JP6978974B2 - Optical circulator and laser equipment - Google Patents

Description

The present invention relates to an optical circulator and a laser device, and more particularly to an optical circulator that can be miniaturized and a laser device including the optical circulator.

Optical circulators are used in fields such as optical communication and optical measurement. An optical circulator is generally an element having three or four ports. For example, in an optical circulator having three ports, it is generally configured such that the light incident from the first port is emitted from the second port and the light incident from the second port is emitted from the third port. .. Further, in an optical circulator having four ports, in general, the light incident from the first port is emitted from the second port, the light incident from the second port is emitted from the third port, and the light is incident from the third port. The light emitted from the fourth port is emitted from the fourth port, and the light incident from the fourth port is emitted from the first port.

The following Patent Document 1 describes an example of a conventional optical circulator. This optical circulator is composed of a pair of cube-shaped polarizing beam splitters, a Faraday rotator and a 1/2 wave plate arranged between these cube-shaped polarizing beam splitters, and a total reflection mirror.

Japanese Unexamined Patent Publication No. 2002-31780

In the conventional optical circulator described in Patent Document 1, a cube-type polarizing beam splitter is used. However, a cube-type polarizing beam splitter is generally composed of two prisms bonded together by an adhesive, and the adhesive absorbs light incident on the cube-type polarizing beam splitter and generates heat. There is.

On the other hand, when two prisms are brought into close contact with each other without using an adhesive to produce a cube-type polarization beam splitter, the mechanical strength of the cube-type polarization beam splitter tends to be low. In a cube-type polarizing beam splitter manufactured without using such an adhesive, it is preferable to bring two prisms of a certain size into close contact with each other in order to secure mechanical strength. However, if the polarization beam splitter becomes large, it is necessary to increase the expensive Faraday rotator and the like, and the optical circulator itself tends to become large. In addition, when miniaturizing a cube-type polarizing beam splitter that is manufactured without using an adhesive, two prisms of a certain size are brought into close contact with each other as described above, and then the circumference of those prisms is scraped to make them smaller. There is a need to. However, if the circumference of the cube-type polarizing beam splitter is trimmed, the outer peripheral portions of the joint surfaces of the two prisms tend to be easily peeled off from each other. Therefore, it is difficult to miniaturize the cube-type polarizing beam splitter while securing a region for transmitting or reflecting light on the joint surface. As described above, it is difficult to miniaturize the conventional optical circulator.

Therefore, an object of the present invention is to provide an optical circulator and a laser device that can be miniaturized.

The optical circulator of the present invention for solving the above problems includes a first port in which light from the outside is incident, a first beam displacer composed of a birefringent crystal in which light from the first port is incident, and the above. A second beam displayer composed of birefringent crystals arranged on the side opposite to the first port side of the first beam displacer, and a Faraday rotation arranged between the first beam displacer and the second beam displacer. The child and the polarizing rotator, the second port provided on the side opposite to the first beam displacer side of the second beam displacer, and the second port provided on the side opposite to the second beam displacer side of the first beam displacer are arranged. A third beam displacer composed of a birefringent crystal and a third port provided on the side opposite to the first beam displacer side of the third beam displacer are provided, and the first beam displacer is provided from the first port. Each of the polarized light incident on the light and separated from each other is rotated in the polarization direction in the Faraday rotator and the polarization rotator, and is birefringent in the second beam displacer so as to overlap with each other at least partially, and is emitted from the second port. The polarizations of the polarized light incident on the second beam displacer from the second port and separated from each other are rotated in the polarization direction in the polarization rotator and the Faraday rotator, and are further separated from each other in the first beam displacer. It is characterized in that it is birefringed in the third beam displacer so as to overlap at least a part thereof and is ejected from the third port.

The optical circulator does not need to use a cube-type polarization beam splitter, but uses a beam displacer composed of birefringent crystals. Such a beam displacer can be easily miniaturized, and the Faraday rotator or the like can also be miniaturized according to the size of the beam displacer. Therefore, the optical circulator can be miniaturized. Further, since each beam displacer provided in the optical circulator can be configured without using an adhesive, heat generation due to light incident on each beam displacer can be suppressed. Therefore, the optical circulator can handle high-power light.

Further, the distance between each polarized light incident on the second beam displacer from the second port and separated from each other when passing through the first beam displacer is the distance between the respective polarized light passing through the third beam displacer. It is preferable that the distance is substantially equal to the distance that can be approached.

By equalizing the distance between the polarized lights that are separated from each other in the second beam displacer and the first beam displacer and the distance that the polarized lights are brought closer to each other in the third beam displacer, the polarized lights are made to each other in the third beam displacer. It becomes easy to stack. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

The optical axis of the first beam displacer and the optical axis of the second beam displacer are parallel to each other, and the optical axis of the third beam displacer and the optical axis of the first beam displacer are the first beam displacer and the above. It is preferably symmetrical with respect to the plane intermediate with the third beam displacer.

The change in the distance between each polarized light propagating through the beam displacer may depend on the orientation of the optical axis of the beam displacer. By setting the orientation of the optical axis of each beam displacer as described above, the distance between the polarized light incident from the second port and separated from each other in the second beam displacer and the first beam displacer, and the third In the beam displacer, it is easy to make the distance that the polarized light is close to each other the same. Therefore, the polarized light incident from the second port and separated from each other in the second beam displacer and the first beam displacer is likely to be overlapped with each other in the third beam displacer. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

Further, it is preferable that the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is substantially equal to the thickness of the third beam displacer.

The change in the distance between each polarized light propagating through the beam displacer may also depend on the thickness of the beam displacer. By selecting the thickness of each beam displacer as described above, the distance between the polarized light incident from the second port and separated from each other in the second beam displacer and the first beam displacer, and the third beam displacer. In, it becomes easy to make the distance that the polarized light is close to each other the same. Therefore, the polarized light incident from the second port and separated from each other in the second beam displacer and the first beam displacer is likely to be overlapped with each other in the third beam displacer. Therefore, the beam diameter of the light emitted from the third port can be reduced, and the light can be easily emitted from the third port.

Further, it is preferable that the thickness of the first beam displacer and the thickness of the second beam displacer are substantially equal to each other.

It is easy to make the distance between the polarized light incident from the first port and separated from each other in the first beam displacer and the distance between the polarized light in the second beam displacer close to each other. Therefore, the polarized light incident from the first port and separated from each other in the first beam displacer is likely to be overlapped with each other in the second beam displacer. Further, by selecting the thickness of the first beam displacer and the second beam displacer in this way, the first beam displacer and the second beam displacer can be configured by the same beam displacer. Therefore, the configuration of the optical circulator can be simplified. Further, when the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is the same as the thickness of the third beam displacer as described above, the same beam as the beam displacer constituting the first beam displacer. A third beam displacer can be configured using two displacers. That is, the first beam displacer, the second beam displacer, and the third beam displacer can all be configured by the same beam displacer. Therefore, the configuration of the optical circulator can be simplified. However, even if the sum of the thickness of the 1st beam displayer and the thickness of the 2nd beam displacer is the same as the thickness of the 3rd beam displacer, even if the 3rd beam displacer is composed of one beam displacer. good. In this case, the number of beam displacers used can be reduced as compared with the case where the third beam displacer is configured by the two beam displacers as described above.

Further, it is preferable that at least one of the first port, the second port, and the third port has a mirror.

By using a mirror, it becomes easy to guide light to a desired position, and the degree of freedom in designing an optical circulator can be improved.

Further, the mirror is provided adjacent to at least one of the first beam displacer, the second beam displacer, and the third beam displacer, and the mirror transmits the beam displacer adjacent to the mirror. It is preferably placed between at least two polarized light paths.

By arranging the mirror in this way, the extra space formed in the optical circulator can be utilized, and the optical circulator can be further miniaturized.

Further, the fourth beam displacer composed of the birefringent crystals arranged on the side opposite to the first beam displacer side of the second beam displacer and the second beam displacer side of the fourth beam displacer are opposite to each other. A fourth port provided on the side is further provided, and each polarized light incident on the fourth beam displacer from the fourth port and separated from each other is incident on the second beam displacer and brought close to each other, and the Faraday It is preferable that the polarization direction is rotated by the rotator and the polarizing rotator, and the first beam displacer is refracted so as to overlap at least a part of each other and is ejected from the first port.

By providing the optical circulator with such a fourth port and a fourth beam displacer, a four-port type optical circulator in which light incident from the fourth port is emitted from the first port can be obtained.

Further, in the optical circulator including the 4th port and the 4th beam displacer, the polarized light incident on the 3rd beam displacer from the 3rd port and separated from each other is incident on the 1st beam displacer and brought close to each other. The polarization direction is rotated in the Faraday rotator and the polarization rotator, further separated from each other in the second beam displacer, refracted so as to overlap at least a part of each other in the fourth beam displacer, and ejected from the fourth port. It is preferable to be done.

By configuring the optical circulator in this way, a 4-port type optical circulator in which light incident from the third port is emitted from the fourth port can be obtained.

