CN108051887B - Apodization grating secondary exposure manufacturing system and method based on dynamic optical shielding plate - Google Patents

Apodization grating secondary exposure manufacturing system and method based on dynamic optical shielding plate Download PDF

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CN108051887B
CN108051887B CN201711440772.7A CN201711440772A CN108051887B CN 108051887 B CN108051887 B CN 108051887B CN 201711440772 A CN201711440772 A CN 201711440772A CN 108051887 B CN108051887 B CN 108051887B
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compensation
exposure
plate
shielding plate
exposure optical
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CN108051887A (en
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陈根祥
田恺
吕敏
王义全
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Minzu University of China
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Minzu University of China
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/02085—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the grating profile, e.g. chirped, apodised, tilted, helical
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

The invention discloses an apodization grating secondary exposure manufacturing system and method based on a dynamic optical shielding plate. The invention adopts a primary exposure optical shielding plate and a secondary exposure optical compensation plate, the centers of the two baffles are respectively provided with an opening which is a conjugate function, and a primary exposure optical shielding plate controller is adopted to control the movement speed of the primary exposure optical shielding plate along the direction vertical to the hydrogen-carrying optical fiber so as to control the exposure time of different areas and complete primary exposure; the secondary exposure optical compensation plate controller controls the movement speed of the secondary exposure optical compensation plate to complete secondary exposure compensation so as to realize direct current refractive index compensation of the apodized grating; the invention has low cost; the optical baffle is adopted as a shielding plate, so that the system is simple in structure and controllable in precision; the digital control of the movement of the optical shielding plate is adopted, so that the adjustment is easy, the control is flexible, the repeatability is good, the efficiency is high, and the industrial production is easy; the invention provides a definite motion function and can realize the manufacture of any apodized grating.

Description

Apodization grating secondary exposure manufacturing system and method based on dynamic optical shielding plate
Technical Field
The invention relates to an optical fiber sensing preparation technology, in particular to an apodization grating secondary exposure manufacturing system based on a dynamic optical shielding plate and a preparation method thereof.
Background
Fiber Bragg Gratings (FBGs) are fiber devices with refractive indexes periodically changing along the axial stroke of the fiber, unique filtering and dispersion characteristics can be manufactured through special refractive index structural design, and the fiber bragg gratings have wide application values in the fields of fiber sensing, laser technology, wavelength division multiplexing and the like. The half-wave linewidth (FWHM) of the grating reflection spectrum, the side-mode rejection ratio (SMSR), and the side-mode roll-off characteristics (SLSR) determine the multiplexing of the system wavelength and the test accuracy. By adopting proper apodization technology in the manufacturing process of the fiber bragg grating, side lobes of the reflection spectrum of the grating can be suppressed and the shape or dispersion property of the reflection spectrum can be improved. Common apodization functions include linear apodization function, cosine apodization function, rising chord apodization function, gao Siqie apodization function, ultra-high-strength apodization function, taer apodization function and the like, and the characteristics of apodized gratings manufactured by different apodization functions are different.
At present, various methods such as an apodization phase mask plate method, an ultraviolet pulse coherent writing apodization grating, a scanning electron microscope method, a point-by-point writing method, a secondary exposure method, a special shielding plate manufacturing method and the like are applied to experimental development of the apodization grating. But the apodization phase mask method needs to accurately design and prepare the phase mask, and different phase mask plates are needed to be customized in different occasions, so that the cost is high; the ultraviolet pulse coherent writing method has high requirements on the coherence of an ultraviolet light source, can not strictly control the shape of an apodization function, and has poor repeatability; although the mirror scanning method can control the shape of the apodization function, the optical path needs to be changed in the grating writing process, so that the stability is poor; the point-by-point writing method is time-consuming to manufacture, has high requirements on accurate motion control of the optical fiber, needs to focus light spots into a grating period, and is difficult to control technically.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an apodized grating secondary exposure manufacturing system based on a dynamic optical shielding plate and a manufacturing method thereof, and a group of dynamic optical shielding plates and a motion function are designed aiming at a commonly used uniform phase mask plate, so that the grating exposure system based on the optical shielding plates can realize controllable preparation of the apodized grating, the control precision can reach 1 mu m, and the grating length can be arbitrarily selected. The system has the advantages of simple structure, low improvement cost, easy adjustment, flexible control, good repeatability, high efficiency, easy industrial production and the like.
An object of the present invention is to provide an apodized grating secondary exposure manufacturing system based on a dynamic optical shielding plate.
The invention relates to an apodization grating secondary exposure manufacturing system based on a dynamic optical shielding plate, which comprises the following steps: an ultraviolet excimer laser, a primary exposure optical shielding plate controller, a plano-convex cylindrical mirror, a uniform phase mask plate, a secondary exposure optical compensation plate and a secondary exposure optical compensation plate controller; the hydrogen-carrying optical fiber of the apodization grating to be prepared, from which the coating layer is removed, is placed along the z axis along the x axis direction by ultraviolet light emitted by an ultraviolet excimer laser; the device comprises a primary exposure optical shielding plate, a primary exposure optical shielding plate controller, a plano-convex cylindrical mirror and a uniform phase mask plate, wherein the primary exposure unit is arranged on an optical path between an ultraviolet excimer laser and a hydrogen-carrying optical fiber, the primary exposure optical shielding plate is electrically connected to the primary exposure optical shielding plate controller, and the plano-convex cylindrical mirror and the uniform phase mask plate are sequentially arranged in front of the primary exposure optical shielding plate along an x-axis; the secondary exposure optical compensation plate, the secondary exposure optical compensation plate controller and the plano-convex cylindrical lens form a secondary compensation unit, the secondary exposure unit is arranged on an optical path between the ultraviolet excimer laser and the hydrogen-carrying optical fiber, the secondary exposure optical compensation plate is electrically connected to the secondary exposure optical compensation plate controller, and the plano-convex cylindrical lens is arranged in front of the secondary exposure optical compensation plate along the x axis; the centers of the baffle plates on the primary exposure optical shielding plate and the secondary exposure optical compensation plate are provided with openings, the planes of the two are yz planes, and the openings on the secondary exposure optical compensation plate are conjugate functions of the primary exposure optical shielding plate; the primary exposure optical shielding plate controller controls the primary exposure optical shielding plate to move along the y axis, and the secondary exposure optical compensation plate controller controls the secondary exposure optical compensation plate to move along the y axis; the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is shaped through the primary exposure optical shielding plate, the motion displacement and the motion speed of the primary exposure optical shielding plate are controlled through the primary exposure optical shielding plate controller according to a motion function, so that the exposure length and the exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the refractive index distribution is changed according to an apodization function, the ultraviolet light is compressed through the plano-convex cylindrical mirror, and a diffraction pattern which is changed periodically is formed through the uniform phase mask plate, and the ultraviolet light is exposed to the hydrogen-carrying optical fiber of the coating layer to complete primary exposure; ultraviolet light excited by the ultraviolet excimer laser is shaped through a secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber of the coating layer, the secondary exposure compensation is completed, and the direct-current refractive index compensation of the apodization grating is realized, so that the apodization grating is obtained.
