JP2003279759A - Machining method of optical fiber and manufacturing method of optical waveguide component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining method of an optical fiber for forming a refractive index change region by performing condensation illumination of laser beams with high positional accuracy without losing the mechanical strength of the optical fiber, and to provide a manufacturing method of an optical fiber type waveguide component using the optical fiber machining method. <P>SOLUTION: The optical fiber 5 is fixed to a V groove 8 on a V groove board 7, the condensation and illumination of femtosecond laser beams 2 are made to the surface of the V groove board 7, and the ablation trace is detected to detect the surface of the V groove board 7. With the surface of the V groove board 7 as a reference, the depth of a target position 6 in the optical fiber 5 where a refractive index change region should be formed from a cladding surface is adjusted. Then, the condensation and illumination of the femtosecond laser beam 2 are made to the target position 6 to form the refractive index change region. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing an optical fiber in which femtosecond laser light is focused and irradiated inside the optical fiber to form a refractive index change region around the focus point, and
The present invention relates to a method for manufacturing an optical fiber type optical waveguide component such as an optical fiber grating.

[0002]

2. Description of the Related Art In the field of optical communication, optical waveguide components such as optical fibers and planar optical waveguides are now indispensable technologies. There are many proposals as a method for manufacturing a highly functional optical waveguide component with high accuracy and efficiency. For example, as disclosed in Japanese Patent Laid-Open No. 9-311237, there is known a method of producing an optical waveguide component by causing a light-induced change in refractive index in a glass material by converging irradiation of femtosecond laser light. The photo-induced refractive index change using femtosecond laser light has a high efficiency of inducing the refractive index change, and thus has attracted attention as a technique capable of efficiently forming a structure such as an optical waveguide.

Among optical waveguide components, optical fiber type optical waveguide components are highly important because they can be easily connected to transmission optical fibers and other optical components, and are widely used. As a proposal of a method for manufacturing an optical fiber type optical waveguide component utilizing the light-induced change in refractive index by femtosecond laser light, for example, there is a method proposed in Japanese Patent Laid-Open No. 2000-155225. This method forms a grating (diffraction grating) by irradiating the core of an optical fiber with femtosecond laser light continuously or intermittently to induce a periodic change in the refractive index, thereby forming an optical fiber grating. Is a method of manufacturing.

[0004]

However, the above-mentioned Japanese Patent Laid-Open No. 2000-155225 discloses a positioning method for converging and irradiating a femtosecond laser beam onto a predetermined target position of the core of an optical fiber. Not not. In fact, for a cylindrical object having an extremely small outer diameter such as an optical fiber, it is extremely difficult to accurately determine the depth of the target position from the clad surface. For this reason, for example, there is a risk of converging and irradiating the clad instead of the core, and with this method, it is difficult to efficiently produce a high-performance optical fiber grating.

As a positioning method for converging and irradiating a glass material with femtosecond laser light, Japanese Patent Application No. 2001-25
There is a method utilizing the ablation phenomenon described in No. 0573. The ablation phenomenon is that when laser light is focused and irradiated on the surface of a glass material such as a glass substrate, irregularities (ablation marks) are formed on the surface of the glass material. Since the ablation trace can be easily detected by using a detection device such as a CCD camera, the position of the glass substrate surface can be detected by focusing on the ablation trace. Furthermore, by displacing the glass substrate in the depth direction by a predetermined length, the target position of the focused irradiation of the femtosecond laser light can be set to a desired depth with high accuracy.

However, when this method is applied to the production of an optical fiber type optical waveguide component, if an ablation mark is formed on the clad surface of the optical fiber to be processed, it causes a crack, which causes cracks. May be broken. Further, in forming an ablation mark, it is difficult to focus on the cladding surface of an optical fiber having a colorless and transparent cylindrical shape.
As described above, there are problems in terms of mechanical reliability and processing accuracy.

