JPH08220387A - Optical coupler and its adjustment method and optical amplifier device - Google Patents

Abstract

PURPOSE: To make it possible to lessen the astigmatism at the imaging point generated by a deviation in the position setting between a semiconductor laser and a collimating lens by simple correction by providing the above optical coupler with a first coupling system, a second coupling system and an optical fiber for receiving the exit beam of this second coupling system. CONSTITUTION: This optical coupler has the first coupling system 9, the second coupling system 12 for receiving the exit beam of the coupling system 9 and imaging the beam within a first plane and a second plane and the optical fiber 2 for receiving the exit beam of the second coupling system. The first coupling system 9 receives the exit beam of the semiconductor laser 1 and images the beam within the first plane parallel with the direction of the exit beam. The exit beam of the semiconductor laser 1 is approximately paralleled within the second plane parallel with the direction of the exit beam of the semiconductor laser 1 and intersecting with the first plane. The second coupling system 12 receives the exit beam of the first coupling system 9 and images the beam within the first and second planes. The optical fiber 2 receives the exit beam of the second coupling system 12, by which the positions of the imaging points within the respective planes are independently adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupling device for efficiently coupling laser light emitted from a laser oscillator to an optical fiber, a method of adjusting the optical coupling device, and an optical amplification device using the optical coupling device. It relates to the device.

[0002]

2. Description of the Related Art First, a conventional optical coupling device will be described. The optical coupling device is used to efficiently enter laser light emitted from a laser oscillator such as a semiconductor laser into an optical fiber. In order to efficiently couple the emitted light of the semiconductor laser to the optical fiber, it is necessary to set the magnification of the coupling system of the optical coupling device provided between the semiconductor laser and the optical fiber to an optimum value.

As shown in FIG. 10, a semiconductor laser 1
On a plane parallel to the active layer 1a (a plane including the X axis).
If the mu-waist spot size is ω _Lx , the beam-waist spot size in the plane perpendicular to the active layer (the plane including the Y axis) is ω _LY , and the spot size of the waveguide mode of the optical fiber is ω _F , The optimum magnification M _OPT is expressed by the following equation. The following equation is described on page 58 of Kenji Kawano, “Basics and Applications of Optical Coupling Systems for Optical Devices” (Hyundai Engineering Co., 1991). M _OPT = ω _F / (ω _LX・ ω _LY ) ^1/2・ ・ ・ (1)

As shown in FIG. 11, the above formula (1) is defined by the magnitudes of the laser light (long axis M _OPT ω _LX and short axis M _OPT irradiating the end face of the optical fiber through the lens of M _OPT magnification. M
_It means that the geometric mean value of _OPT ω _LY ) and the spot size ω _{F of the} optical fiber are equal.

Further, the coupling efficiency η between the semiconductor laser and the optical fiber when the coupling system of the optical coupler is set in this way is expressed by the following equation. η = 4 · Dr / (1 + Dr) ² (2) where Dr is the ratio of ω _Lx and ω _LY (ω _LY / ω _LX ), and the ellipticity of the beam cross section of the semiconductor laser (The ratio of the major axis to the minor axis of the ellipse).

The relationship between the ellipticity Dr calculated based on the equation (2) and the mode shape mismatch loss is shown in the graph of FIG. As can be seen from this graph, the loss is zero when Dr = 1, but the loss due to the mode shape mismatch between the elliptical and circular shapes increases as Dr increases.

A semiconductor laser having a wavelength of 1.3 .mu.m and a wavelength of 1.55 .mu.m currently used for ordinary optical fiber communication and a semiconductor having a wavelength of 1.48 .mu.m for exciting an erbium-doped fiber used for a fiber amplifier. The laser beam ellipticity is about 1.1 to 1.2. In this case,
As can be seen from 2, the shape mismatch loss in these semiconductor lasers is 0.1 dB or less, which is not a serious problem.

However, the pumping wavelength of 0.98 is advantageous for reducing the noise and increasing the efficiency of the erbium-doped fiber amplifier.
The ellipticity of the semiconductor laser of μm is as large as 2-3. In this case, as can be seen from FIG. 12, the shape mismatch loss of this semiconductor laser has a large value of 0.5 to 1.3 dB and cannot be ignored.

In order to solve this problem, an optical coupling device shown in FIG. 13 has been proposed. The figure shows 1993.
FIG. 11A is a cross-sectional view of a conventional optical coupling device shown in C-116 of the National Institute of Electronics, Information and Communication Engineers Autumn National Convention in FIG. FIG. 1B is a sectional view of a vertical coupling surface perpendicular to the active layer of the semiconductor laser. In FIG. 13, 1 is the beam waist spot size ω _LX and ω _LY , and the wavelength is 0.
A semiconductor laser 2 having a diameter of 98 μm is an optical fiber to which the outgoing beam of the semiconductor laser 1 is coupled. Optical fiber 2
The guided mode spot size of is ω _F. Reference numeral 3 is a horizontal plane emitting beam on a horizontal coupling surface horizontal to the active layer of the semiconductor laser 1, 4 is a vertical plane emitting beam on a vertical coupling surface vertical to the active layer of the semiconductor laser 1, and 5 is a horizontal plane. This is a collimating lens for converting the exit beam 3 and the vertical plane exit beam 4 into parallel beams. The collimating lens 5 has the same focal length f ₁ on the horizontal coupling surface and the vertical coupling surface.
The output surface of the semiconductor laser 1 is set substantially at the focal plane of the collimating lens 5. Reference numeral 6 denotes a condenser lens. Focal length f on the horizontal coupling surface of the condenser lens 6
_2X is different from the focal length f _2Y in the vertical coupling plane. These values have the following relationships. f _2X = f ₁ · ω _F / ω _LX (3) f _2Y = f ₁ · ω _F / ω _LY (4)

Reference numeral 7a is a main plane on the horizontal coupling surface of the condenser lens 6, and 7b is a main plane on the vertical coupling surface of the condenser lens 6. The length of the condenser lens 6 is the horizontal coupling plane main plane 7
The distance between a and the image formation point is equal to the horizontal coupling plane focal length f _2X ,
Moreover, the distance between the principal plane 7b of the vertical coupling surface and the image forming point is set to be equal to the focal length f _{2Y of the} vertical coupling surface. The input surface of the optical fiber 2, which is a single mode fiber, is installed at the image forming point. Reference numeral 8a denotes a cylindrical surface provided on the output surface of the condenser lens 6 having a curvature only on the horizontal coupling surface of the condenser lens 6, and 8b has a curvature only on the vertical coupling surface of the condenser lens 6. Is a cylindrical surface provided on the input surface of.

Next, the operation of the conventional optical coupling device will be described. Emitted from the semiconductor laser 1,
The horizontal plane emitting beam 3 and the vertical plane emitting beam 4 which are diverging beams are converted into parallel beams by the collimating lens 5. Here, since the horizontal plane beam waist spot size ω _LX of the semiconductor laser 1 is smaller than the vertical plane beam waist spot size ω _LY (ω _LX <ω _LY ),
The spread of the horizontal plane emitting beam 3 is smaller than that of the vertical plane emitting beam 4. This is because the smaller the beam waist spot size, the larger the beam spread due to diffraction.

First, the operation on the horizontal coupling surface will be described with reference to FIG. The horizontal plane emitting beam 3 converted into the parallel beam by the collimating lens 5 is incident on the condenser lens 6 and is refracted by the cylindrical surface 8a provided on the output surface of the condenser lens 6 to be condensed. To the optical fiber 2 and coupled to the optical fiber 2. Here, the coupling magnification M _X on the horizontal coupling surface is, as shown in the following expression, the focal length f ₁ of the collimating lens 5 and the focal length f _2X of the horizontal coupling surface of the condenser lens 6.
It is expressed by the ratio of. M _X = f _2X / f ₁ (5)

Since f _2X has been set to the value shown in the equation (3), M _X is represented by the following equation. M _X = ω _F / ω _LX (6)

Therefore, the horizontal coupling plane / coupling magnification M _X in this coupling system is set to the optimum magnification ω _F / ω _LX , and the mode shape mismatch loss at the horizontal coupling plane does not occur.

