A laser light source

Abstract

The application provides a laser light source, comprising: a first laser, the first laser is used for generating a first laser light, the first laser light comprises a first single-frequency pulsed laser light and stray light, the first single-frequency pulsed laser light has a first wavelength; a second laser, the second laser is used for generating a second laser light, the second laser light comprises a single-frequency laser light with a second wavelength, the second wavelength is greater than the first wavelength; an optical waveguide, the optical waveguide is used for inputting the first laser light and the second laser light, the first laser light and the second laser light occur stimulated Brillouin scattering in the optical waveguide, and a second single-frequency pulsed laser light is generated, the propagation direction of the second single-frequency pulsed laser light is opposite to the propagation direction of the first single-frequency pulsed laser light. The laser light of the application can reduce the stray light in the generated second single-frequency pulsed laser light, and improve the signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to a laser source, and more particularly to a method and a laser source for converting stimulated Brillouin scattering into stray light-free single-frequency pulses. Background Technology

[0002] Single-frequency pulsed lasers have important applications in fields such as long-range coherent detection, wind power development, and meteorological support for civil aviation safety. To obtain high-energy pulse output, multi-stage amplification of the pulsed laser signal is technically required. Unlike continuous-wave amplification, pulsed laser amplification, due to its temporal discontinuity, results in much stronger spontaneous emission (ASE) stray light generated by inverted particles, which is rapidly amplified in each amplification stage. For example, in the 1550nm single-frequency pulsed fiber laser reported by L. Kotov et al. (J Lightwave Technol. 41, 1526-1532 (2023)), the energy proportion of ASE stray light is as high as over 40%. In lasers, the pulsed laser signal and ASE stray light compete; therefore, the energy proportion of ASE stray light affects the final output energy of the pulsed laser, potentially causing pulse energy saturation or self-oscillation leading to amplifier failure. Spectally, ASE stray light appears as the spectral base of the laser peak, and its spectrum is very broad, generally above 30nm.

[0003] To address the issue of ASE stray light in lasers, existing technologies utilize narrowband filters in amplifiers. Narrowband filters are coated lenses that employ the principle of light interference for optical filtering. These components need to be customized based on the actual laser wavelength, resulting in poor compatibility. For example, a narrowband filter with a center wavelength of 1550nm and an operating bandwidth of 4nm (±2nm) is unusable for 1555nm lasers. While a 1550nm bandpass filter with an operating bandwidth of 10nm can accommodate 1555nm lasers, the increased bandwidth also expands the range of ASE wavelengths that can pass through, thus reducing the effectiveness of ASE stray light filtering. Fiber Bragg gratings (FBGs) can also be used for narrowband filtering. However, both narrowband filters and FBGs operate on the principle of light interference. In principle, regardless of the narrowband filter's bandwidth, this method cannot distinguish between laser signals of the same wavelength and ASE stray light. In other words, narrowband filters and FBGs cannot be used to improve the signal-to-noise ratio of the output laser spectrum. The improvement in spectral signal-to-noise ratio not only greatly enhances the laser's parameters but also lays the foundation for obtaining higher pulse energies.

[0004] To address the aforementioned issues, this application proposes a laser source that can eliminate stray light and improve the signal-to-noise ratio through stimulated Brillouin scattering. Summary of the Invention

[0005] One objective of this application is to provide a laser source that can eliminate stray light in single-frequency pulsed lasers and improve the signal-to-noise ratio, addressing the problems in the prior art.

[0006] To address the aforementioned problems, the technical solution of this application provides a laser source, comprising: a laser source characterized in that it includes: a first laser for generating a first laser, the first laser comprising: a first single-frequency pulsed laser and stray light, the first single-frequency pulsed laser having a first wavelength; a second laser for generating a second laser, the second laser comprising a single-frequency laser having a second wavelength greater than the first wavelength; and an optical waveguide for inputting the first laser and the second laser, wherein the first laser and the second laser undergo stimulated Brillouin scattering in the optical waveguide to generate a second single-frequency pulsed laser, the propagation direction of the second single-frequency pulsed laser being opposite to the propagation direction of the first single-frequency pulsed laser.

[0007] Optionally, the laser source further includes: a beam splitter, used to separate the second single-frequency pulse laser from the first laser according to the propagation direction of the second single-frequency pulse laser, output the second single-frequency pulse laser, and obtain the target laser; the beam splitter is located between the first laser and the optical waveguide.