The apodized grating secondary exposure manufacturing system comprises two exposure modes: a distributed compensation mode and a simultaneous compensation mode.
In the distribution compensation mode, a primary exposure optical shielding plate, a secondary exposure optical compensation plate, a plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along an x-axis between an ultraviolet excimer laser and a light path of a hydrogen-carrying optical fiber to be prepared; removing the secondary exposure optical compensation plate, enabling the ultraviolet excimer laser to emit ultraviolet light along the x-axis direction, shaping through the primary exposure optical shielding plate, controlling the movement displacement and the movement speed of the primary exposure optical shielding plate according to a movement function through the primary exposure optical shielding plate controller, controlling the exposure length and the exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask, and exposing the diffraction pattern on the hydrogen-carrying optical fiber of the coating-removing layer to finish primary exposure; the primary exposure optical shielding plate and the uniform phase mask plate are removed, a secondary exposure optical compensation plate is arranged, ultraviolet light excited by an ultraviolet excimer laser is shaped through the secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation lengths and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber without a coating layer, and secondary exposure compensation is completed, so that direct-current refractive index compensation of the toe-cut grating is realized.
In the simultaneous compensation mode, an ultraviolet excimer laser emits ultraviolet light along the direction of an x axis, the ultraviolet light is divided into two beams by a beam splitter, a primary exposure optical shielding plate, a first plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along the x axis between a first beam of ultraviolet light and a light path of a hydrogen-carrying optical fiber to be prepared, and a secondary exposure optical compensation plate and a second plano-convex cylindrical mirror are sequentially arranged along the x axis between a second beam of ultraviolet light and the light path of the hydrogen-carrying optical fiber to be prepared; shaping the first beam of ultraviolet light through a primary exposure optical shielding plate, controlling the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function through a primary exposure optical shielding plate controller, so as to control the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing the ultraviolet light through a first plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask plate, and exposing the diffraction pattern on the hydrogen-carrying optical fiber of the coating layer to finish primary exposure; meanwhile, the second beam of ultraviolet light is shaped through a secondary exposure optical compensation plate, and the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation lengths and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber of the coating layer, and secondary exposure compensation is completed, so that direct-current refractive index compensation of the apodization grating is realized.
The refractive index of the hydrogen-carrying optical fiber after the primary exposure is uneven, and the direct-current refractive index of the hydrogen-carrying optical fiber is obtained through the secondary exposure compensation.
The invention adopts a primary exposure optical shielding plate and a secondary exposure optical compensation plate, and the refractive index distribution of the grating is controlled to change according to an apodization function through exposure time. The aperture in the center of the baffle plate of the primary exposure optical shielding plate is of a central symmetrical structure, the aperture is in the shape of an isosceles triangle with a vertex angle theta, the high-edge y axis of the isosceles triangle controls the ultraviolet light exposure length z (t) of the hydrogen-carrying optical fiber by controlling the movement displacement l (t) of the primary exposure optical shielding plate according to a movement function through the primary exposure optical shielding plate controller, controls the exposure time of different areas of the hydrogen-carrying optical fiber by controlling the movement speed of the primary exposure optical shielding plate according to the movement function, and moves from the minimum light flux to the maximum light flux along with the movement of the primary exposure optical shielding plate perpendicular to the hydrogen-carrying optical fiber, so that the exposure length on the hydrogen-carrying optical fiber is gradually increased and is proportional to the relative displacement of the primary exposure optical shielding plateThe smaller θ is, the higher the control accuracy is.
Different apodization functions a (z) correspond to different refractive index increment distribution curves n (z), wherein the refractive index increment n (z) is proportional to the exposure time T (z), n (z) =mt (z), and M is the refractive index increment caused by ultraviolet light exposure in unit time. Will have a length of 2Z gratting Is uniformly divided into N small sections, and the length of each small section is deltaz=Z gratting The total increase in refractive index in the ith paragraph is Δn i The total ultraviolet exposure time is delta T i The first exposure optical shielding plate corresponding to the ith small section is regarded as uniform motion v i The method comprises the following steps:
v i ＝Δz/ΔT i ＝Δz/(MΔn i ) (1)
wherein v is i I=1, … …, N, which is the movement speed of the one-shot optical shield plate corresponding to the i-th subsection; the total index increase at any position of the grating is then the sum of the exposure times after that position, where Δt (z) is the time that position starts to be exposed within the kth paragraph:
if the movement velocity v corresponding to the first small section is set 1 Then the corresponding motion speeds of the other segments can be uniquely determined from the apodization function a (z):
wherein DeltaA 1 Total variation of apodization function, deltaA, for paragraph 1 i Total variation for the i-th minor segment apodization function.
The center opening of the baffle plate of the secondary exposure optical compensation plate is a conjugate function of the primary exposure optical shielding plate, and also moves along the direction perpendicular to the hydrogen-carrying optical fiber, and the length z of the secondary exposure compensation is controlled by controlling the movement displacement l (t) of the compensation plate comp (t). The principle of the secondary exposure compensation is to fill up the exposure time of the hydrogen-carrying optical fiber, and the exposure time is the same as that of the primary exposure Exposure time at the heart point T max At the longest, the exposure time needs to be compensated to T in order to make the grating DC refractive index be in a straight line at other points max Refractive index compensation amount n comp (z) is:
the optical shielding plate moves along the same direction as the one-time exposure optical shielding plate, the refractive index compensation is carried out from the edge of the hydrogen-carrying optical fiber, and if the movement speed of the one-time exposure optical shielding plate is v in sequence 1 ,v 2 ,...,v N Then the motion speed of the secondary exposure optical compensation plate is v in turn N ,v N-1 ,...,v 1 。
Another object of the present invention is to provide a method for manufacturing an apodized grating for secondary exposure based on a dynamic optical shielding plate.
