and the second aspheric lens in sequence and then divided into two parts by the second beam splitter. One part is the output photon microwave signal, and the other part is converted into an electrical signal by the photoelectric detector and then used for microwave signal quality detection and adjustment.

[0012] Preferably, the narrow linewidth laser is a wavelength-tunable semiconductor laser or a fiber laser.

[0013] Preferably, the narrow linewidth laser and quantum dot laser are both single-mode laser sources.

[0014] Preferably, the frequency range of the generated microwave signal is changed by adjusting the frequency of the narrow linewidth laser and / or the quantum dot laser.

[0015] Preferably, the bandwidth of the generated microwave signal is changed by adjusting the waveform amplitude output by the fiber Bragg grating.

[0016] Preferably, the bandwidth of the photodetector is 0-150 GHz, and the responsivity is 1 A / W.

[0017] A second object of the present invention is to provide a method for acquiring a photon microwave signal based on a quantum dot laser, using the photon microwave signal generator based on a quantum dot laser as described above, the acquisition method comprising the following steps:

[0018] S1: The continuous light signal generated by the narrow linewidth laser is input into the quantum dot laser;

[0019] S2: The quantum dot laser outputs single-cycle oscillation light, which is focused by the first aspheric lens and then enters the first beam splitter;

[0020] S3: The output end of the first beam splitter is split into two signal beams. The first signal beam passes through the neutral density plate and enters the input end of the fiber Bragg grating. The output end of the fiber Bragg grating is connected to the first beam splitter. The second signal beam passes through the isolator and enters the input end of the second aspheric lens. The signal light focused by the second aspheric lens enters the input end of the second beam splitter. The output ends of the isolator and the second beam splitter are both connected to the first beam splitter.

[0021] S4: The output end of the second beam splitter is split into two signal beams. The first signal beam is reflected and output by the second beam splitter, and the second signal beam enters the input end of the photodetector through the second beam splitter.

[0022] S5: After the second beam signal is converted into an electrical signal by the photoelectric detector, the microwave signal quality is detected and adjusted.

[0023] Preferably, in step S3 and step S4, the first beam splitter and the second beam splitter are arranged at symmetrical angles.

[0024] Compared with the prior art, the present invention has significant advantages and beneficial effects, which are specifically reflected in the following aspects:

[0025] Based on the advantages of quantum dot lasers such as narrow linewidth and low phase noise, the present invention uses frequency-adjustable light emitted by a tunable semiconductor laser to be injected into the quantum dot laser to generate a photon microwave signal. The quantum dot laser outputs single-cycle oscillating light, which is focused by a first aspheric lens and then enters a first beam splitter. The output end of the first beam splitter is divided into two beams of signal light. The first beam of signal light passes through a neutral density plate and enters the input end of a fiber Bragg grating. The neutral density plate is used to adjust the intensity of the feedback light, and the fiber Bragg grating performs optical feedback to further reduce the linewidth and phase noise of the photon microwave signal, thereby obtaining a high-quality photon microwave signal. The second beam of signal light passes through an isolator and enters the input end of a second aspheric lens. The signal light focused by the second aspheric lens enters the input end of a second beam splitter. Part of the light is the output photon microwave signal, and the other part of the light is converted into an electrical signal by a photodetector for microwave signal quality detection and adjustment. The photon microwave signal can be applied to optical wireless communication networks, sensors, and radar systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of a photon microwave signal generator based on quantum dot lasers in an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the process of obtaining photon microwave signals based on quantum dot lasers in an embodiment of the present invention.

[0028] Description of reference numerals:

[0029] 1-tunable semiconductor laser; 2-quantum dot laser; 3-first aspheric lens; 4-first beam splitter; 5-neutral density plate; 6-fiber Bragg grating; 7-isolator; 8-second aspheric lens; 9-second beam splitter; 10-photodetector. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "first", "second", etc. are used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In existing technologies, the line width of photon microwave signals generated by traditional light-injected semiconductor lasers is relatively wide. Some people use ordinary light feedback to lower the line width and improve the quality of photon microwaves.

[0035] The line width of quantum dot lasers is narrow, and the photon microwave signal generated by light injection into quantum dot lasers is of high quality. By using fiber Bragg gratings to reduce the photon microwave line width, a very high-quality photon microwave signal can be obtained.

[0036] To solve the above technical problems, please refer to Figure 1 As shown, an embodiment of the present invention provides a photon microwave signal generator based on a quantum dot laser, wherein the photon microwave signal generator includes a narrow linewidth laser 1, a quantum dot laser 2, an aspheric lens, a neutral density sheet 5, a fiber Bragg grating 6, an isolator 7, a beam splitter, and a photodetector 10. The output end of the fiber Bragg grating 6 is connected to the first beam splitter 4, and the output ends of the isolator 7 and the second beam splitter 9 are both connected to the first beam splitter 4, wherein:

[0037] The aspheric lens includes a first aspheric lens 3 and a second aspheric lens 8, and the beam splitter includes a first beam splitter 4 and a second beam splitter 9.