Next, the operation of the vertical coupling surface will be described with reference to FIG.
A description will be given based on (b). The vertical plane emission beam 4 converted into the parallel beam by the collimating lens 5 enters the condenser lens 6. Then, the light is refracted by the cylindrical surface 8b provided on the input surface of the condenser lens 6, converted into a condenser beam, and coupled to the optical fiber 2. Here, the coupling magnification M _{Y on} the vertical coupling surface is expressed by the ratio of the focal length f ₁ of the collimating lens 5 and the vertical coupling surface focal length f _2Y of the condenser lens 6 as shown in the following equation. M _Y = f _2Y / f ₁ (7)

Here, since f _2Y is set to the value previously shown in the equation (4), M _Y is represented by the following equation. M _Y = ω _F / ω _LY (8)

Therefore, the horizontal coupling plane / coupling magnification M _Y in this coupling system is set to the optimum magnification ω _F / ω _LY, and the _mode shape mismatch loss at the vertical coupling plane does not occur.

As described above, in the conventional optical coupling device of FIG. 13, the mode-shape mismatch loss due to the elliptic beam of the semiconductor laser causes the optimum magnification of the horizontal coupling surface and the vertical coupling surface. Can be set independently as shown in equations (6) and (8), respectively, and thus can be further reduced.

However, on the other hand, when the horizontal coupling surface magnification M _X and the vertical coupling surface M _Y are different, an astigmatic difference occurs at the image forming point depending on the settings of the semiconductor laser 1 and the collimating lens 5. Occurs.

When the set positional relationship between the semiconductor laser 1 and the collimating lens 5 deviates from the design value by ΔZ _{1 in the} optical axis direction, the image forming point is displaced by the square of the magnification in the optical axis direction. . Therefore, if the shifts of the image forming points of the horizontal coupling surface and the vertical coupling surface are respectively set as ΔZ _2X and ΔZ _2Y , these are expressed by the following equations. ΔZ _2X = M _X ² · ΔZ ₁ (9) ΔZ _2Y = M _Y ² · ΔZ ₁ (10)

[0021] Here, if M _X and M _Y are equal to the above formula match [Delta] Z _2X and [Delta] Z _2Y, but as in the optical coupler of Figure 13, if the M _X and M _Y are different and [Delta] Z _2X ΔZ _2Y does not match. Such a shift between the image forming points on the horizontal coupling surface and the vertical coupling surface is called astigmatism. If there is an astigmatic difference, the coupling efficiency with the optical fiber decreases. The magnitude of the astigmatic difference ΔA _S at the image forming point is expressed by the following equation from equations (9) and (10). ^{_{ΔA S = (M Y 2 -M}} X 2) · ΔZ 1 = M X 2 · (Dr 2 -1) · ΔZ 1 ··· (11)

FIG. 14 shows the calculation result of the relation between the positional deviation ΔZ ₁ of the semiconductor laser 1 and the collimating lens 5 in the optical axis direction and the coupling loss due to the astigmatic difference. Therefore, in order to suppress the astigmatic loss to 0.1 dB or less so that the effect of the astigmatic difference can be ignored, ΔZ _{1 is set} to 1
It is necessary to set the thickness to 2 μm or less.

[0023]

As described above, in the conventional optical coupling device, the horizontal coupling plane magnification M _X and the vertical coupling plane M _{Y are used.}
Are different from each other, an astigmatic difference occurs at the image forming point when the setting of the distance between the semiconductor laser 1 and the collimating lens 5 is deviated, resulting in a loss. In order to suppress the loss due to this astigmatic difference to a level that can be ignored, the semiconductor laser 1
The error in the position of the collimating lens 5 must be set to 1-2 μm or less as the setting accuracy in the optical axis direction. This setting accuracy is a very strict value, and there is a problem that assembly becomes very difficult.

The present invention has been made in order to solve such a problem, and simply corrects the astigmatic difference at the image forming point caused by the deviation of the position setting of the semiconductor laser and the collimating lens. The purpose of the present invention is to obtain an optical coupling device and an adjusting method thereof that can be reduced by. Furthermore, it aims at providing the optical amplification apparatus using this optical coupling device.

[0025]

An optical coupling device according to a first aspect of the present invention is a semiconductor laser which emits a laser beam, and a first laser which receives an emission beam of the semiconductor laser and is parallel to the direction of the emission beam. The image is formed in a plane, is parallel to the direction of the emitted beam of the semiconductor laser, and is the first beam.
A first coupling system that makes the emission beam of the semiconductor laser substantially parallel in a second plane that intersects the plane, and an emission beam of the first coupling system that receives the emission beam in the first plane and the first plane. A second coupling system for forming an image in the plane of 2 and an optical fiber for receiving an outgoing beam of the second coupling system.

An optical coupling device according to a second aspect of the present invention is such that the first plane is set in a direction in which the emission angle of the emission beam of the semiconductor laser is reduced.

In the optical coupling device according to a third aspect of the present invention, the first plane is a horizontal coupling surface parallel to the active layer of the semiconductor laser, and the second plane is vertical coupling vertical to the active layer of the semiconductor laser. It is a face.

According to a fourth aspect of the present invention, there is provided an optical coupling device in which the first coupling system has the same focal length in the first plane and the second plane, and the semiconductor laser is in each plane. −
The first lens for converting the outgoing beam of the beam into a parallel beam, and at least one of the input and output surfaces is substantially cylindrical, and receives the outgoing beam of the first lens to receive the first beam. It is composed of a second lens which is converted into a converging beam in the plane and transmits as a parallel beam in the second plane.

According to a fifth aspect of the present invention, there is provided an optical coupling device, wherein the first coupling system has a substantially spherical input surface and a substantially cylindrical output surface, and receives the emitted beam of the semiconductor laser and the first coupling system. Is formed by a lens that converts light into a converging beam in the plane of (1) and emits a parallel beam in the second plane.

According to a sixth aspect of the present invention, in the optical coupling device, the second coupling system has a parabolic shape in which the distribution characteristic of the refractive index decreases from the optical axis in the radial direction, and the input surface and the flat surface are substantially cylindrical. A divergent beam after having been imaged in the first plane by the first coupling system, and has a beam-shaped output surface.
And a third lens for converting the parallel beam in the second plane into a converging beam for coupling to the optical fiber. .

According to a seventh aspect of the present invention, there is provided an optical coupling device, wherein the second coupling system has a substantially cylindrical input surface and a substantially spherical output surface, and the second lens allows the second coupling system to be provided in the first plane. The divergent beam after being imaged at is converted into a converging beam again and coupled to the optical fiber, and at the same time, the parallel beam in the second plane is converted into a converging beam. And a third lens coupled to the optical fiber.

An optical coupling device according to an eighth aspect of the present invention is configured such that the output surface of the second coupling system is inclined so that the outgoing beam intersects the optical axis of the second coupling system. The input surface of the optical fiber is configured to be inclined so that the incident beam is refracted in the optical axis direction of the optical fiber.

A method of adjusting an optical coupling device according to a ninth aspect is:
A first step of checking whether the image formation position in the first plane and the image formation position in the second plane match, the image formation position in the first plane and the second plane The second coupling system is moved in the optical axis direction so as to bring the image forming position in the first plane closer to the image forming position in the second plane when the image forming position in the second plane does not match. A second position for making the image forming position in the first plane coincide with the image forming position in the second plane
And the process of.