The present invention has been made in consideration of such circumstances, and the femtosecond laser light is focused and irradiated with high positional accuracy without impairing the mechanical strength of the optical fiber. An object of the present invention is to provide an optical fiber processing method capable of forming a change region, and an optical fiber type optical waveguide component manufacturing method using the optical fiber processing method.

[0008]

SUMMARY OF THE INVENTION The above object is to provide a method for processing an optical fiber in which a refractive index change region is formed inside the optical fiber by converging and irradiating a femtosecond laser beam, and the optical fiber is formed into a V The surface of the V-groove substrate is fixed by being fixed on the groove, the surface of the V-groove substrate is focused and irradiated with femtosecond laser light to generate an ablation mark, and the surface of the V-groove substrate is detected by detecting the ablation mark. This is solved by concentrating and irradiating a femtosecond laser beam to a desired depth inside the optical fiber with reference to the surface of (1) to form a refractive index change region.

Further, in order to further improve the accuracy of the depth of the target position inside the optical fiber from the cladding surface, the optical fiber is fixed on the V groove of the V groove substrate, and the V
The femtosecond laser light is focused and irradiated onto two or more places on the surface of the groove substrate to generate two or more ablation marks, and the surface of the V-groove substrate is detected by detecting the ablation marks. The position and / or the slope of the surface of the V-groove substrate is adjusted by moving and / or rotating the V-groove substrate so that the focus simultaneously fits all of the two or more ablation traces.
A method of forming a refractive index change region by converging and irradiating a femtosecond laser beam to a desired depth inside the optical fiber with the surface of the groove substrate as a reference can be used.

Further, it is possible to use a V-groove substrate having a plurality of V-grooves and arrange an optical fiber in each of the V-grooves for processing. Thus, if the surface of the V-groove substrate is detected and aligned once, the optical fibers on the V-groove substrate can be sequentially processed thereafter, so that workability is improved. By processing the optical fiber using the above-described optical fiber processing method, it is possible to manufacture an optical fiber type optical waveguide component such as an optical fiber grating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on the embodiments. FIG. 1 shows an example of an apparatus used in the optical fiber processing method of the present invention. In FIG. 1, reference numeral 1 is a light source. The femtosecond laser beam 2 oscillated from the light source 1 is reflected by the half mirror 3 and then focused and irradiated onto a predetermined target position 6 inside the optical fiber 5 via the focusing lens 4. Optical fiber 5
Are placed and fixed on the V-grooves 8 formed on the V-groove substrate 7. The V-groove substrate 7 is fixed on the precision stage 9. The precision stage 9 is controlled based on the position of the optical fiber 5 monitored by the CCD camera 10, and the position of the optical fiber 5 can be adjusted appropriately. Further, this apparatus is provided with a shutter 11 on the optical path of the femtosecond laser light 2, and the irradiation of the femtosecond laser light 2 can be switched by opening / closing the shutter 11.

The optical fiber processing method of this embodiment is
As shown in FIG. 2, the optical fiber 5 is connected to the V groove 8 of the V groove substrate 7.
The surface of the V-groove substrate 7 is detected by detecting the ablation mark A by fixing and applying the femtosecond laser beam 2 to the surface of the V-groove substrate 7 to fix the upper surface. The femtosecond laser light 2 is focused and irradiated to a desired depth inside the optical fiber 5 with the surface of the V-groove substrate 7 as a reference to form a refractive index change region. Since the ablation mark A becomes a minute dent, by using the contrast near the edge of the dent, C
It can be easily detected by a detecting means such as the CD camera 10.

In this way, the optical fiber 5 to be processed is
Since the ablation mark A is not generated on the surface of and the ablation mark A is formed on the V-groove substrate 7, there is no fear of impairing the mechanical strength of the optical fiber 5. Further, the optical fiber 5 is fixed on the V-groove 8, and the height h of the cladding surface of the optical fiber 5 from the surface of the V-groove substrate 7 is determined by the V-groove as shown in equation (1) of FIG. It can be obtained from the width w and the angle θ of 8 and the cladding diameter d of the optical fiber 5.
Since there is a uniquely determined correspondence between the geometric focusing depth from the cladding surface of the optical fiber 5 and the actual focusing depth, the target position 6 inside the optical fiber 5 can be highly accurately determined. You can know the depth.