[0008] Optionally, the beam splitter includes a circulator, which includes a first end, a second end, and an output end. One end of the optical waveguide is connected to the first laser through the circulator. The first laser inputs a first laser beam into the circulator through the first end. The other end of the optical waveguide is connected to the second laser. The output end is used to output the second single-frequency pulse laser beam to obtain the target laser.

[0009] Optionally, the second laser is a fiber laser; the second laser is a fiber laser or a semiconductor laser; the circulator is a fiber optic circulator.

[0010] Optionally, it may also include: an isolator connecting the second laser to the optical waveguide, the isolator being used to prevent the first laser from reaching the second laser.

[0011] Optionally, the first wavelength and the second wavelength satisfy:

[0012]

[0013] Where λ1 is the first wavelength, λ2 is the second wavelength, va is the speed of sound, and n is the refractive index of the optical waveguide.

[0014] Optionally, the wavelength of the second laser is 900nm to 10300nm; the wavelength of the first single-frequency pulsed laser is 1300nm to 1700nm; the second laser is a pulsed laser, and the pulse repetition frequency is greater than or equal to 10MHz; the power of the second laser is less than or equal to 1mW.

[0015] Optionally, the optical waveguide includes an optical fiber, which is a polarization-maintaining fiber; or, the optical waveguide is a crystal with a pigtail output, which includes one or more of LiNO3 or diamond.

[0016] Optionally, the first laser includes an amplifier and a pump laser, wherein the amplifier is a rare-earth metal-doped optical fiber; and the pump laser is a semiconductor laser, a solid-state laser, or a fiber laser.

[0017] Optionally, the second laser may comprise one or more single-frequency pulsed lasers or may be a continuous wave.

[0018] Optionally, the second laser is a mode-locked laser, a semiconductor laser, or a solid-state laser, and the mode-locked laser includes a mode-locked fiber laser or a mode-locked on-chip laser.

[0019] Optionally, the second laser may include one or more wavelengths.

[0020] Compared with the prior art, the technical solution of this invention has the following technical effects:

[0021] This invention provides a laser source that, by inputting a first laser and a second laser into an optical waveguide, satisfies the stimulated Brillouin scattering relation between the first and second lasers. Under the interaction of opposite propagation, the first single-frequency pulse laser in the first laser is converted into the second single-frequency pulse laser that propagates in the opposite direction, thus separating it from the stray light in the first single-frequency laser and achieving the technical effect of reducing stray light.

[0022] Furthermore, by setting a separator in the laser source and utilizing stimulated Brillouin scattering, the propagation direction of the second single-frequency pulsed laser is reversed with that of the first laser, thereby achieving the separation of the second single-frequency pulsed laser and stray light, thus improving the signal-to-noise ratio. Moreover, it can separate lasers of the same wavelength without being limited by the laser wavelength, thereby improving wavelength compatibility.

[0023] Furthermore, by setting the wavelength relationship between the first single-frequency pulsed laser and the second laser, the stimulated Brillouin scattering of the first single-frequency pulsed laser and the second laser can be enhanced, thereby increasing the efficiency of generating the second single-frequency pulsed laser.

[0024] Furthermore, the second laser is a mode-locked laser. Mode-locked lasers typically have a spectral width of tens of nanometers. The second laser generated by the mode-locked laser consists of thousands of equally spaced monochromatic lines, each of which is spectrally and temporally equivalent to a single-frequency laser pulse. The second laser generated by the mode-locked laser includes multiple single-frequency lasers. These multiple single-frequency lasers are combined with the stimulated Brillouin scattering of the first single-frequency laser pulse to generate multiple second single-frequency laser pulses, thereby enabling the separation of stray light from second single-frequency laser pulses with different wavelengths. Attached Figure Description

[0025] Figures 1 to 4 This is a schematic diagram of the structure of the first embodiment of the laser light source of the present invention. Detailed Implementation

[0026] As described in the background art, stray light in lasers can be filtered out using narrowband filters or fiber Bragg gratings in the prior art. However, neither narrowband filters nor fiber Bragg gratings can distinguish between laser signals of the same wavelength and stray light (such as ASE stray light), and they need to be customized according to the wavelength.

[0027] To address the problems of existing technologies, the inventors of this application have discovered that stimulated Brillouin scattering (SBS) is a nonlinear effect in the laser field, generated by the interaction of a pump laser with acoustic phonons in the medium. Assuming the pump laser frequency is ω0 and the phonon frequency is ω1, their interaction will produce an SBS laser with a frequency of ω2, satisfying ω2 = ω0 – ω1, and the generated SBS laser will be in the opposite direction to the pump laser. Therefore, SBS can be used to distinguish between laser signals of the same wavelength and ASE stray light, completely eliminating ASE stray light and thus improving the signal-to-noise ratio of the laser spectrum.

