CN115343797B - Phase shift grating manufacturing system and manufacturing method - Google Patents

Abstract

The invention relates to the technical field of optical fibers, in particular to a phase-shift grating manufacturing system and a manufacturing method. The manufacturing method comprises the following steps: s1, preparing a worker; s2, starting a system; s3, scanning and exposing; s4, generating phase shift; s5, scanning exposure; and S6, closing the system. Compared with the existing phase shift grating manufacturing method, the method has high-consistency batch manufacturing capability; an extremely narrow phase shift region can be manufactured on the optical fiber, and meanwhile, the whole grating has higher reflectivity; the distributed feedback resonant cavity manufactured on the active optical fiber can realize the output of laser with extremely narrow line width; can realize the manufacture of various customized chirped gratings, multi-phase shifted gratings and apodized gratings.

Description

Phase shift grating manufacturing system and manufacturing method

Technical Field

The invention relates to the technical field of optical fibers, in particular to a phase-shift grating manufacturing system and a phase-shift grating manufacturing method.

Background

Compared with the conventional Bragg grating, the phase-shift grating is called as a phase-shift fiber Bragg grating, and the phase-shift grating introduces non-periodic mutation of refractive index at one or more specific parts in the grating region space, so that one or more transmission windows are opened in a grating Bragg reflection band, and the grating has higher selectivity on one or more wavelengths. A resonant cavity formed by single n-shaped phase shift is combined with an active optical fiber as a gain medium, and a fiber laser with extremely narrow line width can be built by matching with a corresponding pumping source, so that the fiber laser is widely applied to the fields of optical fiber sensing, optical communication and spectral analysis.

Currently, the mainstream methods for manufacturing fiber gratings include the following three methods: one is to irradiate a phase mask plate by ultraviolet laser, and form periodic refractive index distribution at the fiber core of the optical fiber by using interference fringes of +/-1 order diffracted light after passing through the phase mask plate, thereby forming the fiber grating. Phase mutation is required to be introduced in the process of manufacturing the grating, and the most direct method is to use a non-uniform phase mask with a prefabricated phase shift, but the method can only manufacture the phase shift grating with a fixed phase shift amount and a phase shift position and is lack of flexibility. Another manufacturing method based on the uniform phase mask is to change the exposure received by part of the fiber grating region to influence the refractive index modulation through partial shielding or secondary exposure, so as to introduce phase shift. The method has the disadvantages that the phase shift quantity is directly influenced by the exposure quantity and is difficult to control accurately, the length of a phase shift area is usually in the order of several millimeters, a short-cavity phase shift grating cannot be manufactured, and the single longitudinal mode output is difficult to realize in the application of an optical fiber laser.

The third phase shift grating making process based on homogeneous phase mask includes setting the homogeneous phase mask on one high precision piezoelectric ceramic micro stage, and making the phase mask produce small displacement in the direction parallel to the fiber after the ultraviolet laser reaches the set position to produce corresponding phase shift in the interference fringe period of ultraviolet light diffraction. The method can conveniently manufacture the phase shift grating with various phase shift amounts and phase shift positions, but because the phase shift occurs in the ultraviolet scanning process, the phase shift region is the superposition of two beams of ultraviolet laser diffraction light spots, and the length of the region limits the longitudinal mode interval of the corresponding narrow-linewidth laser when the phase shift grating is used as a resonant cavity according to the size of the light spots, usually in the order of hundreds of micrometers to one millimeter. Meanwhile, the displacement generated in the laser irradiation process can cause grating chirp and bleaching effect, and the strength and consistency of the finished phase-shift grating are reduced. On the other hand, certain phase errors are accumulated by the movement of the ultraviolet scanning platform in the grating manufacturing process, and the overall reflectivity and the phase shift accuracy of the finally manufactured phase shift grating are influenced to a certain extent.

Therefore, the present application designs a system and a method for manufacturing a phase-shift grating to solve the above problems.

Disclosure of Invention

The invention provides a phase shift grating manufacturing system and a phase shift grating manufacturing method in order to make up for the defects in the prior art.

