JP2020088161A - Protective cap and laser device - Google Patents

Abstract

To provide a protective cap and a laser device having the same, capable of suppressing a characteristic deterioration caused by reflectance in the laser device.SOLUTION: The protective cap includes: a band pass filter 44 arranged being spaced from a light transmission columnar member 32 with an end face 21f of an optical fiber 21 propagating signal light with a predetermined wavelength optically coupled to one end face and on the other end face side of the light transmission columnar member 32 with an outside diameter larger than that of a core 21a of the optical fiber 21; and a stationary member 41 fixing a relative position between the band pass filter 44 and the light transmission columnar member 32. The band pass filter 44 suppresses the transmission of stimulated Raman scattering light generated from signal light at a higher rate than the signal light.SELECTED DRAWING: Figure 2

Description

The present invention relates to a protective cap and a laser device including the protective cap.

A fiber laser device is used in various fields such as a laser processing field and a medical field because it is excellent in light condensing property, has a high power density, and can obtain a light having a small beam spot.

The fiber laser device includes an amplification optical fiber in which an active element is added to a core. For example, the excitation light and the signal light propagate through the amplification optical fiber, whereby the active element is excited by the excitation light, and the signal light is amplified by the light spontaneously emitted from the active element. When the power of the signal light is increased in such an amplification optical fiber, a nonlinear optical effect such as stimulated Raman scattering may occur.

When the light including the stimulated Raman scattered light generated as described above is emitted from the laser device, a part of the stimulated Raman scattered light may be reflected by the irradiation target of the light and return to the laser device. Then, when the stimulated Raman scattered light returned to the laser device propagates to the light source of the laser device, the output of the laser device may be deteriorated or the characteristics may be deteriorated.

Therefore, Patent Document 1 below discloses an amplification optical fiber having a core with a filter function unit that increases the transmission loss of light generated by the nonlinear optical effect. The amplification optical fiber described in Patent Document 1 suppresses the propagation of the stimulated Raman scattered light by reflecting or scattering the stimulated Raman scattered light by the filter function unit.

JP, 2007-123477, A

However, even the laser device including the amplification optical fiber as described in Patent Document 1 may emit light including stimulated Raman scattered light. In this case, the reflected light including the stimulated Raman scattered light may enter the laser device, the stimulated Raman scattered light may propagate to the light source of the laser device, and the characteristics of the laser device may deteriorate.

Therefore, an object of the present invention is to provide a protective cap capable of suppressing characteristic deterioration due to reflected light in the laser device, and a laser device including the protective cap.

In order to solve the above problems, the protective cap of the present invention is such that the end face of an optical fiber that propagates a signal light of a predetermined wavelength is optically coupled to one end face, and the outer diameter is greater than the outer diameter of the core of the optical fiber. On the other end face side of the large light-transmitting columnar member, a bandpass filter arranged apart from the light-transmitting columnar member, and a fixing member for fixing the relative position of the bandpass filter and the light-transmitting columnar member. And the bandpass filter suppresses the transmission of the stimulated Raman scattered light generated from the signal light at a higher rate than that of the signal light.

The light that enters the bandpass filter from the light transmitting columnar member side may include signal light and stimulated Raman scattered light generated from the signal light. Here, the bandpass filter suppresses the transmission of the stimulated Raman scattered light generated from the signal light at a higher rate than that of the signal light. Therefore, while the signal light is transmitted through the bandpass filter, the stimulated Raman scattered light is suppressed from being transmitted through the bandpass filter and emitted. Further, even when the reflected light that passes through the bandpass filter from the light transmitting columnar member side and returns to the bandpass filter again includes stimulated Raman scattered light, the stimulated Raman scattered light passes through the bandpass filter. Is suppressed. Therefore, the stimulated Raman scattered light included in the reflected light can be suppressed from propagating to the light source of the laser device. Therefore, the protective cap including the bandpass filter can suppress characteristic deterioration due to reflected light in the laser device.

Further, it is preferable that the bandpass filter is planar and is arranged non-perpendicular to an optical axis of the signal light propagating through the light transmitting columnar member.

Since the planar bandpass filter is arranged non-perpendicularly to the optical axis of the signal light, part of the stimulated Raman scattered light that enters the bandpass filter from the light transmitting columnar member side is incident by the bandpass filter. It tends to be reflected in a direction different from the direction. Therefore, it becomes difficult for the stimulated Raman scattered light to return to the optical fiber. Further, the stimulated Raman scattered light reflected by the irradiation target of the light emitted from the laser device and returning to the bandpass filter is incident non-perpendicular to the bandpass filter and is easily reflected by the bandpass filter. Therefore, it is possible to further prevent the characteristics of the laser device from being deteriorated by the stimulated Raman scattered light.

