486nm laser based on Raman laser frequency tripling and application

Abstract

The invention belongs to the technical field of lasers, and provides a 486nm laser based on Raman laser frequency tripling and application, the 486nm laser is used for outputting 486.1 nm target blue light, and the 486nm laser comprises a fundamental frequency light source, a frequency tripling module and a dichroscope; the base frequency light source outputs base frequency light of 1458.3 nm, frequency doubling is carried out on the base frequency light of 1458.3 nm with a part of power in the frequency doubling crystal to generate frequency doubling light of 729.15 nm, and sum frequency is carried out on the base frequency light of 1458.3 nm with the other part of power and the frequency doubling light of 729.15 nm in the sum frequency crystal to generate target blue light of 486.1 nm; and 486.1 nm target blue light is separated and output by using a dichroscope. The blue light source with high power, high light beam quality, high stability and narrow linewidth can be realized, and a high-performance light source is provided for underwater application scenes such as underwater detection, communication, photoelectric countermeasure and diving exploration.

Description

486nm Laser Based on Raman Laser Frequency Third Harmonization and Its Applications Technical Field

[0001] This invention mainly relates to the field of fiber laser technology, and in particular to a 486nm laser based on Raman laser third frequency harmonication and its applications. Background Technology

[0002] LiDAR technology, as a high-precision, high-resolution detection method, has significant application value in the field of marine exploration. The blue-green light band (450-550nm) is known as the "underwater transparent window" and is the core band for marine laser detection and communication. Among them, blue lasers in the 450-490nm range have better penetration capabilities than green lasers, especially in deep-sea environments or clear open ocean waters, where blue light can achieve effective transmission over hundreds of meters. Therefore, blue lasers in this band are considered the best light source for marine exploration and communication. In particular, the 486.1nm target blue light is located in the Fraunhofer H-β dark line of the solar spectrum. Due to the extremely low intensity of solar radiation in this band, using this wavelength for underwater detection and communication can significantly reduce ambient light interference and improve resolution and sensitivity. Combined with the superior penetration capability of 486.1nm target blue light compared to traditional 532nm green light, the 486.1nm target blue light source has enormous application potential in deep-sea exploration and achieving high-speed underwater communication.

[0003] Currently, methods for achieving 486.1nm target blue laser light mainly include nonlinear frequency conversion and direct emission from doped ion crystals. However, these methods involve various nonlinear effects and suffer from problems such as complex structural design, low brightness, low conversion efficiency, and linewidths larger than the Fraunhofer dark line channel. To meet the application requirements of underwater detection, there is an urgent need to develop a new and efficient 486.1nm target blue laser light source design scheme. Summary of the Invention

[0004] To address the need for high-performance 486.1nm target blue light sources in marine exploration and the difficulty of achieving both high power and narrow linewidth with current technologies, this invention proposes a 486nm laser based on Raman laser third-harmonic generation and its application. This laser can achieve a high-power, high-beam-quality, high-stability, and narrow-linewidth blue light source, providing a high-performance light source for underwater applications such as underwater exploration, communication, optoelectronic countermeasures, and submarine exploration.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a 486nm laser based on Raman laser third-harmonic generation for outputting 486.1nm target blue light, including a fundamental frequency light source, a third-harmonic generation module, and a dichroic mirror; the fundamental frequency light source is used to output 1458.3nm fundamental frequency light; the third-harmonic generation module includes a frequency-doubling crystal and a sum-frequency crystal, wherein a portion of the 1458.3nm fundamental frequency light is frequency-doubled in the frequency-doubling crystal, converting it into 729.15nm frequency-doubled light, and the remaining 1458.3nm fundamental frequency light is frequency-doubled with the 729.15nm sum-frequency crystal. The frequency-frequency light undergoes sum-frequency generation in the sum-frequency crystal, producing target blue light with a wavelength of 486.1 nm. A dichroic mirror is used to separate and output the target blue light of 486.1 nm, the laser light of 729.15 nm and 1458.3 nm. The fundamental frequency light source includes a 1050 nm pump source with precisely adjustable wavelength. By actively controlling the output wavelength of the 1050 nm pump source, the fundamental frequency light source can stably generate fundamental frequency light with a precise wavelength of 1458.3 nm, thereby achieving precise locking of the wavelength of the target blue light of 486.1 nm, matching it with the Fraunhofer dark line.