Further, the distance between each polarized light incident on the fourth beam displacer from the fourth port and separated from each other when passing through the fourth beam displacer is such that the respective polarized light passes through the second beam displacer. It is preferable that the sum of the distances that are brought close to each other when they are brought close to each other and the distances that the respective polarized lights are brought close to each other when they pass through the first beam displacer is substantially equal to each other.

By equalizing the distance between the polarized lights that are separated from each other in the fourth beam displacer and the distance that the polarized lights are brought close to each other in the second beam displacer and the first beam displacer, the polarized lights are likely to be overlapped with each other. Therefore, the beam diameter of the light emitted from the first port can be reduced, and the light can be easily emitted from the first port.

Further, it is preferable that the optical axis of the 4th beam displacer is parallel to the optical axis of the 3rd beam displacer.

Each of the polarized light incident from the third port and separated from each other in the third beam displacer passes through the Faraday rotator and the polarizing rotator and reaches the fourth beam displacer. Therefore, the polarized light that was normal light in the third beam displacer may become abnormal light in the fourth beam displacer, and the polarized light that was abnormal light in the third beam displacer may become normal light in the fourth beam displacer. That is, the polarized lights that are separated from each other in the third beam displacer are brought closer to each other in the fourth beam displacer. Further, as described above, the change in the distance between each polarized light propagating through the beam displacer may depend on the direction of the optical axis of the beam displacer. Since the optical axis of the 3rd beam displacer and the optical axis of the 4th beam displacer are parallel to each other, the distance between the polarized light separated from each other in the 3rd beam displacer and the polarizations of the polarized light in the 4th beam displacer are separated from each other. It is easy to make the distances that can be brought close to each other the same. Therefore, the polarized light incident from the third port and separated from each other in the third beam displacer is likely to be overlapped with each other in the fourth beam displacer. Therefore, the beam diameter of the light emitted from the fourth port can be reduced, and the light can be easily emitted from the fourth port.

Further, it is preferable that the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is substantially equal to the thickness of the fourth beam displacer.

As described above, the change in the distance between each polarized light propagating through the beam displacer may depend on the thickness of the beam displacer. Therefore, by selecting the thickness of the 1st beam displacer, the 2nd beam displacer, and the 4th beam displacer as described above, the respective polarized light incident from the 4th port and separated from each other in the 4th beam displacer can be obtained. It passes through the second beam displacer and the first beam displacer and easily overlaps with each other.

Further, it is preferable that the fourth port has a mirror.

By using a mirror, it becomes easy to guide light to a desired position, and the degree of freedom in designing an optical circulator can be improved.

Further, it is preferable that the mirror is provided adjacent to the fourth beam displacer and is arranged between at least two polarized light paths passing through the fourth beam displacer.

By arranging the mirror in this way, the extra space formed in the optical circulator can be utilized, and the optical circulator can be further miniaturized.

Further, the laser device of the present invention for solving the above-mentioned problems is a signal light source that emits light incident on any of the above-mentioned optical circulators having the first to third ports and the first port of the above-mentioned optical circulator. A first amplifier that amplifies the light emitted from the second port and incidents at least a part of the amplified light onto the second port, and the optical circulator is incident from the first port. The light is emitted from the second port, and the light incident from the second port is emitted from the third port.

As described above, the optical circulator of the present invention having the first to third ports can be applied to a laser device. The signal light is not limited to the light including the signal.

Further, the laser apparatus of the present invention for solving the above-mentioned problems includes an optical circulator having the first to fourth ports, a signal light source for emitting light incident on the first port of the optical circulator, and the first. The first amplifier that amplifies the light emitted from the two ports and reflects at least a part of the amplified light to the second port side, and the amplified light that amplifies the light emitted from the third port. The optical circulator comprises a second amplifier that reflects at least a part of the light toward the third port, and the optical circulator emits light incident from the first port from the second port and incidents from the second port. The light is emitted from the third port, and the light incident from the third port is emitted from the fourth port.

As described above, the optical circulator of the present invention having the first to fourth ports can be applied to a laser device.

As described above, according to the present invention, there is provided an optical circulator and a laser device that can be miniaturized.

It is a figure which shows schematic structure of the laser apparatus of 1st Embodiment of this invention. It is a figure which shows the arrangement of the optical element in the optical circulator of the 1st Embodiment of this invention, and the optical path of the light incident from the 1st port. It is a figure which shows the optical path of the light incident from the 2nd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light incident from the 3rd port of the optical circulator shown in FIG. It is a figure which shows schematic structure of the laser apparatus of 2nd Embodiment of this invention. It is a figure which shows the arrangement of the optical element in the optical circulator of the 2nd Embodiment of this invention, and the optical path of the light incident from the 1st port. It is a figure which shows the optical path of the light incident from the 2nd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light incident from the 3rd port of the optical circulator shown in FIG. It is a figure which shows the optical path of the light incident from the 4th port of the optical circulator shown in FIG.

Hereinafter, embodiments of the optical circulator according to the present invention will be described in detail with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram schematically showing a configuration of a laser device according to a first embodiment of the present invention. The laser apparatus 100 of the present embodiment shown in FIG. 1 includes a signal light source MO, an optical circulator 1 of the first embodiment, and a first amplifier AM1 as main components. Further, the first amplifier AM1 includes a first collimating lens 3, a glass body for optical amplification 4, a mirror 5, a second collimating lens 6, and an excitation light source 7 as main components.

The signal light source MO is a light source that emits light incident on the optical circulator 1. The signal light source MO emits signal light incident on the first port 31 of the optical circulator 1, which will be described later. The signal light source MO includes, for example, a laser diode, a fiber laser, or the like. One end of the signal optical fiber 51 is connected to the signal light source MO. The signal light emitted from the signal light source MO mainly propagates through the core of the signal optical fiber 51 from one end to the other end of the signal optical fiber 51.

As described above, the signal light source MO is connected to one end of the signal optical fiber 51, and the optical circulator 1 is connected to the other end of the signal optical fiber 51.

FIG. 2 is a diagram showing an arrangement of optical elements in the optical circulator according to the first embodiment of the present invention. As shown in FIG. 2, the optical circulator 1 of the present embodiment has a housing 10, a first beam displacer 11, a second beam displacer 12, a third beam displacer 13, a Faraday rotator 21, a polarizing rotator 22, and a first port. It includes 31, a second port 32, and a third port 33 as main components.

The first port 31 is a portion that guides light incident on one surface of the first beam displacer 11 from the outside of the optical circulator 1. The first port 31 of the present embodiment has a first opening 31h and a first mirror 31m formed in the housing 10. For example, an optical fiber (not shown) is connected to the first opening 31h. The first mirror 31m of the present embodiment is a total reflection mirror, and the light incident on the housing 10 from the first opening 31h is totally reflected by the first mirror 31m and incident on one surface of the first beam displacer 11. do.

The first beam displacer 11 is arranged so that the light from the first port 31 is incident on one surface, and is composed of a parallel plate type birefringent crystal. Therefore, the light incident on one surface of the first beam displacer 11 from the first port 31 is divided into S-polarized light which is normal light according to Snell's law and P-polarized light which is abnormal light which does not follow Snell's law. .. In the first beam displacer 11 of the present embodiment, the light from the first port 31 is vertically incident on one surface of the first beam displacer 11. The polarized light generated by separating the light incident on one surface of the first beam displacer 11 in the first beam displacer 11 is parallel to the traveling direction of the light incident on the first beam displacer 11 and is parallel to the traveling direction of the first beam displacer 11. Emit from the other side of 11.

Further, in the optical axis OA1 of the first beam displacer 11 of the present embodiment, abnormal light is maximally separated from normal light when non-polarized light is vertically incident on one surface of the first beam displacer 11 from the first port 31. It is set to a possible angle. Further, the thickness of the first beam displacer 11 of the present embodiment in the direction in which normal light propagates is such that when non-polarized light is incident on one surface of the first beam displacer 11 from the first port 31, normal light and abnormal light are present. The thickness is set so that it can be emitted from the other surface of the first beam displacer 11 at a sufficient distance. For example, the thickness of the first beam displacer 11 of the present embodiment is such that when unpolarized light is incident on one surface of the first beam displacer 11 from the first port 31, the distance between normal light and abnormal light is the beam diameter thereof. It is set to a thickness that can be emitted from the other surface of the first beam displacer 11 so as to be more than twice the thickness of the first beam displacer 11. By adjusting one or both of the direction of the optical axis OA1 of the first beam displacer 11 and the thickness of the first beam displacer 11, the distance between the normal light and the abnormal light can be adjusted in the first beam displacer 11.

The Faraday rotator 21 is arranged between the first beam displacer 11 and the second beam displacer 12. The light incident on the Faraday rotator 21 of the present embodiment from the first beam displacer 11 side is emitted to the second beam displacer 12 side by rotating the polarization direction by 45 degrees clockwise when viewed along the traveling direction of the light. do. On the other hand, the light incident on the Faraday rotator 21 of the present embodiment from the second beam displacer 12 side has the polarization direction rotated 45 degrees counterclockwise when viewed along the traveling direction of the light, and the first beam displacer 11 It emits to the side.