A phase shift grating manufacturing system comprises an optical vibration isolation table, wherein the optical vibration isolation table is installed on an electric displacement table, a spectroscope which forms an angle of minus 45 degrees with a Y axis is installed on the rear side of the center of the optical vibration isolation table, a plano-convex cylindrical lens is arranged in front of the spectroscope, and an electric control diaphragm is arranged in front of the plano-convex cylindrical lens; the plano-convex cylindrical lens and the electric control diaphragm are arranged on the optical vibration isolation platform;

an ultraviolet laser is arranged on the left side of the optical vibration isolation table, ultraviolet laser emitted by the ultraviolet laser irradiates the spectroscope, and a beam analyzer is arranged on the right side of the spectroscope;

the front side of the optical vibration isolation table is provided with a high-precision piezoelectric ceramic micro-motion table and a clamp, and a phase mask is placed on the high-precision piezoelectric ceramic micro-motion table and the clamp; an optical fiber is arranged in front of the phase mask plate, the optical fiber is fixed through an optical fiber clamp, and the optical fiber is connected with a broadband light source and a spectrometer;

and the phase-shift grating manufacturing system is internally provided with a comprehensive control system which is connected with an ultraviolet laser, a beam analyzer, an electric displacement table, an electric control diaphragm, a high-precision piezoelectric ceramic micro-motion table and a clamp in a control manner.

The ultraviolet laser emitted by the ultraviolet laser irradiates a spectroscope which forms an included angle of minus 45 degrees with the Y axis in the direction parallel to the Y axis, the ultraviolet light with 99 percent of intensity is reflected and changed into the direction parallel to the X axis, and the ultraviolet light passes through an electric control diaphragm which is arranged at the symmetrical center of the X axis on the light path after being shaped and compressed by a plano-convex cylindrical lens which is symmetrically arranged perpendicular to the X axis, and finally enters a phase mask which is arranged on the focus of the plano-convex cylindrical lens in the direction parallel to the Y axis to form diffraction stripes. Meanwhile, 1% of the intensity ultraviolet light propagating along the original Y-axis direction behind the beam splitter is incident on a beam analyzer placed perpendicular to the Y-axis. In the structure, the spectroscope, the plano-convex cylindrical lens and the electric control diaphragm are arranged on an independent optical vibration isolation platform, and the optical vibration isolation platform is fixed on an electric control displacement platform and can move along the parallel direction of the Y axis so as to realize the scanning of ultraviolet laser along the parallel direction of the Y axis. On the other hand, the uniform phase mask is fixed on a high-precision piezoelectric ceramic micro-motion platform by a clamp, micron-level instantaneous micro-motion can be carried out along the Y-axis direction, and the X-axis position of the phase mask is on the focus of the plano-convex cylindrical lens. After a section of optical fiber with a coating layer removed is straightened by applying prestress by two clamps, the optical fiber is fixed at a position 1mm below the X-axis direction of a phase mask in parallel to a Y-axis, the fiber core of the optical fiber is ensured to be positioned at the symmetrical center of a YZ plane of an ultraviolet diffraction stripe by adjusting the height of the clamps, and the left end and the right end of the section of optical fiber are respectively connected to a broadband light source and a spectrometer through jumper wires. In addition, the ultraviolet laser, the beam analyzer, the electric displacement platform, the electric control diaphragm and the high-precision piezoelectric ceramic micropositioner are all connected into a comprehensive control system through wires or data lines, and the comprehensive control system comprises a direct-current power supply, a driving circuit, a signal generator, a collecting card and a computer loaded with related control software.

Further, in order to better implement the present invention, the specification of the spectroscope is that the ultraviolet laser output wavelength band transmittance inverse ratio is 1:99, the diameter of the laser is larger than the diameter of the output light spot of the ultraviolet laser, and the laser is positioned on the axial center of an output light path of the ultraviolet laser; the electric displacement table can be displaced in the parallel direction of the ultraviolet laser emitted by the ultraviolet laser according to a signal provided by the comprehensive control system, the maximum stroke of the electric displacement table is between 60mm and 150mm, and the single-step displacement precision is less than or equal to 1 mu m. The device can enable ultraviolet laser to scan along the parallel direction of the optical fiber axis; the light transmission diameter of the electric control diaphragm is between 0.5mm and 1.5mm, the switching response time is less than or equal to 10 milliseconds, the electric control diaphragm is positioned at a half focal length position on the front optical path axis of the plano-convex cylindrical lens, and the electric control diaphragm can be switched on and off according to signals provided by the comprehensive control system.

