JP2001133640A - Method and device for manufacturing fiber grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for manufacturing a fiber grating which offer high throughput and continuously change the wavelength in a prescribed range. SOLUTION: Laser light outputted from a first coherent light source 1 provided with a fundamental wave laser device 1a, which outputs light converted into a narrow band and that outputted from a second coherent light source 2 provided with a variable wavelength laser 2a which outputs light having the wavelength stabilized are inputted to a sum frequency generation means 3 or sum frequency generation means 3 and 4. Sum frequency generation means 3 and 4 generate sum frequency light having the wavelength of 185 to 250 nm or 185 to 213 nm. This laser light is inputted to a double flux interference optical system to manufacture fiber grating. Light of this wavelength is generated by inputting laser light outputted from a variable wavelength laser 5, which has the wavelength stabilized, to a harmonic generation means 6 constituted of a nonlinear optical crystal, to generate higher harmonic light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for manufacturing a fiber grating for manufacturing a diffraction grating (grating) on an optical fiber.

[0002]

2. Description of the Related Art When performing optical communication using an optical fiber,
Transmit light of different wavelengths to the core of one optical fiber (this is called wavelength multiplex transmission, wavelength multiplex optical communication, etc.)
Only the light of the required wavelength is extracted from the light. To "extract only light of a necessary wavelength" from the fiber means "to remove light of an unnecessary wavelength", and for that purpose, it is necessary to provide a filter function to the core of the optical fiber. In order to remove light of a specific wavelength from the light passing through the optical fiber, a grating (diffraction grating) whose refractive index is changed at a constant period along the axial direction of the optical fiber in a selected region of the core of the optical fiber. The method of providing is known. The grating reflects a specific wavelength determined by the lattice spacing. Therefore, if it is desired to remove light of a specific wavelength from the light passing through the optical fiber, a grating corresponding to the wavelength of the light to be removed may be formed on the core of the optical fiber. The optical fiber in which the grating is provided in the core as described above is called a fiber grating.

FIG. 13 shows the structure of a fiber grating. In FIG. 13, a grating is formed in the core of the optical fiber OP. For example, if the grating spacing of the grating is made to reflect light of wavelength λ1, and if light of wavelength λ1 and light of wavelength λ2 are transmitted to the fiber, this grating gives
The light of wavelength λ1 is reflected and removed, and only the light of wavelength λ2 is transmitted. The material of the optical fiber is quartz, and the fiber grating is manufactured by changing the refractive index of a selected region of the core of the optical fiber of quartz at a constant period along the axial direction.

The following is known as a method of changing the refractive index of quartz, and the following method (2) is generally used for manufacturing a fiber grating. (1) Irradiate the quartz with a carbon dioxide laser (IR laser),
Change the refractive index of the irradiated part. (2) Quartz doped with germanium (Ge), 240
Irradiation with ultraviolet light in the vicinity of nm (± 10 nm). Although the detailed mechanism is unknown, the refractive index of the irradiated part increases. As a light source of ultraviolet light, it is necessary to irradiate with a certain energy or more, so a laser device is used. In order to change the refractive index of the core of the optical fiber in a predetermined inclined region at a constant period along the axial direction by using the method (2), the illuminance of the region to be irradiated with light (the energy to be irradiated) is changed. ) Produces means at constant intervals. That is, when fabricating the fiber grating by the method (2), the following two conditions must be satisfied. Provide a (laser) light source that generates light with a wavelength of 240 nm ± 10 nm. Means for projecting light from the light source so as to generate light and shade at predetermined intervals in a predetermined area.

As a laser light source for generating light having a wavelength of 240 ± 10 nm, there is a harmonic wave of an Ar laser or a KrF excimer laser, which has been conventionally used as a light source for manufacturing a grating. Four wavelengths (250.8 nm, 24
8.2 nm, 244.0 nm, and 238.2 nm), and these four wavelengths are selected and used by a diffraction grating. Also,
Light having a wavelength of 248.3 nm can be obtained from a KrF excimer laser. As a means for projecting light from a light source to generate light and shade at predetermined intervals in a predetermined area, a two-beam interference method and a phase mask method are known. FIG. 14 shows a configuration diagram of manufacturing a grating by two-beam interference method.
FIG. 15 shows a configuration diagram of manufacturing a grating by the phase mask method.