[0038] The output light of the narrow linewidth laser 1 is injected into the quantum dot laser 2. The single-cycle oscillation light output by the quantum dot laser 2 is focused by the first aspheric lens 3 and then split into two parts by the first beam splitter 4:

[0039] A portion of the light is filtered by the fiber Bragg grating 6 and fed back into the cavity of the quantum dot laser 2. The neutral density sheet 5 is used to adjust the intensity of the feedback light, and the fiber Bragg grating further reduces the line width and phase noise of the photon microwave signal after light feedback.

[0040] The other part of the light is focused by the isolator 7 and the second aspheric lens 8 in sequence and then split into two parts by the second beam splitter 9. One part is the output photon microwave signal, and the other part is converted into an electrical signal by the photoelectric detector 10 for microwave signal quality detection and adjustment.

[0041] Specifically, in the embodiment of the present invention, the narrow linewidth laser 1 is a wavelength-tunable semiconductor laser or fiber laser. The narrow linewidth laser 1 in this embodiment is used to generate a local oscillator microwave signal.

[0042] It should be noted that the fiber Bragg grating 6 generates periodic ultraviolet light and dark stripes by the mutual interference of two ultraviolet beams or a ultraviolet beam passing through a phase grating mask, and the optical fiber is exposed using the periodic light and dark ultraviolet stripes.

[0043] The optical fiber core is made of photosensitive material. After absorbing ultraviolet photons, its refractive index n will increase. Therefore, after the optical fiber core is exposed to periodic light and dark ultraviolet stripes, the area illuminated by the ultraviolet stripes absorbs the ultraviolet light, thereby increasing the refractive index, while the refractive index of the area not illuminated by the ultraviolet stripes remains unchanged.

[0044] When an incident light passes through the fiber Bragg grating 6, the incident light with a wavelength that meets the Bragg condition (λ=2neffΛ, where neff is the effective refractive index of the fiber core and Λ is the refractive index variation period of the fiber Bragg grating) is reflected, while light of other wavelengths is not affected by the grating and passes through.

[0045] It is understood that the reflectivity of the fiber Bragg grating 6 is determined by the length of the fiber Bragg grating and the difference in refractive index between the area irradiated by the ultraviolet light stripes and the area not irradiated by the ultraviolet light stripes.

[0046] Specifically, in the embodiment of the present invention, the narrow linewidth laser 1 and the quantum dot laser 2 are both single-mode laser sources.

[0047] It should be noted that the quantum dot laser 2 is a suspended silicon disk structure prepared with an SOI wafer on a silicon substrate as a carrier. A quantum layer containing quantum dots of three sizes is set on the suspended silicon disk structure. After stimulated radiation, the three sizes of quantum dots emit light in the red, green and blue bands, and ultimately realize white light laser through the suspended disk microcavity.

[0048] The quantum dot laser 2 in the embodiment of the present invention utilizes a silicon dioxide pillar layer to separate the silicon layer and the silicon dioxide disk layer to a large extent, which can effectively reduce losses, thereby improving the luminous efficiency of the quantum dot disk microcavity, and reducing the bending loss of the structure and the scattering loss caused by the side roughness. Therefore, the quantum dot laser 2 has the advantages of narrow linewidth and low phase noise.

[0049] Specifically, in the embodiment of the present invention, the frequency range of the generated microwave signal is changed by adjusting the frequency of the narrow linewidth laser 1 and / or the quantum dot laser 2.

[0050] Specifically, in the embodiment of the present invention, the bandwidth of the generated microwave signal is changed by adjusting the waveform amplitude output by the fiber Bragg grating 6 .

[0051] Preferably, the bandwidth of the photodetector 10 is 0-150 GHz, and the responsivity is 1 A / W. The photodetector 10 in the embodiment of the present invention is used to perform beat frequency recovery processing on the delayed optical signal to obtain a microwave signal.

[0052] See also Figure 2 As shown, an embodiment of the present invention further provides a method for acquiring a photon microwave signal based on a quantum dot laser as described above, the acquisition method comprising the following steps:

[0053] S1: The continuous light signal generated by the narrow linewidth laser 1 is input to the quantum dot laser 2;

[0054] S2: Quantum dot laser 2 outputs single-cycle oscillation light, which is focused by the first aspheric lens 3 and then enters the first beam splitter 4;

[0055] S3: The output end of the first beam splitter 4 is split into two signal beams. The first signal beam passes through the neutral density sheet 5 and enters the input end of the fiber Bragg grating 6. The output end of the fiber Bragg grating 6 is connected to the first beam splitter 4. The second signal beam passes through the isolator 7 and enters the input end of the second aspheric lens 8. The signal light focused by the second aspheric lens 8 enters the input end of the second beam splitter 9. The output ends of the isolator 7 and the second beam splitter 9 are both connected to the first beam splitter 4.