The invention discloses a manufacturing method of apodized grating secondary exposure based on a dynamic optical shielding plate, which comprises the following steps:
1) Pretreating an optical fiber to obtain a hydrogen-loaded optical fiber of a grating to be prepared;
2) And (3) setting an optical path:
the device comprises a primary exposure optical shielding plate, a primary exposure optical shielding plate controller, a plano-convex cylindrical mirror and a uniform phase mask plate, wherein the primary exposure unit is arranged on an optical path between an ultraviolet excimer laser and a hydrogen-carrying optical fiber, the primary exposure optical shielding plate is electrically connected to the primary exposure optical shielding plate controller, and the plano-convex cylindrical mirror and the uniform phase mask plate are sequentially arranged in front of the primary exposure optical shielding plate along an x-axis; the secondary exposure optical compensation plate, the secondary exposure optical compensation plate controller and the plano-convex cylindrical lens form a secondary compensation unit, the secondary exposure unit is arranged on an optical path between the ultraviolet excimer laser and the hydrogen-carrying optical fiber, the secondary exposure optical compensation plate is electrically connected to the secondary exposure optical compensation plate controller, and the plano-convex cylindrical lens is arranged in front of the secondary exposure optical compensation plate along the x axis;
3) Determining an apodization function according to a distribution curve of the refractive index increment of the apodization grating to be prepared, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
4) And (3) performing primary exposure:
the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is shaped through a primary exposure optical shielding plate, the primary exposure optical shielding plate moves from a position with minimum luminous flux to a position with maximum luminous flux along the y-axis, the primary exposure optical shielding plate controller controls the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function, so that the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the refractive index distribution is changed according to an apodization function, the ultraviolet light is compressed through a plano-convex cylindrical mirror, a diffraction pattern which is periodically changed is formed through a uniform phase mask, and the ultraviolet light is exposed to the hydrogen-carrying optical fiber of a coating removing layer, so that the primary exposure is completed;
5) And (3) secondary exposure compensation:
ultraviolet light excited by the ultraviolet excimer laser is shaped through a secondary exposure optical compensation plate, the secondary exposure optical compensation plate moves from a position with maximum luminous flux to a position with minimum luminous flux along a y axis, and the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then directly exposed on the hydrogen-carrying optical fiber of a coating layer, and secondary exposure compensation is completed, so that the direct-current refractive index compensation of the toe-cut grating is realized.
Wherein, in step 1), the optical fiber pretreatment comprises the steps of:
i. optical fiber hydrogen loading:
placing the optical fiber in a hydrogen environment at normal temperature and high pressure for several days to improve the photosensitivity of the optical fiber;
optical fiber de-coating layer:
a de-coating operation is performed on the hydrogen loaded fiber portion of the grating to be etched.
In step 2), determining an apodization function according to a distribution curve of refractive index increment of the apodization grating to be prepared, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function, wherein the method specifically comprises the following steps:
i. determining a corresponding apodization function A (z) according to a distribution curve n (z) of the refractive index increment, wherein the refractive index increment n (z) is proportional to the exposure time T (z), n (z) =MT (z), and M is the refractive index increment caused by ultraviolet light exposure in unit time;
ii. will be 2Z in length gratting Is uniformly divided into N small sections, and the length of each small section is deltaz=Z gratting /N；
Total increase in refractive index in the ith paragraph is Δn i The total ultraviolet exposure time is delta T i The first exposure optical shielding plate corresponding to the ith small section moves at a constant speed:
v i ＝Δz/ΔT i ＝Δz/(MΔn i )
wherein v is i I=1, … …, N, which is the movement speed of the one-shot optical shield plate corresponding to the i-th subsection; the total index increase at any position of the grating is then the sum of the exposure times after that position, where Δt (z) is the time that position starts to be exposed within the kth paragraph:
According to the movement velocity v corresponding to the first small segment 1 And according to the apodization function A (z), the movement speeds corresponding to other small segments are uniquely determined:
wherein DeltaA 1 Total variation of apodization function, deltaA, for paragraph 1 i Obtaining a motion function of the primary exposure optical shielding plate for the total variation of the apodization function of the ith small section;
v. the aperture in the center of the baffle plate of the secondary exposure optical compensation plate is the conjugate function of the primary exposure optical shielding plateNumber, also along the direction perpendicular to the hydrogen-carrying optical fiber, the length z of the secondary exposure compensation is controlled by the motion displacement l (t) of the secondary exposure optical compensation plate comp (T) the principle of the secondary exposure compensation is to complement the exposure time of the hydrogen-carrying optical fiber, and the exposure time T at the central point of the primary exposure max At the longest, the exposure time needs to be compensated to T in order to align the DC refractive index of the grating at other points max Refractive index compensation amount n comp (z) is:
the refractive index compensation is carried out from the edge of the hydrogen-carrying optical fiber when the movement of the primary exposure optical shielding plate is in the same direction as that of the primary exposure optical shielding plate, and if the movement speed of the primary exposure optical shielding plate is v 1 ,v 2 ,...,v N Then the motion speed of the secondary exposure compensation plate is v N ,v N-1 ,...,v 1 And obtaining the compensation motion function of the secondary exposure optical compensation plate.
The invention provides a one-shot exposure and two-shot exposure compensation, which comprises two exposure modes: a distributed compensation mode and a simultaneous compensation mode.
Distribution compensation mode:
a) And (3) setting an optical path: a primary exposure optical shielding plate, a secondary exposure optical compensation plate, a plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along an x-axis between an ultraviolet excimer laser and a light path of a hydrogen-carrying optical fiber to be prepared;
b) Determining an apodization function according to the distribution curve of the refractive index increment, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
c) And (3) performing primary exposure:
removing the secondary exposure optical compensation plate, enabling the ultraviolet excimer laser to emit ultraviolet light along the x-axis direction, shaping through the primary exposure optical shielding plate, enabling the primary exposure optical shielding plate to move from a position with minimum luminous flux to a position with maximum luminous flux along the y-axis, controlling the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function through a primary exposure optical shielding plate controller, controlling the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask, and exposing to the hydrogen-carrying optical fiber of the coating layer to finish primary exposure;
d) Repeating the steps b) to c), recording the repetition times and the corresponding movement speed until the ideal transmissivity is achieved, and completing one exposure;
e) And (3) secondary exposure compensation:
the method comprises the steps of removing a primary exposure optical shielding plate and a uniform phase mask plate, setting a secondary exposure optical compensation plate, shaping ultraviolet light excited by an ultraviolet excimer laser, moving the secondary exposure optical compensation plate from a position with maximum luminous flux to a position with minimum luminous flux along a y axis through the secondary exposure optical compensation plate, controlling the movement displacement and the movement speed of the secondary exposure optical compensation plate through a secondary exposure optical compensation plate controller according to a compensation movement function, controlling the ultraviolet light compensation lengths and the compensation time of different areas on a hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, directly exposing to the hydrogen-carrying optical fiber of a coating-removing layer, and completing secondary exposure compensation to realize direct-current refractive index compensation of a toe-cut grating.
