JP2001291922A - Laser diode excitation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively guide laser beam emitted from a light emission region of an emitter to a fiber using a simple constitution. SOLUTION: Laser diode beam from the light emission region of an emitter 2 is propagated inside a fiber 3, by reflecting it to an optical axis direction with a tapered part 13 in a tip of the fiber 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode excitation device for exciting a laser medium of a laser oscillator with a laser diode.

[0002]

2. Description of the Related Art In recent years, laser oscillators which use laser diodes having an absorption wavelength of a laser medium as excitation light have been commercialized in place of laser oscillators which are excited by flash lamps or arc lamps. I have.

The laser diode pumped laser oscillator has advantages over a lamp pumped laser oscillator in that the supplied power is small, there is no maintenance such as lamp replacement, and the oscillator itself is small.

As an apparatus for exciting this laser diode light into a laser medium, Japanese Patent Application Laid-Open No. 5-93 shown in FIG.
No. 828 is known.

In this laser diode excitation device, a laser diode 100 is configured by fixing a plurality of emitters 102 arranged in an array to a base 101. The laser light emitted from the light emitting region of the emitter 102 emits light with a certain spread angle in the horizontal and vertical directions. The horizontal and vertical divergence angles are different, about 30 degrees in the vertical direction and about 10 degrees in the horizontal direction. Therefore, light emission from the emitter 102 is
In the case where the light is guided to the laser beam 03, laser light mainly spreading in the vertical direction having a large spreading angle is condensed by the multi-mode optical fiber 104 forming a microlens.

[0006]

However, it is necessary to provide a multi-mode optical fiber 104 forming a microlens in order to condense the laser light emitted with such a spread angle. The adjustment of the two components of the multimode optical fiber 104 and the fiber 103 to the emission region of the emitter 102 with respect to the base 101 becomes complicated.

For this reason, in US Pat. No. 5,436,990, after the alignment between the emitter 102 and the multimode optical fiber 104 is performed, the base 101 is aligned.
There is also known an apparatus in which one end is held by a metal member and the other end is fixed to the multi-mode optical fiber 104 with an epoxy resin so as to adjust the same.

In terms of maintainability, when the multi-mode optical fiber 104 is damaged by dust or the like, it is necessary to replace the multi-mode optical fiber itself.

An object of the present invention is to provide a laser diode pumping device capable of efficiently guiding a laser beam emitted from a light emitting region of an emitter to a fiber with a simple structure. I do.

[0010]

In order to achieve the above object, in a laser diode pumping apparatus according to the present invention, laser light from a laser diode in which a plurality of emitters are arranged in an array is guided to a solid-state laser medium by a fiber. In the laser diode pumping apparatus for pumping the solid-state laser medium, a plurality of fibers whose tips are arranged opposite to the nearest position are provided in each of the light emitting regions of the plurality of emitters, and the tips of the plurality of fibers are arranged. It is characterized in that it has a tapered shape extending rearward from the center of the tip.

In such a configuration, the tips of the plurality of fibers are formed in a tapered shape extending rearward from the center of the tips, so that the horizontal and vertical directions radiated from the light emitting region of the emitter are obtained. The laser beam incident at an angle can be reflected at the tapered portion formed at the fiber tip at a reflection angle with respect to the optical axis which is smaller than the incident angle of the laser beam, and can be propagated in the fiber. . As a result, the light can be propagated in a linear direction closer to the optical axis of the fiber, so that the reflection in the fiber can be reduced, and the optical loss due to the reflection can be reduced. Accordingly, there is no need to provide a multi-mode optical fiber for condensing laser light, and the number of parts is reduced, the structure is simplified, and as a result, the fiber is merely arranged to face the position immediately adjacent to the light emitting area of the emitter. Alignment is sufficient, and alignment adjustment between the plurality of emitters and each fiber becomes easy.

Further, in the laser diode pumping apparatus of the present invention, the taper shape of each fiber tip is such that the laser beam incident from the light emitting region of the emitter to the tip of the fiber with a horizontal and vertical divergence angle. The laser beam is formed so as to be reflected at the tapered portion and propagated in the fiber at a reflection angle smaller than the critical angle of the laser beam.