A grating is manufactured by the two-beam interference method and the phase mask method as follows. (A) Two-beam interference method In the two-beam interference method, as shown in FIG. 14, laser light having the same wavelength is split into two by a beam splitter BS1, and the light split into two by mirrors M1 and M2 is reflected, and the same light is again emitted. This is a method of causing interference by overlapping at a location (irradiation area), and in the irradiation area, shading of a constant cycle due to interference fringes occurs. By disposing the core of the Ge-doped optical fiber OP in the irradiation region, a portion where the refractive index periodically changes can be formed on the core. The interval between the shading of the interference fringes can be changed by changing the irradiation wavelength or by changing the angles of the mirrors M1 and M2. Therefore, a grating can be made according to the wavelength of light to be removed from the optical fiber. However, in order to form sharp interference fringes with constant intervals and light and shade, the irradiated light needs to have high coherence (spectral width several pm or less).

(B) Phase mask method The phase mask method is a method using a mask M as shown in FIG. 15, and a mask M having irregularities formed at regular intervals corresponding to the grating intervals of a grating on a quartz substrate is used. Use
The core of the optical fiber OP is irradiated with laser light via the mask M. Thereby, the +1 order light from the mask M and -1
Interference fringes due to the next light are generated on the core. Assuming that the interval between the irregularities of the mask M is d, the interval between the interference fringes on the core is d / 2.
Becomes Such a mask is called a phase mask. The mask M is replaced with a mask M having a different interval between the irregularities according to the wavelength to be removed. In the phase interferometry, high coherence is not required for light to be irradiated. However, since the light passes through the mask M, the energy on the irradiation surface tends to be small. Therefore, a light source with high luminance is required. Further, since the defect itself of the mask is transferred, the accuracy of the formed grating is determined by the manufacturing accuracy of the mask. In addition, for one wavelength to be removed, one mask corresponding to the wavelength interval is required.

The production of a fiber grating using the two-beam interference method is described in, for example, Japanese Patent Publication No. Sho 62
See JP-A-500052 and JP-A-8-220316. Further, with respect to the production of a fiber grating using the phase mask method, see JP-A-8-3389.
See No. 19 publication.

[0009]

Conventionally, as described above, A is used as a light source for manufacturing a fiber grating.
A KrF excimer laser light source, which is a harmonic light source of the r laser, has been used. The conventional method has the following problems. (1) Problems when a harmonic light source of Ar laser is used as a light source. The harmonic laser light source of the Ar laser has a spectral width of 2 to 3 pm, particularly 0.005 pm when the band is narrowed, the spectral width is relatively narrow, and high coherent light can be obtained. It can be used as any light source. However, each of the four output wavelengths is 0.1.
The power is as low as 5 W or less. Therefore, there is a problem that the production speed of the fiber grating is low and the throughput is poor. If the discharge tube of the Ar laser device is made longer, the output power can be increased to some extent, but the device becomes larger. The length of a discharge tube of a general Ar laser device is, for example, about 1.5 m. If the length of the discharge tube is further increased, the size of the device becomes considerably large. Further, the discharge tube has a life, and usually needs to be replaced in 1000 to 2000 hours.
When the discharge tube is replaced, complicated readjustment of the optical system in the apparatus is required, and the maintenance is not good.

(2) Problems when a KrF excimer laser is used as a light source. The KrF excimer laser has poor coherence of output light. Therefore, the two-beam interference method cannot be used, and only the phase mask method can be used. When the output power of the laser is increased to increase the throughput, compaction occurs in the quartz as a mask, and the life of the mask is shortened.
Note that compaction refers to damage that changes the refractive index of a quartz laser beam passing portion. The reason will be described below. In order to cause a change in the refractive index of the fiber core, there is a necessary exposure amount, and the “exposure amount” is “energy per pulse: E” × “repetition frequency: f”.
× It is proportional to “time”. On the other hand, “easiness of mask compaction (= mask life)” is proportional to “energy per pulse: E” / “pulse width”. Therefore, in order to increase the throughput, the above “energy per pulse: E” and / or “frequency: f”
Need to be larger. However, the current limit of the excimer laser device is generally f = 1 kHz. Therefore, the “energy per pulse: E” must be increased. However, when "energy per pulse: E" is increased, compaction is likely to occur. At present, to secure a certain throughput,
“Energy per pulse: E” is increased, and the mask is periodically replaced. As described above, when the KrF excimer laser is used, the mask life is shortened. Reduction of mask replacement cost and replacement time is desired.
When an F excimer laser is used, these demands cannot be met.

(3) A problem in the two-bundle interferometry when it is desired to freely set the wavelength to be removed (reflection wavelength: λR). When the two-beam interference method is used, the period 干 渉 of the interference fringe is Λ = λ
/ 2 sin θ (λ: wavelength of light from the light source).
The reflection wavelength λR is λR = 2nΛ = nλ / sin θ
(N: the original refractive index of the fiber core, θ: the incident angle of irradiation light on the fiber core). Here, when it is desired to freely set the reflection wavelength λR, θ and / or λ
Will be changed. When θ is changed, it is necessary to adjust the minute angle of the mirror, but it is difficult to adjust the minute angle of the mirror. JP-A-8-220316 describes a method of changing a wavelength λ by a prism or a diffraction grating provided in a laser device as a light source. However, even when using a harmonic light source of an Ar laser,
The wavelength width that can be changed is only the wavelength variable width (approximately ± 0.1 nm) of each of the four wavelengths output from the harmonic light source of the Ar laser. Therefore, the incident angle θ of the irradiation light to the fiber core
Is fixed, the reflection wavelength λR can be changed only by (± 0.1) × (n / sin θ) nm at one wavelength.