[0028] Based on the above analysis, this invention provides a laser source, including a first laser for generating a first laser beam, the first laser beam comprising: a first single-frequency pulsed laser and stray light, the first single-frequency pulsed laser having a first wavelength; a second laser for generating a second laser, the second laser comprising a single-frequency laser having a second wavelength greater than the first wavelength; and an optical waveguide for inputting the first and second laser beams, wherein the first and second laser beams undergo stimulated Brillouin scattering in the optical waveguide to generate the second single-frequency pulsed laser, the propagation direction of the second single-frequency pulsed laser being opposite to the propagation direction of the first single-frequency pulsed laser. The laser of this application can reduce stray light in the generated second single-frequency pulsed laser, improving the signal-to-noise ratio.

[0029] Figures 1 to 4 A schematic diagram of the structure of the first embodiment of the laser light source provided by the present invention.

[0030] The first embodiment of the laser light source of the present invention will be described in further detail with reference to the accompanying drawings.

[0031] Please refer to Figure 1 The laser source includes: a first laser 10 for generating a first laser, the first laser including a first single-frequency pulse laser and stray light, the first single-frequency pulse laser having a first wavelength; a second laser 40 for generating a second laser, the second laser including a single-frequency laser having a second wavelength greater than the first wavelength; and an optical waveguide 30 for inputting the first laser and the second laser, the first laser and the second laser undergoing stimulated Brillouin scattering in the optical waveguide 30 to generate a second single-frequency pulse laser, the propagation direction of the second single-frequency pulse laser being opposite to the propagation direction of the first single-frequency pulse laser.

[0032] In the technical solution of this application, by inputting the first laser and the second laser into the optical waveguide 30, the first laser and the second laser satisfy the stimulated Brillouin scattering relationship. Under the interaction of opposite transmission, the first single-frequency pulse laser in the first laser is converted into the second single-frequency pulse signal laser that is transmitted in the opposite direction, so that it is separated from the first laser, thereby achieving the technical effect of reducing stray light.

[0033] In this embodiment, the laser source further includes a beam splitter 20, which is used to separate the second single-frequency pulse laser from the first laser, output the second single-frequency pulse laser, and obtain the target laser; specifically, it is used to separate the second single-frequency pulse laser from the first laser according to the second single-frequency pulse laser, output the second single-frequency pulse laser, and obtain the target laser; the beam splitter is located between the first laser and the optical waveguide.

[0034] Specifically, such as Figure 3 As shown, in this embodiment, the beam splitter 20 includes a circulator, which includes a first end 1, a second end 2, and an output end 3. One end of the optical waveguide 30 is connected to the first laser 10 through the circulator. The first laser 10 inputs a first laser beam into the circulator through the first end 1. The other end of the optical waveguide 30 is connected to the second laser 40. The output end 3 is used to output the second single-frequency pulse laser beam to obtain the target laser beam.

[0035] In other embodiments of this application, the beam splitter 20 may also be a semi-transparent, semi-reflective mirror. The first laser 10 and the second laser 40 may also be semiconductor lasers or solid-state lasers. The first laser 10, the second laser 40, the beam splitter 20, and the optical waveguide 30 can transmit light between each other via spatial light.

[0036] In this embodiment, the first laser 10 includes an amplifier and a pump laser 11. During the amplification of the laser in the amplifier 12, stray light, including ASE stray light, is inevitably generated.

[0037] Specifically, the amplifier 12 is an optical fiber amplifier, and the amplifier 12 is an optical fiber doped with rare earth metals; the rare earth metal doped in the amplifier 12 is ytterbium, and the optical fiber amplifier is a ytterbium-doped optical fiber amplifier.

[0038] The pump laser 11 is a semiconductor laser, a solid-state laser, or a fiber laser. In this embodiment, the pump laser 11 is a fiber laser. In other embodiments, the pump laser can be a semiconductor laser or a solid-state laser.