In the present embodiment, the femtosecond laser light 2 having a pulse width of 1 ps or less is used in order to cause the photo-induced refractive index change. This is because the pulse width of the femtosecond laser light 2 is very narrow, so that the peak power is increased by the time compression effect, and the action of the light-induced refractive index change can be increased. The wavelength of the femtosecond laser beam 2 is preferably a wavelength in the near infrared region such as 800 nm. As a result, the femtosecond laser beam 2 is hardly absorbed by the transparent material such as quartz glass, so that the target position 6 can be reached with almost no attenuation. The repetition frequency of the femtosecond laser light 2 is not particularly limited, but is 10 kHz.
Higher than z or 100 kHz is desirable.

The material of the optical fiber 5 is not particularly limited as long as it is used for optical communication and increases the refractive index at the focal point when the femtosecond laser beam 2 is focused and irradiated. Examples of such a material include quartz glass, oxide glass, and fluoride glass. Quartz glass and germanium (Ge)
Examples thereof include doped quartz glass, fluorine-doped quartz glass, germanium-fluorine co-doped quartz glass and the like. Examples of oxide glass include silicate glass, borate glass, phosphate glass, fluorophosphate glass, and bismuth oxide-based glass. Generally, it is preferable to use a silica-based optical fiber for which a low-loss optical fiber can be easily obtained, and a manufacturing method with high mass productivity and high productivity has been established. Further, it is preferable to use an optical fiber element wire that is easy to handle as the optical fiber 5. In that case, the coating around the target position 6 is removed by using an organic solvent or the like before processing.

The material of the V-groove substrate 7 is not particularly limited as long as it increases the refractive index at the focal point when the femtosecond laser beam 2 is focused and irradiated. Examples of such a material include quartz glass, oxide glass, and fluoride glass. Examples of the quartz glass include quartz glass, germanium (Ge) -doped quartz glass, fluorine-doped quartz glass, and germanium-fluorine co-doped quartz glass. Examples of oxide glass include silicate glass, borate glass, phosphate glass, fluorophosphate glass, and bismuth oxide-based glass. The material of the V-groove substrate 7 is such that both the ablation of the V-groove substrate 7 and the refractive index change induction of the optical fiber 5 can be performed by the femtosecond laser light 2 oscillated from the same light source 1. It is preferable to use the same or similar material as the optical fiber 5 to be processed.

An example of a procedure for processing an optical fiber using the above apparatus will be described with reference to FIG. In FIG. 3, the arrow drawn in the vicinity of the V-groove substrate 7 indicates the moving direction (X, Y, Z) of the precision stage 9. First, the V-groove substrate 7 is fixed on the precision stage 9 so that the V-groove 8 extends substantially along the Y-axis direction. Then the optical fiber 5
Is placed on the V groove 8 and fixed. Next shutter 11
So that the condensing point is located on the V-groove substrate 7 with the femtosecond laser beam 2 turned off, in other words, the position of the objective lens is located above the V-groove substrate 7, The precision stage 9 is scanned in the X-axis direction and the Y-axis direction. Further, after moving the condensing point to an arbitrary point A on the surface of the V-groove substrate 7, the shutter 11 is opened, the output of the light source 1 is strengthened, and the femtosecond laser beam 2 is condensed and irradiated. In this state, the precision stage 9 is controlled so as to scan the V-groove substrate 7 in the Z-axis direction to a large extent, and an ablation trace is reliably formed at the point A on the surface of the V-groove substrate 7. CCD on this ablation mark A
Adjust the Z of the precision stage 9 so that the camera 10 is in focus.
Adjust the axial position.