According to a tenth aspect of the present invention, there is provided an optical coupling device adjusting method, wherein the moving amount Δd of the second coupling system in the second step is M _x , the first coupling system in the first plane, and the moving amount Δd. Coupling magnification of the second coupling system, Dr is the ellipticity of the emitted beam of the semiconductor laser, M _x2 is the magnification of the second coupling system in the first plane, ΔZ ₁ is the optical axis direction of the semiconductor laser. The amount of displacement is given by the following equation. Δd = M _x ² (Dr ² −1) / M _x2 ² · ΔZ ₁

An optical amplifying device according to an eleventh aspect of the present invention receives a semiconductor laser that emits a laser beam and an emission beam of the semiconductor laser, and forms an image in a first plane parallel to the direction of the emission beam. A first coupling system for parallelizing the emission beam of the semiconductor laser in a second plane that is parallel to the direction of the emission beam of the semiconductor laser and intersects the first plane. Light composed of a second coupling system for receiving an outgoing beam of the coupling system and forming an image in the first plane and the second plane, and an optical fiber to which the outgoing beam of the second coupling system is coupled A coupling device, a multiplexer for coupling the light input from the outside with the light output by the optical coupling device, and the pumping medium is doped and excited by the output of the multiplexer and input from the outside. Amplify the light that is The is obtained and an optical fiber for outputting light.

[0036]

According to the first aspect of the invention, the semiconductor laser emits a laser beam, and the first coupling system receives the emitted beam of the semiconductor laser and combines it in a first plane parallel to the direction of the emitted beam. While making the image, the emitted beam of the semiconductor laser is made substantially parallel in a second plane which is parallel to the direction of the emitted beam of the semiconductor laser and intersects the first plane. The output beam of the first coupling system is received to form an image in the first plane and the second plane, and the optical fiber receives the output beam of the second coupling system, whereby the second beam is generated. The positions of the image forming points in the first plane and the image forming points in the second plane are independently adjusted by the coupling system.

According to a second aspect of the present invention, the first angle is set so that the emission angle of the emission beam of the semiconductor laser decreases.
Set the plane of to reduce aberration.

In the invention of claim 3, the first plane is a horizontal coupling surface parallel to the active layer of the semiconductor laser, and the second plane is a vertical coupling surface vertical to the active layer of the semiconductor laser. , The output angle of the output beam of the semiconductor is minimized.

In the fourth aspect of the invention, the first lens having the same focal length in the first plane and the second plane and forming the first coupling system is provided in each plane. The output beam of the semiconductor laser is converted into a parallel beam, and at least one of the input and output surfaces is substantially cylindrical, and the second lens forming the first coupling system is The beam emitted from the first lens is converted into a converging beam in the first plane, and is transmitted as a parallel beam in the second plane.

According to a fifth aspect of the present invention, a lens having a substantially spherical input surface and a substantially cylindrical output surface, which constitutes the first coupling system, receives the emission beam of the semiconductor laser, and The light is converted into a converging beam in the first plane and is emitted as a parallel beam in the second plane.

In a sixth aspect of the invention, the distribution characteristic of the refractive index is a parabolic shape that decreases in the radial direction from the optical axis, and has a substantially cylindrical input surface and a planar output surface,
The third lens forming the second coupling system is the first lens.
The diverging beam after being imaged in the first plane is again converted into a converging beam by the coupling system and is coupled to the optical fiber, and at the same time, the parallel beam in the second plane. The beam is converted into a converging beam and coupled to the optical fiber.

According to a seventh aspect of the present invention, the third lens, which has a substantially cylindrical input surface and a substantially spherical output surface and constitutes the above-mentioned second coupling system, is constituted by the above-mentioned second lens. The diverging beam after being imaged in the first plane is converted into a converging beam again to be coupled to the optical fiber, and the parallel beam in the second plane is condensed beam. -The optical fiber and the optical fiber are coupled to the optical fiber.

In the eighth aspect of the invention, the output beam is inclined so that the outgoing beam intersects the optical axis of the second coupling system, and the second coupling system is made incident. The optical fiber configured by tilting the input surface so that the beam is refracted in the optical axis direction of the optical fiber,
The light returning to the semiconductor laser is suppressed.

According to the ninth aspect of the invention, it is checked in the first step whether the image forming position in the first plane and the image forming position in the second plane coincide with each other, and the second step is performed. When the image forming position in the first plane does not coincide with the image forming position in the second plane, the image forming position in the first plane is changed to the image forming position in the second plane. 2nd above to approach
By moving the coupling system in the optical axis direction so that the image forming position in the first plane coincides with the image forming position in the second plane.

In the tenth aspect of the present invention, the movement amount Δd of the second coupling system in the second step can be performed with lower accuracy than the positional deviation ΔZ ₁ of the semiconductor laser in the optical axis direction. The value of the expression. Δd = M _x ² (Dr ² −1) / M _x2 ² · ΔZ ₁

In the eleventh aspect of the present invention, the semiconductor laser emits a laser beam, and the first coupling system receives the emitted beam of the semiconductor laser and couples in the first plane parallel to the direction of the emitted beam. While making the image, the emitted beam of the semiconductor laser is made substantially parallel in a second plane which is parallel to the direction of the emitted beam of the semiconductor laser and intersects the first plane. Receiving the outgoing beam of the first coupling system and forming an image in the first plane and in the second plane, the outgoing beam is coupled to the optical fiber,
The multiplexer couples the light input from the outside and the light emitted from the optical fiber, and the optical fiber in which the pumping medium is doped is excited by the output of the multiplexer and input from the outside. The amplified light is amplified and the amplified light is output.

[0047]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the optical coupling device of the first embodiment. FIG. 1A is a top view of this optical coupling device. This figure shows a state of optical coupling on a horizontal coupling surface which is horizontal to the active layer of the semiconductor laser. FIG. 1B is a side view of this optical coupling device. This figure shows a state of optical coupling on a vertical coupling surface perpendicular to the active layer of the semiconductor laser.

In FIGS. 1 (a) and 1 (b), 1
Is a semiconductor laser. The laser light emitted from the semiconductor laser 1 has a wavelength of 0.98 μm. The beam waist spot size is ω _{Lx on the} horizontal coupling plane and ω _{LY on the} vertical coupling plane. 2 is a semiconductor ray
This is an optical fiber to which the outgoing beam of the 1 is coupled. The waveguide mode spot size of the optical fiber 2 is ω _F.
Reference numeral 3 is a horizontal plane emission beam on a horizontal coupling surface horizontal to the active layer of the semiconductor laser 1, and 4 is a vertical plane emission beam on a vertical coupling surface vertical to the active layer of the semiconductor laser 1.

Numeral 9 is, on the horizontal coupling surface, as shown in FIG. 1 (a), the horizontal plane emitting beam 3 is converted into a converging beam to form an image at a magnification M _X1 , and on the vertical coupling surface. , A first coupling system for converting the vertical plane emission beam 4 into a parallel beam as shown in FIG. 1 (b). The focal length on the vertical coupling surface of the first coupling system 9 is f _Y1 . The semiconductor laser 1 is arranged at the position of this focal length f _Y1 . Reference numeral 9a denotes an input surface of the first coupling system 9 and 9b denotes an output surface of the first coupling system 9. Reference numeral 10 is a first image forming point on the horizontal combination plane by the first combination system 9.