Further, the protective cap further includes a plate-shaped substrate on which the bandpass filter is disposed on at least one surface, the plate-shaped substrate transmitting the signal light, and a plate-shaped light transmitting plate transmitting the signal light. The substrate and the light transmission plate are respectively arranged non-perpendicular to the optical axis of the signal light propagating in the light transmission columnar member, and the inclination direction of the substrate in a cross section overlapping the optical axis of the signal light. And the inclination directions of the light transmitting plate are preferably opposite to each other.

By disposing the substrate non-perpendicular to the optical axis of the signal light propagating through the light transmitting columnar member, the signal light is refracted when entering the substrate and when passing through the substrate and exiting from the substrate. Therefore, the optical axis of the signal light transmitted through the substrate deviates from the optical axis of the signal light before entering the substrate. Further, since the light transmitting plate is also arranged non-perpendicular to the optical axis of the signal light, the signal light is refracted when entering the light transmitting plate and when passing through the light transmitting plate and exiting from the light transmitting plate. .. However, in the cross section that overlaps the optical axis of the signal light, the tilt direction of the substrate and the tilt direction of the light transmission plate are opposite sides. Therefore, in the cross section that overlaps the optical axis of the signal light, the direction in which the optical axis deviates before and after passing through the substrate and the direction in which the optical axis deviates before and after passing through the light transmitting plate are opposite sides. Therefore, the shift of the optical axis of the signal light due to transmission through the substrate can be alleviated by the light transmitting plate.

Further, one of the protection filter including the substrate and the bandpass filter and the light transmission plate, which is arranged on the light transmission columnar member side, is a first light transmission plate, and the other is a second light transmission plate, and The thickness of the first light transmitting plate is d ₁ , the acute angle of inclination of the first light transmitting plate with respect to the plane perpendicular to the optical axis is θ _i , the refractive index of the first light transmitting plate is n ₁ , and the first light transmitting plate is the light transmitting columnar member side of the refractive index n _i of the medium 1 the light transmitting _plate, the thickness of the second light transmitting plate d _2, acute with respect to a plane perpendicular to the optical axis of the second light transmitting plate When the inclination angle is θ _m , the refractive index of the second light transmitting plate is n ₂ , and the refractive index of the medium between the second light transmitting plate and the first light transmitting plate is n _m , the following formula ( It is preferable that 1) holds.

The left side of the above equation (1) is twice the shift amount S ₁ of the optical axis of the signal light after passing through the first light transmitting plate with respect to the optical axis of the signal light before passing through the first light transmitting plate. .. Further, the right side of the above formula (1) is equal to the shift amount S ₂ of the optical axis of the signal light after passing through the second light transmitting plate with respect to the optical axis of the signal light before passing through the second light transmitting plate. Therefore, by arranging the first light transmitting plate and the second light transmitting plate so as to satisfy the above formula (1), the shift amount S ₂ of the optical axis of the signal light by the second light transmitting plate is equal to the first light transmitting plate. The shift amount of the optical axis of the signal light due to the transmission plate is less than twice the shift amount S ₁ . By the way, the direction in which the optical axis of the signal light is displaced by the second light transmitting plate and the direction in which the optical axis of the signal light is displaced by the first light transmitting plate are opposite to each other. Therefore, in the range where the above expression (1) is satisfied, even when the shift amount S ₂ is larger than the shift amount S ₁ , the second light transmitting plate is transmitted with respect to the optical axis of the signal light propagating through the light transmitting columnar member. The deviation amount |S ₂ −S ₁ | of the optical axis of the subsequent signal light is the deviation amount of the optical axis of the signal light after passing through the first light transmitting plate with respect to the optical axis of the signal light propagating in the light transmitting columnar member 32. It becomes smaller than S ₁ . Therefore, the deviation of the optical axis of the signal light due to transmission through the first light transmitting plate can be alleviated by the second light transmitting plate.

Further, it is preferable that the light transmitting plate suppresses transmission of stimulated Raman scattered light generated from the signal light at a higher rate than that of the signal light.

When the light transmission plate functions in the same manner as the bandpass filter, the stimulated Raman scattered light can be further suppressed from passing through the protective cap, and the characteristic deterioration due to the stimulated Raman scattered light can be further suppressed in the laser device.

Further, in order to solve the above problems, the laser device of the present invention has at least one light source that emits the signal light, the optical fiber that propagates the signal light, and an end face of the optical fiber is an optical face on one end face. And the light transmitting columnar member having an outer diameter larger than the outer diameter of the core of the optical fiber and the other end face side of the light transmitting columnar member, the light transmitting columnar member being arranged apart from the light transmitting columnar member. Any one of the above protective caps having a bandpass filter.

Since the protective cap described above can suppress characteristic deterioration of the laser device due to reflected light, the laser device of the present invention including any one of the above protective caps can suppress characteristic deterioration due to reflected light.

As described above, according to the present invention, there is provided a protective cap capable of suppressing characteristic deterioration due to reflected light in the laser device, and a laser device including the protective cap.