In this state, the focus of the femtosecond laser beam 2 is on the ablation mark A, that is, the surface of the V-groove substrate 7. Here, if the target position 6 where the refractive index change region is to be formed is, for example, on the central axis of the core of the optical fiber 5, the ablation mark A and the target position 6 are formed.
The displacements in the Z-axis direction between and are, as shown in FIG.
Is required as. Strictly speaking, due to refraction and the like when incident on the side surface of the optical fiber 5, the geometric focusing depth obtained from FIG. 2 and the actual focusing depth of the femtosecond laser light 2 do not necessarily match. However, if the correspondence between the geometric focusing depth and the depth at which the refractive index change region is actually formed is measured in advance, thereafter, the femtosecond laser will be calculated based on the geometric focusing depth. The actual focusing depth of the light 2 can be uniquely determined.

The alignment of the converging point in the horizontal direction (XY axis direction) is easy to identify the V groove 8 due to the difference in reflectance due to the edge of the V groove 8. Therefore, the alignment is set on the center line of the V groove 8. Good. In this way, the femtosecond laser light 2 can be focused on the central axis of the core of the optical fiber 5. Here, the output of the light source 1 is increased again, and the femtosecond laser light 2 is focused and irradiated at the target position 6,
A refractive index change region can be formed.

Even if the target position 6 is not on the central axis of the core of the optical fiber 5, the designed position of the target position 6 can be determined as a displacement from the central axis of the core of the optical fiber 5. , Focus the femtosecond laser beam 2
It goes without saying that the alignment can be easily performed by, for example, moving the precision stage 9 by a predetermined distance after aligning it on the central axis of the core of the optical fiber 5.

The position of the ablation mark A is preferably closer to the optical fiber 5. This is because if the position of the ablation mark A is too far from the optical fiber 5, the deviation between the target position 6 estimated from the height of the ablation mark A and the actual target position 6 may increase.

The first embodiment can be easily implemented because only one ablation mark A is formed on the surface of the V-groove substrate 7. However, in the case where the surface of the V-groove substrate 7 has a gradient, more precisely, when the degree of the gradient of the surface of the V-groove substrate 7 is not negligible as compared with the required alignment accuracy, the depth is There is a possibility that the positioning accuracy in the (Z-axis) direction may not be sufficiently obtained. In order to improve this problem, as described below, as the precision stage 9, a precision stage 9 having one rotary stage in addition to the XYZ triaxial stage is used, and a technique for forming two ablation traces is used. be able to.

Next, such a second embodiment will be described with reference to FIG. First, one rotary stage is installed on the XYZ triaxial stage in a direction that allows rotation in the φy direction, and the precision stage 9 is obtained. The V-groove substrate 7 is fixed on the precision stage 9 so that the V-groove 8 extends substantially along the Y-axis direction. Then, the optical fiber 5 is placed and fixed on the V groove 8. Then, the target position 6 inside the optical fiber 5
, One on each side of the optical fiber 5 near the
Individual ablation tracks A and B are formed.

Then, these ablation marks A and B
With reference to, the gradient of the V-groove substrate 7 in the φy direction is finely adjusted so that the two points of the ablation marks A and B are simultaneously focused. For this purpose, for example, first the CCD camera 1
The ablation mark A is put in the field of view of 0, the φy stage is rotated to adjust the focus, and then the CCD camera 10
The ablation mark B is placed in the field of view, the φy stage is rotated to adjust the focus, and this is alternately repeated to gradually adjust the focus.

As a result, the gradient in the direction from the ablation traces A to B on the surface of the V-groove substrate 7 can be made extremely small. Since the target position 6 is located substantially between the ablation traces A and B, the target position 6 is used based on the position of the ablation traces A or B in the Z direction by using the method described in the first embodiment. The depth of 6 can be determined with high accuracy. Then, the focal point of the femtosecond laser beam 2 is focused on the target position 6 and focused and irradiated, whereby a refractive index change region can be formed at the target position 6.

