JP2021061343A - Laser output device and manufacturing method thereof - Google Patents

Abstract

To reduce a transmittance in a saturable absorption device using a carbon nanowall.SOLUTION: A laser output device includes an optical fiber 130C having an end face 132, an optical fiber 130D having an end face 134 facing the end face 132, and a plurality of saturable absorption sheets 192 having a carbon nanowall and provided between the end face 132 and the end face 134.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a laser output device and a method for manufacturing the laser output device.

Conventionally, a saturable absorptive element (SA: Saturable Absorber) has been used in order to shorten the pulse width of the laser light output by the laser output device. In the laser output device, the saturable absorption element is arranged on the optical path of the laser light oscillated by the laser oscillator. The saturable absorbing element absorbs incident light having an intensity lower than a predetermined saturation value, but transmits incident light having an intensity equal to or higher than the saturation value. Therefore, the saturable absorption element transmits only the central portion of the pulse whose light intensity is equal to or higher than the saturation value among the one-pulse laser light oscillated by the laser oscillator, and absorbs and does not transmit the portion other than the central portion. Therefore, the pulse width of the laser light (transmitted light) transmitted through the saturable absorbing element is shorter than that of the incident light.

As a saturable absorbing element, a thin film in which carbon nanowalls are embedded in a resin has been proposed (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2015-118348

The transmittance of laser light in a saturable absorption device using the carbon nanowall depends on the density in the film of the carbon nanowall. However, there is a limit to the upper limit of the density of carbon nanowalls. That is, in the saturable absorption device using the carbon nanowall, there is a limit to the reduction of the transmittance.

An object of the present disclosure is to provide a laser output device and a method for manufacturing a laser output device capable of reducing the transmittance in a saturable absorption element using a carbon nanowall.

In order to solve the above problems, the laser output device according to one aspect of the present disclosure includes a first optical fiber having a first end face and a second light having a second end face facing the first end face. It comprises a fiber and a plurality of saturable absorbent sheets that include a carbon nanowall and are provided between a first end face and a second end face.

Further, the laser output device may be one or more of one or more between the first end face and the saturable absorbing sheet, between the second end face and the saturable absorbing sheet, and between the saturable absorbing sheets. The adhesive liquid may be arranged in.

In order to solve the above problems, the method for manufacturing a laser output device according to one aspect of the present disclosure includes a step of bringing a saturable absorption sheet containing a carbon nanowall into contact with a first end face of a first optical fiber. It includes a step of bringing the saturable absorbing sheets into contact with each other and a step of bringing the saturable absorbing sheet into contact with the second end face of the second optical fiber.

The method for manufacturing the laser output device is one or more of a step of contacting the first end face, a step of contacting the saturable absorbing sheets with each other, and a step of contacting the second end face. A step of immersing the saturable absorbent sheet in the adhesive liquid may be included before the execution.

The present disclosure makes it possible to reduce the transmittance in a saturable absorption device using a carbon nanowall.

It is a figure explaining the laser output apparatus which concerns on embodiment. It is a figure explaining an optical connector and a saturable absorption element. It is a figure explaining the saturable absorption sheet. It is a figure explaining the process flow of the manufacturing method of the laser output apparatus of this embodiment. It is a figure explaining the transmittance [%] of a laser light and the output [mW] of a transmitted light.

An embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. The dimensions, materials, other specific numerical values, etc. shown in such an embodiment are merely examples for facilitating understanding, and do not limit the present disclosure unless otherwise specified. In the present specification and the drawings, elements having substantially the same function and configuration are designated by the same reference numerals, so that duplicate description will be omitted. In addition, elements not directly related to the present disclosure are not shown.

[Laser output device 100]
FIG. 1 is a diagram illustrating a laser output device 100 according to the present embodiment. In FIG. 1, the dashed arrow indicates the laser beam. The laser output device 100 outputs laser light. The pulse width of the laser light output by the laser output device 100 is, for example, femtoseconds or picoseconds.

As shown in FIG. 1, the laser output device 100 includes a light source 110 and an oscillator 120. The light source 110 outputs excitation light. The oscillator 120 oscillates a laser beam using the light output from the light source 110.