Reference numeral 12 in FIG.
As shown in (a), the horizontal plane emission beam 3 which is imaged at the first image formation point 10 by the first coupling system 9 and becomes a diverging beam is converted into a converging beam. Optical fiber 2 at magnification M _X2
In the vertical coupling plane as well as in FIG.
As shown in (b), the vertical plane emission beam 4 converted into the parallel beam by the first coupling system 9 is converted into the condensing beam and coupled to the optical fiber 2. It is a combined system. The focal length on the vertical coupling plane of the second coupling system 12 is f _Y2 . The end face of the optical fiber 2 is arranged at the position of this focal length f _Y2 . 11a is the second on the horizontal coupling surface
Is a second coupling point by the coupling system 12, and 11b is a second coupling point by the second coupling system 12 on the vertical coupling surface.
Semiconductor laser 1, first coupling system 9 and second coupling system 12
If the positions are in a predetermined relationship, the second connecting points 11a and 11b are in the same position. Reference numeral 12a is an input surface of the second coupling system 12, and 12b is an output surface of the second coupling system 12. If the magnification of the first coupling system 9 and the second coupling system 12 on the vertical coupling plane is M _Y , then M
The relationship is _Y = f _Y2 / f _Y1 .

FIG. 2 shows a first example of the optical coupling device shown in FIG.
3 is an example of a specific configuration diagram for realizing the coupling system 9 and the second coupling system 12 of FIG. Reference numeral 91 is a first lens on which the emitted beam of the semiconductor laser 1 is incident. First lens 91
Have the same focal length in the horizontal and vertical coupling planes. The first lens 91 converts the outgoing beams 3 and 4 of the semiconductor laser 1 into parallel beams on the horizontal coupling surface and the vertical coupling surface, respectively. Reference numeral 92 is a second lens which is made of a glass material having a uniform refractive index and into which the outgoing beam of the first lens 91 is incident. The input / output surface of the second lens 92 is a curved surface in the horizontal coupling surface and focuses on the first image formation point 10. Further, the second lens 92 has a flat input / output surface in the vertical coupling surface, and directly emits the parallel beam emitted from the first lens 91 as a parallel beam. The first lens 91 and the second lens 92 form the first coupling system 9.

Reference numeral 121 denotes a third lens which has a curved input surface on the horizontal coupling surface, a flat output surface on the horizontal coupling surface, and a flat input / output surface on the vertical coupling surface. The third lens is a gradient index lens in which the refractive index distribution decreases in a parabolic shape as the distance from the optical axis in the radial direction increases. The third lens 121 constitutes the second coupling system 12.

Next, the operation will be described. In FIG. 2, the horizontal plane emitting beam 3 which is a diverging beam emitted from the semiconductor laser 1 is collimated by the first lens 91.
Is converted to Parallel beam emitted from the first lens 91
The horizontal plane emitting beam 3, which is a beam, is incident on the second lens 92. The entrance surface of the horizontal coupling surface of the second lens 92 has a predetermined curvature. The parallel beam is refracted by this curved surface and converted into a converging beam, and the first image forming point 10
Is imaged.

On the other hand, the vertical plane emitting beam 4 which is the diverging beam emitted from the semiconductor laser 1 is the first lens 91.
Is converted into a parallel beam by. The vertical plane emission beam 4, which is a parallel beam emitted from the first lens 91, is incident on the second lens 92. In the vertical coupling plane, the second
Since the input and output surfaces of the lens are flat, they are not refracted. Therefore, the incident parallel beam is emitted from the second lens 92 as a parallel beam.

The horizontal plane exit beam 3 imaged at the first image forming point 10 becomes a divergent beam again and the third lens 121.
Is incident on. The third lens 121 in the horizontal coupling plane
The input surface of is a curved surface having a predetermined curvature, and
The lens 121 has a characteristic that the distribution of the refractive index decreases in a parabolic shape as the lens 121 moves away from the optical axis in the radial direction. Due to this curved surface and this characteristic, the horizontal plane outgoing beam 3 is refracted and converted into a converging beam to be converted into the optical fiber 2.
Bind to.

On the other hand, the vertical plane exit beam 4 which is a parallel beam and is emitted from the second lens 92 is the third lens 121.
Is incident on. In the vertical coupling plane, the third lens 1
Although the input / output surface of 21 is a plane, the vertical plane output beam 4 is refracted due to the change in the refractive index distributed so as to become smaller in a parabolic shape with increasing distance from the optical axis in the radial direction,
It is converted into a condensing beam and coupled to the optical fiber 2. That is, since the third lens 121 is made of a gradient index medium, it is refracted even when the input / output end face is a flat surface.
The parallel beams are collected.

In the horizontal coupling surface, since the input surface of the third lens 121 is a curved surface, the refracting power of this portion is also added, and the refraction effect becomes larger than that in the case of the vertical coupling surface. Therefore, once the image forming point 10
Horizontal plane exit beam 3 which became a divergent beam after being imaged on
Can be imaged again on the optical fiber 2.

Here, since the first lens 91 is a lens having a shape symmetrical about a normal optical axis, it can be easily realized. The second lens 92 can be easily realized by cutting a cylindrical glass rod into slices. Third lens 22
Can be easily realized by forming one end surface of a normal gradient index lens having flat ends at a cylindrical surface.

As described above, according to the first coupling system 9 and the second coupling system 12 of FIG. 2, as shown in FIG. 1, the first coupling system 9 and the second coupling system 12 are connected to each other. In between, the first imaging point 10 is formed on the horizontal coupling surface, and the outgoing beam becomes a parallel beam on the vertical coupling surface.

In the optical system shown in FIG. 1 or 2, the horizontal coupling surface magnification M _X of the entire coupling system including the first coupling system 9 and the second coupling system 10 is represented by the following equation. M _X = M _X1 · M _X2 (12) Further, the vertical coupling surface magnification M _Y of the entire coupling system including the first coupling system 9 and the second coupling system 10 is expressed by the following equation. M _Y = f _Y2 / f _Y1 (13)

Here, the horizontal coupling surface magnification M _X is set so as to satisfy the following conditions (ω _F is the spot size of the guided mode of the optical fiber 2 and ω _LX is the active layer of the semiconductor laser 1). Horizontal beam waist spot size). M _X = ω _F / ω _LX (14) Further, the vertical coupling surface magnification M _Y is set so as to satisfy the following condition (ω _LY is a surface perpendicular to the active layer of the semiconductor laser 1). Beam waist spot size). M _Y = ω _F / ω _LY・ ・ ・ (15)

Therefore, the ratio between the horizontal coupling surface magnification M _X and the vertical coupling surface magnification M _Y is equal to the ellipticity Dr of the beam of the semiconductor laser 1 as shown in the following equation. M _Y / M _X = ω _LX / ω _LY = Dr (16)

In the optical system shown in FIG. 1 or FIG. 2, since the coupling magnification M _{X on the} horizontal coupling surface is set to the value of the equation (14), the semiconductor laser is similar to the case of the conventional example. The horizontal coupling plane beam waist spot size ω _{LX of 1} is converted to ω _F. Therefore, the horizontal plane emitting beam 3 emitted from the semiconductor laser 1 is efficiently coupled to the optical fiber 2.

Since the coupling magnification M _{Y on the} vertical coupling plane is set to the value of the equation (15), the vertical coupling plane beam waist spot size ω _LY of the semiconductor laser 1 is also ω. Converted to _F. Therefore, the vertical plane emitting beam 4 emitted from the semiconductor laser 1 is efficiently coupled to the optical fiber 2.

As described above, in the optical system shown in FIG. 1 or 2, the elliptical beam emitted from the semiconductor laser 1 is efficiently coupled to the optical fiber 2.
In the above description, the case where the first image forming point 10 is on the horizontal coupling surface has been described as an example, but the present invention is not limited to this. For example, the first imaging point 1 on the vertical coupling plane.
There may be 0. Further, the above description is applicable not only to the case where the horizontal coupling surface and the vertical coupling surface orthogonal to each other are used but also to the case where two planes that are parallel to and intersect with the optical axis are used.

