Laser intensity low-pass filtering method and device

Abstract

The present invention discloses a method and device for laser intensity low-pass filtering. By determining a range of energy transmission fiber lengths that stabilizes the output light field, the input laser is connected to the energy transmission fiber. The fiber length of the energy transmission fiber is within this range, and the high-intensity signal in a conventional multi-longitudinal mode fiber laser is converted through the Raman effect, thereby achieving the effect of intensity low-pass filtering. The present invention effectively filters out the high-intensity portion of the light wave signal and is particularly suitable for scenarios requiring high uniformity of laser intensity distribution, providing a new solution for related scientific research fields and engineering applications.

Description

Technical Field

[0001] The present invention mainly relates to the field of optical fiber laser technology, in particular to a laser intensity low-pass filtering method and device. Background Art

[0002] Lasers generated by conventional laser oscillators typically contain a large number of longitudinal mode components, which are prone to self-pulsing and partial mode locking, resulting in a time-domain component with high peak power. From the perspective of time-domain intensity statistics, the laser's intensity probability density distribution is wide and contains components with power levels far exceeding the average. Due to the high power density of this laser, it is very easy to induce nonlinear effects, which has become a major limitation in some high-power laser generation and application fields.

[0003] One solution is to use a single-frequency laser that is stable in the time domain, broaden the spectrum through a certain phase modulation, and then further amplify it. However, this high-power laser generation solution has a complex system structure and high cost.

[0004] Another approach is to filter the laser output time domain, but filtering laser time domain signals is more difficult than filtering electrical signals. The main reason is the lack of high-speed actuators that match the frequency of the light wave. Therefore, there are currently few direct filtering methods for near-infrared laser time domain signals. Summary of the Invention

[0005] In view of the requirement of high-power laser amplifier seed source for high concentration of time-domain intensity and the lack of existing laser time-domain filtering technology, the present invention proposes a laser intensity low-pass filtering method and device.

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

[0007] In one aspect, the present invention provides a laser intensity low-pass filtering method, comprising:

[0008] Determine the time domain signal of the input laser;

[0009] Obtaining a corresponding input light field based on a time domain signal of an input laser;

[0010] Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation.

[0011] The stability of the output light field is determined based on the output light field of the input light field after being transmitted through different lengths of the power transmission fiber. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of the power transmission fiber, the corresponding power transmission fiber length is determined to be the power transmission fiber length that can stabilize the output light field.

[0012] The input laser is connected to an energy transmission fiber, the length of which is sufficient to stabilize the output light field, and the high-intensity signal in the input laser is converted through the Raman effect, thereby achieving the purpose of low-pass filtering.

[0013] On the other hand, a laser intensity low-pass filtering device is provided, comprising an input fiber laser light source and a certain length of energy transmission fiber, wherein the input fiber laser light source is connected to the energy transmission fiber, the input fiber laser light source is used to generate an input laser, and the input laser is input into the certain length of energy transmission fiber, and is transmitted through the certain length of energy transmission fiber to achieve the purpose of low-pass filtering, wherein the length of the energy transmission fiber is the energy transmission fiber length that can stabilize the output light field, and is determined by the following steps:

[0014] Determine the time domain signal of the input laser;

[0015] Obtaining a corresponding input light field based on a time domain signal of an input laser;

[0016] Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation.

[0017] Whether the output light field is stable is determined based on the output light field after the input light field is transmitted through different lengths of power transmission optical fibers. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of power transmission optical fiber, the corresponding power transmission optical fiber length is determined to be the power transmission optical fiber length that can stabilize the output light field.

[0018] Compared with the prior art, the technical effects of the present invention are:

[0019] By determining the range of transmission fiber lengths that stabilize the output light field and connecting the input laser to a transmission fiber with the required length, the present invention can convert the high-intensity signal in the input laser through the Raman effect, thereby achieving the effect of intensity low-pass filtering. This method effectively filters out the high-intensity portion of the lightwave signal and is particularly suitable for scenarios requiring high uniformity in laser intensity distribution, providing a new solution for related scientific research and engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1is a schematic structural diagram of a laser intensity low-pass filter device in one embodiment;

[0022] Figure 2 is a schematic diagram of an input time domain signal in one embodiment;

[0023] Figure 3 is based on Figure 2 The schematic diagram of the output time domain signal after the time domain signal is filtered by the laser intensity low-pass filter device is shown;

[0024] Figure 4 is based on Figure 2 The probability density distribution diagram of the time domain signal after being filtered by the laser intensity low-pass filter device is shown;

[0025] Markings in the figure: 1. Input fiber laser light source, 2. Energy transmission fiber, 3. Filter component, 4. Stripping port, 5. Isolation component. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0027] In one embodiment, a laser intensity low-pass filtering method is provided, comprising:

[0028] Determine the time domain signal of the input laser;

[0029] Obtaining a corresponding input light field based on a time domain signal of an input laser;

[0030] Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation.

[0031] The stability of the output light field is determined based on the output light field of the input light field after being transmitted through different lengths of the power transmission fiber. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of the power transmission fiber, the corresponding power transmission fiber length is determined to be the power transmission fiber length that can stabilize the output light field.