Furthermore, in order to better realize the invention, the diameter of a probe of the beam analyzer is larger than the diameter of an output light spot of the ultraviolet laser, the resolution is smaller than 30 × 30 μm, the trigger frequency is larger than 100 frames, the probe is fixed on the right light path axis of the spectroscope, and the probe can feed back the energy and displacement change of the collected light spot to the comprehensive control system in real time.

Furthermore, in order to better realize the invention, the stroke of the high-precision piezoelectric ceramic micropositioner in the high-precision piezoelectric ceramic micropositioner and the fixture is between 10 and 20 micrometers, the single-step displacement precision is less than or equal to 0.2nm, and the load shaking frequency is more than 600Hz, so that the high-precision piezoelectric ceramic micropositioner and the fixture can perform instantaneous micro-motion at a nanometer level according to signals provided by a comprehensive control system to generate phase shift, and can also shake according to function signals provided by the comprehensive control system to apodize a grating.

Furthermore, in order to better realize the invention, the phase mask is a uniform phase mask, and is fixed at the focal position of the plano-convex cylindrical lens by a high-precision piezoelectric ceramic micropositioner and a clamp, and the phase mask period of the uniform phase mask is vertically orthogonal to the ultraviolet laser spot penetrating through the electric control diaphragm at the center.

Furthermore, in order to better realize the invention, the optical fiber is fixed at the center of the near-field ultraviolet light interference fringe in front of the phase mask by an optical fiber clamp after part of the coating layer is removed, and the direction of the optical fiber is consistent with the direction of the ultraviolet laser facula.

Furthermore, in order to better realize the invention, the comprehensive control system comprises a direct current power supply, a driving circuit, a signal generator, a collecting card and a computer loaded with related control software, wherein one function of the comprehensive control system is to set manufacturing parameters of the phase-shift grating and correspondingly control the scanning exposure process of the ultraviolet laser, the other function of the comprehensive control system is to calculate a corrected phase shift amount according to the beam energy and the phase error fed back by a beam analyzer, and the other function of the comprehensive control system is to control the uniform phase mask plate on the high-precision piezoelectric ceramic micropositioner to generate corresponding displacement according to the phase shift amount subjected to dynamic feedback correction.

The phase shift grating manufacturing method based on the system comprises the following steps:

s1, preparation: a manufacturing system is built according to the figure 1, a collimation laser light path is adjusted, a phase mask plate and an optical fiber with a coating layer removed are installed, and two ends of the optical fiber are connected to a broadband light source and a spectrometer through jumper wires. For hydrogen-carrying optical fibers, annealing is appropriate prior to installation.

S2, starting a system: starting a sufficient heat engine of each component power supply of the system, setting relevant parameters of the laser, then starting the comprehensive control system, operating the scanning platform to reach the initial point of the grating area, then setting a scanning stroke, scanning steps, unit exposure time, phase shift amount and phase shift position, starting the laser on the premise of keeping the diaphragm closed, monitoring the beam quality and output intensity of the laser through a beam analyzer, and adjusting the index of the corresponding laser until the preset requirement is met.

S3, scanning exposure: entering a scanning exposure cycle according to the diagram shown in fig. 3, specifically, firstly, opening a diaphragm, enabling interference fringes of plus or minus 1-order diffracted light after ultraviolet laser passes through a phase mask to form periodic refractive index distribution modulation at a fiber core of an optical fiber, closing the diaphragm after reaching a preset unit exposure time, then driving an electric displacement table to move for a unit stroke according to a set scanning stroke and a set scanning step number, then monitoring light spot energy and displacement by using a light beam analyzer, recording a phase error caused by the movement of the electric displacement table, after determining that the light beam disturbance caused by the movement of the displacement table is finished, opening the diaphragm to enter the next exposure cycle, and closing the diaphragm and stopping the cycle until the scanning stroke reaches a preset phase shift position.