[0006] This invention relates to a fundamental frequency light source comprising a precisely tunable 1050nm pump source. Through active feedback control, the output wavelength of the 1050nm pump source is controlled, enabling the pump light to generate a precise fundamental frequency light with a wavelength of 1458.3nm via frequency conversion. This 1458.3nm fundamental frequency light is injected into a third harmonic module, which then generates a 729.15nm harmonic light through frequency doubling. The 729.15nm harmonic light is then mixed with the remaining 1458.3nm fundamental frequency light through a sum-frequency process to generate a target blue light of 486.1nm. Finally, the target blue light of 486.1nm is separated and output through a dichroic mirror. The purpose of controlling the output wavelength of the 1050nm pump source is to ensure that the fundamental frequency light source can stably generate a precise 1458.3nm fundamental frequency light, thereby achieving precise locking of the 486.1nm target blue light wavelength and matching it with the Fraunhofer dark line.

[0007] Furthermore, the fundamental frequency light source includes a pump source and a Raman oscillator. The pump source is used to output a 1050nm pump laser and injects the 1050nm pump laser into the Raman oscillator to output 1458.3nm Raman light as the 1458.3nm fundamental frequency light for nonlinear frequency conversion.

[0008] Furthermore, the Raman oscillator comprises an input coupler, a Raman gain medium, and an output coupler. The Raman gain medium is a solid material with a Raman gain peak of 40 THz. The input and output couplers provide optical feedback at a first-order Raman conversion wavelength of 1221 nm and a second-order Raman conversion wavelength of 1458.3 nm. The input coupler provides high-reflectivity optical feedback at both the first-order Raman wavelength of 1221 nm and the second-order Raman wavelength of 1458.3 nm, while the output coupler provides high-reverse feedback at the first-order Raman wavelength of 1221 nm and partial output transmittance at 1458.3 nm. The input and output couplers can be coated beam splitters.

[0009] Furthermore, the Raman gain medium is selected from solid materials with a 40THz Raman gain peak, including but not limited to diamond, phosphorus-doped optical fiber, etc.

[0010] Furthermore, another fundamental frequency light source is provided, which includes a pump source, a wavelength division multiplexer, a phosphorus-doped fiber, and a high-reflectivity grating. The pump source is used to output a 1050nm pump laser. The pump laser is injected into the phosphorus-doped fiber through the wavelength division multiplexer and converted into bidirectionally scattered first-order Raman light of 1221nm and second-order Raman light of 1458.3nm. The backscattered light enters the high-reflectivity grating through the wavelength division multiplexer. The high-reflectivity grating provides high-reflectivity feedback for the first-order Raman light of 1221nm and the second-order Raman light of 1458.3nm. The output random laser returns along the original path, and the 1458.3nm fundamental frequency light is separated, output, and injected into the third harmonic module.

[0011] This invention provides a 486.1nm target blue laser based on the nonlinear frequency conversion of a Raman laser, located in the solar H-β Fraunhofer dark line channel, which has long underwater penetration capability while significantly reducing ambient light interference.

[0012] On the one hand, the aforementioned 486nm laser based on Raman laser frequency third harmonic can be used as a detection light source in underwater laser detection systems.

[0013] On the other hand, the aforementioned 486nm laser based on Raman laser frequency third harmonics can be used in underwater communication systems.