[0032] The input laser is connected to an energy transmission fiber, the length of which is sufficient to stabilize the output light field, and the high-intensity signal in the input laser is converted through the Raman effect, thereby achieving the purpose of low-pass filtering.

[0033] Get the time domain signal of the input laser S ( t), then the time domain signal of the input laser S ( t ) preprocessing: including the time domain signal of the detected input laser S ( t ) is normalized and multiplied by the average power of the input laser P 0, divided by the core area of the energy-transmitting fiber (the core radius of the energy-transmitting fiber is ), then take the square root, and then perform interpolation processing to make its data interval meet the subsequent calculation requirements, and use this as the amplitude term of the input light field. Finally, add specific phase noise to the amplitude term of the input light field , such as Gaussian random noise, as the input light field for calculation (That is, the light field at the starting position of the energy transmission fiber );

[0034] ;

[0035] in is the time domain signal of the input laser, is the average power of the input laser, is the core radius of the energy-transmitting optical fiber, represents phase noise.

[0036] Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation. A ( L,t ).

[0037] The bidirectional nonlinear Schrödinger equation is as follows:

[0038] ;

[0039] ;

[0040] in, A ( z,t ) is the envelope of the light field, the superscripts “+” and “−” denote the forward and reverse propagating light, respectively, and the subscripts “p” and “s” denote the pump wave and Raman-Stokes light, respectively. v g is the group velocity; β 2 is the second-order dispersion coefficient; α is the loss coefficient; γ is the nonlinear Kerr coefficient; g R is the Raman gain coefficient; ε is the Rayleigh backscatter coefficient.

[0041] Whether the output light field is stable is determined based on the output light field after the input light field is transmitted through different lengths of power transmission optical fibers. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of power transmission optical fiber, the corresponding power transmission optical fiber length is determined to be the power transmission optical fiber length that can stabilize the output light field. In this way, the available power transmission optical fiber length range can be obtained.

[0042] The input laser is input into the energy transmission optical fiber, and the optical fiber length of the energy transmission optical fiber is within the available energy transmission optical fiber length range to achieve the purpose of low-pass filtering.

[0043] In another embodiment, a laser intensity low-pass filtering device is provided, comprising an input fiber laser light source and a certain length of energy transmission fiber, wherein the input fiber laser light source is connected to the energy transmission fiber, the input fiber laser light source is used to generate an input laser, and the input laser is input into the certain length of energy transmission fiber, and is transmitted through the certain length of energy transmission fiber to achieve the purpose of low-pass filtering, wherein the length of the energy transmission fiber is a length that can stabilize the output light field, and is determined by the following steps:

[0044] Determine the time domain signal of the input laser;

[0045] Obtaining a corresponding input light field based on a time domain signal of an input laser;

[0046] Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation.

[0047] The stability of the output light field is determined based on the output light field after the input light field is transmitted through different lengths of transmission fiber. If the input light field has no self-pulsations in the output light field time domain after transmission through a certain length of transmission fiber, the corresponding transmission fiber length is determined to be the length that can stabilize the output light field. The transmission fiber length in the laser intensity low-pass filter device is selected to ensure a stable output light field. The high-intensity signal in the input laser is converted through the Raman effect, thus achieving the purpose of low-pass filtering.

[0048] Reference Figure 1 The laser intensity low-pass filtering device in one embodiment includes an input fiber laser light source 1, an energy transmission fiber 2, a filter device 3, a stripping port 4, and an isolation device 5. The input fiber laser light source 1 is connected to the energy transmission fiber 2, the energy transmission fiber 2 is connected to the filter device 3, and the filter device 3 is connected to the isolation device 5 before output. The length of the energy transmission fiber 2 is selected to stabilize the output light field, and the high-intensity signal in the input laser is converted through the Raman effect, thereby achieving the purpose of low-pass filtering. The length of the energy transmission fiber 2 is determined according to the method provided in the above embodiment and will not be repeated here.

[0049] The filter device 3 has the function of separating the long wavelength laser light generated by the Raman scattering effect from the input laser light. Its splitting ratio is greater than 20dB, and the fiber size matches the energy transmission fiber. The filter device 3 has a stripping port 4, which is used to guide the Stokes light generated by the Raman effect. The end cap feedback is very small and the reflectivity is less than 10 -4 .

[0050] The input fiber laser light source 1 is a laser light source output by an optical fiber pigtail, and the time domain signal includes pulses with different intensity distributions.

[0051] The energy transmission fiber 2 adopts a large mode field germanium-doped fiber, which is a passive energy transmission fiber. Its core size matches the input fiber laser system. The length of the energy transmission fiber is determined according to the method provided in the above embodiment and will not be repeated here.

[0052] The function of the isolation device 5 is to reduce the subsequent output of the signal laser or to generate feedback when connected to other systems. Its isolation is greater than 20 dB, and the fiber size matches the fiber of the filter device.

[0053] This embodiment utilizes the fast response and intensity-dependent characteristics of stimulated Raman scattering to filter out high-intensity components in the laser time-domain signal, and then obtains useful signal light through spectral filtering.

