Method, device and equipment for predicting raman gain coefficient of gain fiber in fiber laser and medium

Abstract

To address the drawbacks of existing methods for measuring the Raman gain coefficient of optical fibers, such as their cumbersome complexity, this invention proposes a method, apparatus, device, and medium for predicting the Raman gain coefficient of the gain fiber in an optical fiber laser. The method includes inputting the phonon energy distribution, the number of phonons, and the phonon polarizability of the gain fiber in the optical fiber laser; constructing a Raman gain coefficient prediction model based on the phonon energy distribution; and inputting the phonon energy distribution, the number of phonons, and the phonon polarizability into the Raman gain coefficient prediction model to obtain the Raman gain coefficient of the gain fiber. This invention utilizes the magnitude of phonon energy in the gain fiber to rapidly predict the Raman gain coefficient in the optical fiber laser, thereby saving experimental time and significantly improving work efficiency.

Description

Technical Field

[0001] This invention relates to the field of laser parameter prediction technology, and in particular to a method, apparatus, device and medium for predicting the Raman gain coefficient of the gain fiber in a fiber laser. Background Technology

[0002] Fiber Raman amplifiers are lasers that utilize the Raman scattering effect to enhance the intensity of optical signals. In recent years, fiber Raman amplifiers have shown great potential in power enhancement and wavelength extension. Firstly, regarding power enhancement, due to the small quantum defect and absence of photon darkening in Raman lasers, power increases have been exponential in recent years. Secondly, in terms of output wavelength, the Raman gain spectrum has a bandwidth of tens of terahertz. Within this broad gain bandwidth, by selecting an appropriate pump laser wavelength and a suitable Raman cascade order, virtually any wavelength permissible for propagation within the fiber can be obtained. Therefore, Raman fiber lasers are currently the only fiber laser technology capable of achieving flexible wavelength and high-power output, filling output wavelength gaps.

[0003] When designing a fiber Raman amplifier, the combined effects of the fiber, pump light wavelength and power, and signal light must be considered to obtain a certain bandwidth, gain, and gain flatness. First, the Raman gain coefficient g of the fiber must be known. R This is to gain a preliminary prediction and understanding of the power amplification efficiency of fiber Raman amplifiers, and thus better design experimental systems for fiber Raman amplifiers. The g values ​​in different fiber Raman amplifiers... R Since the shapes are similar, the main parameter that needs to be determined is g. R The size of the fiber's Raman gain coefficient g. R Prediction and measurement are therefore quite important.

[0004] Regarding g R The Raman gain coefficient g of the fiber under test is commonly measured using the small-signal gain method. This method involves dividing the output signal of the fiber with and without a fiber laser pump by the signal measured with a small-signal input, and then calculating the gain coefficient g. R However, the small-signal gain method has many drawbacks. For example, it requires point-by-point measurements across the entire band, making the entire testing process cumbersome. Furthermore, point-by-point measurements introduce certain errors, affecting g. RThe accuracy and measurement range are limited. Furthermore, the paper (Raman band intensities of tellurite glasses, *OPTICSLETTERS*, Vol. 30, 2005, 1156-1158) obtains the Raman gain coefficient of the test sample by comparing the spontaneous Raman spectrum of the sample with that of a standard material. The experiment relies on the parametric constants of the standard material (usually silicon dioxide) to obtain the gain coefficient of the test sample, and cannot obtain the Raman gain coefficient experimentally without a standard sample. The paper (Efficient Ramanshifting of picosecond pulses using BaWO4 crystal, *OpticsCommunications*, Vol. 177, 2000, 397-404) obtains the gain coefficient by using picosecond or nanosecond pulses passing through a Raman material in a single pass using stimulated Raman spectroscopy. However, the data processing uses some assumed parameters (such as assumed spontaneous emission noise parameters), which do not consider the influence of different materials on the results, treating the parameters of different materials indiscriminately. The paper (Raman gain measurements in bulk) The glasssamples, J. Opt. Soc. Am. B, Vol. 22, 2005, 1861-1867, utilizes the stimulated Raman phenomenon that occurs when two beams pass through the sample to obtain the Raman gain coefficient by generating energy transfer. The experimental process is complex and difficult to adjust (especially the condition of high temporal and spatial overlap of the two pulses is difficult to meet). Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention proposes a method, apparatus, device, and medium for predicting the Raman gain coefficient of the gain fiber in a fiber laser.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On one hand, the present invention provides a method for predicting the Raman gain coefficient of the gain fiber in a fiber laser, comprising:

[0008] Phonon energy distribution, number of phonons, and polarizability of phonons in the gain fiber of the input fiber laser;

[0009] Construct a Raman gain coefficient prediction model based on phonon energy distribution;

[0010] The Raman gain coefficient of the gain fiber is obtained by inputting the phonon energy distribution, the number of phonons, and the polarization of phonons into the Raman gain coefficient prediction model.