It is a conceptual diagram which shows the laser apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing which expands and shows a part of optical device shown in FIG. It is a figure which shows the transmittance|permeability spectrum of a protective filter, the energy of signal light, and the energy of stimulated Raman scattered light typically. It is a figure which shows a part of laser apparatus which concerns on 2nd Embodiment of this invention similarly to FIG. It is a figure which shows a part of laser apparatus which concerns on 3rd Embodiment of this invention similarly to FIG. It is a figure which expands a part of FIG. 5 and demonstrates the propagation path of signal light. It is a figure which shows the modification of the protection cap of FIG.

Hereinafter, preferred embodiments of a protective cap and a laser device according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, the configuration of the laser device of this embodiment will be described.

FIG. 1 is a conceptual diagram showing a laser device according to an embodiment of the present invention. As shown in FIG. 1, the laser device 1 of the present embodiment includes a plurality of light sources 10, an optical combiner 20, an optical fiber 21, and an optical device 30 as main components.

Each light source 10 is a laser device that emits signal light of a predetermined wavelength, and is, for example, a fiber laser device or a solid-state laser device. When the light source 10 is a fiber laser device, it may be a resonator type fiber laser device or a MO-PA (Master Oscillator Power Amplifier) type fiber laser device. The signal light emitted from each light source 10 is, for example, light having a wavelength of 1070 nm. The signal light is not limited to the light containing the signal.

An optical fiber 11 that propagates the signal light emitted from the light source 10 is connected to each light source 10. Each optical fiber 11 is, for example, a fumode fiber having a core diameter of about 20 μm. Therefore, the signal light emitted from each light source 10 propagates in each optical fiber 11 in the LP mode of about 2 to 4.

The optical combiner 20 is a member that connects the core of each optical fiber 11 and the core of the optical fiber 21. For example, each optical fiber 11 and the optical fiber 21 having a diameter larger than the optical fiber 11 are end-face connected. It will be done.

FIG. 2 is a sectional view showing a part of the optical device 30 shown in FIG. 1 in an enlarged manner. The optical device 30 shown in FIG. 2 includes a part of the optical fiber 21, a light transmitting columnar member 32, a housing 33, and a protective cap 40 as main components.

The optical fiber 21 included in the optical device 30 is a part of the optical fiber 21. However, the optical fiber 21 included in the optical device 30 may be another optical fiber having the same configuration as the optical fiber 21 optically coupled to the optical fiber 21. As shown in FIG. 2, the optical fiber 21 has a core 21a and a clad 21b surrounding the core 21a. A coating layer (not shown) is peeled off in a range of about 20 mm from the end face 21f at the end portion on the emission end side of the optical fiber 21 opposite to the light source 10 side. Further, the end face 21f of the optical fiber 21 is optically coupled to the light transmitting columnar member 32 by being fused to the central portion of one end face of the light transmitting columnar member 32 by, for example, an oxyhydrogen burner or the like. Such an optical fiber 21 is, for example, a multi-mode fiber in which the core 21a has a diameter of about 50 μm to 100 μm and the cladding 21b has an outer diameter of about 360 μm.

The light transmitting columnar member 32 is a columnar body that transmits the signal light propagating through the optical fiber 21. The light transmitting columnar member 32 of the present embodiment is a columnar body made of quartz. The light transmitting columnar member 32 is, for example, a columnar body made of quartz and having a diameter of 8 mm and a length of 23 mm. The light transmitting columnar member 32 has the incident surface 32b to which the end face 21f of the optical fiber 21 is optically coupled as described above and the emitting surface 32a from which the light incident from the optical fiber 21 is emitted. The incident surface 32b of the light transmitting columnar member 32 is larger than the outer diameter of the core 21a of the optical fiber 21. The incident surface 32b of the light transmitting columnar member 32 of this embodiment is larger than the end surface 21f of the optical fiber 21.

The housing 33 is a member that houses the light transmitting columnar member 32 and a part of the optical fiber 21. The housing 33 is formed in a tubular shape, and the light transmitting columnar member 32 and the optical fiber 21 are inserted therein. In the housing 33, the position of the light transmitting columnar member 32 is fixed by fixing the outer peripheral surface 32c to the inner peripheral surface of the housing 33 with an adhesive such as a silicone resin. A space 34 is formed between the inner peripheral surface of the housing 33 and the outer peripheral surface of the optical fiber 21. The space 34 may be filled with air or may be filled with a coolant that cools the optical fiber 21, the light transmitting columnar member 32, and the housing 33.

The housing 33 is preferably made of, for example, a metal such as copper having excellent thermal conductivity. The outer peripheral surface of the housing 33 may be water-cooled or air-cooled depending on the power of the light emitted from the laser device 1 or the like.

Next, the protective cap 40 will be described. The protective cap 40 of this embodiment includes a fixing member 41 and a protective filter 42.

The protection filter 42 of the present embodiment is arranged perpendicular to the optical axis of the signal light propagating through the light transmitting columnar member 32. Further, the protection filter 42 of this embodiment has a substrate 43, a bandpass filter 44, and an antireflection film 45.

The substrate 43 is a translucent plate that transmits signal light. The substrate 43 of this embodiment is a glass plate having a constant thickness.