Examples of the material constituting such a Faraday rotator 21 include a terbium gallium garnet type single crystal (TGG: Tb ₃ Ga ₅ O ₁₂ ) and a terbium aluminum garnet type single crystal (TAG: Tb ₃ Al _5). O ₁₂ ), terbium scandium aluminum garnet type single crystal (TSAG: Tb ₃ Sc ₂ Al ₃ O ₁₂ ), terbium scandium lutetium aluminum garnet type single crystal (TSLAG: Tb ₃ (Sc, Lu) ₂₎ Al ₃ O ₁₂ ) and the like.

A magnetic field (not shown) is provided around the Faraday rotator 21, and a magnetic field with the first beam displacer 11 side of the Faraday rotator 21 as the N pole and the second beam displacer 12 side as the S pole is generated. Given. The Faraday rotator 21 rotates the polarization direction of light as described above based on the magnetic field formed by the magnetic application portion. Examples of the magnetic application unit include magnets such as neodymium magnets.

The polarizing rotator 22 is arranged between the first beam displacer 11 and the second beam displacer 12. The polarizing rotator 22 of the present embodiment is arranged between the first beam displacer 11 and the second beam displacer 12 on the second beam displacer 12 side of the Faraday rotator 21. The light incident on the polarization rotator 22 of the present embodiment from the first beam displacer 11 side is emitted to the second beam displacer 12 side with the polarization direction rotated 45 degrees clockwise when viewed along the traveling direction of the light. .. On the other hand, the light incident on the polarization rotator 22 of the present embodiment from the second beam displacer 12 side is rotated 45 degrees clockwise when viewed along the traveling direction of the light and is directed to the first beam displacer 11 side. Emit. Therefore, the polarizing rotator 22 of the present embodiment rotates the polarization direction of the light incident from the first beam displacer 11 side by 45 degrees in the same direction as the rotation direction of the Faraday rotator 21 and emits the light. On the other hand, the polarizing rotator 22 of the present embodiment rotates the polarization direction of the light incident from the second beam displacer 12 side by 45 degrees in the direction opposite to the rotation direction of the Faraday rotator 21 and emits the light. As the polarizing rotator 22 of this embodiment, for example, a 1/2 wave plate or a crystal polarizing axis rotator is used.

The second beam displacer 12 is arranged on the side opposite to the first port 31 side of the first beam displacer 11, and is composed of a parallel plate type birefringent crystal. The second beam displacer 12 of the present embodiment has the same configuration as the first beam displacer 11 and is arranged in parallel with the first beam displacer 11. That is, the optical axis OA2 of the second beam displacer 12 of the present embodiment is parallel to the optical axis OA1 of the first beam displacer 11, and the thickness of the second beam displacer 12 of the present embodiment is that of the first beam displacer 11. Same as thickness. By adjusting one or both of the direction of the optical axis OA2 of the second beam displacer 12 and the thickness of the second beam displacer 12, the distance between the normal light and the abnormal light can be adjusted in the second beam displacer 12.

The second port 32 is provided on the side opposite to the first beam displacer 11 side of the second beam displacer 12. The second port 32 of this embodiment is an opening formed in the housing 10. One end of the optical fiber 52 is connected to the second port 32.

The third beam displacer 13 is arranged on the side opposite to the second beam displacer 12 side of the first beam displacer 11, and is composed of parallel plate type birefringent crystals. The third beam displacer 13 of the present embodiment is arranged in parallel with the first beam displacer 11. Further, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of the present embodiment are symmetrical with respect to a plane intermediate between the first beam displacer 11 and the third beam displacer 13. .. Further, the thickness of the third beam displacer 13 of the present embodiment is twice the thickness of the first beam displacer 11. By adjusting one or both of the direction of the optical axis OA3 of the third beam displacer 13 and the thickness of the third beam displacer 13, the distance between the normal light and the abnormal light can be adjusted in the third beam displacer 13.

The third port 33 is provided on the side opposite to the first beam displacer 11 side of the third beam displacer 13. The third port 33 of the present embodiment is an opening formed in the housing 10. One end of the delivery fiber 53 is connected to the third port 33.

The first collimating lens 3 shown in FIG. 1 is arranged between the other end of the optical fiber 52 and one end surface of the optical amplification glass body 4. The light emitted from the other end of the optical fiber 52 is collimated by the first collimating lens 3 and incident on one end surface of the optical amplification glass body 4. That is, the signal light emitted from the signal light source MO enters the optical circulator 2 from the first port 31 and is emitted from the second port 32, and is a glass body for optical amplification via the optical fiber 52 and the first collimating lens 3. It is incident on one end face of 4.

An active element such as ytterbium (Yb) excited by the excitation light emitted from the excitation light source 7 is added to the light amplification glass body 4. Examples of such active elements include rare earth elements, and examples of rare earth elements include thulium (Tm), cerium (Ce), neodium (Nd), europium (Eu), erbium (Er), and the like, in addition to the above Yb. Can be mentioned. Further, as the active element, bismuth (Bi) and the like can be mentioned in addition to the rare earth element.

The optical amplification glass body 4 of the present embodiment includes a columnar glass rod made of quartz to which the above-mentioned active element is added. The optical amplification glass body 4 of the present embodiment has a coating layer made of resin or quartz having a refractive index lower than that of the glass rod surrounding the outer peripheral surface of the glass rod for the purpose of protecting the outer peripheral surface of the glass rod. You may be doing it. Examples of the resin constituting the coating layer include an ultraviolet curable resin, and the quartz constituting the coating layer is a dopant such as fluorine (F) that lowers the refractive index so as to have a lower refractive index than, for example, a glass rod. Quartz to which is added can be mentioned.

The excitation light source 7 is provided on the side of the mirror 5 opposite to the light amplification glass body 4, and emits excitation light. The excitation light source 7 of the present embodiment is composed of a plurality of laser diodes 71. In the present embodiment, the laser diode 71 is, for example, a Fabry-Perot type semiconductor laser made of a GaAs-based semiconductor and emits excitation light having a center wavelength of 915 nm. Further, each laser diode 71 of the excitation light source 7 is connected to the excitation optical fiber 72, and the excitation light emitted from the laser diode 71 propagates through the excitation optical fiber 72.

One end of each excitation optical fiber 72 is connected to the laser diode 71, and the other end is connected to one end of the optical combiner 73. Further, an optical fiber 54 is connected to the other end of the optical combiner 73. Therefore, the excitation light emitted from the excitation light source 7 is incident on one end of the optical fiber 54 via the excitation optical fiber 72 and the optical combiner 73.

The second collimating lens 6 is arranged between the other end of the optical fiber 54 and the mirror 5. The excitation light emitted from the other end of the optical fiber 54 is collimated by the second collimating lens 6 and incident on the mirror 5.

The mirror 5 is provided between the optical amplification glass body 4 and the excitation light source 7 on the side opposite to the second port 32 side of the optical amplification glass body 4. The mirror 5 transmits at least a part of the excitation light emitted from the excitation light source 7 to the light amplification glass body 4. That is, the mirror 5 transmits at least a part of the excitation light emitted from the other end of the optical fiber 54 to the optical amplification glass body 4. Further, the mirror 5 reflects at least a part of the signal light amplified by the optical amplification glass body 4 toward the optical amplification glass body 4. In this way, the mirror 5 reflects light of a predetermined wavelength and transmits light of another predetermined wavelength. Such a mirror 5 of the present embodiment is made of, for example, a dielectric multilayer film.

Next, the operation of the laser device 100 of the present embodiment will be described.

First, the excitation light is emitted from each laser diode 71 of the excitation light source 7. This excitation light enters one end of the core of the optical fiber 54 via the excitation optical fiber 72 and the optical combiner 73, and propagates mainly through the core of the optical fiber 54. The excitation light emitted from the other end of the core of the optical fiber 54 is collimated by the second collimating lens 6, passes through the mirror 5, enters the optical amplification glass body 4, and propagates through the optical amplification glass body 4. The excitation light propagating through the optical amplification glass body 4 excites the active element added to the optical amplification glass body 4.

On the other hand, signal light is emitted from the signal light source MO. This signal light is incident on the optical circulator 1 from the first port 31 via the signal optical fiber 51.

In FIG. 2, the path of light incident on the optical circulator 1 from the first port 31 is indicated by an arrow. In FIG. 2 and the following figures, the path of S-polarized light is indicated by a chain double-dashed line, and the path of P-polarized light is indicated by a broken line. Further, in FIG. 2 and the following figures, the polarization direction of light is indicated by an arrow surrounded by a circle. However, for the sake of easy understanding, the polarization direction is shown by replacing the vertical direction on the paper surface with the left-right direction.