[0011] Furthermore, the type of fiber laser described in this invention is not limited, and the fiber laser may be an amplifier structure laser, an oscillator structure laser, or a master oscillation power amplifier structure laser.

[0012] Furthermore, in the fiber laser described in this invention, the gain fiber can be a doped fiber core with rare earth ions doped in the core, wherein the rare earth ions are one or more of ytterbium, erbium, neodymium, holmium, and thulium.

[0013] Furthermore, the gain fiber in the fiber laser described in this invention can also be a purely passive gain fiber, with no rare earth elements in the core and cladding, but may contain conventional elements, such as germanium, phosphorus, fluorine, etc.

[0014] Furthermore, the Raman gain coefficient prediction model described in this invention is as follows:

[0015]

[0016] Where γ is the inherent Raman gain coefficient influence factor of the gain fiber, and A eff N is the effective mode area of ​​the gain fiber. ph n is the number of phonons, α is the polarizability of the phonons, and n is the polarizability of the phonons. ph It refers to the energy distribution of phonons.

[0017] Furthermore, the method for obtaining the phonon energy distribution, number of phonons, and polarizability of the gain fiber in the fiber laser in this invention is not limited. For example, the phonon energy distribution, number of phonons, and polarizability of the gain fiber in the fiber Raman amplifier can be obtained through optical scattering experiments; or the phonon energy distribution, number of phonons, and polarizability of the gain fiber can be obtained by calculating and simulating the phonon spectrum of the gain fiber in the fiber Raman amplifier.

[0018] On the other hand, the present invention provides a Raman gain coefficient prediction device for the gain fiber in a fiber laser, comprising:

[0019] The input module is used to input the phonon energy distribution, number of phonons, and polarizability of the phonons in the gain fiber of the fiber laser.

[0020] The model building module is used to build a Raman gain coefficient prediction model based on phonon energy distribution;

[0021] The prediction module is used to input the phonon energy distribution, the number of phonons, and the polarizability of phonons into the Raman gain coefficient prediction model to obtain the Raman gain coefficient of the gain fiber.

[0022] On the other hand, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0023] Phonon energy distribution, number of phonons, and polarizability of phonons in the gain fiber of the input fiber laser;

[0024] Construct a Raman gain coefficient prediction model based on phonon energy distribution;

[0025] The Raman gain coefficient of the gain fiber is obtained by inputting the phonon energy distribution, the number of phonons, and the polarization of phonons into the Raman gain coefficient prediction model.

[0026] On the other hand, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, performs the following steps:

[0027] Phonon energy distribution, number of phonons, and polarizability of phonons in the gain fiber of the input fiber laser;

[0028] Construct a Raman gain coefficient prediction model based on phonon energy distribution;

[0029] The Raman gain coefficient of the gain fiber is obtained by inputting the phonon energy distribution, the number of phonons, and the polarization of phonons into the Raman gain coefficient prediction model.

[0030] Phonons are quantum vibrations in crystals, similar to photons in optics, but related to the vibrations of solids. Phonons can be viewed as vibrational modes of atoms or molecules in a crystal lattice. When photons interact with matter, especially coupling with molecular or lattice vibrations, they can excite or induce phonon vibrational modes. In stimulated Raman scattering, phonons are the dominant vibrational modes, and this can be understood through the energy conservation in the Raman scattering process. Incident photon energy - stimulated Raman photon energy = phonon energy. This can be expressed by the formula:

[0031] E photon -E Raman =E phonon

[0032] This means that there is an energy difference between the energy of the stimulated Raman photon and the energy of the incident photon, which is equal to the energy of the corresponding phonon. If the optical fiber has the characteristic of high phonon energy, it will be easier to excite Stokes photons with a lower frequency under the excitation of pump light with a high power density, thereby achieving a stronger Raman gain.