In such a configuration, the taper shape at the tip of each fiber is reflected at the taper portion and propagated through the fiber at a reflection angle smaller than the critical angle of the laser beam. As a result, the laser beam incident from the light emitting region of the emitter to the tip of the fiber with a divergence angle in the horizontal and vertical directions is also reflected in the fiber at a reflection angle smaller than the critical angle of the laser beam. Can be propagated. When the laser beam is reflected in the fiber at a reflection angle equal to or larger than the critical angle, a part of this laser beam is refracted and the rest is repeatedly reflected at a short distance that propagates in the fiber. Thus, the bound phenomenon in which the light loss of the laser light becomes large can be prevented, the optical loss can be reduced, and the propagation efficiency in the fiber can be improved.

In the laser diode pumping apparatus of the present invention, the bundle fiber in which the plurality of fibers are bundled is connected to a single fiber having a diameter equal to or larger than the diameter of the bundle fiber. Features.

This means that when the output of each laser beam from a plurality of emitter regions is different due to the life of the emitter or the like, the output distribution at the bundle fiber end where a plurality of fibers are bundled changes and becomes uniform. As a result, the power distribution of the excitation light is disturbed, and the excitation to the laser medium changes, and finally the output laser light also changes,
There is a problem that the beam light and the beam output also change. However, by connecting a bundle fiber in which a plurality of fibers are bundled to a single fiber, the laser light is averaged again by the single fiber connected to the bundle fiber, and the solid-state laser medium is excited by the averaged excitation light. Therefore, even if the output of each individual emitter is reduced due to its life, the optical loss of the single fiber is reduced and the uniformity of light from the single fiber is prevented from being impaired. The solid state laser medium can be excited.

Further objects and features of the present invention can be used alone or in various combinations in combination as far as possible.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

However, the present invention is not limited to the following embodiments, and is not intended to limit the scope of the present invention to them only, but is merely an illustrative example unless otherwise specified. .

In the laser diode excitation device shown in FIG. 1, a plurality of emitters 2 arranged in an array are arranged on a base 1a of a laser diode 1. In each of the light emitting regions of the plurality of emitters 2, a plurality of fibers 3 arranged with the tips 3a opposed to the nearest position are provided, and the laser light emitted from the light emitting region of the emitter 2 is opposed to the nearest position. The fiber 3 is made to enter from the tip.

The fiber 3 has a core 11 formed inside, and a clad 12 formed on the outer periphery of the core 11 so that laser light is propagated in the core 11. This fiber 3
Are larger in diameter than the size of the light-emitting region of the emitter 2, and are arranged in the same number as the emitters 2, with the distance between the tips 3 a being equal to the distance between the emitters 2.

As shown in FIG. 2, a tapered shape which extends rearward from the center of the tip 3a is formed at the tip 3b of the fiber 3 from the tip 3a to the rear.

The laser beam emitted from the light emitting region of the emitter 2 and incident on the core 11 from the distal end 3a of the fiber 3 with a divergence angle C in the horizontal and vertical directions is transmitted to the core 11 of the distal end 3b having a tapered shape. The light is reflected by the tapered portion 13 at the boundary between the clad 12 and propagates in the core 11 in the optical axis direction.

In this case, if the tapered shape is not formed at the tip 3b of the fiber 3 shown in FIG.
The laser beam b incident on the core 11 from the tip 3a of the fiber 3 with a divergence angle C in the horizontal and vertical directions with respect to the optical axis a has an incident angle A with respect to the optical axis a larger than a certain value with respect to the optical axis a. In the case of angle D (critical angle), core 1
At the boundary between the cladding 1 and the cladding 12, a part b3 is refracted, and the other bounces repeatedly at a short distance propagating in the fiber 3 and repeatedly b2 occurs. Light propagation efficiency may decrease.