The simultaneous compensation mode is as follows:
a) And (3) setting an optical path: the ultraviolet excimer laser emits ultraviolet light along the direction of an x axis, the ultraviolet light is split into two beams by the beam splitter, a primary exposure optical shielding plate, a first plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along the x axis between a first beam of ultraviolet light and a light path of a hydrogen-carrying optical fiber to be prepared, and a secondary exposure optical compensation plate and a second plano-convex cylindrical mirror are sequentially arranged along the x axis between a second beam of ultraviolet light and the light path of the hydrogen-carrying optical fiber to be prepared;
b) Determining an apodization function according to the distribution curve of the refractive index increment, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
c) The first beam of ultraviolet light is shaped through a primary exposure optical shielding plate, the motion displacement and the motion speed of the primary exposure optical shielding plate are controlled through a primary exposure optical shielding plate controller according to a motion function, so that the exposure length and the exposure time of ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a first plano-convex cylindrical mirror, a diffraction pattern which is periodically changed is formed through a uniform phase mask plate and is exposed on the hydrogen-carrying optical fiber of a coating layer, the primary exposure is completed, meanwhile, the second beam of ultraviolet light is shaped through a secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, and the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, and the ultraviolet light is directly exposed on the hydrogen-carrying optical fiber of the coating layer after being compressed through the plano-convex cylindrical mirror, so that the secondary exposure compensation is completed, and the direct refractive index compensation of a cut grating is realized;
d) Repeating the steps b) to c), recording the repetition times and the corresponding movement speed until the ideal transmissivity is achieved, and preparing the apodized grating.
The invention has the advantages that:
the invention adopts a primary exposure optical shielding plate and a secondary exposure optical compensation plate, the centers of the two baffles are respectively provided with an opening which is a conjugate function, and a primary exposure optical shielding plate controller is adopted to control the movement speed of the primary exposure optical shielding plate along the direction vertical to the hydrogen-carrying optical fiber so as to control the exposure time of different areas and complete primary exposure; the secondary exposure optical compensation plate controller controls the movement speed of the secondary exposure optical compensation plate to complete secondary exposure compensation so as to realize direct current refractive index compensation of the apodized grating; the invention reforms the uniform fiber grating manufacturing system of the traditional uniform phase mask plate, and has low improvement cost; the optical baffle plate etched by laser is used as a shielding plate, the system structure is simple, and the precision is controllable; the digital control of the movement of the optical shielding plate is adopted, so that the adjustment is easy, the control is flexible, the repeatability is good, the efficiency is high, and the industrial production is easy; the invention provides a definite motion function and can realize the manufacture of any apodized grating.
Drawings
FIG. 1 is a schematic diagram of an apodized grating secondary exposure production system based on a dynamic optical shield of the present invention;
FIG. 2 is a schematic diagram of a primary exposure optical shielding plate and a secondary exposure optical compensation plate according to an embodiment of an apodized grating secondary exposure production system based on a dynamic optical shielding plate according to the present invention, wherein (a) is a schematic diagram of a primary exposure optical shielding plate and a secondary exposure optical compensation plate, and (b) is a schematic diagram of a secondary exposure optical compensation plate;
FIG. 3 is a schematic diagram of an apodized refractive index profile of an apodized grating secondary exposure production system based on a dynamic optical shield according to the present invention;
FIG. 4 is a schematic diagram of a dynamic optical shield-based apodized grating secondary exposure production system according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a second embodiment of an apodized grating secondary exposure production system based on a dynamic optical shield according to the present invention;
fig. 6 shows the reflection spectrum characteristics of apodized gratings with different apodization functions obtained by the dynamic optical shield based apodized grating secondary exposure method according to the present invention, wherein (a) the reflection spectrum of the apodized grating after the primary exposure and (b) the reflection spectrum of the apodized grating after the secondary exposure.
Detailed Description
The invention will be further elucidated by means of specific embodiments in conjunction with the accompanying drawings.
As shown in fig. 1, the apodized grating double exposure manufacturing system based on the dynamic optical shielding plate of the present embodiment includes: an ultraviolet excimer laser 1, a primary exposure optical shielding plate 21, a primary exposure optical shielding plate controller 22, a plano-convex cylindrical mirror 30, a uniform phase mask plate 24, a secondary exposure optical compensation plate 31, and a secondary exposure optical compensation plate controller 32; wherein, the ultraviolet light emitted by the ultraviolet excimer laser 1 is along the x-axis direction, and the hydrogen-carrying optical fiber 4 of the grating to be prepared from which the coating layer is removed is placed along the y-axis; the primary exposure optical shielding plate 21, the primary exposure optical shielding plate controller 22, the plano-convex cylindrical mirror 30 and the uniform phase mask plate 24 form a primary exposure unit, the primary exposure unit is arranged on an optical path between the ultraviolet excimer laser 1 and the hydrogen-carrying optical fiber, the primary exposure optical shielding plate 21 is electrically connected to the primary exposure optical shielding plate controller 22, and the plano-convex cylindrical mirror 30 and the uniform phase mask plate 24 are sequentially arranged in front of the primary exposure optical shielding plate 21 along the x axis; the secondary exposure optical compensation plate 31, the secondary exposure optical compensation plate controller 32 and the plano-convex cylindrical mirror 30 form a secondary compensation unit, the secondary exposure unit is arranged on an optical path between the ultraviolet excimer laser 1 and the hydrogen-carrying optical fiber, the secondary exposure optical compensation plate 31 is electrically connected to the secondary exposure optical compensation plate controller 32, and the plano-convex cylindrical mirror is arranged in front of the secondary exposure optical compensation plate 31 along the x axis; the centers of the baffle plates on the primary exposure optical shielding plate 21 and the secondary exposure optical compensation plate 31 are provided with openings, the planes of the two are yz planes, and the openings on the secondary exposure optical compensation plate 31 are conjugate functions of the primary exposure optical shielding plate 21; the primary exposure optical shielding plate controller 22 controls the speed at which the primary exposure optical shielding plate 21 moves along the y-axis, and the secondary exposure optical compensation plate controller 32 controls the secondary exposure optical compensation plate 31 to move along the y-axis at an opposite speed.
The first exposure optical shielding plate and the second exposure optical compensation plate control the grating refractive index distribution to vary according to an apodization function by exposure time as shown in fig. 2. The aperture in the center of the baffle plate of the primary exposure optical shielding plate is of a central symmetrical structure, the aperture is in the shape of an isosceles triangle with an angle theta, the high-edge y-axis of the isosceles triangle controls the ultraviolet light exposure length z (t) of the hydrogen-carrying optical fiber by controlling the motion displacement l (t) of the primary exposure optical shielding plate through the primary exposure optical shielding plate controller, controls the exposure time of different areas of the hydrogen-carrying optical fiber by controlling the motion speed of the primary exposure optical shielding plate, and the exposure length on the hydrogen-carrying optical fiber is gradually increased along with the motion of the primary exposure optical shielding plate along the direction perpendicular to the hydrogen-carrying optical fiber and is proportional to the relative displacement of the primary exposure optical shielding plateThe smaller θ is, the higher the control accuracy is.