The above is summarized as follows. When an Ar laser device is used as a light source, the output is small and the throughput is poor. When an Ar laser device is used as a light source and the two-beam interference method is used, if the reflection wavelength is to be set freely, only four wavelengths can be used, and there is a limit to the variable width of the wavelength. Accordingly, the angle of the mirror of the two-beam interference optical system must be finely adjusted. However, it is very difficult to mechanically move the mirror to adjust the interval between the interference fringes. When a KrF excimer laser device is used as a light source, only the phase mask method can be used. Further, in order to increase the throughput, the output power must be increased, but since the repetition frequency has an upper limit, the energy per pulse must be increased, and mask damage occurs. The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is an object of the present invention to obtain a large output and a high throughput, and to continuously change the wavelength within a predetermined range. It is possible to manufacture a fiber grating capable of reflecting light of various wavelengths without fine adjustment of the mirror angle.

[0013]

According to the present invention, there is provided a fiber grating manufacturing apparatus having a two-bundle interference optical system for causing a refractive index change in a fiber core. As L
A solid-state laser device that is seeded by a narrowed-band seeding light output from a variable wavelength laser including a D (laser diode) or the like is used. Seeding with the narrowed seeding light narrows the spectrum of the oscillating laser light (narrows the band). Further, by stabilizing the seeding light, the wavelength of the variable wavelength laser light is stabilized, and the wavelength of the laser light output from the solid-state laser device can be stabilized.

FIGS. 1A and 1B show the basic structure of the present invention. The solid-state laser device having the structure shown in FIG. 1A or FIG. Manufacture fiber grating. (1) As shown in FIG. 1A, a fundamental wave laser generator 1a whose output light is narrowed by seeding, and a first coherent light source 1 composed of harmonic generation means 1b are provided. A second coherent light source 2 including a variable wavelength laser 2a or a variable wavelength laser 2a whose wavelength has been narrowed and stabilized by the reading light and a harmonic generation means 2b is provided. The laser light output from the first and second coherent light sources 1 and 2 is input to a first sum frequency generating means 3 composed of non-linear optical means, and the first and second coherent light sources 1 and 2 are input. To generate the sum frequency light of the laser light output from the
(250 nm) to manufacture a fiber grating by two-bundle interferometry. When the wavelength of the sum frequency light generated by the sum frequency generating means 3 is in the range of 230 to 250 nm, the sum frequency light generated by the sum frequency generating means 3 and the fundamental laser light are generated by the second sum frequency generating means 4. Even when a sum frequency light of the fundamental laser light output from the device 1a is generated and the sum frequency light (wavelength: 185 to 213 nm) is incident on the two-bundle interference optical system shown in FIG. Good.

(2) As shown in FIG. 1B, the laser light output from the wavelength tunable laser 5 whose band has been narrowed by the seeding light and whose wavelength has been stabilized is converted into a harmonic wave composed of a nonlinear optical crystal. The harmonic light is input to the wave generation means 6 to generate a harmonic light, and the harmonic light (wavelength 230 to 250 nm or wavelength 193 to 230 nm) is incident on the two-bundle interference optical system shown in FIG. 14 to manufacture a fiber grating. In the above (1) and (2), the wavelength of the seeding light for seeding the second coherent light source 2 or the wavelength tunable laser 5 is selected, and the nonlinear crystal for harmonic generation relating to these lights is phase-matched. The wavelength of the output laser beam can be made variable. Therefore, a plurality of gratings can be manufactured on one fiber by irradiating the laser light while changing the wavelength to different positions of the fiber core. In addition, since a variable wavelength laser beam can be obtained, a fiber grating can be manufactured without finely adjusting the angle of the mirror of the two-beam interference optical system. Further, unlike the phase mask method, there is no need to prepare a mask for each wavelength to be removed, and there is no need to consider mask damage. Also, by using a solid-state laser device as described above,
High output power can be obtained, and high throughput can be obtained. Furthermore, since the narrowed-band seeding light is used, it is possible to obtain a laser light having a narrow spectrum width (high coherence), and it is possible to project a sharp interference fringe having constant intervals and light and shade on the fiber. it can.