In this case, the distance L _AB from the ablation marks A to B is as long as the movable range of the precision stage 9 allows.
Longer is preferable. This is because when finely adjusting the gradient of the V-groove substrate 7 in the φy direction, the Z of the ablation marks A and B is adjusted.
It is considered that a minute error Δz depending on the focusing accuracy of the CCD camera 10 may occur in the depth in the direction. At this time, the gradient in the φy direction from the point A to the point B on the surface of the V-groove substrate 7 is expressed as Δz / L _AB , so that L _AB
If is too short, the gradient in the φy direction may become too large to be ignored. Conversely speaking, L
_{By making AB} sufficiently long, the gradient in the φy direction can be made extremely small.

Next, a third embodiment of the present invention will be described. In the present embodiment, as the precision stage, φx, φy, around each axis of the XYZ triaxial stage,
The one provided with three rotary stages in the φz direction is used.
Then, as shown in FIG. 5, on the V-groove substrate 7, three ablation marks A are formed so as not to be on a straight line.
Form B and C. Of these ablation marks, it is assumed that two of them, A and B, are arranged so as to face the other C, with the optical fiber 5 interposed therebetween.

Then, the CCD camera 10 detects the ablation traces A, B, and C one by one several times in order, and finely adjusts the rotation directions of the φx stage and the φy stage. A, B, C
Try to focus on everything at the same time. This allows the surface of the V-groove substrate 7 to be perpendicular to the observation direction of the CCD camera 10 with extremely high accuracy. This is because three points that are not on a straight line can determine the plane. Furthermore, by rotating the φz stage, the longitudinal direction of the optical fiber 5 is changed to Y
Can be aligned in the axial direction.

In this case, the first to third ablation marks
Distance L between each two points A, B and C_AB, L_BC, L_ACIs precision
As long as the movable range of Stage 9 allows, the longer the better
Yes. The reason for this is that in the second embodiment,
Distance L between traces A and B _ABAnd explained
It is the same. The precision stage 9 is adjusted in this way
According to the above, the three ablation marks A, B, C
The triangle ABC has a very small gradient,
The slope of the surface of the plate 7 becomes extremely small. Therefore, fem
The precision of the depth of the condensing point of the second laser beam 2 is improved.

Now, the femtosecond laser beam 2 is focused and irradiated onto a desired point on the center axis of the optical fiber 5, for example, the point 21, by using the method described in the first embodiment. Can be made. From this state, by moving the precision stage 9 continuously or intermittently in the Y-axis direction, the refractive index change region is continuously or intermittently on the central axis of the optical fiber 5, for example, at points 22 and 23. Can be formed. That is, the refractive index change region can be formed so as not to be displaced from the central axis of the optical fiber 5.

In the third embodiment, three rotary stages are used.
Although the number of the rotating stages is two, the refractive index changing region can be precisely or continuously formed along the longitudinal direction of the optical fiber 5 even if the number of the rotating stages is two. The fourth embodiment will be described with reference to FIG. This 4th
In the embodiment of FIG.
In addition to the Z3 axis stage, a stage having two rotary stages in the φx and φz directions is used.

First, the V-groove substrate 7 is placed on the precision stage 9.
Are fixed so that the V groove 8 is substantially along the Y-axis direction. Then, the optical fiber 5 is placed and fixed on the V groove 8. CC
With the D camera 10, the V groove 8 on the surface of the V groove substrate 7
The φz stage is rotated while detecting the difference in reflectance between the V groove 8 and the V groove 8 so that the V groove 8 is aligned with the Y axis direction. And
2 along the longitudinal direction of the optical fiber 5 on the V-groove substrate 7
Individual ablation marks A and B are formed. While the CCD camera 10 detects these two ablation traces A and B, the φx stage is rotated so that both the ablation traces A and B are in focus.
Fine tune the gradient in the x direction.

By finely adjusting the direction and the gradient of the V-groove substrate 7 in this manner, the optical fiber 5 is adjusted with high accuracy so that the gradient along the Y-axis direction and in the φx direction becomes extremely small. Therefore, the femtosecond laser light 2 is continuously or intermittently provided along the longitudinal direction of the optical fiber 5.
Is condensed and irradiated to obtain a plurality of refractive index change regions 21, 22, 2
3 can be formed.