S4, generating phase shift: and calculating dynamic feedback phase shift according to the preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micro-motion displacement along the Y-axis parallel direction, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable.

S5, scanning exposure: and restarting the scanning exposure cycle, wherein the difference from the step 3 is that the first to tenth cycles after phase shifting are generated, the actual exposure time is three times of the set exposure time so as to achieve the effects of enhancing the modulation intensity and reducing the phase shifting area as much as possible, the original set exposure time is recovered from the eleventh cycle after phase shifting is generated, and the cycle is continued until the set whole scanning stroke is completed.

S6, closing the system: and monitoring the transmission spectrum of the final phase shift grating product by a spectrometer, if the transmission spectrum reaches a preset target, closing the power supply of each part of the system, and taking down the optical fiber to complete the manufacture of the phase shift grating.

The invention has the beneficial effects that:

compared with other existing phase shift grating manufacturing systems and methods, the manufacturing method of the scanning jitter uniform phase mask based on real-time dynamic feedback has the main advantages that:

1. the grating spectrum accurate to sub-nanometer level, phase shift amount and phase shift position control realized based on diaphragm step exposure and real-time energy acquisition of a beam analyzer have high-consistency batch manufacturing capability.

2. The motion of the scanning displacement table is monitored by a light beam analyzer to give dynamic feedback phase shift compensation, an extremely narrow phase shift area is manufactured on the optical fiber, and meanwhile, the whole grating has higher reflectivity. On the other hand, the distributed feedback resonant cavity manufactured on the active optical fiber by the method can realize the output of laser with extremely narrow linewidth.

3. By changing the scanning speed, the exposure time, the phase shift position and the number, various customized chirped gratings, multi-phase shift gratings and apodized gratings can be manufactured.

Drawings

FIG. 1 is a schematic diagram of a phase-shift grating fabrication system according to the present invention;

FIG. 2 is a flow chart of a method for fabricating a phase-shift grating according to the present invention;

FIG. 3 is a scan exposure cycle diagram of the present invention;

FIG. 4 is a transmission spectrum of a single phase shift grating according to the present invention.

In the figure, the position of the upper end of the main shaft,

1. an ultraviolet laser 2, a spectroscope 3, a beam analyzer 4, an electric displacement table 5, a plano-convex cylindrical lens 6, an optical vibration isolation table 7 and an electric control diaphragm, 8, a high-precision piezoelectric ceramic micro-motion platform and clamp, 9, a phase mask, 10, an optical fiber, 11, an optical fiber clamp, 12, a broadband light source, 13, a spectrometer, 14 and a comprehensive control system.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "disposed," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected unless otherwise explicitly stated or limited. Either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Firstly, a set of phase shift grating manufacturing system is set up as shown in fig. 1, which comprises: 1. the ultraviolet laser outputs pulse laser with the wavelength of 248nm, the pulse width is 20ns, the single pulse energy is 80-140mJ, the repetition frequency is 1-100Hz, and the spot area is 12 x 4.5mm2;2. spectroscopic, 248nm transmission inverse ratio 1:99, diameter 80mm;3. a beam analyzer, wherein the diameter of a probe is 10mm, the resolution is 20 x 20 mu m, and the triggering frequency is 200 frames at most; 4. an electric displacement table with the maximum stroke of 100mm and single-step displacement precision of 0.5 mu m;5. plano-convex cylindrical lens with area 50mm and focal length 300mm;6. an optical vibration isolation stage with an area of 500mm;7. an electric control diaphragm with the diameter of 1mm and the switching response time of 6ms;8. the maximum stroke of the high-precision PZT micro-motion stage and the clamp is 15 mu m, the single-step displacement precision is 0.1nm, and the maximum load shaking frequency is 980Hz;9. a uniform phase mask with a period of 1064nm and a phase mask region area of 60 × 10mm2;10. the optical fiber selects the type of the needed optical fiber according to the type of the manufactured grating; 11. the optical fiber clamp is a special clamp with a V-shaped groove and arranged on the three-dimensional optical adjusting frame; 12. the broadband light source outputs broadband ASE light source with wave band matched with Bragg wavelength of the phase shift grating, the bandwidth is more than 30nm, and the power is more than 20mW;13. the spectrometer detects a spectrometer with a frequency band matched with the Bragg wavelength of the phase-shift grating, and the resolution ratio is less than or equal to 0.05nm;14. the comprehensive control system comprises a direct current power supply, a driving circuit, a signal generator, a collecting card and a computer loaded with relevant control software, wherein the direct current power supply, the driving circuit, the signal generator and the collecting card are required by all components of the system.