Next, a case where the positional relationship between the semiconductor laser 1 and the first coupling system 9 deviates from a predetermined position in the optical axis direction will be described with reference to FIGS. 3 and 4. . As shown in FIG. 3, the set positional relationship between the semiconductor laser 1 and the first coupling system 9 deviates from the design value (the position of the dotted line in the figure) by ΔZ _{1 in the} optical axis direction, and the semiconductor laser 1 Is the first
Suppose that the binding system 9 of is approaching. Along with this, Fig. 3
As shown in (a), the second imaging point 1 on the horizontal coupling plane
1c is a regular second image forming point 11a on the horizontal coupling surface.
It moves outward from the position _{indicated by} the dotted line in the figure by ΔZ _{21X in the} optical axis direction. Here, the output surface 12b of the second coupling system 12
The distance between the second image forming point 11c and the second image forming point 11c is W _dx .

Similarly, as shown in FIG. 3B, the second image forming point 11d on the vertical coupling surface is the regular second image forming point 11b on the vertical coupling surface (the position of the dotted line in the figure). ), It moves outward by ΔZ _{21Y in the} optical axis direction. Here, the distance between the output surface 12b of the second coupling system 12 and the second image forming point 11d is W _dy .

By the way, since the image formation point is shifted by the square of the magnification in the optical axis direction, the magnification M _X of the horizontal coupling surface and the vertical coupling surface of the optical system shown in FIG. Since the value of the magnification M _Y is different, the deviation ΔZ _{2X of the} image forming point on the horizontal coupling surface is different from the deviation ΔZ _{2Y of the} image forming point on the vertical coupling surface. _Let this difference be ΔA _S. Where W _dy −W _dx =
ΔZ _21Y −ΔZ _21X = ΔA _S. Thus, the second
The position of the imaging point with respect to the output surface 12b of the coupling system 12 of
Different between the horizontal coupling surface and the vertical coupling surface, a coupling loss occurs due to the astigmatic difference.

In order to eliminate this astigmatic difference, it is considered to adjust the position of the second coupling system 12 so that ΔA _S = 0. Now, consider moving the second coupling system 12 in the optical axis direction. When the semiconductor laser 1 is displaced by ΔZ ₁ so as to approach the first coupling system 9 as shown in FIG. 3, the second coupling system 12 is connected to the first coupling system 9 as shown in FIG.
Move to approach. Then, as shown in FIG. 4A, the second image forming point 11c on the horizontal coupling surface moves toward the outer image forming point 11e. That is, the distance between the output surface 12b of the second coupling system 12 and the second imaging point is W
_{From dx} to W _dx '(that is, W _dx <W _dx ').

On the other hand, as shown in FIG. 4B, the position of the second image forming point 11d on the vertical coupling surface does not change (W _dY
= W _dY '). This is because the beam incident on the second coupling system 12 is a parallel beam on the vertical coupling plane, and
This is because the imaging relationship of the second coupling system 12 does not change even when the coupling system 12 is moved in the optical axis direction. That is, when the second coupling system 12 is moved in the optical axis direction, the position of the image forming point on the optical fiber 2 changes only on the horizontal coupling surface. Therefore, the second image forming point 11c on the horizontal connecting surface is the second connecting point 1 on the vertical connecting surface.
The astigmatic difference can be corrected by moving the second coupling system 12 in the optical axis direction and adjusting it so as to match 1d (that is, W _dx '= W _dY ).

When the semiconductor laser 1 is displaced away from the first coupling system 9, the second coupling system 12 is moved.
Are moved away from the first coupling system 9.

Next, the adjustment amount of the second coupling system 12 required to correct the astigmatic difference by matching the first image forming point 11c on the horizontal coupling surface with the first 11d on the vertical coupling surface. Shows Δd. In the case where the semiconductor laser 1 and the first coupling system 9 are set in the positional deviation ΔZ1 in the optical axis direction, the adjustment amount Δd of the second coupling system 12 necessary for correcting the astigmatic difference is as follows. It is represented by a formula. Δd = G · ΔZ ₁ (17)

Here, G = M _X ² (Dr ² -1) / M _X2 ² (18).

As shown in the above equation, the second coupling system 12
The adjustment amount .DELTA.d of .gamma. Is G times .DELTA.Z1. The larger the value of G, the larger the actual adjustment amount Δd, and the easier the adjustment becomes. Here, this G is referred to as a relaxation coefficient.

Next, the above equations (17) and (18) are derived. FIG.
In (a), the first image formation point 10a when the positional relationship between the semiconductor laser 1 and the first coupling system 9 is correct, and the first image formation when the position of the semiconductor laser 1 is displaced by ΔZ ₁ The point is 10b, and the position of the corrected first image formation point is 10c. Then, the distance between the points 10a and 10b is ΔS _X ,
The distance between the points 10a and 10c is set as ΔS _x '.

[0076] In this ^{_{case, ΔS X = M X1 2 ·}} ΔZ 1 ··· (19) In addition, as can be seen from _{Figure, Δd = ΔS X '-ΔS X} ··· (2
0) On the other hand, ΔS _X '= ΔZ _21Y / M _X2 ² (21)

[0077] Equation (20) and substituting equation (19) (21), Δd = ΔZ 21Y / M X2 2 -M X1 2 · ΔZ 1 further by substituting equation (10) Δd = M _Y ^{2 _{· ΔZ 1 / M X2 2 -M}} X1 2 · ΔZ 1 = {(M Y 2 -M X 2) / M X2 2} · ΔZ 1 = {M X 2 (Dr 2 -1) / M X2 2} · ΔZ ₁ Equations (17) and (18) are thus obtained.

FIG. 5 shows a calculation example of the value of the relaxation coefficient G. Here, as a standard 0.98 μm semiconductor laser, ellipticity Dr = 2.5, ω _LX = 1.9 μm, and ω _LY = 0.7.
6 μm was assumed. As an optical fiber, ω _F = 3μ
Assume m. At this time, M _X is determined by the equation (14) and is 1.6. Further, from the equation (12), M _X2 is M _X1
And the product of M _X2 is determined to match M _X. Figure 5
Is a graph showing the relationship between M _X2 on the horizontal axis and the relaxation coefficient G on the vertical axis.

It can be seen from FIG. 5 that the relaxation coefficient G becomes 10 or more when M _X2 is set to about 1. Therefore, according to the optical coupling device of the first embodiment, the accuracy of 1 to 2 μm required in the conventional example is reduced by 10 times to 10 to 20 μm.

As described above, according to the optical coupling device of the first embodiment, between the first coupling system and the second coupling system,
Since the horizontal coupling surface has the first imaging point of the outgoing beam and the vertical coupling surface is a parallel beam, even if the positional relationship between the semiconductor laser and the first coupling system is deviated, The second imaging position can be adjusted by moving the position of the second coupling system, and the coupling loss due to the astigmatic difference can be reduced. In this adjustment, since the second image forming position on the vertical coupling surface does not change, only the second image forming position on the horizontal coupling surface needs to be adjusted, and the accuracy of the adjustment is remarkably eased. , Very easy to adjust.

In the above description, the relay coupling system is set on the horizontal coupling plane, but the relay coupling system may be set on either the horizontal coupling plane or the vertical coupling plane. Also in this case, it is possible to obtain the effect that the astigmatic difference at the image forming point caused by the deviation of the position setting of the semiconductor laser and the collimating lens can be corrected by looser adjustment.