[0016]

FIG. 2 is a diagram showing a configuration of a solid-state laser device for manufacturing a fiber grating according to a first embodiment of the present invention. The figure shows that the wavelength is 230-250n.
1 shows a configuration example of a laser device that generates m laser light. In the figure, reference numeral 11 denotes a fundamental wave laser generator, and as the fundamental wave laser generator 11, Nd: YL
F, Nd: YAG, YVO ₄ laser or the like can be used, and the wavelength is about 1 μm (for example, the wavelength 1 in the case of Nd: YAG).
064 nm).

The narrow-band laser light generated by the LD seeder 12 is injected into the fundamental-wave laser generator 11, and the fundamental-wave laser generator 11 narrows the spectrum width to 0.1 pm or less by LD seeding. Laser light is generated. The LD seeder 12 converts the light generated by the laser diode 12a into parallel light by a collimator lens 12b as shown in FIG.
The output laser light that is incident on the external resonator formed by the reflection plate 12c and has a narrow band is output. The wavelength of the output laser light can be changed by changing the angle of the reflection plate 12c. Although FIG. 3 shows a case where a laser diode is used, other narrow band laser light sources can be used instead of the laser diode.

Referring back to FIG. 2, the fundamental laser light (for example, wavelength 1064n) emitted from the fundamental laser
m) is a second harmonic (wavelength 532) by the nonlinear optical crystal 13 (for example, LBO, BBO crystal, etc.) which is a wavelength conversion element.
nm). The second harmonic is split into two beams by the beam splitter BS1, and one of them is a nonlinear optical crystal 14.
(For example, LBO, BBO, CLBO crystal, etc.)
It is converted to a harmonic (355 nm). The other is a tunable, for example, a titanium sapphire laser device 15 (hereinafter referred to as T
(referred to as iSa laser device).
Although a titanium sapphire (TiSa) laser is shown in FIG. 2 as a wavelength variable laser, an OPO (optical parametric oscillator) can be used instead of a titanium sapphire (TiSa) laser.

The above-mentioned TiSa laser device 15 and OPO
Is injected with a narrow band laser beam generated by the LD seeder 16 having the same configuration as that shown in FIG.
TiSa laser device 15 or OPO by LD seeder 16
The TiSa laser device 1 by seeding
5 and the laser light emitted from the OPO are narrowed to have a spectral width of 0.1 pm or less. Also, LD seeder 1
6 can be changed or the wavelength of the output light can be changed stepwise within a range of 650 to 800 nm within a range of ± 10 nm per laser diode by adjusting the wavelength of each laser diode or the like. The above nonlinear optical crystal 1
4 and the light generated by the TiSa laser device 15 are transmitted to the nonlinear optical crystal 1 via the beam mixer BS2.
7 (for example, a CLBO crystal) and the nonlinear optical crystal 1
7 generates the sum frequency (wavelength 230 to 250 nm). The details of generation of a laser beam of a variable wavelength by a TiSa laser device or an OPO and generation of a sum frequency by a nonlinear optical crystal are described in, for example,
See U.S. Pat.

FIG. 4 is a view showing a configuration of a laser device for manufacturing a fiber grating according to a second embodiment of the present invention. As in the first embodiment, the wavelength is 230 to 250.
1 shows a configuration example of a laser device that generates a laser beam of nm. In the figure, reference numeral 15 denotes a TiSa laser device, which is excited by an excitation light source (not shown). The narrow band laser light generated by the LD seeder 16 described with reference to FIG.
The laser device 15 outputs a wavelength-variable narrow-band laser beam having a wavelength in the range of 690 to 750 nm. TiS
a The laser light output from the laser device 15 is incident on a nonlinear optical crystal 18 (for example, a BBO or CLBO crystal) and
It is converted into a harmonic wave, and further converted to a nonlinear optical crystal 19 (for example, B
(BO, CLBO crystal). Nonlinear optical crystal 19
Is the wavelength 690 to be output by the TiSa laser device 15
750 nm is converted to a third harmonic, and the wavelength is 230 to 250 n.
m light is output.

The laser light output from the laser device shown in FIGS. 2 and 4 has a spectral width of 0.1 as described above.
Since the laser light has a band narrowed to pm or less, a fiber grating can be manufactured by the two-bundle interferometry described above. That is, the laser light output from the laser device shown in FIGS. 2 and 4 is input to the beam splitter shown in FIG. 14 and split into two, reflected by mirrors M1 and M2, and overlapped again in the irradiation area. Causes interference. If a Ge-doped optical fiber core is arranged in the irradiation area, a portion where the refractive index periodically changes can be formed on the core. Here, the laser diode can change the oscillation wavelength by changing the angle of the reflector in FIG. 3, but its variable range is limited. In addition, since the range of the phase matching angle of a non-linear optical crystal (for example, a CLBO crystal) having a certain cut angle for generating sum frequency light is limited, the wavelength of the output laser light is changed in the range of 230 to 250 nm. It is necessary to replace the laser diode and replace the nonlinear optical crystal (CLBO crystal) according to the wavelength.