In a first embodiment of the present invention, the steps of fabricating a single phase shift grating are as follows:

s1, preparation: a manufacturing system is built according to the figure 1, a collimated laser light path is adjusted, a phase mask and passive optical fibers with coating layers removed are installed, the length of a bare fiber area is 50mm, and two ends of each optical fiber are connected to a broadband light source and a spectrometer through jumper wires.

S2, starting a system: the method comprises the steps of starting a sufficient heat engine of each component power supply of the system, setting pulse energy of an excimer laser to be 50mJ, setting repetition frequency to be 20Hz, starting a comprehensive control system, operating an electric displacement scanning platform to reach a grating area initial point, setting a scanning stroke to be 45mm, setting scanning steps to be 1000, setting unit exposure time to be 500 milliseconds, setting a phase shift amount to be pi, setting the phase shift amount to be a grating area center (stroke 22.5 mm/step number 500), starting the laser on the premise of keeping a diaphragm closed, monitoring beam quality and output intensity of the laser through a beam analyzer, and adjusting corresponding laser indexes until preset values are met.

S3, scanning exposure: entering a scanning exposure cycle according to the diagram shown in fig. 3, specifically, the method includes the steps of firstly opening a diaphragm, allowing interference fringes of ± 1 st order diffracted light of ultraviolet laser passing through a phase mask to form periodic refractive index distribution modulation at a fiber core of an optical fiber, and closing the diaphragm after a preset unit exposure time is reached. And then driving the electric displacement platform to move for a unit stroke according to the set scanning stroke and scanning steps, monitoring the energy and displacement of the light spot by using a light beam analyzer, recording the motion error of the electric displacement platform, and opening the diaphragm to enter the next exposure cycle after determining that the light beam disturbance caused by the motion of the displacement platform is finished. Until the scanning stroke reaches the preset phase shift position (step 500), the diaphragm is closed and the cycle is terminated.

S4, generating phase shift: and calculating dynamic feedback phase shift according to the preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micro-motion displacement along the Y-axis parallel direction, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable.

S5, scanning exposure: and restarting the scanning exposure cycle, wherein the difference from the step 3 is that the first to tenth cycles after phase shift are generated, the actual exposure time is three times of the set exposure time so as to achieve the effects of enhancing the modulation intensity and reducing the phase shift area as much as possible, and the original set exposure time is recovered from the eleventh cycle after phase shift is generated and is continuously circulated until the set whole scanning stroke is completed.

S6, closing the system: the transmission spectrum of the final phase shift grating is monitored by a spectrometer, the result is shown in fig. 3, the preset target is achieved, the power supply of each part of the system is closed according to the operation specification, and the optical fiber is taken down to complete the manufacturing of the phase shift grating.

In a second embodiment of the present invention, the steps of manufacturing the multi-phase shift grating are as follows:

s1, preparation: a manufacturing system is built according to the figure 1, a collimated laser light path is adjusted, a phase mask plate and passive optical fibers with coating layers removed are installed, the length of a bare fiber area is 60mm, and two ends of each optical fiber are connected to a broadband light source and a spectrometer through jumper wires.

S2, starting a system: the method comprises the steps of starting a sufficient heat engine of each component power supply of the system, setting pulse energy of an excimer laser to be 50mJ, setting repetition frequency to be 20Hz, starting a comprehensive control system, operating an electric displacement scanning platform to reach the initial point of a grating area of a grating, setting scanning travel to be 50mm, scanning steps to be 1000, unit exposure time to be 500 milliseconds, phase shift amount to be pi, setting phase shift to be the center of the grating area (at 25 mm/step 500) and three fifths of the grating area (at 30 mm/step 600), starting the laser on the premise of keeping the diaphragm closed, monitoring the beam quality and output intensity of the laser through a beam analyzer, and adjusting corresponding laser indexes until preset values are met.