In the present embodiment, the oscillator 120 includes optical fibers 130A to 130D, an optical coupler 140, an optical gain medium 150, collimator lenses 160 and 162, wave plates 170 and 172, a beam splitter 180, and a saturable absorption element. 190 and an optical connector 200 are included.

The optical fiber 130A connects the optical coupler 140 and the optical gain medium 150. The optical fiber 130B connects the optical gain medium 150 and the collimator lens 160. The optical fiber 130C connects the collimator lens 162 and the saturable absorbing element 190. The optical fiber 130D connects the saturable absorbing element 190 and the optical coupler 140.

The optical coupler 140 is connected to the light source 110 via an optical fiber 112. The optical coupler 140 combines the excitation light of the light source 110 with the laser light guided from the optical fiber 130D. The optical gain medium (laser medium) 150 amplifies the light coupled by the optical coupler 140. The collimator lens 160 adjusts the laser light amplified by the light gain medium 150 to parallel light.

The wave plates 170 and 172 are provided on the optical path of the laser beam output from the collimator lens 160 and guided to the beam splitter 180. Wave plates 170 and 172 adjust the polarization of light. The wave plate 170 is a 1/4 wave plate. The wave plate 172 is a 1/2 wave plate.

The beam splitter 180 splits the laser beam output from the collimator lens 160 and passing through the wave plates 170 and 172 into two. One of the laser beams split by the beam splitter 180 is output to the outside. The other laser beam split by the beam splitter 180 is returned to the optical gain medium 150 via the collimator lens 162, the saturable absorbing element 190, and the optical coupler 140.

The saturable absorbing element 190 is provided between the optical fiber 130C and the optical fiber 130D. The saturable absorbing element 190 is arranged on the optical path of the laser beam passing between the optical fiber 130C and the optical fiber 130D.

The saturable absorbing element 190 absorbs incident light having an intensity lower than a predetermined saturation value, but transmits incident light having an intensity equal to or higher than the saturation value. Therefore, the saturable absorbing element 190 transmits only the central portion of the laser light incident from the optical fiber 130C that is equal to or higher than the saturation value, and absorbs and does not transmit the laser light other than the central portion. Therefore, the pulse width of the laser light (transmitted light) transmitted through the saturable absorbing element 190 is shorter than that of the incident light.

In the present embodiment, the saturable absorbing element 190 includes a plurality of saturable absorbing sheets. The saturable absorbing element 190 is arranged between the optical fiber 130C and the optical fiber 130D by the optical connector 200.

FIG. 2 is a diagram illustrating an optical connector 200 and a saturable absorbing element 190. FIG. 2A is a diagram illustrating a cross section of the optical connector 200. FIG. 2B is a diagram illustrating an enlarged view of a cross section of the ferrule 212 and the saturable absorbing element 190. In FIG. 2A, the hatching of the ferrule 212 is omitted for ease of understanding. Further, in FIG. 2B, hatching of the ferrule 212, the optical fibers 130C and 130D, and the saturable absorption sheet 192 is omitted.

The optical connector 200 is, for example, an FC / APC connector. As shown in FIG. 2A, the optical connector 200 includes a first connector 210, a second connector 220, and an adapter 230.

The second connector 220 differs from the first connector 210 only in that it holds the optical fiber 130D. Therefore, in the present embodiment, the first connector 210 will be described in detail, and the second connector 220 will be designated by the same reference numerals and the description thereof will be omitted.

The first connector 210 includes a ferrule 212 and a connecting portion 214.

The ferrule 212 is made of, for example, ceramics or metal. The ferrule 212 has a cylindrical shape. As shown in FIG. 2B, a through hole 212a extending in the axial direction is formed substantially in the center of the ferrule 212. The tip of the optical fiber 130C is inserted into the through hole 212a of the ferrule 212. The ferrule 212 fixes the tip of the optical fiber 130C.

The end face 212b of the ferrule 212 is polished into a flat shape or a spherical shape. Further, the end face 212b of the ferrule 212 may be perpendicular to the longitudinal direction of the ferrule 212 or may be inclined with respect to the longitudinal direction. The polishing method of the ferrule 212 is, for example, PC (Physical Contact) polishing and APC (Angled Physical Contact) polishing. In the present embodiment, the end face 212b of the ferrule 212 is polished by APC polishing as an example. That is, the end face 212b of the ferrule 212 is inclined with respect to the plane orthogonal to the longitudinal direction of the ferrule 212 and has a spherical shape. The ferrule 212 fixes the optical fiber 130C so that the end surface 132 of the optical fiber 130C (or the end surface 134 of the optical fiber 130D) is located on the end surface 212b.