However, since the relay-coupling system forms an image twice, it requires more refracting surfaces than the collimating system. Generally, an aberration occurs on the refracting surface, and this aberration deteriorates the coupling efficiency. Further, this aberration becomes larger as the position of incidence on the refracting surface is further away from the optical axis.
Therefore, by making the coupling surface (horizontal coupling surface) having the smaller emission angle of the emission beam of the semiconductor laser a relay coupling system, the coupling efficiency to the optical fiber is further increased.

Further, as can be seen from FIG. 5, in order to correct the astigmatic difference, the magnifications at the relay coupling surfaces of the second coupling system and the third lens, which are relay lenses, are set to 1 or less. The position adjustment of the lens in the optical axis direction required for the above is relaxed at least 10 times or more as compared with the conventional method. For example,
If the relay magnification M _X2 is set to 1 or less, the relaxation coefficient G is 10
That is all. Therefore, the adjustment accuracy of 1-2 μm required for ΔZ ₁ in the conventional example is relaxed 10 times or more to at least 10-20 μm.

Example 2. The second embodiment is an optical amplification device using the optical coupling device of the first embodiment. Hereinafter, description will be given with reference to FIG. FIG. 6 is a configuration block diagram of the optical amplifying device of the second embodiment. In the figure, 14 is the same as in FIG.
, An optical coupling device for efficiently coupling the 0.98 μm semiconductor laser and the optical fiber 2, 15 is an input fiber for inputting a 1.55 μm band signal light to be amplified, and 16 is a gain An Er-doped fiber in which Er (erbium) atoms are doped as a medium, and 17 is 0.9 from the optical coupling device 14 with respect to the Er-doped fiber 16.
A multiplexer for inputting the 8 μm pump light and the 1.55 μm band signal light from the input fiber 15, and an isolator 18 for preventing backflow of the 1.55 μm band signal light to prevent laser oscillation, Reference numeral 19 denotes an output fiber for outputting the amplified 1.55 μm band signal light.

Next, the operation will be described. 0.98 μm
The excitation light is efficiently coupled to the optical fiber 2 by the optical coupling device 14. 0.98μ coupled to this optical fiber 2
The m excitation light is input to the multiplexer 17. On the other hand, 1.55μ
The m-band signal light is input to the multiplexer 17 from the input fiber 15. The 0.98 μm pump light and the 1.55 μm band signal light input to the multiplexer 17 are multiplexed by the multiplexer 17 and then input to the Er-doped fiber 16. Here, the 0.98 μm excitation light excites Er atoms in the Er doped fiber 16, and the 1.55 μm band signal light is amplified by receiving the energy of the excited Er atoms. This amplified 1.55 μm band signal light is transmitted to the isolator 18
Is output from the output fiber 19.

Here, a part of the amplified 1.55 μm band signal light output from the output fiber 19 is
Consider the case of propagating in the opposite direction due to reflection. At this time,
The 1.55 μm band signal light propagating in the opposite direction is isolated.
Is input to the data 18. By the way, the isolator 18 blocks the 1.55 μm band signal light traveling in the opposite direction.
It is possible to prevent the 55 μm band signal light from re-entering the Er-doped fiber 16. This prevents laser oscillation in the 1.55 μm band.

In the optical amplifying device of this structure, by using the optical coupling device 14 with good coupling efficiency shown in the first embodiment, more 0.98 μm pumping power is input to the Er-doped fiber 16. Therefore, it is possible to realize an optical amplification characteristic with lower noise and higher efficiency.

Example 3. In the optical coupling device of the first embodiment, the optical axis of the second coupling system 12 and the optical axis of the optical fiber 2 coincide with each other, but these optical axes are shifted to prevent reflection from the optical fiber. It may be configured as follows.

The third embodiment is intended to improve the matching of the beam to the optical fiber having the inclined surface for preventing the reflection. Hereinafter, description will be given with reference to FIG. 7. This figure is a view showing the coupling portion between the second coupling system and the optical fiber of the optical coupling device of the third embodiment on the horizontal coupling surface.

In the figure, the same reference numerals as those in FIG. 2 of the first embodiment described above indicate the same or corresponding portions,
The description of the reference numerals is omitted as appropriate. Although the output surface 121b of the third lens 121 is planar, the normal line of this plane and the optical axis of the third lens 121 do not coincide with each other and form a constant angle (in the case of FIG. 2, these are It was a match). That is, the output surface 121b is an inclined surface. The input surface 2a of the optical fiber 2 is also an inclined surface. Reference numeral 25 denotes reflected light reflected by the inclined surface 2a of the optical fiber 2. The optical axis of the third lens 121 and the optical axis of the optical fiber 2 are set to be parallel.

Next, the operation will be described. The horizontal plane exit beam 3 imaged at the first imaging point 10 is again a divergent beam.
Then, the light enters the third lens 121. The incident beam is refracted by a curved surface having a curvature on the horizontal coupling surface, and also refracted by a refractive index distribution distributed so as to be reduced in a parabolic shape in the radial direction, and converted into a converging beam. Then, the inclined surface 121b is reached. This condensing beam is refracted at the inclined surface 121b. Since the normal line of the inclined surface 121b is inclined with respect to the optical axis, the direction of the emitted beam is inclined with respect to the optical axis. In this state, the horizontal plane outgoing beam 3 is incident on the inclined surface 2a of the optical fiber 2.

Here, the inclined surface 2a of the fiber 2 and the inclined surface 121b of the third lens 121 are parallel to each other. The optical axis of the fiber 2 and the optical axis of the third lens 121 are parallel. Due to this relationship, the horizontal plane emitting beam 3 incident on the inclined surface 2a of the optical fiber 2 becomes a beam which is refracted by the inclined surface 2a and propagates in the optical axis direction of the optical fiber 2. As a result, the outgoing beam is efficiently coupled to the optical fiber 2.

On the other hand, since the reflected light 25 reflected by the inclined surface 2a of the optical fiber 2 is reflected in a direction different from the incident light, it does not return to the second lens 121. Therefore, the returning light to the semiconductor laser is suppressed.

In the above description, the case where the output surface of the third lens 121 is inclined on the horizontal coupling surface has been described as an example, but the case where it is inclined on the vertical coupling surface is also applicable. The same effect can be obtained.

Example 4. In the optical coupling device of Example 1, the ones shown in FIG. 2 were used as the first coupling system and the second coupling system. In this fourth embodiment, another configuration of the second coupling system will be described.

The third lens constituting the second coupling system of the fourth embodiment has a cylindrical surface on the input surface and a spherical surface on the output surface, and the material of the third lens is the refractive index. Is a uniform glass. Hereinafter, description will be given with reference to FIG. In the figure, the same reference numerals as those in the above-mentioned embodiment indicate the same or corresponding portions, and therefore the explanation of the reference numerals will be appropriately omitted. 122 is the third made of glass with a uniform refractive index
Lens 122a is the input surface of the third lens. The input surface 121a is a curved surface having a curvature on the horizontal coupling surface and a flat surface on the vertical coupling surface. 122b is the output surface of the third lens. The output surface 121b is a spherical surface.

Next, the operation will be described. This Example 4
Since the structure of the third lens in Example 1 is changed, the operation of the third lens will be mainly described. The horizontal plane exit beam 3 imaged at the first image forming point 10 by the second image forming system 9 becomes a divergent beam and enters the third lens 122. The incident beam has the input surface 12 of the third lens 122 having a curvature in the horizontal coupling surface.
It is refracted by 2a and is converted into a parallel beam. The parallel beam is further refracted by the output surface 122b of the third lens 122, converted into a converging beam, and coupled to the optical fiber 2.