S3, scanning exposure: entering a scanning exposure cycle according to the diagram shown in fig. 3, specifically, the method includes the steps of firstly opening the diaphragm, enabling the interference fringes of plus or minus 1-order diffracted light of ultraviolet laser passing through the phase mask to form periodic refractive index distribution modulation at the fiber core of the optical fiber, and closing the diaphragm after the preset unit exposure time is reached. And then driving the electric displacement platform to move for a unit stroke according to the set scanning stroke and scanning steps, monitoring the energy and displacement of the light spot by using a light beam analyzer, recording the motion error of the electric displacement platform, and opening a diaphragm to enter the next exposure cycle after determining that the light beam disturbance caused by the motion of the displacement platform is finished. Until the scanning stroke reaches the preset first phase shift position (step 500), the aperture is closed and the cycle is terminated.

S4, generating phase shift: and calculating dynamic feedback phase shift according to the preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micro-motion displacement along the Y-axis parallel direction, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable.

S5, scanning exposure: and restarting the scanning exposure cycle, wherein the difference from the step 3 is that the first to tenth cycles after phase shifting are generated, the actual exposure time is three times of the set exposure time so as to achieve the effects of enhancing the modulation intensity and reducing the phase shifting area as much as possible, the original set exposure time is recovered from the eleventh cycle after phase shifting is generated, and the cycle is continued until the scanning stroke reaches the preset second phase shifting position (step 600), the diaphragm is closed and the cycle is terminated.

S6, generating phase shift: and calculating dynamic feedback phase shift according to the preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micro-motion displacement along the Y-axis parallel direction, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable.

S7, scanning exposure: and restarting the scanning exposure cycle, wherein the difference from the step 3 is that the first to tenth cycles after phase shifting are generated, the actual exposure time is three times of the set exposure time so as to achieve the effects of enhancing the modulation intensity and reducing the phase shifting area as much as possible, the original set exposure time is recovered from the eleventh cycle after phase shifting is generated, and the cycle is continued until the set whole scanning stroke is completed.

S8, closing the system: and monitoring the transmission spectrum of the final phase shift grating product by a spectrometer, closing power supplies of all parts of the system according to the operation specification after a preset target is achieved, and taking down the optical fiber to complete the manufacture of the phase shift grating.

In a third embodiment of the present invention, a method for manufacturing an active phase shift grating comprises:

s1, preparation: a manufacturing system is built according to the figure 1, a collimation laser light path is adjusted, a phase mask plate and an active optical fiber with a coating layer removed are installed, the length of a bare fiber area is 50mm, and two ends of the optical fiber are connected to a broadband light source and a spectrometer through jumper wires.

S2, starting a system: the method comprises the steps of starting a power supply of each component of the system to fully heat the system, setting pulse energy of an excimer laser to be 50mJ, setting repetition frequency to be 20Hz, starting a comprehensive control system, operating an electric displacement scanning platform to reach a starting point of a grating region, setting scanning stroke to be 45mm, scanning step number to be 1000, unit exposure time to be 500 milliseconds, setting phase shift amount to be pi, setting the phase shift amount to be the center of the grating region (stroke 22.5 mm/step number 500), starting the laser on the premise of keeping a diaphragm closed, monitoring beam quality and output intensity of the laser through a beam analyzer, and adjusting indexes of the corresponding laser until preset values are met.

S3, scanning exposure: entering a scanning exposure cycle according to the diagram shown in fig. 3, specifically, the method includes the steps of firstly opening the diaphragm, enabling the interference fringes of plus or minus 1-order diffracted light of ultraviolet laser passing through the phase mask to form periodic refractive index distribution modulation at the fiber core of the optical fiber, and closing the diaphragm after the preset unit exposure time is reached. And then driving the electric displacement platform to move for a unit stroke according to the set scanning stroke and scanning steps, monitoring the energy and displacement of the light spot by using a light beam analyzer, recording the motion error of the electric displacement platform, and opening the diaphragm to enter the next exposure cycle after determining that the light beam disturbance caused by the motion of the displacement platform is finished. Until the scanning stroke reaches the preset phase shift position (step 500), the diaphragm is closed and the cycle is terminated.