Returning to FIG. 2A, the connection portion 214 of the first connector 210 is connected to the adapter 230 so that the ferrule 212 to which the optical fiber 130C is fixed is arranged in the through hole 232 of the adapter 230. To. Similarly, the connection portion 214 of the second connector 220 is connected to the adapter 230 so that the ferrule 212 to which the optical fiber 130D is fixed is arranged in the through hole 232 of the adapter 230.

A split sleeve 234 is provided in the adapter 230. The split sleeve 234 is made of, for example, ceramics or metal. The split sleeve 234 has a cylindrical shape. The split sleeve 234 is formed with a notch in the axial direction. The ferrule 212 of the first connector 210 and the ferrule 212 of the second connector 220 are arranged in the split sleeve 234.

The adapter 230 connects the first connector 210 and the second connector 220 so that the end surface 212b of the ferrule 212 of the first connector 210 and the end surface 212b of the ferrule 212 of the second connector 220 face each other.

Further, as shown in FIG. 2B, in the present embodiment, the saturable absorbing element 190 is the end face 132 (first end face) of the optical fiber 130C (first optical fiber) and the optical fiber 130D (second end face). It is provided between the end face 134 (second end face) of the optical fiber), that is, between the ferrule 212 of the first connector 210 and the ferrule 212 of the second connector 220.

Specifically, the saturable absorbing element 190 is provided between the end face 132 of the core of the optical fiber 130C and the end face 134 of the core of the optical fiber 130D. The saturable absorbing element 190 is larger than the core of the optical fiber 130C and the core of the optical fiber 130D. The core of the optical fiber 130C and the core of the optical fiber 130D are covered with the saturable absorbing element 190.

In the present embodiment, the saturable absorbing element 190 includes a plurality of saturable absorbing sheets 192. The plurality of saturable absorbing sheets 192 are laminated (arranged in series) between the end face 132 and the end face 134. In FIG. 2B, the case where the number of the saturable absorbing sheets 192 is two is taken as an example, but the number of the saturable absorbing sheets 192 constituting the saturable absorbing element 190 is not limited.

FIG. 3 is a diagram illustrating a saturable absorption sheet 192. FIG. 3A is a perspective view of the saturable absorbing sheet 192. FIG. 3B is a cross-sectional view of the saturable absorbing sheet 192. Further, in FIGS. 3A and 3B of the present embodiment, the X-axis, Y-axis, and Z-axis that intersect vertically are defined as shown in the figure. In FIG. 3B, the white arrow indicates the laser beam.

As shown in FIGS. 3 (a) and 3 (b), the saturable absorbing sheet 192 includes a carbon nanowall 192a and a surrounding portion 192b. The thickness of the saturable absorbing sheet 192 (the length in the X-axis direction in FIGS. 3A and 3B) is about 1 μm to 100 μm.

In the present embodiment, the carbon nanowall 192a is a stack of a plurality of graphenes. The thickness of the carbon nanowall 192a (the length in the Z-axis direction in FIG. 3B) is, for example, 1 nm or more and 100 nm or less. The distance between adjacent carbon nanowalls 192a (distance in the Z-axis direction in FIG. 3B) is, for example, 1 nm or more and 10 μm or less.

The surrounding portion 192b surrounds the carbon nanowall 192a. That is, the carbon nanowall 192a is embedded in the surrounding portion 192b. The surrounding portion 192b contains, for example, one or both of polyimide and polymethyl methacrylate (PMMA). Since the surrounding portion 192b contains polyimide, heat resistance can be improved. Further, since the surrounding portion 192b contains PMMA, it is possible to improve the transmittance of the laser light. That is, since the surrounding portion 192b contains polyimide and PMMA, it is possible to improve the heat resistance and the transmittance.

The saturable absorption sheet 192 is arranged between the optical fibers 130C and 130D so that the laser beam is incident in the X-axis direction in FIGS. 3A and 3B.

