A raman suppression device, method of fabrication and apparatus

Abstract

The present application relates to the field of high-power fiber lasers, and particularly relates to a Raman suppression device, a manufacturing method and a manufacturing device.Mainly includes: the cladding is wrapped outside the core, the coating layer is wrapped outside the cladding, and the cross section of the core, the cladding and the coating layer is concentric circle;Wherein, the core contains a core grating, the core grating has a first included angle with the optical fiber axis, and is used to reflect the Raman light in the core to the cladding;The surface of the cladding contains a channel, the channel has a second included angle with the optical fiber axis, and is used to remove the cladding light in the optical fiber.The present application can integrate the Raman suppression grating and the CPS on the same section of optical fiber, reduce the length of optical fiber used in the device, and avoid the optical path loss caused by the additional CPS device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-power fiber lasers, in particular to a Raman suppression device, a manufacturing method and a manufacturing device. BACKGROUND

[0002] In the field of high-power fiber lasers, as the output power of the laser increases, the power density in the fiber core is higher and higher, which directly leads to the easy excitation of nonlinear effects, such as transverse mode instability (TMI) and Raman scattering (RS). The Raman effect will deteriorate with the increase of transmission distance or power density, which seriously affects the continuous improvement of the power of the fiber laser and the beam quality of the output laser. The commonly used Raman suppression device is a Raman suppression grating, which is based on ultraviolet exposure method and uses the photosensitivity principle of the fiber to write the grating structure in the fiber core. The structure presents a certain angle with the core, which can reflect the Raman scattered light (hereinafter referred to as Raman light) in the core to the cladding, so that it is transmitted and lost in the cladding. At present, the traditional Raman suppression grating has the following disadvantages in use:

[0003] 1. The Raman suppression grating is made based on ultraviolet laser exposure method, and the fiber needs to be treated with hydrogen loading and hydrogen removal. After the fiber grating is made, there are still covalent bonds containing hydrogen inside, which will generate heat and cause large loss in use, affecting the normal laser output power and the long-term stability of the system.

[0004] 2. The traditional Raman suppression grating only reflects the Raman light to the cladding, and uses the large transmission loss of the Raman light in the cladding to make it lose in the transmission process. This method has defects. On the one hand, after the Raman light is reflected by the Raman suppression grating, it will be transmitted in the front and back directions. In the transmission process, it will interfere with the beam combiner or resonant cavity grating and other optical devices, and generally the temperature will rise nonlinearly.

[0005] 3. In order to cooperate with the suppression effect of the Raman suppression device, a cladding power stripper (CPS) needs to be added before and after the Raman suppression grating to improve the beam quality of the output laser. However, excessive device fusion will increase the optical path loss, and excessive fiber will reduce the pre-fabrication of Raman effect, reduce the conversion efficiency and beam quality of the laser, and increase the energy consumption ratio of the laser.

[0006] Therefore, how to overcome the defects of the prior art and solve the defects in the use and manufacture of the existing Raman suppression device is a problem to be solved in the technical field. SUMMARY

[0007] In view of the above defects or improvement needs of the prior art, the present application solves the problems of high optical path loss and large heat generation of the existing Raman suppression device.

[0008] The embodiment of the present application adopts the following technical scheme:

[0009] In a first aspect, the present application provides a Raman suppression device, specifically comprising a fiber core, a cladding and a coating layer, specifically: the cladding is wrapped outside the fiber core, and the coating layer is wrapped outside the cladding; the cross section of the fiber core, the cladding and the coating layer is a concentric circle; wherein the fiber core comprises a fiber core grating, the fiber core grating has a first included angle with the optical fiber axis, and is used for reflecting Raman light in the fiber core to the cladding; the surface of the cladding comprises a channel, the channel has a second included angle with the optical fiber axis, and is used for stripping the cladding light in the optical fiber.

[0010] Preferably, the inside of the cladding further comprises a cladding grating, specifically: the cladding grating has a third included angle with the optical fiber axis, and is used for accelerating the leakage of Raman light reflected by the fiber core grating to the cladding, wherein the first included angle and the third included angle make the center wavelengths of the fiber core and the cladding consistent.

[0011] Preferably, the fiber core grating comprises a first grating, a second grating and a third grating, specifically: the first grating, the second grating and the third grating are sequentially connected along the optical fiber axis direction; wherein the first grating and the third grating have a first reflection wavelength, and are used for reflecting Raman light generated in the direction of the resonant cavity; the second grating has a second reflection wavelength, and is used for reflecting Raman light generated in the direction of the optical fiber joint.