On the other hand, the vertical plane exit beam 4 converted into the parallel beam by the second coupling system 9 is the third lens 122.
Is incident on. The incident beam is not refracted by the input surface 122a of the third lens 122, which is a plane having no curvature on the vertical coupling surface, and is transmitted as a parallel beam as it is. This parallel beam is refracted by the output surface 122b of the third lens 122 and converted into a converging beam,
It is coupled to the optical fiber 2. As described above, the function of the second coupling system 12 can be realized by the third lens 122.

The fourth embodiment has the same effect as the optical coupling device of the first embodiment. Furthermore, according to the fourth embodiment,
The input surface 122a and the output surface 122 of the third lens 122.
Each of b is composed of a cylindrical surface and a spherical surface, and the curvature can be changed. Therefore, as compared with the case of using the gradient index lens shown in Example 1, the degree of freedom in designing the magnification, the focus position, and the like is large.

The input surface 122 of the third lens 122 is
The curved surface of the cylindrical surface formed on a may be an aspherical shape, and the spherical surface formed on the output surface 122b may be an aspherical shape. As a result, the wavefront aberration generated on the ordinary cylindrical surface and spherical surface can be reduced, and the coupling efficiency with the optical fiber is increased.

Example 5. In this fifth embodiment, another configuration of the first coupling system 9 will be described. The fifth embodiment integrates the first lens 91 and the second lens 92 of the first embodiment. Hereinafter, description will be given with reference to FIG. In the figure, the same reference numerals as those used in the above-mentioned embodiment indicate the same or corresponding portions, and therefore the explanation of the reference numerals will be appropriately omitted. In the figure, reference numeral 93 is an integrated lens forming the first coupling system 9. The integrated lens 93 converts the outgoing beam of the semiconductor laser 1 into a converging beam in the horizontal coupling plane and a parallel beam in the vertical coupling plane.
Reference numeral 93a is a spherical input surface formed on the input surface of the integrated lens, and 93b is a cylindrical output surface which is a curved surface having a curvature on the horizontal coupling surface and a flat surface on the vertical coupling surface.

Next, the operation will be described. This Example 5
Is a combination of the first lens 91 and the second lens 92 of the first embodiment.
The operation of will be described. The horizontal plane emission beam 3 which is a divergent beam emitted from the semiconductor laser 1 is refracted by the input surface 93a of the integrated lens 93 and is converted into a parallel beam. The horizontal plane exit beam 3 converted into the parallel beam is converted into the converging beam by the output surface 93b which is a cylindrical surface having a curvature at the horizontal coupling surface of the integrated lens 93 and is converted into the first beam. An image is formed at the image point 10.

On the other hand, the vertical plane emission beam 4 which is a diverging beam emitted from the semiconductor laser 1 is integrated lens 93.
The light is refracted by the input surface 93a and is converted into a parallel beam. The output surface 93b is a flat surface having no curvature in the vertical coupling surface. Therefore, the vertical plane exit beam 4 converted into the parallel beam is the output surface 9 of the integrated lens 93.
The parallel beam is emitted from the integrated lens 29 without being refracted by 3b. As described above, the function of the first coupling system 9 in the first embodiment is realized by the integrated lens 93.

The fifth embodiment has the same effect as the optical coupling device of the first embodiment. Furthermore, according to the fifth embodiment,
Since the second coupling system is composed of one lens, there is an effect that the configuration of the optical coupling device becomes simple.

The spherical surface formed on the input surface 93a of the integrated lens 93 may be aspherical, and the curved surface of the cylindrical surface formed on the output surface 93b may be non-cylindrical. As a result, the wavefront aberration generated on the ordinary cylindrical surface and spherical surface can be reduced and the coupling efficiency with the optical fiber can be increased.

[0106]

As described above, according to the first aspect of the present invention, the semiconductor laser which emits the laser beam and the first laser which receives the emitted beam of the semiconductor laser and is parallel to the direction of the emitted beam. A first plane for parallelizing the emission beam of the semiconductor laser in a plane parallel to the direction of the emission beam of the semiconductor laser and intersecting the first plane while forming an image in the plane A coupling system and an output beam of the first coupling system for receiving in the first plane and the second plane;
Of the second coupling system and the optical fiber for receiving the outgoing beam of the second coupling system, the image forming point on the first plane by the second coupling system. The position can be adjusted independently of the image formation point on the second plane, and the adjustment for reducing the astigmatic difference becomes easy.

According to the second aspect of the invention, since the first plane is set in the direction in which the emission angle of the emission beam of the semiconductor laser is reduced, the aberration generated on the refracting surface can be reduced. Thus increasing the coupling efficiency.

Further, according to the invention of claim 3, the first
Since the plane is a horizontal coupling plane parallel to the active layer of the semiconductor laser and the second plane is a vertical coupling plane perpendicular to the active layer of the semiconductor laser, the aberration generated on the refracting surface can be minimized.

According to the invention of claim 4, the first
Has a same focal length in the first plane and in the second plane, and converts the output beam of the semiconductor laser into a parallel beam in each plane. The first lens and at least one of the input / output surfaces have a substantially cylindrical shape, receive the beam emitted from the first lens and convert it into a converging beam in the first plane, and Since it is composed of the second lens which transmits the parallel beam in the plane of No. 2, it is possible to construct the first coupling system with a lens having a simple structure.

Further, according to the invention of claim 5, the first
Has a substantially spherical input surface and a substantially cylindrical output surface, and receives the emission beam of the semiconductor laser to produce the first
Since the light beam is converted into a condensing beam in the plane of (1) and is made up of parallel beams in the second plane and emitted, the number of lenses can be reduced and the configuration is simplified.

According to the invention of claim 6, the second
The coupling system is a parabola whose refractive index distribution characteristic decreases from the optical axis in the radial direction, has a substantially cylindrical input surface and a planar output surface, and has the above-mentioned first coupling system. The divergent beam after being imaged in the first plane is converted into a converging beam again and is coupled to the optical fiber, and the parallel beam in the second plane is condensed beam. -Since it is composed of a third lens which is converted into a lens and is coupled to the optical fiber,
The second coupling system can be configured with a lens having a simple configuration.

According to the invention of claim 7, the second
Has a substantially cylindrical input surface and a substantially spherical output surface, and the divergent beam after the image is formed in the first plane by the second lens is focused again. Since it is composed of a third lens which is converted into a beam and is coupled to the optical fiber, and a parallel beam in the second plane is converted into a converging beam and coupled to the optical fiber, The second coupling system can be configured with a lens having a simple structure, and the degree of freedom in designing the lens magnification, focal position, etc. can be increased.

According to the invention of claim 8, the second
The output surface of the coupling system is tilted so that the outgoing beam intersects the optical axis of the second coupling system, and the input surface of the optical fiber is such that the incident beam is the optical fiber. Since the light beam is tilted so as to be refracted in the optical axis direction, the return light to the semiconductor laser can be suppressed.

According to the invention of claim 9, the first
Of the image forming position in the plane and the image forming position in the second plane, the first step of checking whether the image forming position in the second plane and the image forming position in the second plane coincide with each other. When the image position does not coincide with the image position, the second coupling system is moved in the optical axis direction so that the image forming position in the first plane approaches the image forming position in the second plane. Since the image forming position in the first plane and the image forming position in the second plane are matched with each other, the image forming point on the first plane by the second coupling system is provided. The position can be adjusted independently of the image formation point on the second plane, and the adjustment for reducing the astigmatic difference becomes easy.