In the present embodiment, the taper shape which spreads rearward from the center of the tip 3a of the fiber 3 allows the horizontal and vertical spread angles C radiated from the light emitting region of the emitter 2 to be increased. When the laser beam is incident on the distal end 3a of the fiber 3 as shown in FIG. 2, the laser beam b having an incident angle A with respect to the optical axis a incident on the distal end 3a shown in FIG. Of the tapered portion 13 at the boundary between the core 11 and the clad 12 in the direction of the optical axis a, the reflection angle B with respect to the optical axis a becomes smaller with respect to the incident angle A of the laser light. Can be reflected. As a result, the light can be propagated in a linear direction closer to the optical axis a of the fiber 3, and the reflection in the fiber 3 can be reduced, and the optical loss due to the reflection can be reduced.

Therefore, the laser light emitted from the light emitting region of the emitter 2 with the horizontal and vertical spread angles C has an angle D (critical angle) at which the incident angle A with respect to the optical axis a is larger than a certain value. Even when the light enters the tip 3 a of the fiber 3, the core 1 of the tip 3 b having a tapered shape is formed.
The laser beam is reflected by the tapered portion 13 at the boundary between the laser beam 1 and the cladding 12, so that the laser beam can propagate through the fiber at a reflection angle B with respect to the optical axis a which is smaller than the critical angle D of the laser beam.

As a result, when the light is reflected in the fiber 3 at a reflection angle B equal to or greater than the critical angle D with respect to the optical axis a, a part of the light is refracted b3 at the boundary between the core 11 and the clad 12, and Is frequently repeated at short distances propagating in the fiber 3, thereby preventing the bound phenomenon in which the light loss of the laser light is increased and the optical loss of the laser light is reduced, and the propagation efficiency in the fiber 3 is reduced. Is improved.

In such a configuration, the laser light is transmitted through the fiber 3 as in a conventional laser diode pumping apparatus.
There is no need to provide a multi-mode optical fiber or the like for making the light enter the optical axis a, and the number of components is reduced, and the configuration is simplified. The alignment is simply required to align the fibers 3 in opposition to the position immediately adjacent to the light emitting region of the emitter 2 without making them coincide with each other, and the adjustment is easy.

In this configuration, the tip 3a of the fiber 3
In the case of a tapered shape extending rearward from the center of the fiber 3, if the end face area of the fiber 3 is widened, the light collection efficiency from the light emitting area of the emitter 2 is increased, but the tapered slope of the tip 3 b is reduced. Therefore, the angle of reflection B with respect to the optical axis a reflected by the tapered portion 13 cannot be made much smaller than the angle of incidence A.
When the tip surface area is narrowed, the inclination angle of the tapered shape of the tip portion 3b can be increased to make the reflection angle B considerably smaller than the incident angle A. However, the light collection efficiency of the emitter 2 from the light emitting area is reduced. It is necessary to set an appropriate distal end surface area of the fiber 3 for solving both of them because there is a dislike for lowering.

For example, the emitter size is 0.15 mm, the fiber diameter d2 is 0.2 mm, and the fiber NA (sinB)
Is set to 0.22, and from the relational expression of (d1 × sinA = d2 × sinB), assuming that the vertical divergence angle of the emitter 2 from the light emitting region is an incident angle (sinA) of 35 degrees, d1 (vertical direction) Length) = 0.077 mm.

On the other hand, if the horizontal spread angle of the light emitting region of the emitter 2 is 16 degrees incident angle (sinA), d1 (horizontal length) is set to 0.157 mm.

Based on this setting, the shape of the distal end surface region of the fiber 3 is such that the major axis d1 (horizontal length) is 0.157 m.
It is desirable to form it into an elliptical shape having a shape with m and the minor axis d1 (vertical length) being 0.077 mm.

Therefore, the fiber 3 has a diameter of 0.3 mm.
It is made of a fiber 3 of 2 mm.
1 (horizontal length) is 0.157 mm, and the minor axis d1 (vertical length) is 0.077 mm. An elliptical distal end region of the fiber 3 is formed. It has a tapered shape that spreads out.

The end surface area of the fiber 3 is not limited to the above setting, but can be set arbitrarily according to the emitter size, the fiber diameter and the like.