[0012] In a second aspect, the present application provides a manufacturing method of a Raman suppression device, specifically: for manufacturing the Raman suppression device provided in the first aspect, characterized in that it specifically comprises: adjusting the focal point of the processing laser spot on the fiber core of the target optical fiber, placing a mask between the laser light source and the target optical fiber, adjusting the laser parameters using the mask, and writing the fiber core grating on the fiber core of the target optical fiber according to the first included angle; adjusting the focal point of the processing laser spot to a specified depth inside the cladding, adjusting the laser parameters again using the mask, and writing the cladding grating inside the cladding of the target optical fiber according to the third included angle; adjusting the focal point of the processing laser spot to the surface of the cladding, rotating the target optical fiber with the central axis as the axis, and writing the channel on the surface of the cladding according to the second angle.

[0013] Preferably, the laser parameter is adjusted by using the mask, specifically including: adjusting the chirp rate of the laser light source, so that the bandwidth covered by the phase mask can cover the first included angle and the second included angle; setting the phase mask to the first inclination angle, so that the angle of the laser incident on the core meets the first included angle, for writing the core grating; setting the phase mask to the second inclination angle, so that the angle of the laser incident on the cladding meets the third included angle, for writing the cladding grating.

[0014] Preferably, the laser parameter is adjusted by using the mask, specifically including: setting the mask structure corresponding to the first grating and the second grating on the phase mask, so as to write the first grating and the second grating on the core grating.

[0015] In a third aspect, the present application provides a device for manufacturing a Raman suppression device, specifically: for completing the Raman light suppression method provided in the second aspect, characterized in that it comprises a laser writing assembly 1, a phase mask clamp 2, a fiber clamp 3 and a controller, specifically: the laser writing assembly 1 is located above the phase mask clamp 2 and the fiber clamp 3, the phase mask clamp 2 is located between the light outlet of the laser writing assembly 1 and the target optical fiber clamped on the fiber clamp 3, and the controller is connected with the control ports of the laser writing assembly 1, the phase mask clamp 2 and the fiber clamp 3; wherein the phase mask clamp 2 is used to rotate the phase mask to the first inclination angle and the second inclination angle; the fiber clamp 3 is used to fix the target optical fiber in a horizontal state and rotate the target optical fiber to write the channel; and the controller controls other devices to complete the manufacturing according to the Raman light suppression method in any one of claims 4-6.

[0016] Preferably, the device further comprises a horizontal displacement platform 4, and specifically: the fiber clamp 3 is fixed on the horizontal displacement platform 4, which is used to drive the target optical fiber clamped by the fiber clamp 3 to move horizontally, so as to write the core grating and the cladding grating.

[0017] Preferably, the device further comprises a three-dimensional moving table 5, and specifically: the laser writing assembly 1 is fixed on the three-dimensional moving table 5, which is used to drive the laser writing assembly 1 to move, so as to adjust the position of the focal point of the laser writing assembly 1.

[0018] Preferably, the device further comprises a coaxial observation device 6 and a selective transmission lens 7, and specifically: the selective transmission lens 7 is located above the processing position of the target optical fiber, so that the coaxial observation device 6 can observe the processing position through the reflection of the selective transmission lens 7.

[0019] Compared with the prior art, the embodiment of the present application has the beneficial effects that the Raman suppression grating and the CPS are integrated on the same optical fiber, the length of the optical fiber used in the device is reduced, and the optical path loss caused by the additional CPS device is avoided. In the preferred scheme, the leakage speed of the Raman light is further accelerated by adding the cladding grating, and the interference on other devices caused by the propagation of the Raman light in the cladding is avoided.

[0020] In the second aspect, the manufacturing method provided by the embodiment of the present application is processed by laser engraving, and the phase mask is used to adjust the processing parameters. The manufacturing precision and efficiency are improved by using the characteristics of high precision and high speed of laser processing, and the input of polluting materials is reduced.

[0021] In the third aspect, the manufacturing device provided by the embodiment of the present application is used in cooperation with the laser engraving assembly and the special fixture, and can simply and quickly complete the manufacturing method provided in the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0023] Figure 1 A structure schematic diagram of a Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0024] Figure 2 A structure schematic diagram of another Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0025] Figure 3 A structure schematic diagram of another Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0026] Figure 4 A flowchart of a manufacturing method of a Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0027] Figure 5 A principle diagram of a manufacturing method of a Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0028] Figure 6 A structure schematic diagram of a manufacturing device of a Raman suppression device provided by the embodiment of the present application is shown in the figure.

[0029] Figure 7 A schematic diagram of different use states of the mask in the device provided by the embodiment of the present application is shown in the figure.