The bandpass filter 44 of the present embodiment is formed on the surface of the substrate 43 opposite to the light transmissive columnar member 32 side. Therefore, the bandpass filter 44 of this embodiment has a planar shape. The bandpass filter 44 is a filter that suppresses the transmission of stimulated Raman scattered light generated from the signal light at a higher rate than that of the signal light. Therefore, the protection filter 42 suppresses the transmission of the stimulated Raman scattered light generated from the signal light at a higher rate than the signal light. Such a bandpass filter 44 is composed of, for example, a dielectric multilayer film.

FIG. 3 is a diagram schematically showing the transmittance spectrum of the protection filter 42, the energy of signal light emitted from the optical fiber 21, and the energy of stimulated Raman scattered light generated from the signal light and emitted from the optical fiber 21. The horizontal axis of FIG. 3 is the wavelength [nm], the transmittance [%] of the protective filter 42 is shown by a solid line, and the energy [a. u. ] Is indicated by a dashed-dotted line, and the energy [a. u. ] Is indicated by a broken line. As shown in FIG. 3, the protective filter 42 of the present embodiment has a transmittance of light having a wavelength of 1050 nm or more and 1090 nm or less of 95% or more, and a light of a wavelength of 900 nm or more and 1020 nm or less and a wavelength of 1110 nm or more and 1140 nm or less. The light transmittance is 10% or less. With such a property of the protection filter 42, the protection filter 42 can transmit the signal light and reflect the light having a wavelength different from that of the signal light. More specifically, the protection filter 42 transmits the signal light having a wavelength of about 1070 nm at a higher rate than the stimulated Raman scattered light having a wavelength of about 1125 nm. Therefore, the protective filter 42 generally reflects the stimulated Raman scattered light having a wavelength of 1070 nm. In the case where the light source 10 is a fiber laser device as described above, excess pump light having a wavelength of 915 nm or 970 nm emitted from the light source 10 propagates through the clad 21 b of the optical fiber 21 via the optical fiber 11. Even when the light is emitted from the light transmitting columnar member 32, the protection filter 42 generally reflects the excitation light. By suppressing the transmission of the excitation light through the protection filter 42 in this way, it is possible to suppress the deterioration of the beam quality of the light emitted from the laser device 1.

The antireflection film 45 is a film formed on the surface of the substrate 43 on the light transmitting columnar member 32 side to reduce the reflection of light on the surface of the protective filter 42. The antireflection film 45 is formed by, for example, a dielectric coating. By providing the antireflection film 45, the signal light incident on the protection filter 42 from the light transmitting columnar member 32 side easily passes through the protection filter 42. The antireflection film 45 is, for example, a film having a reflectance of 0.2% or less for light having a wavelength of 1050 nm or more and 1090 nm or less.

The fixing member 41 is a member that fixes the relative positions of the bandpass filter 44 and the light transmitting columnar member 32. For example, the protection filter 42 having the bandpass filter 44 formed on the surface is fixed to the fixing member 41, and the fixing member 41 is fixed to the housing 33 that fixes the light transmitting columnar member 32. The relative position to the light transmitting columnar member 32 is fixed. The fixing member 41 of the present embodiment is a cylindrical body in which at least a part of the protection filter 42 and the light transmitting columnar member 32 is arranged on the inner peripheral surface side. The protection filter 42 is fixed to the fixing member 41 with an adhesive such as silicone resin. Further, the fixing member 41 is fixed to the housing 33 by screwing a female screw formed on the inner peripheral surface of the fixing member 41 and a male screw formed on the outer peripheral surface of the housing 33. However, the method of fixing the fixing member 41 to the housing 33 is not limited to this, and the fixing member 41 may be fixed to the housing 33 with an adhesive or the like, for example. That is, the fixing member 41 may be detachably fixed to the housing 33, or may be fixed to the housing 33 in a non-removable state from the housing 33. Further, the protective filter 42 may be detachably fixed to the fixing member 41, or may be fixed to the fixing member 41 in a state in which it cannot be removed from the fixing member 41 as described above.

Such a fixing member 41 is preferably made of metal such as stainless steel, iron, and aluminum plated with nickel. Since the fixing member 41 is made of metal, the heat resistance of the fixing member 41 can be improved. Further, when the fixing member 41 is made of aluminum plated with nickel, the strength of the fixing member 41 can be increased. Further, the inner peripheral surface of the fixing member 41 is preferably subjected to black alumite processing treatment or the like in order to suppress reflection of light.

Next, the operation and action of the laser device 1 of this embodiment will be described.