As shown in FIG. 2, the light incident on the optical circulator 1 from the first port 31 is totally reflected by the first mirror 31m after being incident on the optical circulator 1 from the first opening 31h, and the first beam displacer 11 It is incident on one surface. The light incident on one surface of the first beam displacer 11 is divided into S-polarized light, which is normal light polarized perpendicular to each other, and P-polarized light, which is abnormal light, in the first beam displacer 11. Light from the first port 31 is incident perpendicular to one surface of the first beam displacer 11, normal light travels straight through the first beam displacer 11 and is transmitted from the other surface of the first beam displacer 11. Emit. On the other hand, the abnormal light travels in the first beam displacer 11 in a direction away from the normal light and is transmitted, and is emitted from the other surface of the first beam displacer 11 so that the traveling direction is parallel to the normal light. Therefore, the normal light and the abnormal light propagate to the second beam displacer 12 while the distance d1 between them remains substantially constant.

Each polarized light transmitted through the first beam displacer 11 is incident on the Faraday rotator 21. In the Faraday rotator 21, the polarization direction of the polarized light is rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light as described above. Further, each polarized light transmitted through the Faraday rotator 21 is incident on the polarization rotator 22. In the polarization rotator 22, the polarization direction of the polarized light is further rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light as described above. Therefore, the polarized light that was S-polarized in the first beam displacer 11 is rotated by 90 ° in the polarization direction by passing through the Faraday rotator 21 and the polarization rotator 22, becomes P-polarized light, and is incident on the second beam displacer 12. .. Further, the polarized light that was P-polarized light in the first beam displacer 11 is transmitted by the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 °, becomes S-polarized light, and is incident on the second beam displacer 12. ..

The second beam displacer 12 has the same configuration as the first beam displacer 11 as described above, and is arranged parallel to the first beam displacer 11. Therefore, the polarized light that was abnormal light in the first beam displacer 11 becomes normal light in the second beam displacer 12 and goes straight by rotating the polarization direction in the Faraday rotator 21 and the polarization rotator 22 as described above. And transparent. Further, the polarized light that was normal light in the first beam displacer 11 becomes abnormal light in the second beam displacer 12 due to the rotation of the polarization direction in the Faraday rotator 21 and the polarizing rotator 22 as described above. Similar to the abnormal light in the beam displacer 11, it is refracted and transmitted. As a result, the respective polarized light incident on the surface of the second beam displacer 12 on the first beam displacer 11 side overlaps and emits on the surface of the second beam displacer 12 opposite to the first beam displacer 11 side.

The polarized light that has passed through the second beam displacer 12 and overlapped with each other is emitted from the second port 32 to the outside of the optical circulator 1. As described above, the light incident on the optical circulator 1 from the first port 31 is emitted from the second port 32 to the outside of the optical circulator 1.

The signal light emitted from the second port 32 is incident on one end surface of the optical fiber 52, is emitted from the other end, is collimated by the first collimating lens 3, and is incident on one end surface of the optical amplification glass body 4. The signal light incident on one end face of the light amplification glass body 4 propagates through the light amplification glass body 4 to the other end face, and is amplified by the stimulated emission of the active element excited as described above. The signal light amplified in the optical amplification glass body 4 in this way is emitted from the other end face of the optical amplification glass body 4 and reflected by the mirror 5 to the optical amplification glass body 4 side, and is again the optical amplification glass body 4. It is incident on the optical amplification glass body 4 from the other end face of the body 4. Then, the signal light amplified as described above is further amplified in the optical amplification glass body 4 and emitted from one end surface of the optical amplification glass body 4. In this way, the first amplifier AM1 amplifies the light emitted from the second port 32, and reflects at least a part of the amplified light to the second port 32 side.

As described above, the signal light amplified by the optical amplification glass body 4 and emitted from one end surface of the optical amplification glass body 4 is an optical circulator from the second port 32 via the first collimating lens 3 and the optical fiber 52. It is incident on 1.

FIG. 3 shows the arrangement of the optical elements in the optical circulator 1 of the present embodiment as in FIG. 2, and the optical path of the light incident on the optical circulator 1 from the second port 32 is indicated by an arrow.

As shown in FIG. 3, the light incident on the optical circulator 1 from the second port 32 is incident on the optical circulator 1 from the second port 32, and then is different from the first beam displacer 11 side of the second beam displacer 12. It is incident on the opposite surface. As described above, the light incident on the second beam displacer 12 is divided into S-polarized light which is normal light and P-polarized light which is abnormal light in the second beam displacer 12. The light from the second port 32 is vertically incident on the surface of the second beam displacer 12, and the normal light travels straight through the second beam displacer 12 and is transmitted to the first beam displacer 11 side of the second beam displacer 12. Emit from the surface of. On the other hand, the abnormal light travels in the second beam displacer 12 in a direction away from the normal light and is transmitted, and is emitted from the surface of the second beam displacer 12 on the first beam displacer 11 side so that the traveling direction is parallel to the normal light. .. Therefore, the normal light and the abnormal light propagate to the first beam displacer 11 while the distance d2 between them remains substantially constant. As described above, the first beam displacer 11 and the second beam displacer 12 of the present embodiment have the same configuration, and the distance d2 is the same as the distance d1.

Each polarized light transmitted through the second beam displacer 12 is incident on the polarization rotator 22. In the polarization rotator 22, as described above, the polarization direction of the polarized light is rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light. Further, each polarized light transmitted through the polarizing rotator 22 is incident on the Faraday rotator 21. In the Faraday rotator 21, the polarization direction of the polarized light is rotated by 45 ° counterclockwise when viewed along the traveling direction of the polarized light as described above. Therefore, the polarized light that was S-polarized in the second beam displacer 12 is transmitted through the polarization rotator 22 and the Faraday rotator 21 to return to the original polarization direction and become S-polarized light, and is incident on the first beam displacer 11. Further, the polarized light that was P-polarized light in the second beam displacer 12 also returns to the original polarization direction by passing through the polarization rotator 22 and the Faraday rotator 21, becomes P-polarized light, and is incident on the first beam displacer 11.

The first beam displacer 11 has the same configuration as the second beam displacer 12 as described above, and is arranged parallel to the second beam displacer 12. Therefore, the light that was normal light in the second beam displacer 12 becomes normal light in the first beam displacer 11 and travels straight through. Further, the light that was abnormal light in the second beam displacer 12 becomes abnormal light in the first beam displacer 11 and is refracted and transmitted in the same manner as the abnormal light in the second beam displacer 12. As a result, the polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side is opposite to each other on the surface of the first beam displacer 11 opposite to the second beam displacer 12 side. The distance d3 of is increased and the light is emitted. Since the first beam displacer 11 and the second beam displacer 12 of the present embodiment have the same configuration as described above, this distance d3 is twice the above distance d2.

Each of the polarized light transmitted through the first beam displacer 11 propagates to the third beam displacer 13 with the mutual distance d3 being substantially constant, and is incident on the surface of the third beam displacer 13 on the first beam displacer 11 side. As described above, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of the present embodiment refer to a plane between the first beam displacer 11 and the third beam displacer 13. It is symmetric. Therefore, the propagation direction of the abnormal light in the third beam displacer 13 and the propagation direction of the abnormal light in the first beam displacer 11 are symmetrical with respect to the plane between the first beam displacer 11 and the third beam displacer 13. .. Therefore, the abnormal light incident on the surface of the third beam displacer 13 on the first beam displacer 11 side is refracted in a direction approaching normal light and passes through the third beam displacer 13. Further, the thickness of the third beam displacer 13 of the present embodiment is twice the thickness of the first beam displacer 11. Therefore, the distance that the normal light and the abnormal light approach each other while propagating through the third beam displacer 13 is equal to the distance d3 that is separated in the first beam displacer 11 and the second beam displacer 12. As a result, the respective polarized light incident on the surface of the third beam displacer 13 on the first beam displacer 11 side overlaps and emits on the surface of the third beam displacer 13 opposite to the first beam displacer 11 side.

The polarized light that has passed through the third beam displacer 13 and overlapped with each other is emitted from the third port 33 to the outside of the optical circulator 1. As described above, the light incident on the optical circulator 1 from the second port 32 is emitted from the third port 33 to the outside of the optical circulator 1.

The light emitted from the third port 33 is incident on one end of the delivery fiber 53, is emitted from the other end of the delivery fiber 53, and is irradiated on an object to be processed or the like.

A part of the return light reflected by the surface of the object to be processed and returned to the delivery fiber 53 may be incident on the optical circulator 1 from the third port 33.

FIG. 4 shows the arrangement of the optical elements in the optical circulator 1 of the present embodiment as in FIG. 2, and the optical path of the light incident on the optical circulator 1 from the third port 33 is indicated by an arrow.

As shown in FIG. 4, the light incident on the optical circulator 1 from the third port 33 is incident on the optical circulator 1 from the third port 33, and then is different from the first beam displacer 11 side of the third beam displacer 13. It is incident on the opposite surface. The light incident on the third beam displacer 13 in this way is divided into S-polarized light which is normal light and P-polarized light which is abnormal light in the third beam displacer 13. The light from the third port 33 is vertically incident on the surface of the third beam displacer 13, and the normal light travels straight through the third beam displacer 13 and is transmitted to the first beam displacer 11 side of the third beam displacer 13. Emit from the surface of. On the other hand, the abnormal light travels in the third beam displacer 13 in a direction away from the normal light and is transmitted, and is emitted from the surface of the third beam displacer 13 on the first beam displacer 11 side so that the traveling direction is parallel to the normal light. ..