[0030] Among them, the reference signs are as follows:

[0031] 1. A laser writing assembly, 11, a laser light source, 12, an objective lens system,

[0032] 2. A phase mask holder, 22, a phase mask,

[0033] 3. A fiber holder, 4, a horizontal displacement platform, 5, a three-dimensional moving stage, 6, a coaxial observation device, 7, a selective transmission lens, 8, a test light source, 9, a spectrometer, 10, a target optical fiber. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0035] The present application is a system architecture of a specific function system, so in the specific embodiments, the functional logical relationship of each structure module is mainly described, and the specific software and hardware implementation is not limited.

[0036] In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0037] Embodiment 1:

[0038] In the existing Raman suppression device, usually only a Raman suppression grating is included, but in actual use, in order to cooperate with the suppression effect of the Raman suppression device, a CPS usually needs to be added before and after the Raman suppression grating, but the fusion of the Raman suppression device and the CPS will reduce the conversion efficiency and light speed quality of the laser. In order to solve this problem, the Raman suppression device provided in the embodiment integrates the CPS and the Raman suppression grating, and simultaneously provides the functions of the CPS and the Raman light suppression in the same light.

[0039] As shown in Figure 1 The Raman suppression device provided in the embodiment includes a fiber core, a cladding and a coating layer, the cladding is wrapped outside the fiber core, and the coating layer is wrapped outside the cladding, and the cross sections of the fiber core, the cladding and the coating layer are concentric circles. Among them, the fiber core includes a fiber core grating, the fiber core grating has a first included angle with the optical fiber axis, and is used for reflecting the Raman light in the fiber core to the cladding. The surface of the cladding includes a channel, the channel has a second included angle with the optical fiber axis, and is used for stripping the cladding light in the optical fiber. In a specific implementation, since the device provided in the embodiment corresponds to a Raman wave band, it needs to cover a wide wave band, so the fiber core grating preferably uses a chirped grating that can cover the entire Raman wave band.

[0040] In the Raman suppression device provided in this embodiment, the fiber core grating with a first included angle serves as a Raman suppression grating, reflecting Raman light to the cladding and providing Raman light suppression in the fiber core. On the other hand, in the same fiber segment, a channel with a second included angle on the cladding surface acts as a CPS (Cyclic PS) to strip cladding light. To provide the CPS function, the channel shape is a spiral channel surrounding the cladding surface. Therefore, the Raman suppression device provided in this embodiment integrates the functions of a Raman suppression device and a CPS in the same fiber segment, eliminating the need for an additional CPS connection, making it simpler to use and providing higher beam quality.

[0041] Furthermore, in existing Raman suppression devices, Raman light is usually only reflected to the cladding, allowing it to be naturally lost during transmission. However, during transmission, Raman light may interfere with other optical path devices.

[0042] like Figure 2 The middle arrow indicates the optical path direction. The left side represents the laser cavity direction, where the Raman light propagates primarily in the fiber core. The right side represents the QBH or fiber processing head direction, where the light is reflected from the end face. The reflected light returns to the fiber core and cladding, thus the Raman light propagates within these components. Therefore, in the device provided in this embodiment, as... Figure 2 The structure shown includes a cladding grating inside the cladding. This cladding grating has a third angle with the fiber axis, used to accelerate the leakage of Raman light reflected from the core grating to the cladding. The cladding grating with the third angle also acts as a Raman suppression grating, reflecting the Raman light reflected from the core grating into the cladding again, allowing it to leak out more quickly. In practical applications, due to the different refractive indices of the cladding and the core, different slit spacings are needed to reflect Raman light in the same Raman band. This ensures consistent Raman light reflection by the core grating and the cladding grating. Therefore, the angles of the first and second slits need to be determined according to actual needs, ensuring that the first and third slits match the center wavelengths of the core and cladding. During actual fabrication, the slit spacing can be adjusted by changing the angle between the phase mask and the fiber. This adjustment will result in different periods, and the product of the period and the effective refractive index at that position is proportional to the final grating wavelength.

[0043] Furthermore, in the practical application of fiber lasers, Raman light comes from two sources: one propagating forward from the resonant cavity, and the other returning from the fiber optic connector (Quartz Block Head, abbreviated as QBH). These two sources of Raman light have different optical properties and therefore require separate processing.

[0044] like Figure 3As shown, the device provided by the embodiment comprises a first grating and a second grating, and specifically, the first grating and the second grating are both gradually changed from long-wavelength phase at one end to short-wavelength phase at the other end, and the short-wavelength ends of the first grating and the second grating are connected along the axial direction of the optical fiber; and the device is used for reflecting the Raman light generated in the direction of the resonant cavity and the Raman light generated in the direction of the optical fiber joint. Since the chirped grating has directionality, the suppression efficiency of the Raman grating to the light incident in the positive direction is higher, and therefore, the device uses two Raman suppression gratings with different reflection wavelengths to be connected and combined, so that the Raman light in the two directions can be suppressed respectively, and the suppression effect of the Raman light is further improved.