Subsequently, a method of manufacturing the laser output device 100 will be described. FIG. 4 is a diagram illustrating a processing flow of the manufacturing method of the laser output device 100 of the present embodiment. As shown in FIG. 4, the manufacturing method of the laser output device 100 includes a number determination step S110, a dipping step S120, a first contact step S130, an increment step S140, a second contact step S150, and a third contact step. Includes S160. Hereinafter, each step will be described.

[Number determination step S110]
The number-of-sheet determination step S110 is a step of determining whether or not the number of laminated saturable absorption sheets 192 is equal to or greater than a predetermined set number of sheets. The set number of sheets is the number of saturable absorption sheets 192 determined based on the desired transmittance. When it is determined that the number of laminated saturable absorbing sheets 192 is not more than the set number of sheets, that is, less than the set number of sheets (NO in S110), the process is transferred to the dipping step S120. On the other hand, when it is determined that the number of laminated saturable absorbing sheets 192 is equal to or greater than the set number (YES in S110), the process is transferred to the second contact step S150.

[Immersion step S120]
The dipping step S120 is a step of dipping the saturable absorbing sheet 192 in the adhesive liquid. The adhesive liquid is a liquid that does not dissolve the optical fibers 130C, 130D and the saturable absorbing sheet 192, and does not modify the optical fibers 130C, 130D and the saturable absorbing sheet 192. The adhesive liquid is a liquid that does not dissolve the resin, glass, and carbon nanowalls and does not denature them. The adhesive liquid is, for example, methanol, ethanol, 1-propanol, 2-propanol, and water. Here, ethanol is taken as an example of the adhesive liquid.

[First contact step S130]
The first contact step S130 is a step of bringing the saturable absorbing sheet 192 immersed in the adhesive liquid in the dipping step S120 into contact with the laminated saturable absorbing sheet 192. That is, the first contact step S130 is a step of bringing the saturable absorbing sheets 192 into contact with each other.

[Increment step S140]
In the increment step S140, 1 is substituted (incremented) for the number of laminated saturable absorption sheets 192, and the process is transferred to the number determination step S110.

[Second contact step S150]
In the second contact step S150, first, the optical fiber 130C (first connector 210) is connected to one side of the adapter 230. Then, the laminated saturable absorbing sheet 192 is brought into contact with the end face 132 of the optical fiber 130C.

[Third contact step S160]
In the third contact step S160, the optical fiber 130D (second connector 220) is connected to the other side of the adapter 230. As a result, the saturated absorbent sheet 192 at the end end is brought into contact with the end face 134 of the optical fiber 130D. That is, the third contact step S160 is a step of bringing the laminated saturable absorbing sheet 192 into contact with the end face 134 of the optical fiber 130D.

In this way, the saturable absorbing element 190 provided between the optical fiber 130C, the optical fiber 130D, the end face 132 of the optical fiber 130C, and the end face 134 of the optical fiber 130D (a plurality of continuous saturable absorbing sheets 192 (saturable)). A laser output device 100 including a laminated body of absorption sheets 192)) is manufactured.

As described above, the laser output device 100 and the method for manufacturing the laser output device 100 of the present embodiment include a saturable absorbing element 190 including a plurality of saturable absorbing sheets 192. As a result, the laser output device 100 can reduce the transmittance of the laser light as compared with the laser output device of the comparative example including the saturable absorption element 190 composed of only one saturable absorption sheet 192. It becomes.

Further, the laser output device 100 can control the transmittance of the laser light only by changing the number of the saturable absorption sheets 192. Therefore, the laser output device 100 can control the output of the laser light only by changing the number of the saturable absorption sheets 192.

Further, as described above, the saturable absorbing sheet 192 is immersed in the adhesive liquid before the saturable absorbing sheet 192 is brought into contact with the end face 132 of the optical fiber 130C or the saturable absorbing sheet 192. As a result, the end face 132 of the optical fiber 130C and the saturable absorbing sheet 192, the saturable absorbing sheets 192, and the end face 132 of the optical fiber 130D and the saturable absorbing sheet 192 can be easily separated by utilizing the surface tension of the adhesive liquid. It becomes possible to make contact.