Each polarized light transmitted through the third beam displacer 13 propagates to the first beam displacer 11 while the distance d4 from each other remains substantially constant, and is incident on one surface of the first beam displacer 11. As described above, the optical axis OA3 of the third beam displacer 13 and the optical axis OA1 of the first beam displacer 11 of the present embodiment refer to a plane between the first beam displacer 11 and the third beam displacer 13. It is symmetric. Therefore, the propagation direction of the abnormal light in the third beam displacer 13 and the propagation direction of the abnormal light in the first beam displacer 11 are symmetrical with respect to the plane between the first beam displacer 11 and the third beam displacer 13. .. Therefore, the abnormal light incident on one surface of the first beam displacer 11 is refracted in a direction approaching normal light and passes through the first beam displacer 11. Further, the thickness of the first beam displacer 11 of the present embodiment is ½ of the thickness of the third beam displacer 13. Therefore, the distance that the abnormal light and the normal light approach each other while propagating through the first beam displacer 11 is half of the distance d4 separated in the third beam displacer 13. As a result, the respective polarized light incident on one surface of the first beam displacer 11 is emitted from the other surface of the first beam displacer 11 while being separated from each other by a distance d5 which is half of the distance d4.

Each polarized light transmitted through the first beam displacer 11 is incident on the Faraday rotator 21. In the Faraday rotator 21, the polarization direction of the polarized light is rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light as described above. Further, each polarized light transmitted through the Faraday rotator 21 is incident on the polarization rotator 22. In the polarization rotator 22, the polarization direction of the polarized light is further rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light as described above. Therefore, the polarized light that was S-polarized in the first beam displacer 11 is rotated by 90 ° in the polarization direction by passing through the Faraday rotator 21 and the polarization rotator 22, becomes P-polarized light, and is incident on the second beam displacer 12. .. Further, the polarized light that was P-polarized light in the first beam displacer 11 is transmitted by the Faraday rotator 21 and the polarization rotator 22 so that the polarization direction is rotated by 90 °, becomes S-polarized light, and is incident on the second beam displacer 12. ..

The second beam displacer 12 has the same configuration as the first beam displacer 11 as described above, and is arranged parallel to the first beam displacer 11. Therefore, the light that was abnormal light in the first beam displacer 11 becomes normal light in the second beam displacer 12 and travels straight through. Further, the light that was normal light in the first beam displacer 11 becomes abnormal light in the second beam displacer 12, and is refracted and transmitted in the same manner as the abnormal light in the first beam displacer 11. As a result, the respective polarized light incident on the surface of the second beam displacer 12 on the first beam displacer 11 side has a larger distance from each other on the surface of the second beam displacer 12 opposite to the first beam displacer 11 side. It emits. The distance d6 between the polarized lights after passing through the second beam displacer 12 is the same as the distance d4.

The polarized light that has passed through the second beam displacer 12 apart from each other is irradiated to the inner surface of the housing 10 without reaching the second port 32. It is preferable that the light absorbing member is arranged on the inner surface of the housing 10 where the polarized light is irradiated in this way. As described above, the light incident on the optical circulator 1 from the third port 33 is suppressed from being emitted to the outside of the optical circulator 1. Therefore, even if the return light is incident on the optical circulator 1 from the third port 33, it can be suppressed that the return light reaches the signal light source MO or the excitation light source 7.

As described above, the optical circulator 1 of the present embodiment is a first beam displayer composed of a first port 31, a second port 32 and a third port 33 to which light from the outside is incident, and a birefringent crystal. 11. A second beam displacer 12 and a third beam displacer 13, and a Faraday rotator 21 and a polarizing rotator 22 arranged between the first beam displacer 11 and the second beam displacer 12. Further, the polarized light incident on the first beam displacer 11 from the first port 31 and separated from each other is refracted so that the polarization directions are rotated by the Faraday rotator 21 and the polarization rotator 22 and overlap with each other in the second beam displacer 12. Then, it exits from the second port 32. Further, the polarized light incident on the second beam displacer 12 from the second port 32 and separated from each other is further separated from each other in the first beam displacer 11 by rotating the polarization direction in the polarizing rotator 22 and the Faraday rotator 21. The third beam displacer 13 is refracted so as to overlap each other, and is emitted from the third port 33.

As described above, in the optical circulator 1 of the present embodiment, the light incident from the first port 31 is emitted from the second port 32, and the light incident from the second port 32 is emitted from the third port 33. Further, the optical circulator 1 of the present embodiment does not need to use a cube-type polarizing beam splitter, and uses a beam displacer composed of birefringent crystals. Such a beam displacer can be easily miniaturized, and the Faraday rotator 21 and the like can also be miniaturized according to the size of the beam displacer. Therefore, the optical circulator 1 of the present embodiment can be reduced in size as well as the manufacturing cost can be suppressed. Further, since each beam displacer included in the optical circulator 1 of the present embodiment can be configured without using an adhesive, heat generation due to light incident on each beam displacer can be suppressed. Therefore, each beam displacer included in the optical circulator 1 of the present embodiment can cope with high output light. The high-output light is, for example, light having an average output power or energy of 300 W or more. Since each beam displacer included in the optical circulator 1 can cope with high output light, the optical circulator 1 has, for example, a peak power of 2 kW or more, preferably 7 kW or more, of the laser light emitted from the laser apparatus 100. It can also be applied when. Therefore, the optical circulator 1 can be applied to a processing laser device that outputs light to the outside of the laser device. Further, for example, the wavelength of the laser light emitted to the outside by the laser device 100 is a single wavelength.

Further, by making each beam displacer provided in the optical circulator 1 of the present embodiment correspond to high output light as described above, the power density of the light incident on each beam displacer is increased to increase the beam diameter of the light. It can be made smaller. The smaller the beam diameter of the light incident on the beam displacer, the smaller the distance between the polarized light separated from each other in the beam displacer. For example, as shown in FIG. 4, in order to suppress the light incident on the optical circulator 1 from the third port 33 from being emitted from the second port 32 to the outside of the optical circulator 1, the distance d6 is the second beam displacer 12 It is preferable that the beam diameter is sufficiently large for each polarized light transmitted through the light beam. In order to make the distance d6 sufficiently large, it is preferable that the distances d4 and d5 are sufficiently large with respect to the beam diameter of the polarized light transmitted through the respective beam displacers. The distance d5 is preferably, for example, twice or more the diameter of the polarized light transmitted through the first beam displacer 11. Thus, the preferred distance between the polarized lights depends on the beam diameter of the polarized light. Therefore, the smaller the beam diameter of the polarized light, the smaller the distances d4, d5, and d6 between the polarized lights may be, and the smaller the beam displacer may be. By miniaturizing each beam displacer included in the optical circulator 1, the optical circulator 1 can be further miniaturized.

Further, in the optical circulator 1 of the present embodiment, the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is equal to the thickness of the third beam displacer 13. The change in the distance between each polarized light propagating through the beam displacer may depend on the thickness of the beam displacer. By selecting the thickness of each beam displacer as described above, the distance between the polarized light incident from the second port 32 and separated from each other in the second beam displacer 12 and the first beam displacer 11 and the first In the 3-beam displacer 13, it becomes easy to make the distance at which the polarized lights are brought close to each other the same. Therefore, the polarized light incident from the second port 32 and separated from each other in the second beam displacer 12 and the first beam displacer 11 is likely to be overlapped with each other in the third beam displacer 13.

Further, in the optical circulator 1 of the present embodiment, the distance d3 between the polarized light incident on the second beam displacer 12 from the second port 32 and being separated from each other when passing through the first beam displacer 11 is the respective distance d3. The polarization of the light is equal to the distance that they can approach each other when they pass through the third beam displacer 13. By equalizing the distance d3 between the polarized lights separated from each other in the second beam displacer 12 and the first beam displacer 11 and the distance between the polarized lights being brought close to each other in the third beam displacer 13, the polarized lights are separated from each other in the third beam displacer 13. At 13, it becomes easy to overlap with each other. Therefore, the beam diameter of the light emitted from the third port 33 can be reduced, and the light can be easily emitted from the third port 33.

Further, in the optical circulator 1 of the present embodiment, the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 are equal to each other. Therefore, it becomes easy to make the distance between the polarized lights incident from the first port 31 and separated from each other in the first beam displacer 11 and the distance between the polarized lights in the second beam displacer 12 close to each other. Therefore, the polarized light incident from the first port 31 and separated from each other in the first beam displacer 11 is likely to be overlapped with each other in the second beam displacer 12. Further, by selecting the thickness of the first beam displacer 11 and the second beam displacer 12 in this way, the first beam displacer 11 and the second beam displacer 12 can be configured by the same beam displacer. Therefore, the configuration of the optical circulator 1 can be simplified. Further, when the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is the same as the thickness of the third beam displacer 13 as described above, the beam displacer constituting the first beam displacer 11 is further formed. The third beam displacer 13 can be configured by using two beam displacers similar to the above. That is, the first beam displacer 11, the second beam displacer 12, and the third beam displacer 13 can all be configured by the same beam displacer. Therefore, the configuration of the optical circulator 1 can be simplified. However, even if the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is the same as the thickness of the third beam displacer 13, the third beam displacer 13 is a single beam displacer. It may be configured. In this case, the number of beam displacers used can be reduced as compared with the case where the third beam displacer 13 is configured by the two beam displacers as described above.