[0045] In the device provided by the embodiment, the CPS and the Raman suppression grating of the existing scheme are effectively integrated, the multifunctionalization of a single device is realized, the amount of optical fiber in the whole system of the fiber laser is reduced, meanwhile, the length of the optical fiber in the fiber laser is greatly reduced, the optical path loss is greatly reduced, the quality of the output laser is improved, and the conversion efficiency of the system is improved. Meanwhile, the Raman light leakage speed is further improved through the cladding grating, the Raman light in different directions is suppressed through the combination of the Raman gratings with different reflection wavelengths, the nonlinear effect of the whole machine of the fiber laser is further reduced, the quality of the whole machine is improved, the heat generation is low, and the reliability is high.

[0046] Embodiment 2

[0047] In order to more quickly and simply complete the processing and manufacturing of the Raman suppression device provided by embodiment 1, the embodiment further provides a manufacturing method of the Raman suppression device. Laser is focused at different depths of the core and cladding of the optical fiber, and the Raman suppression grating and the CPS are written and manufactured on the target optical fiber. Laser is a flexible processing tool, and by adjusting the position of the focal point, the effect of processing at different distances can be realized, and the internal or external structure of the target material can be modified or etched according to the size of the spot focal point power.

[0048] During the manufacturing, since the coating layer blocks the laser, the middle section of the target optical fiber is first stripped of the coating layer corresponding to the processing length of the Raman suppression grating and the CPS, and after being wiped and cleaned, the target optical fiber is fixed at the processing position. In actual processing, considering the balance of the length of the optical fiber, the suppression effect and the processing technology, the stripping length is preferably 100 mm.

[0049] After the target optical fiber is fixed in place, the indicating light in the same optical path as the processing laser of the laser light source is turned on, or a low-power processing laser is used. The position of the laser spot on the optical fiber is observed through the coaxial observation system to perform preliminary positioning. In order to facilitate subsequent accurate positioning, the target of the preliminary positioning is the midpoint of the core of the optical fiber. In the actual processing process, in order to ensure safety and avoid personnel injury or equipment damage caused by optical path deflection, the power of the processing laser should be less than 10% of the maximum power

[0050] After the initial positioning is completed, as shown in Figure 4 The method for manufacturing the Raman suppression device provided by the embodiment of the present application can be completed using the following steps.

[0051] Step 101: Adjust the focal point of the processing laser to the core of the target optical fiber, place a mask between the laser light source and the target optical fiber, adjust the laser parameters using the mask, and inscribe the core grating on the core of the target optical fiber at a first included angle.

[0052] Since the core is located more centrally in the target optical fiber relative to the cladding, in order to avoid the optical properties of the processing laser passing through being changed after the grating or channel is inscribed on the outer layer of the optical fiber, the core grating closer to the center of the optical fiber needs to be inscribed first.

[0053] First, the actual coordinates of the core grating processing area are obtained, which can be achieved by recording the coordinate points of the first and last ends of the predetermined inscribed position of the core grating on the target optical fiber by continuously moving the position of the light spot. Then, the various displacement parameters of the laser inscribing assembly during processing are obtained by conversion based on the coordinate points of the first and last ends. Since the grating structure of the Raman suppression grating is at a certain angle with the axial direction of the optical fiber, during displacement, the relative positions of the X and Y coordinates of the laser spot and the optical fiber change at the same time, thereby ensuring that the grating area of the core grating is at a certain included angle with the central axis of the optical fiber. In the actual processing process, the displacement of the X and Y coordinates can be achieved by controlling the position change of the light spot of the laser galvanometer, or by driving the position change of the target optical fiber by a horizontal displacement platform.

[0054] In the Raman suppression device provided by Embodiment 1, there are two types of core grating and cladding grating, and since the refractive indices of the core and the cladding are different, the modulation depth required during inscribing is different. Generally, the central wavelength of the cladding grating is smaller than that of the core grating at the same period. In order to facilitate the adjustment of the modulation depth of the processing laser, the method provided in this embodiment uses a phase mask to adjust the phase of the processing laser, thereby ensuring the consistency of the central wavelengths of the core and the cladding after the core grating and the cladding grating are inscribed. Figure 5 The figure is a processing diagram of the phase mask, which can diffract incident light. The mask has many slits, and each slit will diffract. The diffractive structure is reflected on the optical fiber, thereby forming the same diffractive structure on the optical fiber. The diffractive intensity is related to the intensity of the incident light and the included angle between the mask and the optical fiber. Different angles correspond to different periods, and different periods correspond to different wavelengths. Therefore, using the phase mask can facilitate the processing of different wavelength gratings on the optical fiber.

[0055] Step 102: Adjust the focal point of the processing laser to a specified depth in the cladding, and again adjust the laser parameters using the mask, and inscribe the cladding grating in the cladding of the target optical fiber at a third included angle.