[0014] Compared with existing technologies, this invention achieves the following technical effects: Compared with mainstream OPO technology, this invention does not require a complex cavity structure, nor does it require the additional use of 486.1nm target blue light generated by 972.2nm semiconductor frequency doubling or other technologies as seed light in OPO. By using nonlinear crystals with waveguide structures (such as PPLN crystals) and Raman gain media (such as diamond, phosphorus-doped fiber, etc.), the system can be made entirely of fiber.

[0015] The selection of the fundamental frequency wavelength is crucial, determining whether the target wavelength can be achieved. If the fundamental frequency wavelength is misselected, it will not be covered by the Fraunhofer dark line, significantly reducing the system's signal-to-noise ratio. The selection of a precisely tunable 1050nm pump source directly determines whether a stable target wavelength of 486.1nm blue light can be output. This invention obtains a stable 1458.3nm fundamental frequency light through precise control of the 1050nm pump source wavelength, and then uses a third harmonic module to generate a stable 486.1nm target blue light output. For example, for a scheme that uses a 1050nm fiber optic oscillator with a fiber Bragg grating as the pump source, the temperature or stress of the fiber Bragg grating can be adjusted by a temperature control module or piezoelectric ceramic to change the feedback wavelength of the fiber Bragg grating. A beam splitter is used to separate a low-power 1458.3nm laser and inject it into a wavelength meter or spectrometer. A computer or PID controller is used to read the wavelength readings and dynamically adjust the temperature of the pump source or the piezoelectric ceramic (PZT) to enable the fundamental frequency light source to stably generate a precise fundamental frequency light with a wavelength of 1458.3nm.

[0016] Compared to direct emission of 486.1nm target blue light technology and frequency quadruple technology, this invention benefits from a high-brightness pump source (such as a high-power superfluorescent fiber light source or a high-power fiber laser), which can obtain high-power 1458.3nm fundamental frequency light output, thereby obtaining high-power 486.1nm target blue light output. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 is a structural diagram of a 486nm laser based on Raman laser third frequency harmonication provided in one embodiment of the present invention; Figure 2 is a structural diagram of a 486nm laser based on Raman laser third frequency harmonication provided in another embodiment of the present invention; the figures are labeled as follows: 1, pump source; 2, input coupler; 3, Raman gain medium; 4, output coupler; 5, frequency doubling crystal; 6, sum-frequency crystal; 7, dichroic mirror; 8, 486.1nm target blue light; 9, 729.15nm and 1458.3nm lasers; 10, high-reflectivity grating; 11, wavelength division multiplexer; 12, phosphorus-doped fiber. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a 486nm laser based on Raman laser third frequency harmonication for outputting 486.1nm target blue light. It includes: a fundamental frequency light source for outputting 1458.3nm fundamental frequency light; and a third frequency harmonication module including a frequency doubling crystal 5 and a sum-frequency crystal 6. A portion of the 1458.3nm fundamental frequency light is frequency-doubled in the frequency doubling crystal 5, converting it into 729.15nm frequency-doubled light. The remaining 1458.3nm fundamental frequency light and the 729.15nm frequency-doubled light are summed in the sum-frequency crystal 6 to produce a wavelength of [wavelength missing]. The system includes a 486.1nm target blue light source 8 and a dichroic mirror 7, used to separate and output the 486.1nm target blue light 8, the 729.15nm laser, and the 1458.3nm laser 9. The fundamental frequency light source includes a 1050nm pump source with precisely adjustable wavelength. By actively controlling the output wavelength of the 1050nm pump source, the fundamental frequency light source can stably generate a fundamental frequency light with a precise wavelength of 1458.3nm, thereby achieving precise locking of the wavelength of the 486.1nm target blue light and matching it with the Fraunhofer dark line.