S4, generating phase shift: and calculating dynamic feedback phase shift according to a preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micromotion displacement along the parallel direction of the Y axis, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable.

S5, scanning exposure: and restarting the scanning exposure cycle, wherein the difference from the step 3 is that the first to tenth cycles after phase shifting are generated, the actual exposure time is three times of the set exposure time so as to achieve the effects of enhancing the modulation intensity and reducing the phase shifting area as much as possible, the original set exposure time is recovered from the eleventh cycle after phase shifting is generated, and the cycle is continued until the set whole scanning stroke is completed.

S6, closing the system: and monitoring the transmission spectrum of the final phase shift grating product by a spectrometer, closing power supplies of all parts of the system according to the operation specification after a preset target is achieved, and taking down the optical fiber to complete the manufacture of the phase shift grating.

Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims (9)

1. A phase-shift grating fabrication system comprising an optical isolation stage (6), characterized in that:

the optical vibration isolation platform (6) is arranged on the electric displacement platform (4), the spectroscope (2) which forms an angle of minus 45 degrees with the Y axis is arranged on the rear side of the center of the optical vibration isolation platform (6), the plano-convex cylindrical lens (5) is arranged in front of the spectroscope (2), and the electric control diaphragm (7) is arranged in front of the plano-convex cylindrical lens (5); the plano-convex cylindrical lens (5) and the electric control diaphragm (7) are arranged on the optical vibration isolation table (6);

an ultraviolet laser (1) is arranged on the left side of the optical vibration isolation table (6), ultraviolet laser emitted by the ultraviolet laser (1) irradiates the spectroscope (2), and a beam analyzer (3) is arranged on the right side of the spectroscope (2);

a high-precision piezoelectric ceramic micropositioner and a clamp (8) are arranged on the front side of the optical vibration isolation table (6), and a phase mask (9) is placed on the high-precision piezoelectric ceramic micropositioner and the clamp (8); an optical fiber (10) is arranged in front of the phase mask (9), the optical fiber (10) is fixed through an optical fiber clamp (11), and the optical fiber (10) is connected with a broadband light source (12) and a spectrometer (13);

the phase-shift grating manufacturing system is internally provided with a comprehensive control system (14), and the comprehensive control system (14) is in control connection with an ultraviolet laser (1), a beam analyzer (3), an electric displacement table (4), an electric control diaphragm (7), a high-precision piezoelectric ceramic micro-motion table and a clamp (8); the comprehensive control system (14) comprises a direct current power supply, a driving circuit, a signal generator, a collecting card and a computer loaded with related control software, one function of the comprehensive control system is to set manufacturing parameters of a phase shift grating and correspondingly control the scanning exposure process of ultraviolet laser, the other function is to calculate a corrected phase shift amount according to the beam energy and the phase error fed back by a beam analyzer, and the other function is to control a uniform phase mask plate on the high-precision piezoelectric ceramic micropositioner to generate corresponding displacement according to the phase shift amount subjected to dynamic feedback correction.

2. The phase-shift grating fabrication system of claim 1, wherein:

the specification of the spectroscope (2) is that the ultraviolet laser output waveband transmittance inverse ratio is 1:99, the diameter is larger than the output spot diameter of the ultraviolet laser, and the position is on the axial center of the output optical path of the ultraviolet laser (1).

3. The phase-shift grating fabrication system of claim 1, wherein:

the electric displacement table (4) can perform displacement in the parallel direction of ultraviolet laser emitted by the ultraviolet laser (1) according to signals provided by the comprehensive control system (14), the maximum stroke of the electric displacement table is between 60mm and 150mm, the single-step displacement precision is less than or equal to 1 mu m, and the electric displacement table can enable the ultraviolet laser to scan in the parallel direction of the axis of the optical fiber (10).

4. The phase-shift grating fabrication system of claim 1, wherein:

the light transmission diameter of the electric control diaphragm (7) is between 0.5mm and 1.5mm, the switching response time is less than or equal to 10 milliseconds, the electric control diaphragm is positioned at a half of the focal length of the optical path axis in front of the plano-convex cylindrical lens (5), and the electric control diaphragm can be switched on and off according to signals provided by the comprehensive control system (14).