[0056] After the core grating is processed, the focal point of the processing laser is adjusted to the writing depth of the cladding grating, and the phase of the processing laser is adjusted again using a mask to make the center wavelengths of the core and the cladding consistent after the cladding grating is written. After adjustment, the writing of the cladding grating can be performed in the manner of step 101.

[0057] Step 103: Adjust the focal point of the processing laser to the cladding surface, and rotate the target optical fiber around the central axis at a second angle to write the channel on the cladding surface.

[0058] The device provided in Example 1 integrates a Raman grating and a CPS. After the writing of the Raman grating is completed through steps 101 and 102, the writing of the CPS needs to be performed. The structure of the CPS is a channel, which can be processed by rotating the target grating while horizontally displacing it. The rotation speed is specific. First, the position of the optical fiber is restored to the starting point, the focal point of the laser spot is adjusted to the cladding of the optical fiber, the rotation and displacement parameters of the target optical fiber are calculated according to the required angle, the target grating is rotated, and the relative translation of the laser spot position and the target optical fiber is performed to finally form the channel structure of the CPS.

[0059] After steps 101-103 provided in this embodiment, the Raman suppression device integrating a Raman grating and a CPS provided in Example 1 can be manufactured.

[0060] In specific processing, the type of processing laser can be selected according to actual needs, such as femtosecond laser, ultraviolet laser, CO2 laser, HeNe laser, etc. The commonly used processing laser type is ultraviolet laser. In the method provided in this embodiment, femtosecond laser is preferably used as the processing laser. The femtosecond laser has short pulse, high energy and large peak power. Compared with the traditional grating ultraviolet writing method and the etching manufacturing process of the mode stripper, the manufacturing process of the femtosecond laser is more efficient.

[0061] In steps 101 and 102, the phase mask needs to be used to change the phase of the processing laser to achieve the consistency of the center wavelengths of the core grating and the cladding grating. The commonly used method is to use two phase masks to switch to compensate for the wavelength difference, which is simple in phase mask design but high in cost. In the method provided in the embodiment, the design parameters of the phase mask can be determined according to the different processing needs of the core grating and the cladding grating. For example, in the case where the length parameter of the mask area is unchanged, the chirp rate of the laser light source is adjusted to increase the range of the bandwidth covered by the phase mask, so that the range of the bandwidth covered by the phase mask can cover the first included angle and the second included angle, and the processing parameters of the core grating and the cladding grating can both meet the processing requirements of the Raman suppression grating. The phase mask can diffract incident light, and when the mask is rotated, the diffraction fringes of the processing laser after passing through the mask will also rotate, and the diffraction fringes irradiated on the optical fiber will also rotate by a certain angle. Different angles will result in different lengths of the diffraction fringes in the core direction, thereby causing the period to change. Therefore, for the tilted gratings made of the same phase mask, the larger the tilt angle of the phase mask, the larger the center wavelength of the Raman suppression grating obtained. Therefore, the center wavelengths of the cladding and the core can be made consistent by rotating the angle of the phase mask. As shown in the figure, the phase mask is set to a first tilt angle, the angle of the laser incident on the core is adjusted to meet the first included angle by rotating the phase mask, and the core grating is written; the phase mask is set to a second tilt angle, and the angle of the laser incident on the cladding is adjusted to meet the third included angle by rotating the phase mask again, and the cladding grating is written. The above method adjusts the tilt angles of the core and the cladding grating by changing the angle of the phase mask, and then controls the center wavelength of the cladding by controlling the tilt angle, so that the processing of the two Raman suppression gratings in the core and the cladding can be completed by using only one phase mask.

[0062] Further, in the device provided in Embodiment 1, the core grating can be composed of multiple Raman suppression gratings connected by different reflection wavelengths. In the method provided in the embodiment, the phase mask can also be used to realize the one-time processing of gratings with different wavelengths. According to the lengths and optical properties of the first grating, the second grating and the third grating, the corresponding parameters of the phase mask are designed, and the mask structure corresponding to the first grating and the second grating is set on the phase mask, so as to write the first grating and the second grating on the core grating. By using the phase mask, the adjustment of the laser parameters during processing can be avoided, and the efficiency and accuracy of the processing can be improved.

[0063] After the processing is completed, the two ends of the target optical fiber after the processing can also be connected to a test light source and an optical spectrum analyzer respectively to form a test loop, and whether the target optical fiber can achieve the desired Raman suppression and CPS effect can be confirmed according to the analysis result of the optical spectrum analyzer.