[0021] In this invention, the selection of the fundamental frequency wavelength is crucial, determining whether the target blue light output of 486.1nm can be achieved. If the fundamental frequency wavelength is selected incorrectly, it will not be covered by the Fraunhofer dark line, thus significantly reducing the system signal-to-noise ratio. The selection of a 1050nm pump source with precisely adjustable wavelength in the fundamental frequency light source directly determines whether the target wavelength of 486.1nm can be stably output as the target blue light.

[0022] This invention achieves a stable 1458.3nm fundamental frequency light by precisely controlling the 1050nm pump source wavelength in the fundamental frequency light source, and then uses a third harmonic module to generate a stable 486.1nm target blue light output. For example, in a scheme using a 1050nm fiber optic oscillator with a fiber Bragg grating as the pump source, the temperature or stress of the FBG can be adjusted by a temperature control module or piezoelectric ceramic to change the feedback wavelength of the fiber Bragg grating. A beam splitter is used to separate a low-power 1458.3nm laser and inject it into a wavelength meter or spectrometer. A computer or PID controller is used to read the wavelength readings and dynamically adjust the temperature of the pump source or the piezoelectric ceramic (PZT) to lock the pump light at a wavelength that produces 1458.3nm.

[0023] As shown in Figure 1, an embodiment of a 486nm laser based on Raman laser third frequency harmonics includes a pump source 1, a Raman oscillator, a third frequency harmonic module, and a dichroic mirror 7. A 1050nm pump laser output from the pump source 1 is injected into the Raman oscillator, outputting 1458.3nm Raman light as the fundamental frequency light for nonlinear frequency transformation. The 1458.3nm fundamental frequency light output from the Raman oscillator is injected into the third frequency harmonic module composed of a frequency doubling crystal 5 and a sum-frequency crystal 6. The module comprises three components: a portion of the 1458.3nm fundamental frequency light is frequency-doubled in a frequency-doubled crystal 5 to generate 729.15nm frequency-doubled light; the remaining portion of the 1458.3nm fundamental frequency light and the 729.15nm frequency-doubled light are combined in a frequency-multiplier crystal 6 to generate the target wavelength laser, i.e., 486.1nm target blue light 8; and a dichroic mirror is used to separate and output the 486.1nm target blue light 8, the 729.15nm laser, and the 1458.3nm laser 9. The selection of the fundamental frequency light wavelength directly determines whether the target wavelength, i.e., 486.1nm target blue light 8, can be output. This invention achieves high-quality, high-power, and stable output of 486.1nm target blue light 8 by precisely selecting the fundamental frequency light wavelength and utilizing a third-multiplier module based on the 1458.3nm fundamental frequency light.

[0024] Referring to Figure 1, the Raman oscillator consists of an input coupler 2, a Raman gain medium 3, and an output coupler 4. The Raman gain medium 3 is a solid material with a Raman gain peak of 40 THz. The input coupler 2 and the output coupler 4 provide optical feedback with a first-order Raman conversion wavelength of 1221 nm and a second-order Raman conversion wavelength of 1458.3 nm. This invention utilizes the Raman oscillator to obtain a high-power 1458.3 nm fundamental frequency light output, thereby obtaining a high-power 486.1 nm target blue light 8 output.

[0025] In a preferred embodiment, based on the optical path structure shown in Figure 1, a 486nm laser based on Raman laser third-harmonic generation is proposed. The pump laser output from pump source 1 in the fundamental frequency source can be continuous light or pulsed light. Pump source 1 can be a superfluorescent fiber source or a fiber laser. Pump source 1 is used to emit a pump laser with a wavelength of 1050nm. The 1050nm pump laser is injected into a Raman laser oscillator composed of input coupler 2, Raman gain medium 3, and output coupler 4, and is converted into a 1458.3nm fundamental frequency light through second-order Raman spectroscopy. Raman gain medium 3 can be a solid material with a 40THz Raman gain peak, such as diamond, phosphorus-doped fiber, or other solid materials with a 40THz Raman gain peak. Input coupler 2 provides high reflectivity feedback for first-order Raman light at 1221nm and second-order Raman light at 1458.3nm. Input coupler 4 provides high back-feedback for first-order Raman light at 1221nm and partial output transmittance at 1458.3nm. Input coupler 2 and output coupler 4 can be implemented using coated beam splitters.