[0033] To address the drawbacks of existing methods for measuring the Raman gain coefficient of optical fibers, such as their cumbersome complexity, this invention discloses a method for rapidly predicting the Raman gain coefficient of the gain fiber in an optical fiber laser. By utilizing the magnitude of phonon energy in the gain fiber, the Raman gain coefficient of the fiber laser can be rapidly predicted, thereby saving experimental time and significantly improving work efficiency. Attached Figure Description

[0034] 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.

[0035] Figure 1 This is a flowchart of a method for predicting the Raman gain coefficient of the gain fiber in a fiber laser, provided in one embodiment. Detailed Implementation

[0036] 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.

[0037] Raman scattering is an inelastic scattering process in which photons interact with lattice vibrations (phonons), causing a change in the photon's energy. The high phonon energy leads to a high Raman gain primarily due to the following factors: Resonant Raman scattering: Raman scattering is more effective when there is resonance between the incident photon energy and the phonon energy levels of the lattice vibrations, resulting in high Raman gain. Under resonance conditions, energy transfer is more efficient, thus increasing the gain. High phonon energy density: If a large number of phonons exist in the crystal, the chances of interaction with photons increase, thereby improving the Raman gain.

[0038] Lattice inhomogeneity: Inhomogeneities or defects in the crystal lattice can also increase the phonon scattering cross section, thereby enhancing Raman scattering. This inhomogeneity can lead to the dispersion of phonon energy levels, thus increasing the chance of interaction with photon energy levels. Resonance enhancement: In some materials, there are resonance enhancement mechanisms that can improve the efficiency of Raman scattering. This involves the resonance of phonon excited states or polaron excited states, thereby increasing the interaction with photons. Wave vector conservation: Like the conservation laws of frequency and energy, the wave vector conservation law also applies to Raman scattering. The wave vector conservation law requires that the sum of the wave vectors of the incident photon and the phonon equals the wave vector of the scattered photon. This ensures phase matching in the interaction between phonons and photons.

[0039] Based on the above analysis, the Raman gain coefficient g R It is expressed as follows:

[0040]

[0041] Where, n r It is a nonlinear refractive index, A eff It is the effective mode field area of ​​the gain fiber, and γ represents the Raman gain coefficient influence factor of the gain fiber, which is caused by factors such as different materials, different temperatures and material inhomogeneities of the gain fiber.

[0042] The energy E of a phonon ph Its frequency ω ph There is a relationship between them; the energy of a phonon can be expressed as:

[0043]

[0044] Among them, E ph It is the energy of phonons. It is Planck's constant, ω ph It is the angular frequency of the phonon.

[0045] The energy distribution function of phonons is usually described by the Bose-Einstein distribution function, which is related to the temperature and angular frequency of the phonons.

[0046]

[0047] Where, n ph It is the energy distribution of phonons. It is Planck's constant, ω ph ω is the angular frequency of the phonon, K is the Boltzmann constant, and T is the temperature of the phonon.

[0048] Nonlinear refractive index n in Raman gain coefficient r It is usually related to the polarizability of phonons and the energy distribution function of phonons:

[0049]

[0050] Where, N ph α is the number of phonons, and α is the polarizability of the phonons, which represents the strength of the interaction between the phonons and the electric field.

[0051] Therefore, substituting equation (4) into equation (1) yields the following Raman gain coefficient prediction model constructed in this invention:

[0052]

[0053] Therefore, the higher the phonon energy, the greater the corresponding Raman gain coefficient. In certain optical applications, a high Raman gain coefficient can be used to achieve laser amplification, frequency conversion, and other fields.

[0054] Phonon energy density is at 1×10 5 -1×10 6 eV / cm 3 At this time, it is defined as the high phonon energy, corresponding to the Raman gain coefficient g. R Ideally located at 5×10 -14 -1×10 -13 Within the W / m range; phonon energy is located at 1×10 4 -1×10 5 eV / cm 3 When the energy is low, it is defined as the Raman gain coefficient g. R Ideally located at 2×10 -14 -5×10 -14 Within the W / m range.

[0055] Based on the constructed Raman gain coefficient model, the relationship between phonon distribution, phonon quantity, phonon polarizability and Raman gain coefficient can be quantified. Based on the Raman gain coefficient prediction model constructed by formula (5), the Raman gain coefficient of the gain fiber in the fiber Raman amplifier under different conditions can be accurately calculated, thereby determining the peak value of the Raman gain coefficient.