[0039] Specifically, the pump laser 11 includes a continuous light source and a modulator. The continuous light source generates continuous laser light, and the modulator converts the continuous laser light into pulsed laser light. Specifically, the continuous light source is a single-frequency ytterbium-doped fiber laser, and the modulator is an acousto-optic modulator. The amplifier is a fiber amplifier, specifically a ytterbium-doped fiber amplifier. The initial laser light output from the continuous light source is a continuous-wave single-frequency laser. After passing through the acousto-optic modulator, the initial laser light generates a single-frequency pulsed laser light. The single-frequency pulsed laser light is input into the amplifier 30 and amplified through multiple stages to form the first laser light. The first laser light contains the first single-frequency pulsed laser light and the stray light. The wavelength of the first single-frequency laser light is 1064 nm. The pump laser 11 is a single-frequency ytterbium-doped fiber laser.

[0040] In this embodiment, the optical waveguide 30 includes an optical fiber, specifically a single-mode polarization-maintaining fiber. Alternatively, the optical waveguide 30 is a crystal with a pigtail output, the crystal comprising one or more of LiNO3 or diamond.

[0041] The second laser 40 is a mode-locked laser, a semiconductor laser, or a solid-state laser. The mode-locked laser includes a single-frequency fiber laser, a mode-locked fiber laser, or a mode-locked on-chip laser.

[0042] like Figure 2 As shown, in this embodiment, the laser source further includes an isolator 50 connecting the second laser 40 and the optical waveguide 30. The isolator 50 is used to prevent the first laser from reaching the second laser 40. The isolator 50 can block the first laser transmitted to the second laser 40, thereby ensuring the stability of the second laser 40.

[0043] Figure 3 This is a schematic diagram of the circulator structure in the first embodiment of the laser source of this application.

[0044] refer to Figure 3 In this embodiment, the first laser generated by the first laser 10 enters the circulator through the first end 1 and is output from the second end 2 of the circulator to the optical waveguide 30. The second laser generated by the second laser 40 enters the optical waveguide 30 through the isolator 50. The second laser and the first laser meet in the optical waveguide 30. The first single-frequency pulse laser in the first laser and the second laser undergo stimulated Brillouin scattering to generate the second single-frequency pulse laser. The second single-frequency pulse laser is opposite in direction to the first single-frequency pulse laser. The stray light does not have an effect and its propagation direction remains unchanged. Therefore, the second single-frequency pulse is opposite in propagation direction to the stray light. The second single-frequency pulse is transmitted from the optical waveguide 30 to the beam splitter 20 and is output from the output end 3 of the beam splitter 20 to form the target laser.

[0045] When the first laser and the second laser meet the following conditions, the stimulated Brillouin scattering of the first laser and the second laser can be enhanced, thereby increasing the efficiency of generating the second single-frequency laser.

[0046] Specifically, the first wavelength and the second wavelength satisfy:

[0047]

[0048] Where λ1 is the first wavelength, λ2 is the second wavelength, and v a Let n be the speed of sound and n be the refractive index of the optical waveguide.

[0049] In the technical solution of this application, the wavelength of the second laser is 900nm to 10300nm; the wavelength of the first single-frequency pulsed laser is 1300nm to 1700nm, and the first single-frequency pulsed laser is a single-frequency laser. The second laser can be a single-frequency laser or a multi-wavelength laser, and the second laser can be pulsed light or continuous light.

[0050] Reference Figure 4 , Figure 4 (a) is the input spectrum of the first terminal 1 of the beam splitter 20. Figure 4 (b) shows the output spectrum of the output terminal 3 of the beam splitter 20.

[0051] Specifically, in one embodiment of the present invention, the second laser 40 is a semiconductor laser, the second wavelength is 1550.13 nm, and the first wavelength is 1550 nm. The second laser is a continuous wave, and the power of the second laser is less than or equal to 1 mW; specifically, the laser power is 50 μW.

[0052] The optical waveguide 30 is a single-mode polarization-maintaining fiber, reference... Figure 4The wavelength of the second single-frequency pulsed laser is the same as that of the second single-frequency pulsed laser, which is 1550.13 nm. ASE stray light has been eliminated in the output second single-frequency pulsed laser, improving the signal-to-noise ratio.

[0053] In another embodiment of the invention, the second laser comprises one or more single-frequency pulsed lasers.

[0054] Specifically, the second laser 40 is a mode-locked laser. The mode-locked laser is a mode-locked fiber laser. In other embodiments, the mode-locked laser is a mode-locked on-chip laser. The first laser 10 is a fiber laser, the second laser 40 is a fiber laser, the optical waveguide 30 is an optical fiber, and the circulator is an optical fiber circulator. Thus, the first laser 10, the second laser 40, the beam splitter 20, and the optical waveguide 30 can all be coupled together via optical fibers, thereby reducing optical energy loss.