[0026] It should be noted that, in the embodiment using the structure shown in Figure 1, if diamond is selected as the Raman gain medium 3, then in the 486nm laser based on Raman laser third harmonics provided in the above embodiment, the spaces between pump source 1 and input coupler 2, between input coupler 2 and Raman gain medium 3, and between Raman gain medium 3 and output coupler 4 are all spatial optical paths. If phosphorus-doped fiber is selected as the Raman gain medium 3, then the input coupler 2, Raman gain medium 3, and output coupler 4 can be connected by optical fiber to form an optical fiber path.

[0027] The 1458.3nm fundamental frequency light then enters the third harmonic generation module. A portion of the 1458.3nm fundamental frequency light undergoes frequency doubling in the frequency doubling crystal 5, generating 729.15nm frequency-doubled light. The remaining portion of the 1458.3nm fundamental frequency light and the generated 729.15nm frequency-doubled light enter the sum-frequency crystal 6 for sum-frequency generation, producing the 486.1nm target blue light 8. This light is then split by a dichroic mirror 7, which separates and outputs the 486.1nm target blue light 8, the 729.15nm laser, and the 1458.3nm laser 9, resulting in the 486.1nm target blue light 8, the 729.15nm laser, and the 1458.3nm laser 9. The frequency doubling crystal 5 and the sum-frequency crystal 6 are nonlinear crystals, including but not limited to lithium borate (LBO), barium metaborate (BBO), or periodically polarized lithium niobate (PPLN) nonlinear crystals.

[0028] In another preferred embodiment, based on the optical path structure shown in Figure 2, a 486nm laser based on Raman laser third-harmonic generation is proposed. Essentially, it is a 486.1nm target blue light source based on a random Raman pulse laser third-harmonic generation using phosphorus-doped fiber. The pump source 1 in the fundamental frequency source can be a superfluorescent fiber source or a fiber laser. Pump source 1 emits a pump laser with a wavelength of 1050nm. The pump laser is injected into the phosphorus-doped fiber 12 through a wavelength division multiplexer 11 and converted into bidirectionally scattered first-order Raman light (1221nm) and second-order Raman light (1458.3nm). The backscattered light enters the high-reflectivity grating 10 through the wavelength division multiplexer 11. The high-reflectivity grating 10 provides high-reflectivity feedback for the first-order Raman light (1221nm) and the second-order Raman light (1458.3nm), outputting a random laser that returns along the original path. The 1458.3nm fundamental frequency light is then separated, output, and injected into the third-harmonic generation module.

[0029] The 1458.3nm fundamental frequency light then enters the third harmonic generation module. A portion of the 1458.3nm fundamental frequency light undergoes frequency doubling in the frequency doubling crystal 5, generating 729.15nm frequency-doubled light. The remaining portion of the 1458.3nm fundamental frequency light and the generated 729.15nm frequency-doubled light enter the sum-frequency crystal 6 for sum-frequency generation, producing the 486.1nm target blue light 8. This light is then split by a dichroic mirror 7, which separates and outputs the 486.1nm target blue light 8, the 729.15nm laser, and the 1458.3nm laser 9. The frequency doubling crystal 5 and the sum-frequency crystal 6 are nonlinear crystals, including but not limited to lithium borate (LBO), barium metaborate (BBO), or periodically polarized lithium niobate (PPLN) nonlinear crystals.

[0030] It should be noted that in the embodiment using the structure shown in Figure 2, the pump source 1, the high-reflectivity grating 10, the wavelength division multiplexer 11, and the phosphorus-doped fiber 12 can all be fiber optic devices. The pump source 1, the high-reflectivity grating 10, the wavelength division multiplexer 11, and the phosphorus-doped fiber 12 are directly connected through optical fibers to form an optical fiber path.