[0064] The manufacturing method of the Raman suppression device provided by the embodiment uses a laser processing method to complete the writing of the core grating, cladding grating and CPS of the Raman suppression device in Embodiment 1, reduces the manufacturing process steps of the device, reduces the processing difficulty, improves the processing efficiency and processing quality. Moreover, the laser direct writing method is used, without hydrogen loading and without etching, reducing the input of polluting materials. At the same time,

[0065] Embodiment 3:

[0066] Based on Embodiments 1 to 2, the embodiment further provides a manufacturing device of a Raman suppression device, which can execute the method in Embodiment 2 to manufacture the device of the Raman suppression device in Embodiment 1.

[0067] As shown in Figure 6 , it is a device architecture schematic diagram of the embodiment of the application. The device includes a laser writing assembly 1, a phase mask clamp 2, a fiber clamp 3 and a horizontal displacement platform 4. The laser writing assembly 1 is located above the phase mask clamp 2 and the fiber clamp 3, the phase mask clamp 2 is located between the light outlet of the laser writing assembly 1 and the target optical fiber 10 clamped on the fiber clamp 3, and the controller is connected with the control ports of the laser writing assembly 1, the phase mask clamp 2 and the fiber clamp 3.

[0068] The laser writing assembly 1 includes a laser light source 11 and an objective lens system 12. The laser light source 11, the objective lens system 12 and the target optical fiber 10 are located on the same XZ plane, the laser light source 11 is coaxial with the objective lens system 12, and the light spot output by the processing laser emitted by the laser light source 11 after focusing by the objective lens system 12 is located at the radial center position of the optical fiber. Figure 6 In the embodiment, the solid arrowhead indicates the emission direction of the processing laser. In the specific implementation, the model and parameters of the laser light source and the optical path structure and optical parameters of the objective lens system can be determined according to actual processing needs. Preferably, the laser light source 11 is a femtosecond laser light source, the central wavelength of the femtosecond laser is 515 nm, the pulse width is 290 fs, the maximum repetition frequency is 50 KHz and adjustable, and the average power is 20 W. The objective lens system is composed of cylindrical lenses, diaphragms, objective lenses and the like, can realize high transmission of 515 nm band light, and can physically shape the spot size of the laser beam, the spatial position of the focused spot and the like. The typical parameters of the objective lens are: magnification is 50 times, working distance is 17 mm, and numerical aperture is NA0.42.

[0069] The phase mask clamp 2 is used to rotate the phase mask 22 to the first inclination angle and the second inclination angle as shown in Figure 7 , which respectively meet the processing needs of the core grating in step 101 and the cladding grating in step 102. Figure 7In the embodiment, θext represents the included angle of the first and second inclination angles.

[0070] The fiber clamp 3 is used to fix the target fiber 10 in a horizontal state and rotate the target fiber 10 so as to perform groove inscription to meet the groove processing requirement of the cladding surface in step 103.

[0071] Since the core grating, the cladding grating and the spiral groove structure all have a certain length, the relative position between the processing laser spot and the target fiber 10 needs to be horizontally moved when processing. When the target fiber 10 is moved, the horizontal displacement platform 4 can be used in the device. The horizontal displacement platform 4 is used to horizontally move the target fiber 10 clamped by the fiber clamp 3 so as to perform inscription of the core grating and the cladding grating. The horizontal displacement platform 4 can freely move the target fiber 10 fixed on the fiber clamp 3 in the XY plane, move the incident laser along the axial direction of the target fiber, and inscribe through the phase mask to diffract different period and direction of the diffraction fringes on the core and the cladding to complete the fabrication of the core grating and the cladding grating. After being matched with the rotatable fiber clamp 3, the target fiber 10 can complete 360-degree rotation in the axial direction during the translation process to complete the groove processing.

[0072] During the processing, the core grating is located on the core, the cladding grating is located inside the cladding, and the groove is located on the surface of the cladding. The focal point of the processing laser spot needs to be respectively focused on the corresponding depth of the target fiber 10 during the processing. In the embodiment, the focal position of the processing laser spot can be adjusted by changing the optical parameters or the optical path structure of the objective lens system 12, or by changing the relative position between the laser light outlet and the target fiber. In the embodiment, the optical parameters and the optical path structure of the objective lens system 12 are usually difficult to change, while the relative position between the laser light outlet and the target fiber can be easily changed by using common mechanical structure. The laser inscription assembly 1 is fixed on the three-dimensional moving table 5, and the three-dimensional moving table 5 is used to move the laser inscription assembly 1 so as to adjust the focal position of the laser spot of the laser inscription assembly 1. During the processing, the three-dimensional moving table 5 can be used to move the laser inscription assembly 1 along the Z axis to make the focal point of the laser spot fall on different depths of the target fiber.