The plurality of fibers 3 are converted into a bundle fiber 4 in which each fiber 3 is bundled into a single fiber 6 having a diameter equal to or larger than the bundle diameter by the relay connector 5. It is connected. At the other end of this single fiber 6,
It is detachably connected by a detachable connection connector 8 installed in the laser head. Thus, light from the single fiber 6 is condensed by the condensing lens 9 in the laser head 7 to excite the solid-state laser medium 10.

Conventionally, when the output of each laser beam from the light emitting region of a plurality of emitters is different due to the life of the emitter 2 or the like, the output distribution at the end of the bundle fiber in which the plurality of fibers 3 are bundled changes. Loss of uniformity
As a result, there is a problem that the output distribution of the excitation light is disturbed, and the excitation of the laser medium is changed, and finally the output laser light is also changed, so that the beam light and the beam output are also changed. However, once the single fiber 6 is connected from the bundle fiber 4 in which the plurality of fibers 3 are bundled, the laser light is averaged again by the single fiber 6 connected to the bundle fiber 4, and the solid state is generated by the averaged excitation light. Since the laser medium 10 can be excited, the uniformity of the light from the single fiber 6 is prevented from being impaired even if the output of each individual emitter 2 is reduced due to its life. 10
Can be excited, and together with the taper shape that extends rearward from the center of the tip of the fiber 3, it is possible to further improve the propagation efficiency.

[0036]

According to the laser diode pumping apparatus of the present invention, since the tips of the plurality of fibers are formed in a tapered shape extending rearward from the center of the tips, the fibers are radiated from the light emitting region of the emitter. The laser beam incident with horizontal and vertical divergence angles is directed in the direction of the optical axis at a tapered portion formed at the fiber tip at a reflection angle with respect to the optical axis that is smaller than the incident angle of the laser beam. The light can be reflected and propagated in the fiber. As a result, the light can be propagated in a linear direction closer to the optical axis of the fiber, so that the reflection in the fiber can be reduced, and the optical loss due to the reflection can be reduced.

Accordingly, it is not necessary to provide a multimode optical fiber or the like, so that the number of parts is reduced and the configuration is simplified. As a result, alignment that only requires the fiber to be arranged facing the immediate vicinity of the emitter region is sufficient. This makes it easy to adjust the alignment between the plurality of emitters and each fiber.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a laser diode excitation device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a fiber tip of the laser diode excitation device in FIG.

FIG. 3 is a schematic perspective view of a conventional laser diode excitation device.

FIG. 4 is an enlarged cross-sectional view of a fiber tip of the laser diode excitation device in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode 1a Base 2 Emitter 3 Fiber 4 Bundle fiber 3a Tip 3b Tip 5 Relay connector 6 Single fiber 7 Laser head 8 Coupling connector 9 Condenser lens 10 Solid laser medium 11 Core 12 Clad 13 Tapered portion

Continued on the front page F term (reference) 2H037 AA04 BA03 BA06 CA07 CA17 2H046 AA39 AA69 AB12 AD11 5F072 AB00 KK30 PP07 5F073 AB05 AB21 AB27 AB28 BA09 FA06

Claims (3)

[Claims] 1. A laser diode excitation device for guiding laser light from a laser diode having a plurality of emitters arranged in an array to a solid-state laser medium by a fiber and exciting the solid-state laser medium, wherein each of the light-emitting regions of the plurality of emitters is provided. In addition, a plurality of fibers whose tips are arranged to face each other at the nearest position are provided, and the tips of the plurality of fibers are formed in a tapered shape extending rearward from the center of the tips. Laser diode excitation device. 2. The tapered shape of each fiber tip is:
The laser beam incident from the light emitting region of the emitter to the fiber end with a divergence angle in the horizontal and vertical directions is reflected by this tapered portion to have a reflection angle smaller than the critical angle of the laser beam. 2. The laser diode pumping device according to claim 1, wherein the laser diode pumping device is formed so as to be propagated in the fiber. 3. The laser diode according to claim 1, wherein the bundle fiber in which the plurality of fibers are bundled is connected to a single fiber having a diameter equal to or larger than the diameter of the bundle fiber. Exciter.