Fig. 2 (a) shows a design size of a single exposure optical shielding plate, which has a total length of 165mm, a width of 40mm, a center hole length l=135 mm, θ=6°, and an apodized grating maximum exposure length z=14 mm, and if the single exposure optical shielding plate controller is a stepper motor with an accuracy of 10 μm, the control accuracy of the shielding plate is 0.5 μm, which is about one mask period. As shown in FIG. 2 (b), the aperture in the center of the shutter of the secondary exposure optical compensation plate is the conjugate function of the primary exposure optical shielding plate
Fig. 3 is a schematic diagram of an apodization refractive index profile, wherein different apodization functions a (z) correspond to different refractive index increment profiles n (z), the refractive index increment n (z) is proportional to the exposure time T (z), n (z) =mt (z), and M is the refractive index increment caused by uv exposure in unit time. Will have a length of 2Z gratting Is uniformly divided into N small sections, and the length of each small section is deltaz=Z gratting The total increase in refractive index in the ith paragraph is Δn i The total ultraviolet exposure time is delta T i The primary exposure optical shielding plate moves at a constant speed:
v i ＝Δz/ΔT i ＝Δz/(MΔn i )
wherein v is i I=1, … …, N for the movement speed corresponding to the i-th segment; the total index increase at any position of the grating is then the sum of the exposure times after that position, where Δt (z) is the time that position starts to be exposed within the kth paragraph:
if the movement velocity v corresponding to the first small section is set 1 Then the corresponding motion speeds of the other segments can be uniquely determined from the apodization function a (z):
wherein DeltaA 1 Total variation of apodization function, deltaA, for paragraph 1 i Total variation for the i-th minor segment apodization function.
The center opening of the baffle plate of the secondary exposure optical compensation plate is a conjugate function of the primary exposure optical shielding plate, and also moves along the direction perpendicular to the hydrogen-carrying optical fiber, and the length z of the secondary exposure compensation is controlled by controlling the movement displacement l (t) of the compensation plate comp (t). The principle of the secondary exposure compensation is to complement the exposure time of the hydrogen-carrying optical fiber, and the exposure time T at the central point during the primary exposure max At the longest, the exposure time needs to be compensated to T in order to align the DC refractive index of the grating at other points max Refractive index compensation amount n comp (z) is:
the optical shielding plate moves along the same direction as the one-time exposure optical shielding plate, the refractive index compensation is carried out from the edge of the hydrogen-carrying optical fiber, if the movement speed of the one-time exposure optical shielding plate is v 1 ,v 2 ,...,v N Then the motion speed of the compensation plate is v N ,v N-1 ,...,v 1 。
Example 1
In this embodiment, as shown in fig. 4, a primary exposure optical shielding plate 21, a secondary exposure optical compensation plate 31, a plano-convex cylindrical mirror 30, a uniform phase mask 24 and a uniform phase mask controller 52 are sequentially disposed along the x-axis between the uv excimer laser 1 and the optical path of the hydrogen-carrying optical fiber to be prepared; the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is shaped through a primary exposure optical shielding plate, the primary exposure optical shielding plate moves from a position with minimum luminous flux to a position with maximum luminous flux along the y-axis, the motion displacement and the motion speed of the primary exposure optical shielding plate are controlled through a primary exposure optical shielding plate controller according to a motion function, so that the exposure length and the exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber 4 are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror, a diffraction pattern which is periodically changed is formed through a uniform phase mask plate, and the ultraviolet light is exposed on the hydrogen-carrying optical fiber of a coating removing layer to finish primary exposure; removing the primary exposure optical shielding plate and the uniform phase mask plate, shaping ultraviolet light excited by the ultraviolet excimer laser through the secondary exposure optical compensation plate, moving the secondary exposure optical compensation plate from the position with maximum luminous flux to the position with minimum luminous flux along the y axis, controlling the movement displacement and the movement speed of the secondary exposure optical compensation plate according to a compensation movement function through a secondary exposure optical compensation plate controller, thereby controlling the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber, compressing the ultraviolet light through the plano-convex cylindrical mirror, and then directly exposing the ultraviolet light to the hydrogen-carrying optical fiber without the coating layer to complete secondary exposure compensation so as to realize direct current refractive index compensation of the toe-cut grating. The uniform phase mask controller 52 controls the displacement of the uniform phase mask 24.
The manufacturing method of apodized grating secondary exposure in the distribution compensation mode of the embodiment comprises the following steps:
1) Moving the primary exposure optical shielding plate 21 to the position with the minimum ultraviolet light flux, moving the secondary exposure optical compensation plate 31 to the position with the maximum light flux, moving the uniform phase mask plate 24 to the light path, adjusting the central axes of the three to be aligned, removing the coating layer of the hydrogen-carrying optical fiber 4, fixing the hydrogen-carrying optical fiber, and enabling the grating area to be etched to be close to the uniform phase mask plate as much as possible;
2) Setting the output pulse frequency and pulse energy power of the ultraviolet excimer laser 1, and setting the initial velocity v of the primary exposure optical shielding plate 21 1 Setting the movement speeds v of different segments of the corresponding one-shot optical shielding plate 21 according to the formula (3) and the apodization function 2 ,v 3 ...,v N I.e., the motion function of the one-shot optical shield;
3) The ultraviolet excimer laser 1 starts to emit ultraviolet light, and the primary exposure optical shielding plate 21 is v determined by the apodization function 1 ,v 2 ,...,v N The secondary exposure optical compensation plate 31 is stationary perpendicular to the movement of the hydrogen-carrying optical fiber 4. Monitoring the transmission spectrum of the apodized grating, if the desired transmittance is not achieved, adjusting the initial velocity v appropriately 1 Repeating the steps 2) and 3), recording the repetition times and the corresponding movement speed until the ideal transmissivity is achieved, and completing one exposure;
4) The primary exposure optical shielding plate 21 is moved to a position with high ultraviolet light flux, the secondary exposure optical compensation plate 31 is moved to a position with minimum light flux, and the uniform phase mask 24 is moved out of the light path through the phase mask controller 52;
5) The ultraviolet excimer laser 1 starts the ultraviolet light emitted by the primary exposure according to the parameters of the primary exposure, the primary exposure optical shielding plate 21 is static, and the secondary exposure optical compensation plate 31 is arranged according to v according to the cycle number and the initial speed of the primary exposure record N ,v N-1 ,...,v 1 Namely, the motion function of the secondary exposure optical compensation plate moves perpendicular to the hydrogen-carrying optical fiber 4 until the compensation is finished, and the apodized grating manufacturing is completed.