[0056] S4: The output end of the second beam splitter 9 is split into two signal beams. The first signal beam is reflected and output by the second beam splitter 9, and the second signal beam enters the input end of the photodetector 10 through the second beam splitter 9.

[0057] S5: After the second beam signal is converted into an electrical signal by the photoelectric detector 10, microwave signal quality detection and adjustment are performed.

[0058] Thus, the single-cycle dynamics generated by the light-injected quantum dot laser 2 is used to generate a frequency-tunable photon microwave signal, and the fiber Bragg grating 6 is introduced for optical feedback to further reduce the linewidth and phase noise of the photon microwave signal, thereby obtaining a high-quality photon microwave signal, which can be applied to optical wireless communication networks, sensors and radar systems.

[0059] Specifically, in the embodiment of the present invention, in step S3 and step S4, the first beam splitter 4 and the second beam splitter 9 are arranged at symmetrical angles.

[0060] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A photon microwave signal generator based on quantum dot laser, characterized in that: The invention comprises a narrow linewidth laser (1), a quantum dot laser (2), a first aspheric lens (3), a second aspheric lens (8), a first beam splitter (4), a second beam splitter (9), a neutral density plate (5), a fiber Bragg grating (6), an isolator (7) and a photodetector (10), wherein the output end of the fiber Bragg grating (6) is connected to the first beam splitter (4), and the output ends of the isolator (7) and the second beam splitter (9) are both connected to the first beam splitter (4), wherein: The output light of the narrow linewidth laser (1) is injected into the quantum dot laser (2); the single-cycle oscillation light output by the quantum dot laser (2) is focused by the first aspheric lens (3) and then split into two parts by the first beam splitter (4); A portion of the light is filtered by the neutral density sheet (5) and the fiber Bragg grating (6) in sequence and then fed back into the cavity of the quantum dot laser (2), wherein the neutral density sheet (5) is used to adjust the intensity of the feedback light, and the fiber Bragg grating (6) is used to reduce the line width and phase noise of the photon microwave signal; Another part of the light is sequentially focused by the isolator (7) and the second aspheric lens (8) and then split into two parts by the second beam splitter (9), one part being the output photon microwave signal, and the other part being converted into an electrical signal by the photoelectric detector (10) for microwave signal quality detection and adjustment.

2. The photon microwave signal generator based on quantum dot laser according to claim 1, characterized in that: The narrow linewidth laser (1) is a semiconductor laser or a fiber laser in a tunable wavelength form.

3. The photon microwave signal generator based on quantum dot laser according to claim 1, characterized in that: The narrow linewidth laser (1) and the quantum dot laser (2) are both single-mode laser sources.

4. The photon microwave signal generator based on quantum dot laser according to any one of claims 1 to 3, characterized in that: By adjusting the frequency of the narrow linewidth laser (1) and / or the quantum dot laser (2), the frequency range of the generated microwave signal is changed.

5. The photon microwave signal generator based on quantum dot laser according to claim 4, characterized in that: The bandwidth of the generated microwave signal is changed by adjusting the waveform amplitude output by the fiber Bragg grating (6).

6. The photon microwave signal generator based on quantum dot laser according to claim 1, characterized in that: The bandwidth of the photodetector (10) is 0-150 GHz, and the responsivity is 1 A / W.

7. A method for acquiring a photon microwave signal based on a quantum dot laser, using the photon microwave signal generator based on a quantum dot laser according to any one of claims 1 to 6, characterized in that: The acquisition method comprises the following steps: S1: Inputting the continuous light signal generated by the narrow linewidth laser (1) into the quantum dot laser (2); S2: the quantum dot laser (2) outputs single-cycle oscillation light, which is focused by the first aspheric lens (3) and then enters the first beam splitter (4); S3: The output end of the first beam splitter (4) is split into two beams of signal light. The first beam of signal light enters the input end of the fiber Bragg grating (6) after passing through the neutral density plate (5). The output end of the fiber Bragg grating (6) is connected to the first beam splitter (4). The second beam of signal light enters the input end of the second aspheric lens (8) after passing through the isolator (7). The signal light focused by the second aspheric lens (8) enters the input end of the second beam splitter (9). The output ends of the isolator (7) and the second beam splitter (9) are both connected to the first beam splitter (4). S4: The output end of the second beam splitter (9) is split into two signal beams, the first signal beam is reflected and output by the second beam splitter (9), and the second signal beam enters the input end of the photodetector (10) through the second beam splitter (9); S5: After the second beam of signal light is converted into an electrical signal by the photoelectric detector (10), microwave signal quality detection and adjustment are performed.

8. The method for acquiring photon microwave signals based on quantum dot lasers according to claim 7, characterized in that: In step S3 and step S4, the first beam splitter (4) and the second beam splitter (9) are arranged at symmetrical angles.

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