The signal light of a predetermined wavelength emitted from each light source 10 propagates through the optical fiber 11, is combined by the optical combiner 20, and enters the optical device 30 through the optical fiber 21. The signal light incident on the optical device 30 mainly propagates through the core 21 a of the optical fiber 21 and enters the light transmitting columnar member 32. The signal light incident on the light transmitting columnar member 32 propagates in the light transmitting columnar member 32 while spreading according to the numerical aperture, and is emitted from the emitting surface 32a. The signal light emitted from the emission surface 32 a passes through the protection filter 42 and is emitted from the optical device 30. The signal light emitted from the optical device 30 is condensed by a processing head (not shown) and is irradiated onto the irradiation target. The light applied to the irradiation target becomes heat by being absorbed by the irradiation target and contributes to the processing.

However, a part of the light emitted to the irradiation target object is reflected by the surface of the irradiation target object and becomes reflected light. Further, some of the reflected light may enter the optical device 30 again. The reflected light thus entering the optical device 30 first enters the protective filter 42. Since the protective filter 42 suppresses the transmission of the stimulated Raman scattered light as described above, the stimulated Raman scattered light can propagate to the light source 10 of the laser device 1 even when the reflected light includes the stimulated Raman scattered light. Can be suppressed.

The light that enters the protective filter 42 from the light transmitting columnar member 32 side may also include the stimulated Raman scattered light, and when the protective filter 42 reflects the light including the stimulated Raman scattered light to the light transmitting columnar member 32 side, A part of the stimulated Raman scattered light may enter the optical fiber 21. However, the stimulated Raman scattered light reflected by the protection filter 42 in this way becomes the stimulated Raman scattered light included in the light reflected by the irradiation target of the light emitted from the laser device 1, as described below. It is considered that the influence on the characteristics of the laser device 1 is slight in comparison.

The light incident on the incident surface 32b of the light transmitting columnar member 32 from the core 21a of the optical fiber 21 propagates while spreading in the light transmitting columnar member 32 and is emitted from the emitting surface 32a of the light transmitting columnar member 32 as described above. To do. The protective filter 42 is disposed on the light emitting surface 32a side of the light transmitting columnar member 32, so that the light emitted from the light emitting surface 32a of the light transmitting columnar member 32 is substantially incident on the protective filter 42. Therefore, as described above, a part of the stimulated Raman scattered light included in the light incident on the protective filter 42 from the light transmitting columnar member 32 side may be reflected by the protective filter 42 to the light transmitting columnar member 32 side. However, since the stimulated Raman scattered light propagates while spreading in the light transmitting columnar member 32 as described above, the energy density tends to be low and is reflected by the protective filter 42 toward the light transmitting columnar member 32 side. However, it is difficult to return to the optical fiber 21. On the other hand, the reflected light reflected by the irradiation target of the light emitted from the laser device 1 and returning to the protection filter 42 may be parallel light. Therefore, the stimulated Raman scattered light included in the reflected light tends to have a higher energy density than the light reflected to the light transmitting columnar member 32 side by the protective filter 42 as described above. Therefore, the stimulated Raman scattered light included in the reflected light reflected by the irradiation target is guided by the light reflected by the protective filter 42 toward the light transmitting columnar member 32 unless the protective filter 42 suppresses the transmission. Compared to Raman scattered light, it is easier to return to the optical fiber 21.

As described above, the protective cap 40 of the present embodiment includes the bandpass filter 44 and the fixing member 41 that fixes the relative position between the bandpass filter 44 and the light transmitting columnar member 32. In the bandpass filter 44, the end face 21f of the optical fiber 21 that propagates the signal light of a predetermined wavelength is optically coupled to one end face, and the outer diameter is larger than the outer diameter of the core 21a of the optical fiber 21. On the other end face side of 32, it is arranged apart from the light transmitting columnar member 32. Further, the bandpass filter 44 suppresses the transmission of the stimulated Raman scattered light generated from the signal light at a higher rate than the signal light.

The light that enters the bandpass filter 44 from the light transmitting columnar member 32 side may include signal light and stimulated Raman scattered light generated from the signal light. Here, the bandpass filter 44 suppresses the transmission of the stimulated Raman scattered light generated from the signal light at a higher rate than the signal light. Therefore, while the signal light is transmitted through the bandpass filter 44, the stimulated Raman scattered light is suppressed from being transmitted through the bandpass filter 44 and emitted. Further, even when the reflected light that passes through the bandpass filter 44 from the light transmitting columnar member 32 side and returns to the bandpass filter 44 includes the stimulated Raman scattered light, the stimulated Raman scattered light is the bandpass filter. Transmission through 44 is suppressed. Therefore, the stimulated Raman scattered light included in the reflected light can be suppressed from propagating to the light source 10 of the laser device 1. Therefore, the protective cap 40 including the bandpass filter 44 can suppress the characteristic deterioration due to the reflected light in the laser device 1.

Further, the protective cap 40 is easy to remove. Therefore, the protection cap 40 can be easily replaced when a problem occurs in the protection filter 42 or the like.

Further, the protective cap 40 is provided at a position near the light emitting end of the laser device 1. Therefore, the protective cap 40 can efficiently suppress the return of the stimulated Raman scattered light included in the reflected light reflected by the irradiation target object to the optical fiber 21.