Further, in the optical circulator 1 of the present embodiment, the first port 31 has a first mirror 31 m. By having at least one of the first port 31, the second port 32, and the third port 33 having a mirror in this way, it becomes easy to guide the light to a desired position, and the degree of freedom in designing the optical circulator 1 can be improved. ..

Further, the first mirror 31m is provided so as to be adjacent to the first beam displacer 11 and is arranged at a position sandwiched between the light paths of the respective polarized light transmitted through the first beam displacer 11 at a distance from each other. In this way, the mirrors of either port are provided next to each other with either beam displacer, and are sandwiched between the optical paths of the respective polarized lights that transmit the mirror and the beam displacers adjacent to each other apart from each other. It is preferable to be arranged in. By arranging the mirror in this way, the extra space formed in the optical circulator 1 can be utilized, and the optical circulator 1 can be further miniaturized.

(Second Embodiment)
Next, the second embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components as those in the first embodiment are designated by the same reference numerals and duplicated description will be omitted unless otherwise specified.

FIG. 5 is a diagram schematically showing the configuration of the laser apparatus according to the second embodiment of the present invention. The laser apparatus 200 of the present embodiment shown in FIG. 5 includes a signal light source MO, an optical circulator 2 of the second embodiment, a first amplifier AM1, and a second amplifier AM2 as main components. The optical circulator 2 has a different configuration from the optical circulator 1 of the first embodiment as described later. Further, the second amplifier AM2 has the same configuration as the first amplifier AM1 except for the arrangement.

FIG. 6 is a diagram showing the arrangement of optical elements in the optical circulator according to the second embodiment of the present invention. As shown in FIG. 6, the optical circulator 2 of the present embodiment further includes a fourth beam displacer 14 and a fourth port 34, in that the second port 32 has a second mirror 32m and a second opening 32h. It is different from the optical circulator 1 of the first embodiment.

The fourth beam displacer 14 is arranged on the side opposite to the first beam displacer 11 side of the second beam displacer 12, and is composed of parallel plate type birefringent crystals. The fourth beam displacer 14 of the present embodiment has the same configuration as the third beam displacer 13, and is arranged in parallel with the third beam displacer 13. That is, the optical axis OA4 of the fourth beam displacer 14 of the present embodiment is parallel to the optical axis OA3 of the third beam displacer 13, and the thickness of the fourth beam displacer 14 of the present embodiment is that of the third beam displacer 13. Same as thickness. That is, the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is equal to the thickness of the fourth beam displacer 14. By adjusting one or both of the thicknesses of the optical axis OA4 of the fourth beam displacer 14 and the thickness of the fourth beam displacer 14, the distance between the normal light and the abnormal light can be adjusted in the fourth beam displacer 14.

The fourth port 34 is provided on the side opposite to the second beam displacer 12 side of the fourth beam displacer 14. The fourth port 34 of the present embodiment is an opening formed in the housing 10. One end of the delivery fiber 53 is connected to the fourth port 34.

The second port 32 of the present embodiment has a second opening 32h and a second mirror 32m formed in the housing 10. One end of the optical fiber 52 is connected to the second opening 32h. The second mirror 32m of the present embodiment is a total reflection mirror, and the light incident on the housing 10 from the second opening 32h is totally reflected by the second mirror 32m, and the first beam displacer 11 of the second beam displacer 12 It is incident on the surface opposite to the side.

Further, one end of the optical fiber 55 is connected to the third port 33 of the present embodiment. The optical fiber 55 is an optical fiber having the same structure as the optical fiber 52.

Next, the operation of the laser device 200 of this embodiment will be described.

First, similarly to the laser device 100 of the first embodiment, excitation light is emitted from each laser diode 71 of the excitation light source 7 of the first amplifier AM1, and the excitation light is the light amplification glass of the first amplifier AM1. It propagates through the body 4 and excites the active element added to the light amplification glass body 4. Further, the excitation light is also emitted from each laser diode 71 of the excitation light source 7 of the second amplifier AM2, and the excitation light propagates through the optical amplification glass body 4 of the second amplifier AM2 and the optical amplification glass body. Exciting the active element added to 4.

On the other hand, signal light is emitted from the signal light source MO, and the signal light is incident on the optical circulator 1 from the first port 31 via the signal optical fiber 51.

In FIG. 6, the optical path of the light incident on the optical circulator 2 from the first port 31 in the optical circulator 2 is indicated by an arrow.

As shown in FIG. 6, the path of light incident on the optical circulator 2 from the first port 31 is the same as that of the optical circulator 1 of the first embodiment until it passes through the second beam displacer 12. The polarized light that has passed through the second beam displacer 12 and overlapped with each other is totally reflected by the second mirror 32m and emitted from the second opening 32h to the outside of the optical circulator 2. As described above, the light incident on the optical circulator 1 from the first port 31 is emitted from the second port 32 to the outside of the optical circulator 2.

The signal light emitted from the second port 32 propagates through the optical amplification glass body 4 and is amplified, and is incident on the optical circulator 2 again from the second port 32, similarly to the laser device 100 of the first embodiment.

FIG. 7 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of the light incident on the optical circulator 2 from the second port 32 is indicated by an arrow.

As shown in FIG. 7, the light incident on the optical circulator 2 from the second port 32 is totally reflected by the second mirror 32m after being incident on the optical circulator 2 from the second opening 32h, and the second beam displacer 12 It is incident on the surface opposite to the first beam displacer 11 side of the above. The subsequent path of light is the same as that after the light from the second port 32 is incident on the second beam displacer 12 in the optical circulator 1 of the first embodiment. As described above, the light incident on the optical circulator 2 from the second port 32 is emitted from the third port 33 to the outside of the optical circulator 2.

The light emitted from the third port 33 is incident on one end of the optical fiber 55, emitted from the other end, and is incident on the second amplifier AM2. Similar to the first amplifier AM1, the second amplifier AM2 amplifies the incident light and reflects at least a part of the amplified light to the side where the light is incident. That is, the second amplifier AM2 amplifies the light emitted from the third port 33, and reflects at least a part of the amplified light toward the third port 33 side. The light reflected by the second amplifier AM2 is incident on the optical circulator 2 again from the third port 33.

FIG. 8 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of the light incident on the optical circulator 2 from the third port 33 is indicated by an arrow.

As shown in FIG. 8, the path of light incident on the optical circulator 2 from the third port 33 is the same as that of the optical circulator 1 of the first embodiment until it passes through the second beam displacer 12. Each polarized light transmitted through the second beam displacer 12 propagates to the fourth beam displacer 14 while the distance d6 is substantially constant, and is incident on the surface of the fourth beam displacer 14 on the second beam displacer 12 side. Further, the 4th beam displacer 14 has the same configuration as the 3rd beam displacer 13 as described above, and is arranged in parallel with the 3rd beam displacer 13. Therefore, the light that was abnormal light in the third beam displacer 13 becomes normal light in the fourth beam displacer 14 and travels straight through. Further, the light that was normal light in the third beam displacer 13 becomes abnormal light in the fourth beam displacer 14, and is refracted and transmitted in the same manner as the abnormal light in the third beam displacer 13. As a result, the respective polarized light incident on one surface of the fourth beam displacer 14 overlaps and emits on the other surface of the fourth beam displacer 14.

The polarized light that has passed through the fourth beam displacer 14 and overlapped with each other is emitted from the fourth port 34 to the outside of the optical circulator 2. As described above, the light incident on the optical circulator 2 from the third port 33 is emitted from the fourth port 34 to the outside of the optical circulator 2.

The light emitted from the fourth port 34 is incident on one end of the delivery fiber 53, is emitted from the other end of the delivery fiber 53, and is irradiated on an object to be processed or the like.

A part of the return light reflected by the surface of the object to be processed and returned to the delivery fiber 53 may be incident on the optical circulator 2 from the fourth port 34.

FIG. 9 shows the arrangement of the optical elements in the optical circulator 2 of the present embodiment as in FIG. 6, and the optical path of the light incident on the optical circulator 2 from the fourth port 34 is indicated by an arrow.

As shown in FIG. 9, the light incident on the optical circulator 2 from the fourth port 34 is incident on the optical circulator 2 from the fourth port 34, and then is different from the second beam displacer 12 side of the fourth beam displacer 14. It is incident on the opposite surface. The light incident on the 4th beam displacer 14 in this way is divided into S-polarized light which is normal light and P-polarized light which is abnormal light in the 4th beam displacer 14. The light from the fourth port 34 is vertically incident on the surface of the fourth beam displacer 14 opposite to the second beam displacer 12 side, and the ordinary light travels straight through the fourth beam displacer 14 and is transmitted to the second beam. The light is emitted from the surface of the 4-beam displacer 14 on the second beam displacer 12 side. On the other hand, the abnormal light travels in the fourth beam displacer 14 in a direction away from the normal light and is transmitted, and is emitted from the surface of the fourth beam displacer 14 on the second beam displacer 12 side so that the traveling direction is parallel to the normal light. ..