As an example, the wavelength variable range, the number of replacements of the laser diode and the nonlinear optical crystal for sum frequency generation (CLBO crystal) in the laser device of the first embodiment, and the reflection wavelength of the manufactured fiber grating are described. The range is shown in FIG. For example, the wavelength variable range of one laser diode is 654 to 68 as shown in FIG.
5 nm, 685 to 697 nm, ..., 805 to 854 nm
It is. Therefore, the wavelength of LD seeding is set to 654 to
To change the wavelength in the range of 854 nm, LD seeder 1
The six laser diodes need to be replaced six times as shown in FIG. Thereby, the sum frequency light output from the nonlinear optical crystal 17 can be changed in the range of 230 to 250 nm.

On the other hand, as a nonlinear optical crystal (CLBO crystal) that generates sum frequency light, it is necessary to use a crystal having a cut angle corresponding to the wavelength of the sum frequency light. 82.5-76.7 as shown in FIG.
°, 76.7-70.9 °, ..., 65.1-59.4 °
It is. Therefore, in order to change the sum frequency light within the range of 230 to 250 nm, it is necessary to exchange the crystal with a crystal having a different cut angle four times. By changing the wavelength of the sum frequency light as described above, the reflection wavelength of the fiber grating can be changed in the range of 1226 to 1332 nm as shown in FIG. In addition, the reflection wavelength λR of the manufactured grating is obtained by setting the refractive index n of the fiber core to 1.
46, the incident angle of the irradiation light to the fiber core was determined as 15.9. In the first and second embodiments, laser light having a narrow wavelength range of 230 to 250 nm can be obtained as described above.
It is possible to change the interval of the shading of the interference fringes generated in the irradiation area without changing the angles of 1, M2. For this reason, a grating having a desired wavelength can be manufactured without fine adjustment of the mirror angle. Further, it is not necessary to prepare a mask corresponding to the wavelength of the grating as in the phase mask method.

Incidentally, quartz doped with germanium (Ge) is not only light having a wavelength of 240 nm but also light having a wavelength of 19 nm.
It is also known that the refractive index changes (the refractive index decreases) even when light near 0 nm is irradiated. However, conventionally, only an ArF excimer laser (oscillation wavelength: 193 nm) has been known as a laser device capable of irradiating light having a wavelength of about 190 nm, and a fiber grating in this wavelength range has not been manufactured. Note that the ArF excimer laser has poor coherence like the above-described KrF excimer laser, and only the phase shift method can be used in manufacturing a fiber grating. Therefore, in the present invention, the solid-state laser device having the same configuration as that of the first and second embodiments is used to generate narrow-band laser light having the wavelength of about 190 nm, and use this laser light. To manufacture a fiber grating.

FIG. 6 is a diagram showing a configuration of a solid-state laser device according to a third embodiment of the present invention for generating light having a wavelength of approximately 190 nm, and a configuration of a laser device outputting laser light having a wavelength of 185 to 213 nm. Is shown. The wavelength 18
5 nm is the lower limit of the oscillation wavelength of the solid-state laser. In FIG. 6, reference numeral 11 denotes a fundamental wave laser generator similar to that shown in the first embodiment, and the fundamental wave laser generator 11 oscillates a laser beam having a wavelength of about 1 μm as described above. The narrow-band laser light generated by the LD seeder 12 shown in FIG. 3 is injected into the fundamental-wave laser generator 11, and the spectrum is narrowed to 0.1 pm or less from the fundamental-wave laser generator 11. The emitted laser light is generated.

The fundamental wave laser light emitted from the fundamental wave laser generator 11 is split into two beams by the beam splitter BS1, and a part of the beam is split into the nonlinear optical crystal 13 (for example, LB).
O, BBO crystal, etc.), 2nd harmonic (wavelength 532 nm)
Is converted into a wavelength. The other light split into two beams by the beam splitter BS1 passes through a beam mixer BS4 to a non-linear optical crystal 17b that generates a sum frequency to be described later.
Is input to The second harmonic is further split into two by the beam splitter BS3, and one is converted into a third harmonic (355 nm) by the nonlinear optical crystal 14 (for example, LBO, BBO, CLBO crystal, etc.). The other is input as excitation light of a wavelength-variable, for example, TiSa laser device 15 (or OPO). TiSa laser device 1 described above
5 and the OPO are injected with the narrow band laser light generated by the LD seeder 16 shown in FIG. 3, and the TiSa laser device 15 has a wavelength tunable band within a wavelength range of 695 to 1061 nm. The laser beam is output.