Example two
In this embodiment, as shown in fig. 5, the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, and is split into two beams by the beam splitter 7, a primary exposure optical shielding plate 21, a first plano-convex cylindrical mirror 23 and a uniform phase mask plate 24 are sequentially disposed along the x-axis between the first beam of ultraviolet light and the optical path of the hydrogen-carrying optical fiber to be prepared, and a secondary exposure optical compensation plate 31 and a second plano-convex cylindrical mirror 33 are sequentially disposed along the x-axis between the second beam of ultraviolet light and the optical path of the hydrogen-carrying optical fiber to be prepared; shaping the first beam of ultraviolet light through a primary exposure optical shielding plate, controlling the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function through a primary exposure optical shielding plate controller, so as to control the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing the ultraviolet light through a first plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask plate, and exposing the diffraction pattern on the hydrogen-carrying optical fiber of the coating layer to finish primary exposure; meanwhile, the second beam of ultraviolet light is shaped through a secondary exposure optical compensation plate, and the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation lengths and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber of the coating layer, and secondary exposure compensation is completed, so that direct-current refractive index compensation of the apodization grating is realized. The optical path direction is changed by the first to third mirrors 61 to 63.
The manufacturing method of the apodized grating secondary exposure based on the dynamic optical shielding plate of the embodiment comprises the following steps:
1) Moving the primary exposure optical shielding plate 21 to the position with the minimum ultraviolet light flux, moving the secondary exposure optical compensation plate 31 to the position with the minimum light flux, removing the coating layer of the hydrogen-carrying optical fiber 4, fixing the hydrogen-carrying optical fiber, enabling a grating area to be inscribed to be as close to the uniform phase mask plate 24 as possible, and adjusting each device to be aligned to the central axis;
2) Setting the output pulse frequency and pulse energy power of the ultraviolet excimer laser 1, and setting the initial velocity v of the primary exposure optical shielding plate 21 1 Setting the movement speeds v of different sections of the one-shot optical shielding plate 21 according to the formula (3) and the apodization function 2 ,v 3 ...,v N ；
3) The ultraviolet excimer laser 1 starts to emit ultraviolet light, and the primary exposure optical shielding plate 21 is v determined by the apodization function 1 ,v 2 ,...,v N The speed is perpendicular to the movement of the hydrogen carrying optical fiber 4; meanwhile, the secondary exposure optical compensation plate 31 is set to v N ,v N-1 ,...,v 1 Is moved perpendicular to the hydrogen-carrying optical fiber 4;
4) After completing a periodic movement, the transmission spectrum of the apodized grating is monitored, and if the ideal transmittance is not achieved, the initial speed v is properly adjusted 1 Repeating the steps 2) and 3) until the ideal transmissivity is achieved, and manufacturing the apodized grating.
The first embodiment and the second embodiment have the same principle and are based on a dynamic optical shielding plate apodization grating secondary exposure manufacturing system. The first embodiment has simple light path, can monitor in real time in the grating writing process, but has long writing period; the second embodiment is a recommended system scheme, the light path is not changed once, the repeatability and the stability are good, the inscription period is short, and the industrial production is easy to realize.
In summary, the utility model designs a dynamic optical shielding plate apodization grating secondary exposure manufacturing system aiming at a common grating inscription system of a uniform phase mask plate, provides a control principle and a motion function of the shielding plate, can realize random apodization grating inscription with the control precision of 0.5 mu m, and can randomly select the grating length in the ultraviolet light source length. The system has the advantages of low improvement cost, simple structure, controllable precision, easy adjustment, flexible control, good repeatability, high efficiency and easy industrialized production, and can write common fiber gratings with any length.
The utility model can customize any apodized grating with any apodized function, and different apodized gratings have respective characteristics in half-wave line width (FWHM), side Mode Suppression Ratio (SMSR) and side mode roll-off characteristics (SLSR). The present utility model gives four apodization functions in table 1: a Uniform grating function (uniformity), a linear apodization function (Line), a Gaussian apodization function (Gaussian), a tale apodization function (nuttal). Where L is the grating length, a is the apodization amplitude, and b is the Gaussian coefficient. Fig. 6 shows theoretical analysis of the reflectance spectra after the corresponding primary exposure and secondary compensation at 90% reflectance for several apodization functions of table 1. As can be seen from fig. 6 (a), the one-time apodization function causes the left side mode rejection ratio to deteriorate drastically at high transmittance, and is substantially independent of the apodization function; the right side mode rejection ratio is basically related to the apodization function characteristics, and the right side mode rejection degree of the apodization function with good apodization characteristics is high. Fig. 6 (b) shows the reflection spectrum after the different apodized gratings have 10dB of transmissivity and are completely compensated, wherein the apodization effect of the linear apodization function is the lowest, but basically, the system improvement of more than 10dB can be ensured, the apodization effect of the gaussian function is moderate, the Nuttall apodization function is the best apodization function found so far, and the side mode rejection ratio can reach more than 90dB theoretically. Meanwhile, as the apodization depth increases, the half-wave line width gradually increases.
List one
TABLE 1 apodized grating function
The present invention can customize the above four gratings, but is not limited to these four gratings, and should also include any other apodized gratings that can improve the sidelobe characteristics of the gratings, such as a tailed apodized function, an ascending tailed apodized function, and an ultra-high-order apodized function.
Finally, it should be noted that the examples are disclosed for the purpose of aiding in the further understanding of the present invention, but those skilled in the art will appreciate that: various alternatives and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the disclosed embodiments, but rather the scope of the invention is defined by the appended claims.

Claims (8)

1. An apodization grating secondary exposure manufacturing system based on a dynamic optical shielding plate is characterized by comprising the following components: an ultraviolet excimer laser, a primary exposure optical shielding plate controller, a plano-convex cylindrical mirror, a uniform phase mask plate, a secondary exposure optical compensation plate and a secondary exposure optical compensation plate controller; the hydrogen-carrying optical fiber of the apodization grating to be prepared, from which the coating layer is removed, is placed along the z axis along the x axis direction by ultraviolet light emitted by the ultraviolet excimer laser; the single exposure optical shielding plate, the single exposure optical shielding plate controller, the plano-convex cylindrical mirror and the uniform phase mask plate form a single exposure unit, the single exposure unit is arranged on a light path between the ultraviolet excimer laser and the hydrogen-carrying optical fiber, the single exposure optical shielding plate is electrically connected to the single exposure optical shielding plate controller, and the plano-convex cylindrical mirror and the uniform phase mask plate are sequentially arranged in front of the single exposure optical shielding plate along the x axis; the secondary exposure optical compensation plate, the secondary exposure optical compensation plate controller and the plano-convex cylindrical mirror form a secondary compensation unit, the secondary compensation unit is arranged on a light path between the ultraviolet excimer laser and the hydrogen-carrying optical fiber, the secondary exposure optical compensation plate is electrically connected to the secondary exposure optical compensation plate controller, and the plano-convex cylindrical mirror is arranged in front of the secondary exposure optical compensation plate along the x axis; the centers of the baffle plates on the primary exposure optical shielding plate and the secondary exposure optical compensation plate are provided with openings, the planes of the two are yz planes, and the openings on the secondary exposure optical compensation plate are conjugate functions of the primary exposure optical shielding plate; the primary exposure optical shielding plate controller controls the primary exposure optical shielding plate to move along the y axis, and the secondary exposure optical compensation plate controller controls the secondary exposure optical compensation plate to move along the y axis; the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is shaped through the primary exposure optical shielding plate, the motion displacement and the motion speed of the primary exposure optical shielding plate are controlled through the primary exposure optical shielding plate controller according to a motion function, so that the exposure length and the exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the refractive index distribution is changed according to an apodization function, the ultraviolet light is compressed through the plano-convex cylindrical mirror, and a diffraction pattern which is changed periodically is formed through the uniform phase mask plate, and the ultraviolet light is exposed to the hydrogen-carrying optical fiber of the coating layer to complete primary exposure; the ultraviolet light excited by the ultraviolet excimer laser is shaped through a secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed on the hydrogen-carrying optical fiber of the coating layer, the secondary exposure compensation is completed, and the direct-current refractive index compensation of the apodization grating is realized, so that the apodization grating is obtained; the aperture in the center of the baffle plate of the one-time exposure optical shielding plate is of a central symmetrical structure, the shape of the aperture is an isosceles triangle with a vertex angle theta, and the high-edge y axis of the isosceles triangle is provided with a plurality of holes; the apodization grating secondary exposure manufacturing system comprises two exposure modes: a distributed compensation mode and a simultaneous compensation mode.