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

FIG. 4 is a diagram showing a part of the laser device according to the second embodiment of the present invention similarly to FIG. As shown in FIG. 4, the protective cap 40 of the present embodiment is the same as the protective cap 40 of the first embodiment except for the installation angle of the protective filter 42. That is, the bandpass filter 44 of the present embodiment is different in installation angle from the bandpass filter 44 of the first embodiment.

The protective filter 42 of the protective cap 40 of the present embodiment is arranged non-perpendicular to the optical axis OA of the signal light propagating through the light transmitting columnar member 32. That is, the bandpass filter 44 of the present embodiment is formed in a planar shape and is arranged non-perpendicularly to the optical axis OA of the signal light propagating through the light transmitting columnar member 32.

Since the planar band-pass filter 44 is arranged non-perpendicularly to the optical axis OA of the signal light, part of the stimulated Raman scattered light incident on the band-pass filter 44 from the side of the light transmitting columnar member 32 is a band. The pass filter 44 facilitates reflection in a direction different from the incident direction. Therefore, it becomes difficult for the stimulated Raman scattered light to return to the optical fiber 21. Further, the stimulated Raman scattered light reflected by the irradiation object of the light emitted from the laser device 1 and returning to the bandpass filter 44 enters non-perpendicular to the bandpass filter 44 and is reflected by the bandpass filter 44. It is easy to be done. Therefore, the protective cap 40 of the present embodiment can further suppress deterioration of the characteristics of the laser device 1 due to stimulated Raman scattered light.

(Third Embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to FIG. Note that the same or equivalent components as those of the second embodiment are designated by the same reference numerals unless otherwise specified, and redundant description will be omitted.

FIG. 5: is a figure which shows a part of laser apparatus which concerns on 3rd Embodiment of this invention similarly to FIG. As shown in FIG. 5, the protective cap 40 provided in the laser device of the present embodiment differs from the protective cap 40 of the second embodiment in that a protective filter 46 is provided.

As described above, the protection filter 42 includes the plate-shaped substrate 43 that transmits the signal light, the bandpass filter 44 and the antireflection film 45 formed on the substrate 43. The protective filter 46, like the protective filter 42, includes a substrate 43, a bandpass filter 44, and an antireflection film 45. The protection filter 42 and the protection filter 46 are arranged non-perpendicular to the optical axis OA of the signal light propagating through the light transmitting columnar member 32. However, in the cross section that overlaps the optical axis OA of the signal light, the inclination direction of the protection filter 42 and the inclination direction of the protection filter 46 are opposite to each other. That is, in the cross section that overlaps the optical axis OA of the signal light, the protection filter 42 and the protection filter 46 are arranged so that the optical axis OA between the protection filter 42 and the protection filter 46 increases from one end to the other end. The surfaces are perpendicular to each other and are inclined so as to be separated from each other on opposite sides.

Next, the propagation path of the signal light in the protective cap 40 of this embodiment will be described. FIG. 6 is a diagram for enlarging a part of FIG. 5 to explain a propagation path of signal light. In FIG. 6, the propagation path of the signal light is indicated by a dashed arrow.

Since the protection filter 42 is arranged non-perpendicular to the optical axis OA of the signal light propagating through the light transmitting columnar member 32, the signal light entering the protection filter 42 from the light transmitting columnar member 32 side is protected by the protection filter 42. Refracts when the light enters the protective filter 42 and when the light passes through the protective filter 42 and exits from the protective filter 42. Therefore, the optical axis of the signal light transmitted through the protection filter 42 is deviated from the optical axis of the signal light before entering the protection filter 42. Further, since the protection filter 46 is also arranged non-perpendicularly to the optical axis of the signal light, the signal light is refracted when entering the protection filter 46 and when passing through the protection filter 46 and exiting from the light transmitting plate. .. However, in the cross section that overlaps the optical axis of the signal light, the inclination direction of the protection filter 42 and the inclination direction of the protection filter 46 are opposite to each other. Therefore, the direction in which the optical axis deviates before and after passing through the protective filter 42 and the direction in which the optical axis deviates before and after passing through the protective filter 46 are opposite sides in the cross section overlapping the optical axis of the signal light. Therefore, the shift of the optical axis of the signal light caused by passing through the protection filter 42 can be mitigated by the protection filter 46. Since the thickness of the bandpass filter 44 and the antireflection film 45 is extremely smaller than the thickness of the substrate 43, the thickness and the refractive index of the bandpass filter 44 and the antireflection film 45 can be ignored. Therefore, in the description of the shift of the optical axis, the protection filter 42 and the protection filter 46 can be rephrased as the substrate 43 included in the protection filter 42 and the substrate 43 included in the protection filter 46, respectively.

When the protection filter 42 and the protection filter 46 have the same configuration as described above, the protection filter 42 and the protection filter 46 face each other between the protection filter 42 and the protection filter 46 in a plane perpendicular to the optical axis OA of the signal light. Are preferably arranged symmetrically. By disposing the protective filter 42 and the protective filter 46 in this way, the deviation between the optical axis of the signal light before entering the protective cap 40 and the optical axis of the signal light after exiting from the protective cap 40 is suppressed. It will be easier.