[0073] In the embodiment, the model and the motion parameters of the fiber clamp 3, the horizontal displacement platform 4 and the three-dimensional moving table 5 can be determined according to the actual processing requirement. Preferably, the rotating motor for rotating the fiber clamp 3, the linear motor for driving the horizontal displacement platform 4 and the linear motor for driving the three-dimensional moving table 5 all have four degrees of freedom electrically controlled adjustable function, and the minimum step precision is ±200 nm and the repeat positioning precision is ±1 um.

[0074] The device provided in the embodiment further comprises a controller, which controls the movement of the optical fiber clamp 3, the horizontal displacement platform 4 and the three-dimensional moving table 5 according to the preset processing parameters, and realizes the controllable adjustment of the focused spot of the femtosecond laser on the optical fiber through the linkage of multiple devices, so as to control other devices to complete the manufacturing according to the Raman light suppression method provided in the embodiment 2.

[0075] Further, since the processing size is small and the laser is dangerous, it is inconvenient to directly observe the focusing and processing process with the naked eye. In order to observe the position of the spot and the processing state, the device provided in the embodiment further comprises a coaxial observation device 6 and a selective transmission lens 7. The selective transmission lens 7 is located above the processing position of the target optical fiber 10, so that the coaxial observation device 6 can observe the processing position through the reflection of the selective transmission lens 7. Figure 7 In the embodiment, the dotted arrow indicates the observation visual light path. For example, when performing preliminary positioning, the position of the focused spot of the laser on the target optical fiber is observed and fed back to the controller for automatic focusing; when processing, the processing state is observed, and the processing is stopped in time when a problem occurs. In specific implementation, the coaxial observation device 6 can use a high-resolution CCD.

[0076] Further, in order to ensure the processing quality, the device can further comprise a test loop of devices, which comprises a test light source 8 and a spectrometer 9. The test light source 8 is used to input a test light signal into the target optical fiber 10, and the spectrometer 9 is used to receive the light signal output by the target optical fiber 10, so as to form a test loop to test the Raman light suppression effect of the target optical fiber 10.

[0077] Hereinafter, a process of processing a Raman suppression device using the device provided in the embodiment in an actual scene is provided. In specific implementation, the specific parameters and processes can be set and adjusted as needed.

[0078] (1) The middle section of the target optical fiber 10 is stripped of a 100mm long coating layer, and after being wiped and cleaned, it is placed on the optical fiber clamp 3. At the same time, the two ends of the target optical fiber are connected to the test light source 8 and the spectrometer 9 respectively to form a test loop.

[0079] (2) Turn on the laser light source 11. In this scene, femtosecond laser is used as the laser light source, and 10% of the laser power is used. First, the position of the laser spot on the optical fiber is observed through the coaxial observation system, and the target position is the midpoint of the fiber core. Then, the position of the spot is adjusted by continuously moving the three-dimensional moving table 5 or the horizontal displacement platform 4, and the coordinate points of the head and tail of the fiber grating and the cladding grating to be inscribed are recorded.

[0080] (3) According to step 101, the displacement parameters of the horizontal displacement platform 4 during the processing of the core grating are calculated by converting the coordinate points at the head and tail ends, and the horizontal displacement platform 4 is set accordingly. The phase mask 22 is set at the first inclination angle, the three-dimensional moving platform 5 is adjusted through the coaxial observation system 10, and the focal point of the light spot is adjusted to the required processing depth of the core grating. The femtosecond laser energy value is adjusted to 80%-90%, and the frequency is 20-50KHz. According to the displacement parameters and process parameters, the X and Y axes of the horizontal displacement platform 4 are moved simultaneously, the X direction travels a length of 80-90mm, and the grating processed is ensured to be at a certain angle with the target optical fiber. After processing, the core grating is completed.

[0081] (4) According to step 102, the position of the optical fiber is restored to the starting point, the phase mask 22 is set at the second inclination angle, and the focal point of the light spot is adjusted to the required processing depth of the cladding grating. The core grating processing process is adjusted, the femtosecond laser energy value is adjusted, and the X and Y axes of the horizontal displacement platform 4 are moved simultaneously according to the displacement parameters and process parameters, to complete the processing of the cladding grating.

[0082] (5) According to step 103, the position of the optical fiber is restored to the starting point, the focal point of the light spot is adjusted to the required processing depth of the trench, and the focal point is about 3-5um away from the cladding interface in the cladding. The femtosecond laser energy parameter is turned on to 100%, and the laser frequency is 50KHz. The rotation function of the optical fiber clamp 3 is started, the rotation speed is about 180° / s, and the horizontal displacement of the horizontal displacement platform 4 is simultaneously started, the horizontal movement speed is about 1mm / s, and the horizontal stroke is about 80-90mm. Finally, the trench structure of the cladding can be formed, and the CPS is completed.