The third harmonic generated by the nonlinear optical crystal 13 and the light generated by the TiSa laser device 15 are transmitted through the beam mixer BS2 to the nonlinear optical crystal 17a (eg, CLB).
O crystal), and the nonlinear optical crystal 17a generates its sum frequency (wavelength 235 to 266 nm). The sum frequency output from the nonlinear optical crystal 17a is further added to the beam mixer BS.
Then, the light enters the nonlinear optical crystal 17b which generates a sum frequency. The nonlinear optical crystal 17b includes a beam mixer BS
The laser light (wavelength 1064 nm) generated by the fundamental wave laser device 11 is incident on the non-linear optical crystal 17 b via the laser beam 4, and the non-linear optical crystal 17 b generates the sum frequency (wavelength 185 to 213 nm).

FIG. 7 is a diagram showing a configuration of a solid-state laser device according to a fourth embodiment of the present invention. As in the third embodiment, the configuration of a laser device that outputs laser light having a wavelength of 193 to 230 nm is shown. Is shown. In the figure, reference numeral 15 denotes a TiSa laser device, which is excited by an excitation light source (not shown). The TiSa laser device 15 has the L described in FIG.
The narrow band laser light generated by the D seeder 16 is injected, and the TiSa laser device 15 has a wavelength of 772 to 92.
It outputs a laser light with a wavelength tunable in a range of 0 nm and a narrow band. Laser light output from the TiSa laser device 15 is incident on a nonlinear optical crystal 18 (for example, a BBO or CLBO crystal), is converted into a second harmonic, and is then incident on a nonlinear optical crystal 19 (for example, a BBO or CLBO crystal). The nonlinear optical crystal 19 generates its third harmonic. The output of the nonlinear optical crystal 19 is the nonlinear optical crystal 2 that generates the fourth harmonic.
0 (for example, a BBO crystal) and the nonlinear optical crystal 10
Are the wavelengths 772 to 772 output from the TiSa laser device 15.
920 nm is converted to a fourth harmonic, and the wavelength is 193 to 230 n.
m light is output. In the third and fourth embodiments, the wavelength is 185 nm to 213 nm or the wavelength is 193 nm to 213 nm.
In order to change the wavelength in the range of 230 nm, it is necessary to replace the laser diode as described above and to replace the laser diode with a nonlinear optical crystal having a different cut angle.

FIG. 8 is a diagram showing the configuration of a solid-state laser device according to a fifth embodiment of the present invention for generating light having a wavelength of approximately 190 nm, and the configuration of a laser output device for outputting laser light having a wavelength of 185 to 196 nm. Is shown. In FIG.
Reference numeral 11 denotes a fundamental wave laser generator similar to that shown in the first and third embodiments. The fundamental wave laser generator 11 oscillates a laser beam having a wavelength of about 1 μm as described above. The narrow-band laser light generated by the LD seeder 12 shown in FIG. 3 is injected into the fundamental-wave laser generator 11, and the spectrum is narrowed to 0.1 pm or less from the fundamental-wave laser generator 11. The emitted laser light is generated.

The fundamental wave laser light radiated from the fundamental wave laser generator 11 is applied to a nonlinear optical crystal 13 (for example, LB).
O, BB0 crystal, etc.), 2nd harmonic (wavelength 532 nm)
Is converted into a wavelength. This second harmonic is applied to the nonlinear optical crystal 20.
(For example, BBO, CLBO crystal, etc.), the wavelength is converted to a fourth harmonic (wavelength: 266 nm), and this fourth harmonic is converted to a fifth harmonic (wavelength: 213 nm) by the nonlinear optical crystal 21 (for example, BBO, CLBO crystal, etc.). ). Reference numeral 22 denotes a wavelength-variable OPO laser device,
The narrow band laser light generated by the LD seeder 16 shown in FIG. 3 is injected, and the OPO laser device 22 outputs the narrow band laser light whose wavelength is variable in the range of 1407 to 2500 nm. .

The fifth harmonic generated by the nonlinear optical crystal 21 and the light generated by the OPO laser device 22 are transmitted to the nonlinear optical crystal 17 (eg, LBO, C
The nonlinear optical crystal 17 generates the sum frequency (wavelength: 185 to 196 nm).

FIG. 9 is a diagram showing the configuration of a solid-state laser device according to a sixth embodiment of the present invention for generating light having a wavelength of about 190 nm.
1 shows a configuration of a laser output device that outputs 10 nm laser light. In FIG. 9, reference numeral 11 denotes a fundamental wave laser generator similar to that shown in the first, third, and fifth embodiments. The fundamental wave laser generator 11 has a wavelength of about 1 μm as described above. Oscillates laser light. The narrow-band laser light generated by the LD seeder 12 shown in FIG. 3 is injected into the fundamental-wave laser generator 11, and the spectrum is narrowed to 0.1 pm or less from the fundamental-wave laser generator 11. The emitted laser light is generated.