In this case, it is preferable that the distance L _AB between the ablation marks A and B is as long as the movable range of the precision stage 9 allows. When finely adjusting the gradient of the V-groove substrate 7 in the φx direction, the depths of the ablation marks A and B in the Z direction are
It is considered that a minute error Δz depending on the focusing accuracy of the CCD camera 10 may occur. In this case, the gradient of the φx direction from a point A on the V-groove substrate 7 surface toward B, since expressed as Delta] z / L _AB, the L _AB is excessively short,
This is because the gradient in the φx direction may become too large to be ignored. Conversely, by taking a sufficiently long L _AB, it can be made extremely small gradient of the φx direction.

The positions of the ablation traces A and B are preferably closer to the optical fiber 5. These two
If the position of the point is too far from the optical fiber 5, even if the gradient in the φx direction from the ablation traces A to B is finely adjusted to be extremely small, the point deviates from the gradient in the φx direction along the optical fiber 5, and the position This is because the accuracy of alignment may be reduced.

In the above embodiment, the V groove 8 is 1
Only one V-groove substrate 7 was provided on the V-groove substrate 7.
It is also possible to use a V-groove substrate having a plurality of. The method of forming the ablation mark and the method of adjusting the gradient and the depth of the V-groove substrate 7 using the ablation mark can be performed according to the above-described method. Even in this case, the position of the V-groove substrate 7 can be adjusted by forming at most three ablation marks on the V-groove substrate 7.
Moreover, since it is possible to process a plurality of optical fibers in a single step, it is possible to greatly reduce the labor for preparation of the manufacturing apparatus and the like, and the productivity is greatly improved.

In the above description, the precision stage 9 is moved as a means for focusing or scanning the femtosecond laser beam 2 on the surface of the V-groove substrate 7 or the target position 6 inside the optical fiber 5. However, the present invention is not limited to this. For example, the focal point of the femtosecond laser beam 2 may be moved by moving the condenser lens 4 itself or using a galvanometer mirror or the like.

Next, a method of manufacturing the optical waveguide component of the present invention will be described. Various optical fiber type optical waveguide components can be manufactured by forming the refractive index changing region inside the optical fiber by using the above-described optical fiber processing method. As an example thereof, a method of manufacturing an optical fiber grating will be described.

FIG. 7 is a side sectional view showing an example of the optical fiber grating. Fiber optic grating
Optical fiber core 31 having core 31 and clad 32
The grating 33 is formed on a part of the above.
The grating 33 has a function of reflecting and blocking light in a predetermined wavelength band that travels in the optical waveguide.

The wavelength characteristic of the grating 33 depends on the period of change in the refractive index, the length of the grating, and the amount of change in the refractive index that compose the grating 33, but all of these parameters can be controlled. That is, the cycle of the refractive index change can be adjusted by the relative movement distance of the condensing point of the femtosecond laser light 2. Further, the grating length is determined by the entire moving distance when the focused irradiation of the femtosecond laser light 2 is repeated continuously or intermittently. In addition, the amount of change in the refractive index is determined by the femtosecond laser light 2
It can be controlled by the converging irradiation time.

Such an optical fiber grating is
For example, it can be manufactured by the following procedure. First, the first refractive index change region 34 is formed in the core 31 of the optical fiber 5 by using the optical fiber processing method of the present invention. Next, the precision stage 9 for the grating period
Is moved along the longitudinal direction of the optical fiber 5, and the next refractive index change region 35 is formed by converging and irradiating the optical fiber 5 with the same femtosecond laser light 2. Hereinafter, the grating 33 can be formed by repeating the focused irradiation of the femtosecond laser beam 2 and the movement of the precision stage 9 in accordance with the required grating length to form a plurality of refractive index change regions 36, .... it can.

Alternatively, the precision stage 9 is moved at a constant speed or a predetermined movement state controlled by a program,
In synchronization with this movement, the shutter 11 inserted in the optical path of the femtosecond laser light 2 is opened and closed at predetermined time intervals, and the femtosecond laser light 2 is irradiated only at a predetermined position to change a plurality of refractive indexes. By forming the regions 36, ...
The grating 33 can be formed.