[0056] In one embodiment of the present invention, reference is made to... Figure 1 A method for predicting the Raman gain coefficient of the gain fiber in a fiber laser is provided, comprising:

[0057] Phonon energy distribution, number of phonons, and polarizability of phonons in the gain fiber of the input fiber laser;

[0058] Construct a Raman gain coefficient prediction model based on phonon energy distribution;

[0059] The Raman gain coefficient of the gain fiber is obtained by inputting the phonon energy distribution, the number of phonons, and the polarization of phonons into the Raman gain coefficient prediction model.

[0060] The type of fiber laser described in the above embodiments is not limited. It can be an amplifier structure laser, an oscillator structure laser, or a master oscillation power amplifier structure laser.

[0061] In the fiber laser described in the above embodiments, the gain fiber is a doped fiber core with rare earth ions doped in the core. The type of rare earth ions is not limited, and the rare earth ions can be one or more of ytterbium, erbium, neodymium, holmium, thulium, germanium, and phosphorus.

[0062] Furthermore, the methods for obtaining the phonon energy distribution, the number of phonons, and the phonon polarizability of the gain fiber in the fiber laser of this invention are not limited, such as:

[0063] The phonon energy distribution, number of phonons, and phonon polarizability in the gain fiber of a fiber Raman amplifier can be obtained through optical scattering experiments. Specifically, the distribution and number of phonons in the gain fiber can be measured using optical scattering techniques. The scattering spectrum can provide information on the energy, momentum, and polarization of the phonons. This method can be achieved through Raman scattering or Brillouin scattering.

[0064] Furthermore, the mid-infrared absorption spectrum can provide information about phonon vibration modes. The energy of the phonon can be obtained by measuring the absorption spectrum of the gain fiber in the mid-infrared spectral range.

[0065] Alternatively, the phonon spectrum of the gain fiber in a fiber Raman amplifier can be calculated using computational simulation techniques such as density functional theory (DFT) or molecular dynamics simulations. This requires considering factors such as the structure, atomic arrangement, and material properties of the gain fiber. These simulations can yield information such as the phonon energy distribution, the number of phonons, and the phonon polarizability of the gain fiber.

[0066] Furthermore, phonons have a significant impact on the thermal conductivity of materials. By measuring the thermal conductivity of gain optical fibers, information about phonons can be indirectly obtained, including the phonon energy distribution, the number of phonons, and the phonon polarization. Thermal conductivity can be measured using methods such as thermocouple methods and laser scintillation methods.

[0067] In practical applications, it is often necessary to combine multiple technologies and methods to obtain comprehensive phonon information. Those skilled in the art can select appropriate methods based on the actual situation to determine the phonon energy distribution, number of phonons, and phonon polarization in the gain fiber of a fiber laser. The selection of methods mainly depends on the specific requirements of the research and the experimental equipment or simulation tools currently available and utilized.

[0068] The Raman gain coefficient is a parameter describing the intensity gain of the Raman effect in a Raman fiber amplifier. Rapid prediction of the Raman gain coefficient has several potential applications in lasers and optical communications, such as:

[0069] Optimizing optical communication systems: Understanding Raman gain can help optimize the design of optical communication systems. By adjusting the parameters in the fiber optic amplifier, the Raman effect can be utilized to the maximum extent, increasing signal gain and thus improving the performance of the communication system.

[0070] Fiber Optic Sensing: Raman scattering is related to the environment within the optical fiber, such as temperature, stress, and pressure. By measuring the Raman gain coefficient, devices for fiber optic sensing can be designed that can detect changes in environmental parameters based on variations in Raman scattering.

[0071] Laser Design: Understanding the Raman gain factor is crucial for designing lasers with specific wavelengths and power outputs. This helps optimize laser performance, including improving efficiency and stability.

[0072] Raman lasers: For Raman lasers that use the Raman effect to generate laser light, measuring the Raman gain coefficient is crucial. This helps in tuning the parameters of the excitation light to achieve maximum laser gain and efficiency.

[0073] Fiber Optic Amplifier Performance Evaluation: In fiber optic communication systems, Raman fiber amplifiers are one of the commonly used types of optical amplifiers. Measuring the Raman gain coefficient helps evaluate the performance of fiber optic amplifiers and ensures that they function optimally in the communication system.

[0074] In summary, the measurement of Raman gain coefficient is of great significance for research and application in fields such as optical communication, fiber optic sensing, and laser design.