[0083] (6) The device completed is tested using a test circuit, and after the test is completed, the target optical fiber is removed, and the high-efficiency Raman device is completed.

[0084] As can be seen from the above examples, the device provided in the embodiment can complete the manufacturing method of the Raman suppression device provided in embodiment 2, and the target optical fiber is manufactured as the Raman suppression device provided in embodiment 1.

[0085] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A Raman suppressing device, characterized by, The fiber includes a core, a cladding and a coating layer, and specifically: The cladding is wrapped outside the core, and the coating layer is wrapped outside the cladding, and the cross section of the core, the cladding and the coating layer is concentric circle; The core contains a core grating, and the core grating has a first included angle with the optical fiber axis, and is used for reflecting Raman light in the core to the cladding; The surface of the cladding contains a channel, and the channel has a second included angle with the optical fiber axis, and is used for stripping the cladding light in the optical fiber; The inside of the cladding further contains a cladding grating, and specifically: the cladding grating has a third included angle with the optical fiber axis, and is used for accelerating the leakage of Raman light reflected by the core grating to the cladding, wherein the first included angle and the third included angle make the center wavelengths of the core and the cladding consistent; The core grating contains a first grating and a second grating, and specifically: The first grating and the second grating gradually change from long wavelength phase at one end to short wavelength phase at the other end, and the short wavelength ends of the first grating and the second grating are connected along the axial direction of the optical fiber; It is used for reflecting Raman light generated in the direction of the resonant cavity and Raman light generated in the direction of the optical fiber joint.

2. A method for manufacturing the Raman suppressing device according to claim 1, characterized by, Specifically, it includes: Adjusting the focal point of the processing laser spot on the core of the target optical fiber, placing a mask between the laser light source and the target optical fiber, adjusting the laser parameters using the mask, and inscribing the core grating on the core of the target optical fiber according to the first included angle; Adjusting the focal point of the processing laser spot to a specified depth inside the cladding, and again adjusting the laser parameters using the mask to inscribe the cladding grating inside the cladding of the target optical fiber according to the third included angle; Adjusting the focal point of the processing laser spot to the surface of the cladding, rotating the target optical fiber with the central axis as the axis, and inscribing the channel on the surface of the cladding according to the second angle.

3. The method of making a Raman suppression device of claim 2, wherein, The use of the mask to adjust the laser parameters specifically includes: Adjusting the chirp rate of the laser light source so that the bandwidth covered by the phase mask can cover the first included angle and the second included angle; Setting the phase mask to a first inclination angle so that the angle of laser incident on the core conforms to the first included angle for inscribing the core grating; Setting the phase mask to a second inclination angle so that the angle of laser incident on the cladding conforms to the third included angle for inscribing the cladding grating.

4. The method of making a Raman suppression device of claim 2, wherein, The use of the mask to adjust the laser parameters specifically includes: Setting the mask structure corresponding to the first grating and the second grating on the phase mask to inscribe the first grating and the second grating on the core grating.

5. An apparatus for manufacturing a Raman suppression device for performing the Raman light suppression method according to any one of claims 2 to 4, characterized by, It includes a laser inscription assembly (1), a phase mask holder (2), an optical fiber holder (3) and a controller, and specifically: The laser inscription assembly (1) is located above the phase mask holder (2) and the optical fiber holder (3), the phase mask holder (2) is located between the light outlet of the laser inscription assembly (1) and the target optical fiber clamped on the optical fiber holder (3), and the controller is connected with the control ports of the laser inscription assembly (1), the phase mask holder (2) and the optical fiber holder (3); The phase mask holder (2) is used to rotate the phase mask to a first inclination angle and a second inclination angle; The optical fiber holder (3) is used to fix the target optical fiber in a horizontal state and rotate the target optical fiber to inscribe the channel; The controller controls other devices to complete the manufacturing according to the Raman light suppression method in any one of claims 2-4.

6. The apparatus according to claim 5, wherein The device further comprises a horizontal displacement platform (4), in particular: The fiber clamp (3) is fixed on the horizontal displacement platform (4), and is used to drive the target fiber clamped by the fiber clamp (3) to move horizontally, so as to perform the inscription of the core grating and the cladding grating.

7. The apparatus according to claim 5, wherein The device further comprises a three-dimensional moving table (5), in particular: The laser inscription assembly (1) is fixed on the three-dimensional moving table (5), and the three-dimensional moving table (5) is used to drive the laser inscription assembly (1) to move, so as to adjust the position of the focal spot of the laser inscription assembly (1).

8. The apparatus according to claim 5, wherein The device further comprises a coaxial observation device (6) and a selective transmission lens (7), in particular: The selective transmission lens (7) is located above the processing position of the target fiber, so that the coaxial observation device (6) can observe the processing position through the reflection of the selective transmission lens (7).

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