2. The apodization grating secondary exposure manufacturing system according to claim 1, wherein in the distribution compensation mode, a primary exposure optical shielding plate, a secondary exposure optical compensation plate, a plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along an x-axis between an ultraviolet excimer laser and a light path of a hydrogen-carrying optical fiber to be prepared; removing the secondary exposure optical compensation plate, enabling the ultraviolet excimer laser to emit ultraviolet light along the x-axis direction, shaping through the primary exposure optical shielding plate, controlling the movement displacement and the movement speed of the primary exposure optical shielding plate according to a movement function through the primary exposure optical shielding plate controller, controlling the exposure length and the exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask, and exposing the diffraction pattern on the hydrogen-carrying optical fiber of the coating-removing layer to finish primary exposure; the primary exposure optical shielding plate and the uniform phase mask plate are removed, a secondary exposure optical compensation plate is arranged, ultraviolet light excited by an ultraviolet excimer laser is shaped through the secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation lengths and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber without a coating layer, and secondary exposure compensation is completed, so that direct-current refractive index compensation of the toe-cut grating is realized.
3. The apodization grating secondary exposure manufacturing system according to claim 1, wherein in the simultaneous compensation mode, the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is split into two beams by the beam splitter, a primary exposure optical shielding plate, a first plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along the x-axis between the first beam of ultraviolet light and the optical path of the hydrogen-carrying optical fiber to be prepared, and a secondary exposure optical compensation plate and a second plano-convex cylindrical mirror are sequentially arranged along the x-axis between the second beam of ultraviolet light and the optical path of the hydrogen-carrying optical fiber to be prepared; shaping the first beam of ultraviolet light through a primary exposure optical shielding plate, controlling the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function through a primary exposure optical shielding plate controller, so as to control the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing the ultraviolet light through a first plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask plate, and exposing the diffraction pattern on the hydrogen-carrying optical fiber of the coating layer to finish primary exposure; meanwhile, the second beam of ultraviolet light is shaped through a secondary exposure optical compensation plate, and the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation lengths and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then is directly exposed to the hydrogen-carrying optical fiber of the coating layer, and secondary exposure compensation is completed, so that direct-current refractive index compensation of the apodization grating is realized.
4. A method of manufacturing an apodized grating double exposure manufacturing system based on a dynamic optical shield according to claim 1, the method comprising the steps of:
1) Pretreating an optical fiber to obtain a hydrogen-loaded optical fiber of a grating to be prepared;
2) And (3) setting an optical path:
the device comprises a primary exposure optical shielding plate, a primary exposure optical shielding plate controller, a plano-convex cylindrical mirror and a uniform phase mask plate, wherein the primary exposure unit is arranged on an optical path between an ultraviolet excimer laser and a hydrogen-carrying optical fiber, the primary exposure optical shielding plate is electrically connected to the primary exposure optical shielding plate controller, and the plano-convex cylindrical mirror and the uniform phase mask plate are sequentially arranged in front of the primary exposure optical shielding plate along an x-axis; the secondary exposure optical compensation plate, the secondary exposure optical compensation plate controller and the plano-convex cylindrical mirror form a secondary compensation unit, the secondary compensation unit is arranged on an optical path between the ultraviolet excimer laser and the hydrogen-carrying optical fiber, the secondary compensation optical compensation plate is electrically connected to the secondary exposure optical compensation plate controller, and the plano-convex cylindrical mirror is arranged in front of the secondary exposure optical compensation plate along the x axis;
3) Determining an apodization function according to a distribution curve of the refractive index increment of the apodization grating to be prepared, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
4) And (3) performing primary exposure:
the ultraviolet excimer laser emits ultraviolet light along the x-axis direction, the ultraviolet light is shaped through a primary exposure optical shielding plate, the primary exposure optical shielding plate moves from a position with minimum luminous flux to a position with maximum luminous flux along the y-axis, the primary exposure optical shielding plate controller controls the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function, so that the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the refractive index distribution is changed according to an apodization function, the ultraviolet light is compressed through a plano-convex cylindrical mirror, a diffraction pattern which is periodically changed is formed through a uniform phase mask, and the ultraviolet light is exposed to the hydrogen-carrying optical fiber of a coating removing layer, so that the primary exposure is completed;
5) And (3) secondary exposure compensation:
ultraviolet light excited by the ultraviolet excimer laser is shaped through a secondary exposure optical compensation plate, the secondary exposure optical compensation plate moves from a position with maximum luminous flux to a position with minimum luminous flux along a y axis, and the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, so that the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a plano-convex cylindrical mirror and then directly exposed on the hydrogen-carrying optical fiber of a coating layer, and secondary exposure compensation is completed, so that the direct-current refractive index compensation of the toe-cut grating is realized.
5. The method of manufacturing according to claim 4, wherein in step 1), the optical fiber pretreatment includes the steps of:
i. optical fiber hydrogen loading:
placing the optical fiber in a hydrogen environment at normal temperature and high pressure for several days to improve the photosensitivity of the optical fiber;
optical fiber de-coating layer:
a de-coating operation is performed on the hydrogen loaded fiber portion of the grating to be etched.