Next, the present invention will be described in detail with reference to specific examples. (Example 1) As the optical fiber 5, a relative refractive index difference of 0.3
%, A silica-based optical fiber having a cladding diameter of 125 μm was used. The light source 1 has a center wavelength of 800 nm and a pulse width of 1
A titanium sapphire laser with 80 fs (femtoseconds), a repetition rate of 200 kHz and an average output of 700 mW was used. The V-groove substrate 7 has a thickness of 1.6 mm, a width of 5 mm, and a length of 4
It is made of 8 mm synthetic quartz glass. The groove width of the V groove 8 is 18
The groove angle is 0 μm and the groove angle is 60 °. As the precision stage 9, one having an XYZ triaxial stage was used.

A position away from the target position 6 by about 0.1 mm was appropriately determined, and the femtosecond laser beam 2 was focused and irradiated to form one ablation mark. After focusing the CCD camera 10 on the ablation mark, the precision stage 9 was moved in the Z direction by a predetermined distance according to the depth of the target position 6. Further, the position in the horizontal direction (on the XY plane) was adjusted by detecting the image of the V groove 8 and aligning the center of the scope of the CCD camera 10 with the center line of the V groove 8. Here, in a state where the femtosecond laser beam 2 is focused and irradiated, the precision stage 9 is moved in the Y direction at a constant speed of 0.5 m.
It was moved by m to form a refractive index change region. Optical fiber 5
When removed from the apparatus and inspected, the refractive index change region was formed in the core of the optical fiber 5 with sufficient accuracy.

(Embodiment 2) The same light source 1, optical fiber 5 and V groove substrate 7 as in Embodiment 1 were used. As the precision stage 9, in addition to the XYZ triaxial stage, φx, φ
The one having three rotary stages attached in the y and φz directions was used. The V-groove substrate 7 was attached and fixed on the precision stage 9, and the optical fiber 5 was further fixed along the V-groove 8.
By rotating the φz rotary stage while detecting the image of the V groove 8, the direction of the V groove 8 was aligned with the Y direction.

Then, as shown in FIG. 8, the ablation trace A was formed by moving the V-groove substrate 7 from the target position 6 in the Y direction by about 10 mm and concentrating and irradiating the femtosecond laser beam 2. Then, the ablation trace B was formed by moving the point A in the direction opposite to the Y direction by about 20 mm and converging and irradiating the femtosecond laser beam 2. Further, a third ablation mark C was formed on the opposite side of the V groove 8. These ablation marks A, B, and C were all formed at positions separated from the V groove 8 by about 0.1 mm in the vertical direction.

Then, in order to focus all of these three ablation marks A, B and C at the same time, φ
The rotary stage in the x and φy directions was rotated. At this time,
The gradient between AB was 0.05 μm / mm. After the CCD camera 10 was focused on the first ablation mark A, the precision stage was moved in the Z direction by a predetermined distance according to the depth of the target position 6. At the horizontal position (on the XY plane), the image of the V groove 8 is detected, and the CCD
It was adjusted by aligning the center of the scope of the camera 10 with the center line of the V groove 8.

The precision stage 9 is moved while the shutter 11 is closed, and the femtosecond laser beam 2 is moved onto the target position 6.
After the position is adjusted so that the light can be condensed and irradiated, the precision stage 9 is moved in the Y direction at a constant speed, and the shutter 11 is opened and closed at a constant time interval.
Refractive index changing regions were sequentially formed with a period of m, and writing was performed on the grating.

When the optical fiber 5 was detached from the apparatus and inspected, each of the refractive index changing regions was found to have the optical fiber 5.
Was formed with sufficient accuracy in the core. Also, when the transmission characteristics of the obtained optical fiber grating were observed with an optical spectrum analyzer, it was found that the desired transmission characteristics as a grating were obtained.