Next, with reference to FIG. 6, a method for alleviating the deviation of the optical axis of the signal light, including the case where the protection filter 42 and the protection filter 46 have different thicknesses and different materials, will be generalized and described.

One of the protection filter 42 and the protection filter 46, which is arranged on the light transmission columnar member 32 side, is the first light transmission plate, and the other is the second light transmission plate. Therefore, in the form shown in FIG. 6, the protection filter 42 is the first light transmission plate, and the protection filter 46 is the second light transmission plate. The thickness of the first light transmitting plate is d ₁ , the acute angle of inclination of the first light transmitting plate with respect to the plane perpendicular to the optical axis OA is θ _i , the refractive index of the first light transmitting plate is n ₁ , the refractive index of the light transmission columnar member 32 side of the medium of the light transmission plate n _i, d ₂ the thickness of the second light transmitting _plate, the acute angle of inclination of for a plane perpendicular to the optical axis OA of the second light transmitting plate When θ _m , the refractive index of the second light transmitting plate is n ₂ , and the refractive index of the medium between the second light transmitting plate and the first light transmitting plate is n _m , the following (1) is satisfied: The protection filter 42 and the protection filter 46 are arranged.

The left side of the above equation (1) is twice the shift amount S ₁ of the optical axis of the signal light after passing through the first light transmitting plate with respect to the optical axis of the signal light before passing through the first light transmitting plate. .. Further, the right side of the above formula (1) is equal to the shift amount S ₂ of the optical axis of the signal light after passing through the second light transmitting plate with respect to the optical axis of the signal light before passing through the second light transmitting plate. Therefore, by arranging the first light transmitting plate and the second light transmitting plate so as to satisfy the above formula (1), the shift amount S ₂ of the optical axis of the signal light by the second light transmitting plate is equal to the first light transmitting plate. The shift amount of the optical axis of the signal light due to the transmission plate is less than twice the shift amount S ₁ . By the way, the direction in which the optical axis of the signal light is displaced by the second light transmitting plate and the direction in which the optical axis of the signal light is displaced by the first light transmitting plate are different from each other. Therefore, in the range where the above expression (1) is satisfied, the optical axis of the signal light propagating through the light transmissive columnar member 32 is large even when the shift amount S ₂ is larger than the shift amount S ₁ in the cross section shown in FIG. The deviation amount |S ₂ −S ₁ | of the optical axis of the signal light after passing through the second light transmitting plate with respect to is after passing through the first light transmitting plate with respect to the optical axis of the signal light propagating through the light transmitting columnar member 32. It can be smaller than the shift amount S ₁ of the optical axis of the signal light. Therefore, the shift of the optical axis of the signal light due to transmission through the first light transmitting plate is mitigated by the second light transmitting plate.

It is preferable that the above formula (1) holds in an arbitrary cross section that overlaps the optical axis OA of the signal light propagating through the light transmitting columnar member 32.

Although the present invention has been described above by taking the above embodiment as an example, the present invention is not limited to these.

For example, the number and the arrangement angle of the protection filters 42 are not limited to the form illustrated in the above embodiment. Therefore, for example, the protection cap 40 may include a plurality of protection filters 42 that are perpendicular to the optical axis OA of the signal light propagating through the light transmitting columnar member 32, and the light of the signal light propagating through the light transmitting columnar member 32 may be provided. There may be a plurality of protection filters 42 that are non-perpendicular to the axis OA.

Further, in the third embodiment described above, the protective cap 40 has been described by exemplifying the form having the two protective filters 42 and 46, but the protective cap 40 may have at least one protective filter. Therefore, for example, in the third embodiment, one of the protection filter 42 and the protection filter 46 may be replaced with a light transmission plate that does not have the bandpass filter 44. The light transmitting plate transmits the signal light propagating through the light transmitting columnar member 32. That is, one of the protection filter 42 and the protection filter 46 may be composed of only the substrate 43, or may be composed of the substrate 43 and the antireflection film 45.

Further, when the protection filter 42 is arranged non-perpendicularly to the optical axis OA of the signal light propagating in the light transmitting columnar member 32, the optical axis of the signal light with respect to the optical axis OA of the signal light propagating in the light transmitting columnar member 32. The protective cap 40 may include a plurality of the light transmitting plates for the purpose of alleviating the deviation. However, by providing the plurality of bandpass filters 44 like the protective cap 40 of the third embodiment, the transmission of the stimulated Raman scattered light is further suppressed, and the characteristic deterioration due to the stimulated Raman scattered light in the laser device is further suppressed. Can be done.

Further, in the above embodiment, the protective filters 42 and 46 have been described by exemplifying the form having the substrate 43 and the antireflection film 45. However, the substrate 43 antireflection film 45 is not an essential configuration. Therefore, the protection filters 42 and 46 may be configured by only the bandpass filter 44, or may be configured by disposing the bandpass filter 44 on both surfaces of the substrate 43. Further, the shape of the bandpass filter 44 is not limited to the planar shape.