[0054] The following is based on Figure 1 The structure of the laser intensity low-pass filter device provided is proposed in a corresponding specific embodiment: Figure 2 , is a schematic diagram of the input time-domain signal. The input fiber laser source 1 has a central wavelength of 1070 nm, the output fiber is a 10 / 125 μm double-clad fiber, and the average power is 150 W. The fiber length of the power transmission fiber 2 is determined according to the method provided in the above embodiment. Specifically, calculations show that a 200 m length of the power transmission fiber achieves optimal filtering of the output time-domain signal, so the power transmission fiber length is set to 200 m. The filtering device 3 is a wavelength division multiplexer (WDM). The input fiber is a 10 / 125 μm double-clad fiber. The output fiber has a spectral range of <1100 nm, and the spectral range of the stripping port 4 is ≥1100 nm. The output of the stripping port 4 is subjected to anti-feedback treatment, such as an 8° bevel cut. The isolation device 5 has a pass wavelength of 1070 nm, a 3 dB bandwidth of ±10 nm, and an isolation of 22 dB. The fiber type is 10 / 125 μm double-clad fiber. By using the above structure, the time domain characteristics of the output signal after the time domain signal is filtered by the laser intensity low-pass filter device can be obtained as follows: Figure 3 shown. Figure 4 is based on Figure 2The probability density distribution diagram of the time domain signal after filtering by the laser intensity low-pass filtering device is shown. After filtering, the high-intensity signal in the time domain signal can be better filtered out, thereby achieving the effect of time domain filtering.

[0055] Matters not covered by the present invention are known technologies.

[0056] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0057] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are intended to fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0058] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. Laser intensity low-pass filtering method, characterized in that, include: Determine the time domain signal of the input laser; Obtaining a corresponding input light field based on a time domain signal of an input laser; Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation. The stability of the output light field is determined based on the output light field of the input light field after being transmitted through different lengths of the power transmission fiber. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of the power transmission fiber, the corresponding power transmission fiber length is determined to be the power transmission fiber length that can stabilize the output light field. The input laser is connected to an energy transmission fiber, the length of which is sufficient to stabilize the output light field, and the high-intensity signal in the input laser is converted through the Raman effect, thereby achieving the purpose of low-pass filtering.

2. The laser intensity low-pass filtering method according to claim 1, characterized in that: Obtain the corresponding input light field based on the time domain signal of the input laser ,as follows: in is the time domain signal of the input laser, is the average power of the input laser, is the core radius of the energy-transmitting optical fiber, represents phase noise.

3. The laser intensity low-pass filtering method according to claim 2, characterized in that: Gaussian random noise is used as the phase noise.

4. Laser intensity low-pass filter device, characterized in that, The method comprises an input fiber laser light source and a certain length of energy transmission fiber, wherein the input fiber laser light source is connected to the energy transmission fiber, and the input fiber laser light source is used to generate input laser light, and the input laser light is input into the certain length of energy transmission fiber, and is transmitted through the certain length of energy transmission fiber to achieve the purpose of low-pass filtering, wherein the length of the energy transmission fiber is the energy transmission fiber length that can stabilize the output light field, and is determined by the following steps: Determine the time domain signal of the input laser; Obtaining a corresponding input light field based on a time domain signal of an input laser; Based on the calculated input light field, the output light field after the input light field is transmitted through different energy transmission fiber lengths is calculated using the bidirectional nonlinear Schrödinger equation. Whether the output light field is stable is determined based on the output light field after the input light field is transmitted through different lengths of power transmission optical fibers. If there is no self-pulse in the output light field time domain after the input light field is transmitted through a certain length of power transmission optical fiber, the corresponding power transmission optical fiber length is determined to be the power transmission optical fiber length that can stabilize the output light field.

5. The laser intensity low-pass filter device according to claim 4, characterized in that: Obtain the corresponding input light field based on the time domain signal of the input laser ,as follows: in is the time domain signal of the input laser, is the average power of the input laser, is the core radius of the energy-transmitting optical fiber, represents phase noise.

6. The laser intensity low-pass filter device according to claim 5, characterized in that: Gaussian random noise is used as the phase noise.

7. The laser intensity low-pass filter device according to claim 4, 5 or 6, characterized in that: It also includes a filter device, a stripping port, and an isolation device. The input fiber laser light source is connected to the energy transmission fiber, the energy transmission fiber is connected to the filter device, and the filter device is connected to the isolation device before output.

8. The laser intensity low-pass filter device according to claim 7, characterized in that: The filter device is used to separate the long-wavelength laser generated by the Raman scattering effect from the input laser, with a splitting ratio greater than 20 dB, and the optical fiber size matches the energy transmission optical fiber.

9. The laser intensity low-pass filter device according to claim 8, characterized in that: The filter device has a stripping port, which is used to guide the Stokes light generated by the Raman effect. The reflectivity of the end cap is lower than 10 -4 .

10. The laser intensity low-pass filter device according to claim 8, characterized in that: The energy transmission optical fiber adopts a large mode field germanium-doped optical fiber, and the core size of the optical fiber matches the input optical fiber laser light source.

Images