[0055] The second laser 40 is a mode-locked laser. Mode-locked lasers typically have a spectral width of tens of nanometers. The second laser generated by the mode-locked laser consists of thousands of equally spaced monochromatic lines, each of which is spectrally and temporally equivalent to a single-frequency laser pulse. The second laser generated by the mode-locked laser includes multiple single-frequency lasers. By combining these multiple single-frequency pulses with stimulated Brillouin scattering, stray light can be separated from the second single-frequency laser pulse.

[0056] The second laser includes one or more wavelengths. Specifically, in this embodiment, the second laser has multiple wavelengths; specifically, the second wavelength of the second laser is 1030nm to 1090nm, and the pulse repetition frequency of the second laser is 10MHz to 100MHz; specifically, the pulse repetition frequency of the second laser is 50MHz.

[0057] The optical waveguide 30 is a single-mode polarization-maintaining fiber. The first single-frequency pulsed laser and the second laser meet in the optical waveguide 30. The temperature or current of the first single-frequency laser is adjusted to match the comb teeth of the mode-locked laser of the second laser. The first single-frequency pulsed laser and the second laser undergo stimulated Brillouin scattering in the optical waveguide 30 to generate a second single-frequency pulsed laser that is opposite to the transmission direction of the first single-frequency pulsed laser. The wavelength of the second single-frequency pulsed laser is 1064.06 nm.

[0058] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A laser light source, characterized in that: include: A first laser, used to generate a first laser, the first laser comprising: a first single-frequency pulsed laser and stray light, the first single-frequency pulsed laser having a first wavelength; A second laser is used to generate a second laser, the second laser comprising a single-frequency laser having a second wavelength greater than a first wavelength; An optical waveguide is used to input the first laser and the second laser. The first laser and the second laser undergo stimulated Brillouin scattering in the optical waveguide to generate a second single-frequency pulse laser. The propagation direction of the second single-frequency pulse laser is opposite to that of the first single-frequency pulse laser.

2. The laser source as described in claim 1, characterized in that: The laser source further includes a beam splitter, used to separate the second single-frequency pulse laser from the first laser according to the propagation direction of the second single-frequency pulse laser, output the second single-frequency pulse laser, and obtain the target laser; the beam splitter is located between the first laser and the optical waveguide.

3. The laser source as described in claim 2, characterized in that: The beam splitter includes a circulator, which includes a first end, a second end, and an output end. One end of the optical waveguide is connected to the first laser through the circulator. The first laser inputs a first laser beam into the circulator through the first end. The other end of the optical waveguide is connected to the second laser. The output end is used to output the second single-frequency pulse laser beam to obtain the target laser beam.

4. The laser light source as described in claim 3, characterized in that: The second laser is a fiber laser; the second laser is a fiber laser or a semiconductor laser; the circulator is a fiber optic circulator.

5. The laser source as described in claim 1, characterized in that: Also includes: An isolator connecting the second laser to the optical waveguide, the isolator being used to prevent the first laser from reaching the second laser.

6. The laser source as described in claim 1, characterized in that: The first wavelength and the second wavelength satisfy: ； Where λ1 is the first wavelength and λ2 is the second wavelength. v a For the speed of sound, n is the refractive index of the optical waveguide.

7. The laser source as described in claim 6, characterized in that: The wavelength of the second laser is 900nm~10300nm; the wavelength of the first single-frequency pulsed laser is 1300nm~1700nm; the second laser is a pulsed laser, and the pulse repetition frequency is greater than or equal to 10MHz; the power of the second laser is less than or equal to 1 mW.

8. The laser source as described in claim 1, characterized in that: The optical waveguide includes an optical fiber, which is a polarization-maintaining optical fiber; or, The optical waveguide is a crystal with a pigtail output, and the crystal includes one or more of LiNO3 or diamond.

9. The laser source as described in claim 1, characterized in that: The first laser includes an amplifier and a pump laser, wherein the amplifier is a rare-earth metal-doped optical fiber; and the pump laser is a semiconductor laser, a solid-state laser, or a fiber laser.

10. The laser source as described in claim 1, characterized in that: The second laser may include one or more single-frequency pulsed lasers or the second laser may be a continuous wave.

11. The laser source as described in claim 10, characterized in that: The second laser is a mode-locked laser, a semiconductor laser, or a solid-state laser, and the mode-locked laser includes a mode-locked fiber laser or a mode-locked on-chip laser.

12. The laser source as described in claim 11, characterized in that: The second laser includes one or more wavelengths.

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