The fundamental wave laser light radiated from the fundamental wave laser generator 11 is applied to the nonlinear optical crystal 13 (for example, LB
O, BB0 crystal, etc.), 2nd harmonic (wavelength 532 nm)
Is converted into a wavelength. This second harmonic is applied to the nonlinear optical crystal 20.
(For example, BBO, CLBO crystal, etc.), the wavelength is converted to the fourth harmonic (wavelength: 266 nm). Reference numeral 22 denotes a wavelength-variable OPO laser device into which a narrow-band laser beam generated by the LD seeder 16 shown in FIG. 3 is injected, and the OPO laser device 22 has a wavelength of 670 to 2500.
It outputs laser light with a wavelength tunable in the range of nm and narrow band.

The fourth harmonic generated by the nonlinear optical crystal 20 and the light generated by the OPO laser device 22 are transmitted through the beam mixer BS2 to the nonlinear optical crystal 17 (eg, LBO, CBO).
The nonlinear optical crystal 17 generates the sum frequency (wavelength 190 to 240 nm).

Incidentally, instead of the above-mentioned OPO laser device,
A wavelength-variable TiSa laser device 15 may be used. The TiSa laser device 15 is injected with a narrow band laser beam generated by the LD seeder 16 shown in FIG. 3, and the TiSa laser device 15 has a wavelength of 670 to 100.
It outputs a laser light with a wavelength tunable in a range of 0 nm and a narrow band. A fourth harmonic generated by the nonlinear optical crystal 20,
The light generated by the TiSa laser device 15 is a beam mixer B.
The nonlinear optical crystal 17 (for example, LBO, CL
(A BO crystal or the like), and the nonlinear optical crystal 17 generates the sum frequency (wavelength 190 to 210 nm).

FIG. 10 is a diagram showing a configuration of a solid-state laser device according to a seventh embodiment of the present invention for generating light having a wavelength of approximately 190 nm, and a configuration of a laser output device for outputting laser light having a wavelength of 190 to 240 nm. Is shown. In FIG. 10, reference numeral 11 denotes a fundamental laser generator similar to that shown in the first, third, fifth, and sixth embodiments, and the fundamental laser generator 11 has a wavelength as described above. About 1μm
Oscillate. The narrow-band laser light generated by the LD seeder 12 shown in FIG. 3 is injected into the fundamental-wave laser generator 11, and the spectrum is narrowed to 0.1 pm or less from the fundamental-wave laser generator 11. The emitted laser light is generated.

The fundamental wave laser light radiated from the fundamental wave laser generator 11 is applied to the nonlinear optical crystal 13 (for example, LB
O, BB0 crystal, etc.), 2nd harmonic (wavelength 532 nm)
Is converted into a wavelength. This second harmonic is applied to the nonlinear optical crystal 20.
(For example, BBO, CLBO crystal, etc.), the wavelength is converted to the fourth harmonic (wavelength: 266 nm).

Reference numeral 22 denotes a wavelength-variable OPO laser device into which a narrow band laser beam generated by the LD seeder 16 shown in FIG. 3 is injected. It outputs laser light with a wavelength tunable within a range of ５5000 nm and narrowed. The laser light emitted from the fundamental wave laser generator 11 is applied to the nonlinear optical crystal 23 (for example, LBO, BB0, CLBO, ABO).
Second harmonic (wavelength 670 to 2500n) by GS crystal etc.
m).

The fourth harmonic generated by the nonlinear optical crystal 20 and the second harmonic generated by the nonlinear optical crystal 23 are transmitted through the beam mixer BS2 to the nonlinear optical crystal 17 (for example, LB).
O, CLBO crystal, etc.), and the nonlinear optical crystal 17 generates its sum frequency (wavelength 190 to 240 nm).

In the fifth, sixth and seventh embodiments, the wavelengths are 185 to 196 nm, 190 to 240 nm or 19
In order to change the wavelength in the range of 0 to 210 nm, it is necessary to replace the laser diode as described above and to replace the laser diode with a nonlinear optical crystal having a different cut angle.