[0031] Matters not covered in this invention are common knowledge.

[0032] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0033] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A 486nm laser based on Raman laser frequency third harmonics, used to output 486.1nm target blue light, characterized in that, The system includes a fundamental frequency light source, a third-harmonic generation module, and a dichroic mirror. The fundamental frequency light source outputs 1458.3nm fundamental frequency light. The third-harmonic generation module includes a frequency-doubling crystal and a sum-frequency crystal. A portion of the 1458.3nm fundamental frequency light is frequency-doubled in the frequency-doubling crystal, converting it into 729.15nm frequency-doubled light. The remaining 1458.3nm fundamental frequency light and the 729.15nm frequency-doubled light are summed in the sum-frequency crystal to produce target blue light with a wavelength of 486.1nm. The dichroic mirror... A mirror is used to separate and output the target blue light at 486.1 nm, the laser at 729.15 nm, and the laser at 1458.3 nm. The fundamental frequency light source includes a 1050 nm pump source with precisely adjustable wavelength. By actively controlling the output wavelength of the 1050 nm pump source, the fundamental frequency light source can stably generate fundamental frequency light with a precise wavelength of 1458.3 nm, thereby achieving precise locking of the wavelength of the target blue light at 486.1 nm, making it match the Fraunhofer dark line.

2. The 486nm laser based on Raman laser third frequency harmonics according to claim 1, characterized in that, The fundamental frequency light source includes a pump source and a Raman oscillator. The pump source is used to output a 1050nm pump laser and injects the 1050nm pump laser into the Raman oscillator to output 1458.3nm Raman light as the 1458.3nm fundamental frequency light for nonlinear frequency conversion.

3. The 486nm laser based on Raman laser third frequency harmonics according to claim 2, characterized in that, The Raman oscillator consists of an input coupler, a Raman gain medium, and an output coupler. The Raman gain medium is a solid material with a Raman gain peak of 40 THz. The input coupler and the output coupler provide optical feedback with a first-order Raman conversion wavelength of 1221 nm and a second-order Raman conversion wavelength of 1458.3 nm.

4. The 486nm laser based on Raman laser third frequency harmonics according to claim 3, characterized in that, The Raman gain medium is a solid material with a 40THz Raman gain peak, including diamond and phosphorus-doped optical fiber.

5. The 486nm laser based on Raman laser third frequency harmonics according to claim 3, characterized in that, The input coupler and output coupler are coated beam splitters.

6. The 486nm laser based on Raman laser third frequency harmonics according to claim 1, characterized in that, The fundamental frequency light source includes a pump source, a wavelength division multiplexer, a phosphorus-doped fiber, and a high-reflectivity grating. The pump source is used to output a 1050nm pump laser. The pump laser is injected into the phosphorus-doped fiber through the wavelength division multiplexer and converted into bidirectionally scattered first-order Raman light at 1221nm and second-order Raman light at 1458.3nm. The backscattered light enters the high-reflectivity grating through the wavelength division multiplexer. The high-reflectivity grating provides high-reflectivity feedback for the first-order Raman light at 1221nm and the second-order Raman light at 1458.3nm. The output random laser returns along the original path, and the 1458.3nm fundamental frequency light is separated, output, and injected into the third harmonic module.

7. The 486nm laser based on Raman laser third frequency harmonication according to any one of claims 1 to 6, characterized in that, The frequency doubling crystal and the sum frequency crystal are nonlinear crystals, including lithium borate, barium metaborate, and periodically polarized lithium niobate.

8. The application of the 486nm laser based on Raman laser third harmonic as a detection light source in an underwater laser detection system, as described in any one of claims 1 to 6.

9. The application of a 486nm laser based on Raman laser third frequency harmonication as described in any one of claims 1 to 6 in an underwater communication system.

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