In the above embodiment, the case where the number of the light sources 10 is plural has been described, but the number of the light sources 10 may be one. In this case, the optical fiber 21 is directly connected to the light source 10.

Further, in the above-described embodiment, the protection filters 42 and 46 are fixed to the fixing member 41 that is fixed to the housing 33, so that the protection filters 42 and 46 are arranged on the side of the emitting surface 32a that is the other end surface of the light transmitting columnar member 32. However, the housing 33 and the fixing member 41 may be integrated. FIG. 7: is a figure which shows such a modification of the protection cap 40 of FIG. It should be noted that, in describing the present modified example, the description of the same configuration as that of the first embodiment will be omitted unless otherwise mentioned. As shown in FIG. 7, in this modification, the fixing member 41 also serves as the housing 33 in the first embodiment. Therefore, in this modification, the outer peripheral surface 32c of the light transmitting columnar member 32 is fixed to the inner peripheral surface of the fixing member 41. Similarly, in the second embodiment described with reference to FIG. 4 and the protection cap 40 of the third embodiment described with reference to FIGS. 5 and 6, the housing 33 and the fixing member 41 are integrated. The fixing member 41 may also serve as the housing 33.

Further, in the above embodiment, the end face 21f of the optical fiber 21 is fused to the central portion of the incident surface 32b which is one end face of the light transmitting columnar member 32, so that the optical fiber 21 and the light transmitting columnar member 32 are optically coupled. I showed an example that they are combined with each other. As long as the optical fiber 21 is optically coupled to the light transmitting columnar member 32, the optical fiber 21 and the light transmitting columnar member 32 may not be fused.

As described above, according to the present invention, there is provided a protective cap capable of suppressing characteristic deterioration due to reflected light in a laser device, and a laser device including the protective cap, which is used in fields such as processing machines and medical laser devices. Expected to do.

DESCRIPTION OF SYMBOLS 1... Laser device 10... Light source 20... Optical combiner 30... Optical device 21... Optical fiber 21a... Core 32... Light transmitting columnar member 33... Housing 40. ..Protection cap 41...Fixing members 42, 46...Protection filter 43...Substrate 44...Bandpass filter 45...Antireflection film

Claims (6)

The end face of an optical fiber that propagates a signal light of a predetermined wavelength is optically coupled to one end face, and the outer diameter is larger than the outer diameter of the core of the optical fiber on the other end face side of the light transmitting columnar member, the light A band-pass filter arranged apart from the transmissive columnar member,
A fixing member for fixing the relative position of the bandpass filter and the light transmitting columnar member,
Equipped with
The protective cap, wherein the bandpass filter suppresses transmission of stimulated Raman scattered light generated from the signal light at a higher rate than that of the signal light. The protective cap according to claim 1, wherein the bandpass filter has a planar shape and is arranged non-perpendicularly to an optical axis of the signal light propagating through the light transmitting columnar member. A plate-shaped substrate in which the bandpass filter is disposed on at least one surface and which transmits the signal light,
A plate-shaped light transmitting plate that transmits the signal light,
Further equipped with,
The substrate and the light transmitting plate are respectively arranged non-perpendicular to the optical axis of the signal light propagating in the light transmitting columnar member,
The protective cap according to claim 1, wherein, in a cross section that overlaps the optical axis of the signal light, the tilt direction of the substrate and the tilt direction of the light transmission plate are opposite to each other. Of the protection filter including the substrate and the bandpass filter and the light transmission plate, the one arranged on the light transmission columnar member side is the first light transmission plate and the other is the second light transmission plate,
The thickness of the first light transmitting plate is d ₁ , the acute angle of inclination of the first light transmitting plate with respect to the plane perpendicular to the optical axis is θ _i , the refractive index of the first light transmitting plate is n ₁ , and the refractive index n _i of the light transmitting columnar member side of the medium of the first light transmitting _plate, the thickness d ₂ of the second light transmitting _plate, acute against a plane perpendicular to the optical axis of the second light transmitting plate Where θ _{m is} the tilt angle, n _{2 is} the refractive index of the second light transmitting plate, and n _m is the refractive index of the medium between the second light transmitting plate and the first light transmitting plate. The protective cap according to claim 3, wherein (1) is established.

The protective cap according to claim 3 or 4, wherein the light transmission plate suppresses the transmission of stimulated Raman scattered light generated from the signal light at a higher rate than the signal light. At least one light source for emitting the signal light;
The optical fiber for propagating the signal light,
An end surface of the optical fiber is optically coupled to one end surface, the outer diameter of the light transmitting columnar member is larger than the outer diameter of the core of the optical fiber,
The protective cap according to any one of claims 1 to 5, further comprising: the band-pass filter disposed apart from the light-transmitting columnar member on the other end surface side of the light-transmitting columnar member.
A laser device comprising:

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