Each of the polarized light transmitted through the fourth beam displacer 14 propagates to the second beam displacer 12 while the distance d7 from each other remains substantially constant, and reaches the surface of the second beam displacer 12 opposite to the first beam displacer 11 side. Incident. The optical axis OA2 of the second beam displacer 12 and the optical axis OA4 of the fourth beam displacer 14 of the present embodiment are symmetrical with respect to a plane intermediate between the second beam displacer 12 and the fourth beam displacer 14. Therefore, the propagation direction of the abnormal light in the second beam displacer 12 and the propagation direction of the abnormal light in the fourth beam displacer 14 are symmetrical with respect to the plane between the second beam displacer 12 and the fourth beam displacer 14. .. Therefore, the abnormal light incident on the second beam displacer 12 from the fourth beam displacer 14 side is refracted in a direction approaching normal light and passes through the second beam displacer 12. Further, the thickness of the second beam displacer 12 of the present embodiment is ½ of the thickness of the fourth beam displacer 14. Therefore, the distance that the abnormal light and the normal light approach each other while propagating through the second beam displacer 12 is half of the distance d7 in which the polarized lights are separated from each other in the fourth beam displacer 14. As a result, the respective polarized light incident on the surface of the second beam displacer 12 opposite to the first beam displacer 11 side is the surface on the first beam displacer 11 side while being separated from each other by the distance d8, which is half of the distance d7. Emit from.

Each polarized light transmitted through the second beam displacer 12 is incident on the polarization rotator 22. In the polarization rotator 22, as described above, the polarization direction of the polarized light is rotated by 45 ° clockwise when viewed along the traveling direction of the polarized light. Further, each polarized light transmitted through the polarizing rotator 22 is incident on the Faraday rotator 21. In the Faraday rotator 21, the polarization direction of the polarized light is rotated by 45 ° counterclockwise when viewed along the traveling direction of the polarized light as described above. Therefore, the polarized light that was S-polarized in the second beam displacer 12 is transmitted through the polarization rotator 22 and the Faraday rotator 21 to return to the original polarization direction and become S-polarized light, and is incident on the first beam displacer 11. Further, the polarized light that was P-polarized light in the second beam displacer 12 also returns to the original polarization direction by passing through the polarization rotator 22 and the Faraday rotator 21, becomes P-polarized light, and is incident on the first beam displacer 11.

The first beam displacer 11 has the same configuration as the second beam displacer 12 as described above, and is arranged parallel to the second beam displacer 12. Therefore, the light that was normal light in the second beam displacer 12 becomes normal light in the first beam displacer 11 and travels straight through. Further, the light that was abnormal light in the second beam displacer 12 becomes abnormal light in the first beam displacer 11 and is refracted and transmitted in the same manner as the abnormal light in the second beam displacer 12. As a result, the polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side is opposite to each other on the surface of the first beam displacer 11 opposite to the second beam displacer 12 side. The distance is reduced and the light is emitted. The total of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 of the present embodiment is the same as the thickness of the fourth beam displacer 14. Therefore, in the 4th beam displacer 14, the distance d7 where the polarized light is separated, the distance where the polarized light approaches each other while propagating in the 2nd beam displacer 12, and the respective polarized light while propagating in the 1st beam displacer 11. The total distance to approach each other is the same. Therefore, the respective polarized light incident on the surface of the first beam displacer 11 on the second beam displacer 12 side overlaps and emits on the surface of the first beam displacer 11 opposite to the second beam displacer 12 side.

The polarized light that has passed through the first beam displacer 11 and overlapped with each other is totally reflected by the first mirror 31m and emitted from the first opening 31h to the outside of the optical circulator 2. As described above, the light incident on the optical circulator 2 from the fourth port 34 is emitted from the first port 31 to the outside of the optical circulator 2.

From the viewpoint of suppressing the light emitted from the first port 31 to the outside of the optical circulator 2 from entering the signal light source MO as described above, the signal light source MO and the first port 31 of the optical circulator 2 are separated from each other. It is preferable to arrange an isolator (not shown).

As described above, in the laser apparatus 200 of the present embodiment, the signal light emitted by the signal light source MO is amplified by the optical amplification glass body 4 of the first amplifier AM1 and then for optical amplification of the second amplifier AM2. It is further amplified in the glass body 4.

Further, the optical circulator 2 of the present embodiment is a fourth beam composed of a fourth port 34 on which light from the outside is incident and a birefringent crystal in which light incident on the optical circulator 2 from the fourth port 34 is incident. A displacer 14 is provided. Further, in the optical circulator 2 of the present embodiment, the polarized light incident on the fourth beam displacer 14 from the fourth port 34 and separated from each other is incident on the second beam displacer 12 and brought close to each other, and the Faraday rotator 21 is used. And in the polarization rotator 22, the polarization direction is rotated, and in the first beam displacer 11, it is refracted so as to overlap each other and is ejected from the first port 31. By providing the optical circulator 2 with the fourth port 34 and the fourth beam displacer 14 as described above, a 4-port type optical circulator 2 in which the light incident from the fourth port 34 is emitted from the first port 31 can be obtained. ..

Further, in the optical circulator 2 of the present embodiment, the polarized light incident on the third beam displacer 13 from the third port 33 and separated from each other is incident on the first beam displacer 11 and brought close to each other, and the Faraday rotator 21 is used. And in the polarization rotator 22, the polarization direction is rotated, and in the second beam displacer 12, they are further separated from each other, and in the fourth beam displacer 14, they are refracted so as to overlap each other at least partially and are ejected from the fourth port 34. By configuring the optical circulator 2 in this way, as described above, a 4-port type optical circulator 2 in which the light incident from the third port 33 is emitted from the fourth port 34 can be obtained.

Further, in the optical circulator 2 of the present embodiment, the distance d7 between the polarized light incident on the fourth beam displacer 14 from the fourth port 34 and being separated from each other when passing through the fourth beam displacer 14 is the respective distance d7. Is equal to the sum of the distances that the polarized lights of the above are brought close to each other when they pass through the second beam displacer 12 and the distance that the respective polarized lights are brought close to each other when they pass through the first beam displacer 11. By equalizing the distance d7 between the polarized lights separated from each other in the fourth beam displacer 14 and the distance between the polarized lights being brought close to each other in the second beam displacer 12 and the first beam displacer 11, the polarized lights are overlapped with each other. It becomes easy to be. Therefore, the beam diameter of the light emitted from the first port 31 can be reduced, and the light can be easily emitted from the first port 31.

Further, in the optical circulator 2 of the present embodiment, the sum of the thickness of the first beam displacer 11 and the thickness of the second beam displacer 12 is equal to the thickness of the fourth beam displacer 14. As described above, the change in the distance between each polarized light propagating through the beam displacer may depend on the thickness of the beam displacer. Therefore, by selecting the thicknesses of the first beam displacer 11, the second beam displacer 12, and the fourth beam displacer 14 as described above, they are incident from the fourth port 34 and separated from each other in the fourth beam displacer 14. Each polarized light passes through the second beam displacer 12 and the first beam displacer 11 and easily overlaps with each other.

Although the present invention has been described above by exemplifying embodiments, the present invention is not limited to these embodiments.

For example, the orientation and thickness of the optical axes of the first beam displacer 11, the second beam displacer 12, the third beam displacer 13, and the fourth beam displacer 14 are described in the description of the first embodiment and the second embodiment. It is not limited to the illustrated form. For example, in the first embodiment, the first beam displacer 11 and the first beam displacer 11 and the polarized light incident on the first beam displacer 11 from the first port 31 and separated from each other at least partially overlap each other in the second beam displacer 12. The orientation and thickness of the optical axis of the second beam displacer 12 can be adjusted as appropriate. Further, the direction and thickness of the optical axis of the third beam displacer 13 are such that the polarized light incident on the second beam displacer 12 from the second port 32 is separated from each other and further separated from each other by the first beam displacer 11. The 3-beam displacer 13 may be appropriately adjusted within a range in which at least a part of the beam displacer 13 overlaps with each other. Further, in the second embodiment, the direction and thickness of the optical axis of the fourth beam displacer 14 are such that the polarized light incident on the fourth beam displacer 14 from the fourth port 34 and being separated from each other is the second beam displacer 12. And can be appropriately adjusted to the extent that it passes through the first beam displacer 11 and at least partially overlaps with each other.

Further, in the above embodiment, an example in which each beam displacer is composed of parallel plate type birefringent crystals has been described. However, the shape of each beam displacer is not limited to this. For example, the cross-sectional shape of each beam displacer may be a shape in which the entrance surface and the emission surface are non-parallel to each other, such as a wedge shape, or may be a parallelogram other than a rectangle.