Using the tunable solid-state laser device described above, it is possible to manufacture a fiber grating for removing light of a plurality of wavelengths. For example, as shown in FIG. 11, four types of light having wavelengths of λ1, λ2, λ3, and λ4 are transmitted to a fiber, and among them, a fiber grating for removing four types of light of λ1, λ2, and λ3 is manufactured as follows. Is done. As shown in FIG. 12A, first, the output light of the solid-state laser device 10 of the present invention is
At the predetermined position of the core of the optical fiber OP.
Create a grating to reflect the light of The laser device 10 outputs light having a wavelength at which a grating that reflects light at the wavelength λ1 (at a constant interval) can be manufactured. Adjustment of the wavelength is performed in the same manner as described above. Next, FIG.
As shown in (b), the optical fiber OP is moved, and a grating for reflecting light of the wavelength λ2 is created at a predetermined position different from the above. The wavelength of the laser light output from the laser device 10 is changed so that a grating that reflects light of the wavelength λ2 can be manufactured. Further, FIG.
As shown in (1), the optical fiber OP is moved, and a grating that reflects light of the wavelength λ3 is manufactured in the same manner as described above. In this manner, a fiber grating for removing light of a plurality of wavelengths can be easily manufactured.

As described in the conventional example, when the light source is an Ar laser device, four wavelengths (250.8 n
m, 248.2 nm, 244.0 nm, 238.2 n
m) can be output. For this reason, the wavelength can be made variable within the spectrum width of the wavelength, but in principle, only a grating that removes four wavelengths corresponding to the four wavelengths can be manufactured. On the other hand, the laser device of the present invention has a variable wavelength and can continuously change the wavelength within the variable wavelength range of the laser diode to output light, so that a fiber grating that removes light of various wavelengths is used. Can be manufactured. In addition, by exchanging the laser diode and the nonlinear optical crystal as described above, the wavelength can be changed over a wide range, and a fiber grating for removing light of various wavelengths can be manufactured.

[0043]

As described above, the following effects can be obtained in the present invention. (1) In a fiber grating manufacturing apparatus provided with a two-bundle interference optical system that causes a change in the refractive index of a fiber core, a solid-state laser device seeded by narrowed seeding light is used as a light source device. Therefore, a high output power of 0.5 W or more can be obtained, and a high throughput can be obtained. In addition, a laser beam having a narrow spectrum width (high coherence) of 0.1 pm or less can be output, and sharp interference fringes having constant intervals and shades can be projected on the fiber. (2) Since the wavelength conversion laser seeded by the seeding light is provided, the wavelength of the laser light to be output can be selected by selecting the seeding wavelength. Therefore, it is possible to easily form a grating having a grating interval corresponding to a wavelength to be removed. Further, since the wavelength is variable, fine adjustment of the mirror angle of the two-bundle interference optical system is not required, and operability can be improved. (3) Since the sum frequency light is generated by the non-linear optical crystal, light having a wavelength of around 190 nm can be obtained, which can be useful for manufacturing a fiber grating in a wavelength region that has not been known conventionally.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram illustrating a configuration of a solid-state laser device according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration example of an LD seeder that generates seeding light.

FIG. 4 is a diagram illustrating a configuration of a solid-state laser device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a wavelength variable range and a reflection wavelength range of a manufactured fiber grating in the laser device of the first embodiment.

FIG. 6 is a diagram illustrating a configuration of a solid-state laser device according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a solid-state laser device according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a solid-state laser device according to a fifth embodiment of the present invention.

FIG. 9 is a diagram illustrating a configuration of a solid-state laser device according to a sixth embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of a solid-state laser device according to a seventh embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a fiber grating that removes four types of light.

FIG. 12 is a diagram showing a method of manufacturing a fiber grating for removing four types of light.

FIG. 13 is a diagram illustrating a configuration of a fiber grating.

FIG. 14 is a diagram illustrating the production of a fiber grating by the two-beam interference method.

FIG. 15 is a diagram illustrating the production of a fiber grating by a phase mask method.

[Explanation of symbols]

 1, 1st, 2nd coherent light sources 3, 4 Sum frequency generation means 5 Variable wavelength laser 6 Harmonic generation means 10 Laser device 11 Fundamental wave laser generation device 12 LD seeder 13, 14 Nonlinear optical crystal 15 Titanium sapphire laser device Reference Signs List 16 LD seeder 17, 18, 19, 20, 21 Nonlinear optical crystal 22 OPO laser device 23 Nonlinear optical crystal

Claims (3)

[Claims] 1. A fiber grating manufacturing apparatus having a two-bundle interference optical system for causing a refractive index change in a fiber core, wherein a light source of the manufacturing apparatus uses a narrow band laser beam as a seed beam. An apparatus for manufacturing a fiber grating, wherein the apparatus is a solid-state laser device that oscillates at one frequency. 2. The fiber grating manufacturing apparatus according to claim 1, wherein said seed light has a variable wavelength. 3. A method of manufacturing a fiber grating using a two-bundle interference optical system, wherein a single-frequency oscillation solid-state laser device is used at a different position of a fiber core by using a laser beam having a narrow band by changing a wavelength as a seed beam. Irradiating a laser beam from a fiber to produce a plurality of gratings on one fiber.