[0050]

As described above, according to the optical fiber processing method of the present invention, the surface of the V-groove substrate, which is a flat surface, is compared with the surface of the V-groove substrate with reference to the ablation mark formed on the surface of the V-groove substrate. Since the focus is adjusted by using the optical fiber, the position of the optical fiber in the depth direction can be determined with extremely high accuracy.
And the reproducibility is high. Positioning is facilitated, productivity is improved, and manufacturing time can be shortened. Moreover, since no ablation mark is formed on the surface of the optical fiber, there is no fear that the mechanical strength and the reliability of the optical fiber are deteriorated.

In the optical fiber processing method of the present invention, an array type V groove substrate having a plurality of V grooves can be used as the V groove substrate. In this case, a plurality of optical fibers can be collectively processed by one batch processing, and further improvement in productivity can be expected. By using the optical fiber processing method of the present invention, various highly functional and highly reliable optical waveguide components can be manufactured with high accuracy and high productivity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an apparatus used in the optical fiber processing method of the present invention.

FIG. 2 is a diagram illustrating a method of calculating a height of a clad surface of an optical fiber fixed on a V groove from the surface of a V groove substrate.

FIG. 3 is a diagram illustrating a first embodiment of a method for processing an optical fiber according to the present invention.

FIG. 4 is a diagram for explaining a second embodiment of the optical fiber processing method of the present invention.

FIG. 5 is a diagram for explaining the third embodiment of the optical fiber processing method of the present invention.

FIG. 6 is a diagram for explaining the fourth embodiment of the optical fiber processing method of the present invention.

FIG. 7 is a schematic configuration diagram showing an example of an optical fiber grating.

FIG. 8 is a perspective view illustrating an implementation state of the second embodiment of the present invention.

[Explanation of symbols]

2 ... Femtosecond laser light, 5 ... Optical fiber, 6 ... Target position, 7 ... V groove substrate, 8 ... V groove, A ... Ablation mark.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Fukuda             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office (72) Inventor Yu Ishii             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office (72) Inventor Ken Sakuma             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office (72) Inventor Hideyuki Hosoya             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office F-term (reference) 2H050 AB03Z AC82 AC84 AD00

Claims (6)

[Claims] 1. A method of processing an optical fiber, wherein a refractive index change region is formed inside an optical fiber by converging and irradiating a femtosecond laser beam, wherein the optical fiber is fixed on a V groove of a V groove substrate. Femtosecond laser light is focused and irradiated on the surface of the substrate to generate an ablation mark, the surface of the V-groove substrate is detected by detecting the ablation mark, and the inside of the optical fiber is based on the surface of the V-groove substrate. A method for processing an optical fiber, which comprises irradiating a femtosecond laser beam to a desired depth to form a refractive index changing region. 2. A method for processing an optical fiber, wherein a refractive index change region is formed inside an optical fiber by converging and irradiating a femtosecond laser beam, the optical fiber being fixed on the V groove of a V groove substrate, The femtosecond laser light is focused and irradiated onto two or more positions on the surface of the substrate to generate two or more ablation marks, and the surface of the V-groove substrate is detected by detecting the ablation marks, and the focus of the detection means is detected. The V-groove substrate by moving and / or rotating the V-groove substrate in such a way that all of the two or more ablation tracks are simultaneously adjusted, and then the surface of the V-groove substrate is adjusted. A method for processing an optical fiber, comprising: forming a refractive index change region by converging and irradiating a femtosecond laser beam to a desired depth inside the optical fiber with reference to. 3. A V-groove substrate having a plurality of V-grooves is used,
The optical fiber processing method according to claim 1 or 2, wherein an optical fiber is fixed to each of the V grooves and processed. 4. The method for processing an optical fiber according to claim 1, wherein the V-groove substrate is made of quartz glass or quartz glass. 5. The method of processing an optical fiber according to claim 1, wherein the optical fiber is a silica optical fiber. 6. A method of manufacturing an optical waveguide component, which comprises processing an optical fiber by using the method of processing an optical fiber according to claim 1.