Further, in the above embodiment, an example in which the light incident on each beam displacer is vertically incident on the surface of the beam displacer has been described. However, light may be incident non-perpendicularly to the surface of each beam displacer. For example, even if the shape or arrangement of each beam displacer is different from the above embodiment so that the light is intentionally incident on the beam displacer at a predetermined angle from the viewpoint of suppressing the reflection of the light emitted from the beam displacer. good.

Further, the position of the mirror is not particularly limited. Therefore, any of the first port 31, the second port 32, the third port 33, and the fourth port 34 may have a mirror. However, when a mirror is provided, it is preferable that the mirror is provided adjacent to at least one of the first beam displacer 11, the second beam displacer 12, the third beam displacer 13, and the fourth beam displacer 14. Further, it is preferable that the mirror is arranged between the optical path of at least two polarized light passing through the beam displacer adjacent to the mirror. The mirror may not be provided. When the port does not have a mirror, an optical fiber or the like may be provided in the port, and the light may be guided to the beam displacer by the optical fiber. For example, when the first port 31 does not have the first mirror 31m, the first port 31 has an optical fiber that guides the light emitted by the signal light source MO from the first opening 31h to one surface of the first beam displacer 11. Is preferable. In this case, the light incident from the first opening 31h propagates through the optical fiber and is guided to one surface of the first beam displacer 11.

Further, in the above embodiment, an example in which the mirror included in the port of the optical circulator is a total reflection mirror has been described. However, if the port of the optical circulator has a mirror, the mirror may be a partially reflective mirror that reflects some of the incident light and passes through the other. For example, the mirror included in the port of the optical circulator is a partially reflected mirror that transmits incident light by about 0.1%. When the port of the optical circulator has a partially reflected mirror in this way, the power of the light incident on the optical circulator can be indirectly observed by observing the light transmitted through the partially reflected mirror. For example, when the first mirror 31m of the first embodiment is a partially reflecting mirror, a part of the light incident on the optical circulator 1 from the first opening 31h passes through the first mirror 31m. The light transmitted through the first mirror 31m is guided to the inner surface of the housing 10 on the side opposite to the first opening 31h with the first mirror 31m interposed therebetween. By arranging a photodiode or the like having a light receiving surface at a position where the light transmitted through the first mirror 31 m reaches in this way, the power of the light incident on the optical circulator 1 from the first opening 31h is indirectly observed. be able to.

Further, in the above embodiment, an example in which the excitation light is incident on the optical amplification glass body 4 from the side opposite to the signal light has been described. However, the excitation light source may be configured so that the excitation light is incident on the optical amplification glass body 4 from the same side as the signal light.

Further, in the above embodiment, the example in which the first amplifier AM1 and the second amplifier AM2 have the same configuration has been described, but the first amplifier AM1 and the second amplifier AM2 may have different configurations from each other. .. Further, in the above embodiment, the configuration in which the first amplifier AM1 and the second amplifier AM2 reflect the signal light by the mirror 5 has been described, but it does not have to be a reflection type.

The optical circulator of the present invention is not limited to the usage examples shown in the above embodiments, and is also used, for example, for a reflected light monitor, an oscillation wavelength lock, a guide light combined wave, and the like. When the optical circulator of the present invention is used in a laser device, the laser device is not limited to the MOPA type fiber laser device, for example, a CW (continuous oscillation) type, a CO ₂ (carbon dioxide) laser, a YAG laser, or the like. It may be another laser device.

As described above, according to the present invention, an optical circulator that can be miniaturized is provided, and is used in fields such as fiber laser devices for high output applications, optical communication, and optical measurement.

1,2 ... Optical circulator 10 ... Housing 11 ... 1st beam displacer 12 ... 2nd beam displacer 13 ... 3rd beam displacer 14 ... 4th beam displacer 21 ... Faraday rotator 22 ... Polarized rotator 31 ... 1st port 31h ... 1st opening 31m ... 1st mirror 32 ... 2nd port 32h ... 2nd opening 32m ... 2nd Mirror 33 ... 3rd port 34 ... 4th port 100, 200 ... Laser device MO ... Signal light source AM1 ... 1st amplifier AM2 ... 2nd amplifier

Claims (16)

The first port where light from the outside enters and
A first beam displacer composed of a birefringent crystal to which light from the first port is incident, and
A second beam displacer composed of birefringent crystals arranged on the side opposite to the first port side of the first beam displacer.
A Faraday rotator and a polarizing rotator arranged between the first beam displacer and the second beam displacer,
A second port provided on the side of the second beam displacer opposite to the first beam displacer side, and
A third beam displacer composed of birefringent crystals arranged on the side opposite to the second beam displacer side of the first beam displacer.
A third port provided on the side of the third beam displacer opposite to the first beam displacer side,
Equipped with
The polarized light incident on the first beam displacer from the first port and separated from each other is rotated in the polarization direction by the Faraday rotator and the polarization rotator, and at least partially overlaps with each other in the second beam displacer. It is refracted and ejected from the second port.
The polarized light incident on the second beam displacer from the second port and separated from each other is rotated in the polarization direction in the polarization rotator and the Faraday rotator, further separated from each other in the first beam displacer, and at least from each other. An optical circulator characterized in that it is refracted by the third beam displacer so as to partially overlap and is emitted from the third port. The distance between the polarized light incident on the second beam displacer from the second port and separated from each other when they pass through the first beam displacer is the distance between them when the polarized light passes through the third beam displacer. The optical circulator according to claim 1, wherein the optical circulator is substantially equal to a distance close to each other. The optical axis of the first beam displacer and the optical axis of the second beam displacer are parallel to each other.
Claim 1 is characterized in that the optical axis of the third beam displacer and the optical axis of the first beam displacer are symmetrical with respect to a plane intermediate between the first beam displacer and the third beam displacer. Or the optical circulator according to 2. The one according to any one of claims 1 to 3, wherein the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is substantially equal to the thickness of the third beam displacer. Optical circulator. The optical circulator according to any one of claims 1 to 4, wherein the thickness of the first beam displacer and the thickness of the second beam displacer are substantially equal to each other. The optical circulator according to any one of claims 1 to 5, wherein at least one of the first port, the second port, and the third port has a mirror. The mirror is provided adjacent to at least one of the first beam displacer, the second beam displacer, and the third beam displacer.
The optical circulator according to claim 6, wherein the mirror is arranged between an optical path of at least two polarized light passing through a beam displacer adjacent to the mirror. A fourth beam displacer composed of birefringent crystals arranged on the side opposite to the first beam displacer side of the second beam displacer.
A fourth port provided on the side of the fourth beam displacer opposite to the second beam displacer side, and
Further prepare
The polarized light incident on the fourth beam displacer from the fourth port and separated from each other is incident on the second beam displacer and brought close to each other, and the polarization direction is rotated in the Faraday rotator and the polarization rotator. The optical circulator according to any one of claims 1 to 6, wherein the first beam displacer is refracted so as to be at least partially overlapped with each other and emitted from the first port. The polarized light incident on the third beam displacer from the third port and separated from each other is incident on the first beam displacer and brought close to each other, and the polarization direction is rotated in the Faraday rotator and the polarization rotator. The optical circulator according to claim 8, wherein the optical circulator is further separated from each other in the second beam displacer, refracted so as to be at least partially overlapped with each other in the fourth beam displacer, and emitted from the fourth port. The distance between each polarized light incident on the fourth beam displacer from the fourth port and separated from each other when passing through the fourth beam displacer is the distance between each polarized light when the polarized light passes through the second beam displacer. The optical circulator according to claim 8 or 9, wherein the distances brought close to each other and the respective polarizations are substantially equal to the sum of the distances brought close to each other when passing through the first beam displacer. The optical circulator according to any one of claims 8 to 10, wherein the optical axis of the fourth beam displacer is parallel to the optical axis of the third beam displacer. The one of claims 8 to 11, wherein the sum of the thickness of the first beam displacer and the thickness of the second beam displacer is substantially equal to the thickness of the fourth beam displacer. Optical circulator. The optical circulator according to any one of claims 8 to 12, wherein the fourth port has a mirror. 13. The optical circulator according to claim 13, wherein the mirror is provided adjacent to the fourth beam displacer and is arranged between at least two polarized light paths passing through the fourth beam displacer. The optical circulator according to any one of claims 1 to 7.
A signal light source that emits light incident on the first port of the optical circulator, and
A first amplifier that amplifies the light emitted from the second port and incidents at least a part of the amplified light onto the second port.
Equipped with
The optical circulator is a laser device characterized in that light incident from the first port is emitted from the second port and light incident from the second port is emitted from the third port. The optical circulator according to any one of claims 8 to 14,
A signal light source that emits light incident on the first port of the optical circulator, and
A first amplifier that amplifies the light emitted from the second port and reflects at least a part of the amplified light to the second port side.
A second amplifier that amplifies the light emitted from the third port and reflects at least a part of the amplified light to the third port side.
Equipped with
The optical circulator emits light incident from the first port from the second port, emits light incident from the second port from the third port, and emits light incident from the third port to the first port. A laser device characterized by emitting light from 4 ports.

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