According to the tenth aspect of the invention, the movement amount Δd of the second coupling system in the second step is M
_x is the first coupled system in the first plane and the second coupled system
Of the coupling system, Dr is the ellipticity of the emitted beam of the semiconductor laser, M _x2 is the second plane in the first plane.
When the magnification of the coupling system, ΔZ _1, is the positional deviation in the optical axis direction of the semiconductor laser, the amount is given by the following equation, so that the required accuracy is lower than the positional deviation in the optical axis direction of the semiconductor laser. The point difference can be reduced. Δd = M _x ² (Dr ² −1) / M _x2 ² · ΔZ ₁

According to the eleventh aspect of the invention, a semiconductor laser for emitting a laser beam and an emission beam of the semiconductor laser are received to form an image in a first plane parallel to the direction of the emission beam. At the same time, a first coupling system that makes the emission beam of the semiconductor laser substantially parallel in a second plane that is parallel to the direction of the emission beam of the semiconductor laser and intersects the first plane, the first coupling system A second coupling system for receiving the outgoing beam of the coupling system and forming an image in the first plane and the second plane, and an optical fiber to which the outgoing beam of the second coupling system is coupled. An optical coupling device, a multiplexer for coupling the light input from the outside and the light output by the optical coupling device, and the pumping medium is doped, and excited by the output of the multiplexer to be excited from the outside. Amplifies and increases the input light Since an optical fiber for outputting the light, at a lower noise can be realized an optical amplification apparatus having a light amplification characteristic of the high efficiency.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical coupling device according to a first embodiment of the present invention.

FIG. 2 is a first of the optical coupling device according to the first embodiment of the present invention.
It is a block diagram of a coupling system and a second coupling system.

FIG. 3 is an explanatory diagram of an adjusting method of the optical coupling device according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an adjusting method of the optical coupling device according to the first embodiment of the present invention.

FIG. 5 is an example of a graph of a relaxation coefficient G showing how many times the accuracy of correction when adjusting the optical coupling device according to the first embodiment of the present invention is relaxed compared to the conventional case.

FIG. 6 is a configuration diagram of an optical amplifying device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a main part of an optical coupling device according to a third embodiment of the present invention.

FIG. 8 is a first optical coupling device according to a fourth embodiment of the present invention.
It is a block diagram of a coupling system and a second coupling system.

FIG. 9 is a first optical coupling device according to a fifth embodiment of the present invention.
It is a block diagram of a coupling system and a second coupling system.

FIG. 10 is an explanatory diagram of a beam waist spot size of a semiconductor laser.

FIG. 11 is an explanatory diagram of an optimum magnification of a coupling system for coupling an outgoing beam of a semiconductor laser with an optical fiber.

FIG. 12: Ellipticity D of beam cross section of semiconductor laser
5 is an example of a graph showing the relationship between r and mode shape mismatch loss.

FIG. 13 is a configuration diagram of a conventional optical coupling device.

FIG. 14 is an example of a graph showing the relationship between the positional deviation ΔZ ₁ of the semiconductor laser 1 and the collimating lens 5 in the optical axis direction and the coupling loss due to the astigmatic difference caused thereby in the conventional optical coupling device.

[Explanation of symbols]

1 semiconductor laser, 2 optical fibers, 3 horizontal plane emitting beam, 4 vertical plane emitting beam, 9 first coupling system, 12
Second coupling system, 14 Optical coupling device, 15 Input fiber, 16 Er-doped fiber, 17 Multiplexer, 18
Isolator, 19 Output fiber, 91 First lens, 92 Second lens, 93 Integrated lens, 121
Third lens, 122 Third lens made of glass with a uniform refractive index.

Claims (11)

[Claims] 1. A semiconductor laser that emits a laser beam, and an emission beam of the semiconductor laser, which receives the emission beam of the semiconductor laser and forms an image in a first plane parallel to the direction of the emission beam. A first coupling system that makes the emitted beam of the semiconductor laser substantially parallel in a second plane that is parallel to the direction of and that intersects the first plane;
A second coupling system which receives the outgoing beam of the first coupling system and forms an image in the first plane and in the second plane;
An optical coupling device comprising: an optical fiber that receives the outgoing beam of the second coupling system. 2. The optical coupling device according to claim 1, wherein the first plane is set in a direction in which the emission angle of the emission beam of the semiconductor laser is reduced. 3. The first plane is a horizontal coupling plane parallel to the active layer of the semiconductor laser, and the second plane is a vertical coupling plane vertical to the active layer of the semiconductor laser. The optical coupling device according to claim 1. 4. The first coupling system has the same focal length in the first plane and the second plane, and an emission beam of the semiconductor laser is provided in each plane. At least one of the first lens for converting to a parallel beam and the input / output surface is substantially cylindrical, and receives a beam emitted from the first lens and collects a beam in the first plane. 2. The optical coupling device according to claim 1, wherein the optical coupling device comprises a second lens which is converted into a beam and is transmitted as a parallel beam in the second plane. 5. The first coupling system has a substantially spherical input surface and a substantially cylindrical output surface, receives an emitted beam of the semiconductor laser, and collects a beam within the first plane. 2. The optical coupling device according to claim 1, wherein the optical coupling device comprises a lens that converts the light into a beam and outputs a parallel beam in the second plane. 6. The second coupling system is parabolic in which the distribution characteristic of the refractive index decreases in the radial direction from the optical axis, and has a substantially cylindrical input surface and a planar output surface, The divergent beam after being imaged in the first plane by the first coupling system is converted into a converging beam again to be coupled to the optical fiber, and at the same time, in the second plane. 2. The optical coupling device according to claim 1, wherein the optical beam is formed by a third lens which converts a parallel beam into a converging beam and couples it to the optical fiber. 7. The divergence after the second coupling system has a substantially cylindrical input surface and a substantially spherical output surface and is imaged in the first plane by the second lens. The beam is converted into a converging beam again and coupled to the optical fiber, and the parallel beam in the second plane is converted into a condensing beam and coupled to the optical fiber. The optical coupling device according to claim 1, wherein the optical coupling device comprises three lenses. 8. The output surface of the second coupling system is configured so as to be inclined so that the outgoing beam intersects the optical axis of the second coupling system, and the input surface of the optical fiber is 2. The optical coupling device according to claim 1, wherein the incident beam is tilted so as to be refracted in the optical axis direction of the optical fiber. 9. The imaging position in the first plane and the second position
The first step of checking whether or not the image forming position in the plane of the first image plane and the image forming position in the second plane do not coincide with each other. The second coupling system is moved in the optical axis direction so that the image forming position in the first plane approaches the image forming position in the second plane.
2. The method for adjusting an optical coupling device according to claim 1, further comprising a second step of matching an image forming position in the plane of 1) with an image forming position in the second plane. 10. A moving amount Δd of the second coupling system in the second step, M _x is a coupling magnification of the first coupling system and the second coupling system in a first plane, and Dr is The ellipticity of the emitted beam of the semiconductor laser, M _{x2, is set} to the first
Magnification of the in plane second bond system, when a [Delta] Z ₁ to the position shift of the optical axis of the semiconductor laser, an optical coupling device according to claim 9, characterized in that the amount given by the following equation Adjustment method. Δd = M _x ² (Dr ² −1) / M _x2 ² · ΔZ ₁ 11. A semiconductor laser emitting a laser beam.
The receiving beam of the semiconductor laser is imaged in a first plane parallel to the direction of the emitting beam, and the image is formed on the first plane parallel to the direction of the emitting beam of the semiconductor laser. A first coupling system that makes the emitted beams of the semiconductor lasers substantially parallel in a second plane that intersects with each other, and the first coupled system and the second plane that receive the emitted beams of the first coupled system An optical coupling device formed of a second coupling system for forming an image with the optical coupling device and an optical fiber to which an output beam of the second coupling system is coupled, and light input from the outside and light output from the optical coupling device. A coupling multiplexer and an optical fiber which is pumped by the pumping medium, amplifies the light that is excited by the output of the multiplexer and is input from the outside, and outputs the amplified light, are provided. Optical amplifier.