5. The phase-shift grating fabrication system of claim 1, wherein:

the diameter of a probe of the light beam analyzer (3) is larger than the diameter of an output light spot of the ultraviolet laser (1), the resolution is smaller than 30 x 30 mu m, the trigger frequency is larger than 100 frames, the light beam analyzer is fixed on the axis of a right light path of the spectroscope (2), and the light beam analyzer can feed back the energy and displacement change of the collected light spot to the comprehensive control system (14) in real time.

6. The phase-shift grating fabrication system of claim 1, wherein:

the stroke of the high-precision piezoelectric ceramic micro-motion stage in the high-precision piezoelectric ceramic micro-motion stage and the clamp (8) is between 10 and 20 micrometers, the single-step displacement precision is less than or equal to 0.2nm, the load shaking frequency is greater than 600Hz, the high-precision piezoelectric ceramic micro-motion stage and the clamp can perform nano-level instantaneous micro-motion according to signals provided by the comprehensive control system (14) so as to generate phase shift, and can also perform shaking according to function signals provided by the comprehensive control system (14) so as to perform apodization on gratings.

7. The phase-shift grating fabrication system of claim 1, wherein:

the phase mask (9) is a uniform phase mask, and is fixed at the focal length position of the plano-convex cylindrical lens (5) by a high-precision piezoelectric ceramic micro-motion stage and a clamp (8), and the phase mask period of the phase mask is vertically orthogonal to the ultraviolet laser light spot penetrating through the electric control diaphragm (7) in the center.

8. The phase-shift grating fabrication system of claim 1, wherein:

the optical fiber (10) is fixed in the center of the near-field ultraviolet light interference fringe in front of the phase mask (9) by an optical fiber clamp (11) after a part of the coating layer is removed, and the direction of the optical fiber is consistent with the direction of an ultraviolet laser spot.

9. A method for manufacturing a phase shift grating is characterized by comprising the following steps:

s1, preparation: building a manufacturing system, adjusting a collimated laser light path, installing a phase mask and an optical fiber with a coating removed, and connecting two ends of the optical fiber to a broadband light source and a spectrometer by using jumper wires;

s2, starting a system: starting a sufficient heat engine of each component power supply of the system, setting relevant parameters of the laser, then starting the comprehensive control system, operating the scanning platform to reach the initial point of a grating area, then setting a scanning stroke, scanning steps, unit exposure time, phase shift amount and phase shift position, starting the laser on the premise of keeping the diaphragm closed, monitoring the beam quality and output intensity of the laser through a beam analyzer, and adjusting the index of the corresponding laser until the preset requirement is met;

s3, scanning exposure: firstly, opening a diaphragm, enabling interference fringes of +/-1 st-order diffraction light of ultraviolet laser passing through a phase mask to form periodic refractive index distribution modulation at a fiber core of an optical fiber, closing the diaphragm after reaching preset unit exposure time, then driving an electric displacement platform to move for a unit stroke according to a set scanning stroke and scanning steps, monitoring light spot energy and displacement by using a light beam analyzer, recording phase errors caused by movement of the electric displacement platform, opening the diaphragm to enter the next exposure cycle after determining that light beam disturbance caused by movement of the displacement platform is finished, and closing the diaphragm and stopping the cycle until the scanning stroke reaches a preset phase shift position;

s4, generating phase shift: calculating dynamic feedback phase shift according to a preset phase shift amount and the recorded accumulated phase error, enabling the phase mask to generate corresponding micro-motion displacement along the Y-axis parallel direction, and then waiting for 100 milliseconds to enable the phase mask to recover to be stable;

s5, scanning exposure: restarting the scanning exposure cycle, wherein the difference from S3 is that the first to tenth cycles after phase shift are generated, the actual exposure time is three times of the set exposure time, the original set exposure time is recovered from the eleventh cycle after phase shift is generated, and the cycle is continued until the set whole scanning stroke is completed;

s6, closing the system: and monitoring the transmission spectrum of the final phase shift grating product by a spectrometer, if the transmission spectrum reaches a preset target, closing the power supply of each part of the system, and taking down the optical fiber to complete the manufacture of the phase shift grating.

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