6. The method of manufacturing as claimed in claim 4, wherein in step 2), an apodization function is determined according to a distribution curve of refractive index increase of the apodized grating to be manufactured, and a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate are determined according to the apodization function, specifically comprising the steps of:
i. determining a corresponding apodization function A (z) according to a distribution curve n (z) of the refractive index increment, wherein the refractive index increment n (z) is proportional to the exposure time T (z), n (z) =MT (z), and M is the refractive index increment caused by ultraviolet light exposure in unit time;
ii. will be 2Z in length gratting Is uniformly divided into N small sections, and the length of each small section is deltaz=Z gratting /N；
Total increase in refractive index in the ith paragraph is Δn i The total ultraviolet exposure time is delta T i The one-time exposure optical shielding plate corresponding to the ith small section is in uniform motion v i The method comprises the following steps:
v i ＝Δz/ΔT i ＝Δz/(MΔn i )
wherein v is i I=1, …, k, …, N for the movement speed of the first exposure optical shielding plate corresponding to the i-th subsection; the total index increase at any position of the grating is then the sum of the exposure times after that position, where Δt (z) is the time that position starts to be exposed within the kth paragraph:
according to the movement velocity v corresponding to the first small segment 1 And according to the apodization function A (z), the movement speeds corresponding to other small segments are uniquely determined:
wherein DeltaA 1 Total variation of apodization function, deltaA, for paragraph 1 i Obtaining a motion function of the primary exposure optical shielding plate for the total variation of the apodization function of the ith small section;
v. the aperture in the center of the baffle plate of the optical compensation plate for secondary exposure is the conjugate function of the optical shielding plate for primary exposure, and the aperture moves along the direction perpendicular to the hydrogen-carrying optical fiber, and the displacement l (t) of the optical compensation plate for secondary exposure is used for controlling the secondary exposureLength z of exposure compensation comp (T) the principle of the secondary exposure compensation is to complement the exposure time of the hydrogen-carrying optical fiber, and the exposure time T at the central point of the primary exposure max At the longest, the exposure time needs to be compensated to T in order to align the DC refractive index of the grating at other points max Refractive index compensation amount n comp (z) is:
The refractive index compensation is carried out from the edge of the hydrogen-carrying optical fiber when the movement of the primary exposure optical shielding plate is in the same direction as that of the primary exposure optical shielding plate, and if the movement speed of the primary exposure optical shielding plate is v 1 ,v 2 ,...,v N Then the motion speed of the secondary exposure compensation plate is v N ,v N-1 ,...,v 1 And obtaining the compensation motion function of the secondary exposure optical compensation plate.
7. The method of claim 4, wherein the exposing means using a distributed compensation means comprises the steps of:
a) And (3) setting an optical path: a primary exposure optical shielding plate, a secondary exposure optical compensation plate, a plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along an x-axis between an ultraviolet excimer laser and a light path of a hydrogen-carrying optical fiber to be prepared;
b) Determining an apodization function according to the distribution curve of the refractive index increment, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
c) And (3) performing primary exposure:
removing the secondary exposure optical compensation plate, enabling the ultraviolet excimer laser to emit ultraviolet light along the x-axis direction, shaping through the primary exposure optical shielding plate, enabling the primary exposure optical shielding plate to move from a position with minimum luminous flux to a position with maximum luminous flux along the y-axis, controlling the movement displacement and movement speed of the primary exposure optical shielding plate according to a movement function through a primary exposure optical shielding plate controller, controlling the exposure length and exposure time of the ultraviolet light in different areas on the hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, forming a diffraction pattern which changes periodically through a uniform phase mask, and exposing to the hydrogen-carrying optical fiber of the coating layer to finish primary exposure;
d) Repeating the steps b) to c), recording the repetition times and the corresponding movement speed until the ideal transmissivity is achieved, and completing one exposure;
e) And (3) secondary exposure compensation:
the method comprises the steps of removing a primary exposure optical shielding plate and a uniform phase mask plate, setting a secondary exposure optical compensation plate, shaping ultraviolet light excited by an ultraviolet excimer laser, moving the secondary exposure optical compensation plate from a position with maximum luminous flux to a position with minimum luminous flux along a y axis through the secondary exposure optical compensation plate, controlling the movement displacement and the movement speed of the secondary exposure optical compensation plate through a secondary exposure optical compensation plate controller according to a compensation movement function, controlling the ultraviolet light compensation lengths and the compensation time of different areas on a hydrogen-carrying optical fiber, compressing through a plano-convex cylindrical mirror, directly exposing to the hydrogen-carrying optical fiber of a coating-removing layer, and completing secondary exposure compensation to realize direct-current refractive index compensation of a toe-cut grating.
8. The method of claim 4, wherein the exposing means using the simultaneous compensation means comprises the steps of:
a) And (3) setting an optical path: the ultraviolet excimer laser emits ultraviolet light along the direction of an x axis, the ultraviolet light is split into two beams by the beam splitter, a primary exposure optical shielding plate, a first plano-convex cylindrical mirror and a uniform phase mask plate are sequentially arranged along the x axis between a first beam of ultraviolet light and a light path of a hydrogen-carrying optical fiber to be prepared, and a secondary exposure optical compensation plate and a second plano-convex cylindrical mirror are sequentially arranged along the x axis between a second beam of ultraviolet light and the light path of the hydrogen-carrying optical fiber to be prepared;
b) Determining an apodization function according to the distribution curve of the refractive index increment, and determining a motion function of the primary exposure optical shielding plate and a motion compensation function of the secondary exposure optical compensation plate according to the apodization function;
c) The first beam of ultraviolet light is shaped through a primary exposure optical shielding plate, the motion displacement and the motion speed of the primary exposure optical shielding plate are controlled through a primary exposure optical shielding plate controller according to a motion function, so that the exposure length and the exposure time of ultraviolet light in different areas on the hydrogen-carrying optical fiber are controlled, the ultraviolet light is compressed through a first plano-convex cylindrical mirror, a diffraction pattern which is periodically changed is formed through a uniform phase mask plate and is exposed on the hydrogen-carrying optical fiber of a coating layer, the primary exposure is completed, meanwhile, the second beam of ultraviolet light is shaped through a secondary exposure optical compensation plate, the motion displacement and the motion speed of the secondary exposure optical compensation plate are controlled through a secondary exposure optical compensation plate controller according to a compensation motion function, and the ultraviolet light compensation length and the compensation time of different areas on the hydrogen-carrying optical fiber are controlled, and the ultraviolet light is directly exposed on the hydrogen-carrying optical fiber of the coating layer after being compressed through the plano-convex cylindrical mirror, so that the secondary exposure compensation is completed, and the direct refractive index compensation of a cut grating is realized;
d) Repeating the steps b) to c), recording the repetition times and the corresponding movement speed until the ideal transmissivity is achieved, and preparing the apodized grating.
CN201711440772.7A 2017-12-27 2017-12-27 Apodization grating secondary exposure manufacturing system and method based on dynamic optical shielding plate Active CN108051887B (en)

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