[0075] In another embodiment, a Raman gain coefficient prediction device for the gain fiber in a fiber laser is provided, comprising:

[0076] The input module is used to input the phonon energy distribution, number of phonons, and polarizability of the phonons in the gain fiber of the fiber laser.

[0077] The model building module is used to build a Raman gain coefficient prediction model based on phonon energy distribution;

[0078] The prediction module is used to input the phonon energy distribution, the number of phonons, and the polarizability of phonons into the Raman gain coefficient prediction model to obtain the Raman gain coefficient of the gain fiber.

[0079] The implementation methods of the above modules and the construction of the model can all adopt the methods described in any of the foregoing embodiments, and will not be repeated here.

[0080] On the other hand, the present invention provides a computer device including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the Raman gain coefficient prediction method for the gain fiber in the fiber laser provided in any of the above embodiments. The computer device may be a server. The computer device includes a processor, a memory, a network interface, and a database connected via a system bus. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device stores sample data. The network interface of the computer device is used for communication with external terminals via a network connection.

[0081] On the other hand, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the steps of the Raman gain coefficient prediction method for the gain fiber in the fiber laser provided in any of the above embodiments.

[0082] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0083] Matters not covered in this invention are common knowledge.

[0084] 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.

[0085] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. 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 all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0086] 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 method for predicting the Raman gain coefficient of the gain fiber in a fiber laser, characterized in that, include: To obtain the phonon energy distribution, number of phonons, and polarizability of phonons in the gain fiber of a fiber laser; A Raman gain coefficient prediction model based on phonon energy distribution is constructed as follows: in The Raman gain coefficient is... This refers to the inherent Raman gain coefficient influencing factor of the gain fiber. It is the effective mode area of ​​the gain fiber. It is the number of phonons. It is the polarizability of the phonon. It is the energy distribution of phonons; The Raman gain coefficient of the gain fiber is obtained by inputting the phonon energy distribution, the number of phonons, and the polarization of phonons into the Raman gain coefficient prediction model.

2. The method for predicting the Raman gain coefficient of the gain fiber in a fiber laser according to claim 1, characterized in that, The fiber laser is an amplifier structure laser, an oscillator structure laser, or a master oscillation power amplifier structure laser.

3. The method for predicting the Raman gain coefficient of the gain fiber in a fiber laser according to claim 1, characterized in that, The gain fiber is a core doped with rare earth ions, wherein the rare earth ions are one or more of ytterbium, erbium, neodymium, holmium, and thulium. Alternatively, the gain fiber is a purely passive gain fiber, with no rare earth elements doped in the core and cladding, and the elements doped in the core being one or more of germanium, phosphorus, and fluorine.

4. The method for predicting the Raman gain coefficient of the gain fiber in a fiber laser according to claim 1, 2, or 3, characterized in that, The phonon energy distribution, number of phonons, and polarizability of the phonons in the gain fiber of the fiber Raman amplifier were obtained through optical scattering experiments.

5. The method for predicting the Raman gain coefficient of the gain fiber in a fiber laser according to claim 1, 2, or 3, characterized in that, By calculating and simulating the phonon spectrum of the gain fiber in the fiber Raman amplifier, the phonon energy distribution, the number of phonons, and the polarizability of the phonons in the gain fiber are obtained.

6. A device for predicting the Raman gain coefficient of the gain fiber in a fiber laser, characterized in that, include: The parameter acquisition module is used to obtain the phonon energy distribution, number of phonons, and polarizability of the gain fiber in the fiber laser. Specifically, the phonon energy distribution, number of phonons, and polarizability of the gain fiber in the fiber Raman amplifier are obtained through optical scattering experiments, or by calculating and simulating the phonon spectrum of the gain fiber in the fiber Raman amplifier. The model building module is used to construct a Raman gain coefficient prediction model based on phonon energy distribution, as follows: in The Raman gain coefficient is... This refers to the inherent Raman gain coefficient influencing factor of the gain fiber. It is the effective mode area of ​​the gain fiber. It is the number of phonons. It is the polarizability of the phonon. It is the energy distribution of phonons The prediction module is used to input the phonon energy distribution, the number of phonons, and the polarizability of phonons into the Raman gain coefficient prediction model to obtain the Raman gain coefficient of the gain fiber.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: The processor executes a computer program to implement the steps of the Raman gain coefficient prediction method for the gain fiber in a fiber laser as described in claim 1.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the Raman gain coefficient prediction method for the gain fiber in the fiber laser as described in claim 1.

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