[Example]
The saturable absorbing element 190 of Example A, Example B, and Example C was manufactured. Example A is a saturable absorbing element 190 including one saturable absorbing sheet 192. Example B is a saturable absorbing element 190 including two saturable absorbing sheets 192. Example C is a saturable absorbing element 190 including three saturable absorbing sheets 192.

Using the laser output device 100 incorporating Examples A to C, the transmittance [%] of the laser light and the output [mW] of the transmitted light in the saturable absorbing element 190 were measured.

FIG. 5 is a diagram for explaining the transmittance [%] of the laser light and the output [mW] of the transmitted light. In FIG. 5, the vertical axis indicates the output [mW] of transmitted light. In FIG. 5, the horizontal axis represents the transmittance [%] of the laser light.

As shown in FIG. 5, in Example A, the transmittance of the laser light was about 42%. Further, in Example A, the output of transmitted light (pulse output) was about 0.7 mW. Further, in Example B, the transmittance of the laser light was about 18%. Further, in Example B, the output of transmitted light was about 1.5 mW. Further, in Example C, the transmittance of the laser light was about 8%. Further, in Example C, the output of transmitted light was about 2.6 mW.

From the above results, when the number of saturable absorbing sheets 192 is increased, the transmittance decreases (42% → 18% → 8%) and the output of transmitted light increases (0.7 mW → 1.5 mW). → 2.6mW) was confirmed.

Although one embodiment has been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to the above-described embodiment. It is clear to those skilled in the art that various modifications or modifications can be conceived within the scope of the claims, and it is understood that they also naturally belong to the technical scope of the present disclosure. Will be done.

For example, in the above-described embodiment, the case where the adhesive liquid is ethanol has been taken as an example. Since ethanol is volatile, it is between the end face 132 of the optical fiber 130C and the saturable absorbing sheet 192, between the end face 134 of the optical fiber 130D and the saturable absorbing sheet 192, and between the saturable absorbing sheets 192. The adhesive liquid evaporates from any one or more of them. However, if the adhesive is non-volatile or refractory, or if the adhesive is volatile but is incorporated between the optical fibers 130C and 130D before it evaporates, the end face 132 is acceptable. The adhesive liquid remains between the saturated absorbing sheets 192, between the end faces 134 and the saturable absorbing sheets 192, and between the saturated absorbing sheets 192 and one or more of them. Therefore, in this case, the adhesive liquid is applied to any one or more of between the end face 132 and the saturable absorbing sheet 192, between the end face 134 and the saturable absorbing sheet 192, and between the saturated absorbing sheets 192. Will be arranged.

Further, in the above embodiment, a configuration in which a laminated body of the saturable absorbing sheet 192 (saturable absorbing element 190) is manufactured and then the saturable absorbing element 190 is sandwiched between the end face 132 and the end face 134 is given as an example. .. However, first, a plurality of saturable absorption sheets 192 are laminated on the end face 132 of the optical fiber 130C or the end face 134 of the optical fiber 130D, and then the end face 134 of the optical fiber 130D or the end face 132 of the optical fiber 130C is laminated with the saturable absorption sheet 192. May be brought into contact with the laminate of.

Further, one or more saturable absorbing sheets 192 may be brought into contact with the end face 132 of the optical fiber 130C and the end face 134 of the optical fiber 130D, and then the saturable absorbing sheets 192 may be brought into contact with each other. In any case, the method for manufacturing the laser output device 100 includes a step of bringing the saturable absorbing sheet 192 containing the carbon nanowall into contact with the first end face 132 of the first optical fiber 130C and the saturable absorbing sheets 192. It may include a step of contacting the saturable absorbing sheet 192 and a step of contacting the second end face 134 of the second optical fiber 130D.

The present disclosure can be used for a laser output device and a method for manufacturing a laser output device.

100 Laser output device 130C optical fiber (first optical fiber)
130D optical fiber (second optical fiber)
132 End face (first end face)
134 End face (second end face)
140 Optical Coupler 192 Saturable Absorption Sheet 192a Carbon Nanowall

Claims (4)

A first optical fiber having a first end face,
A second optical fiber having a second end face facing the first end face,
A plurality of saturable absorbing sheets containing carbon nanowalls and provided between the first end face and the second end face.
A laser output device equipped with. Adhesion to any one or more of the first end face and the saturable absorbing sheet, the second end face and the saturable absorbing sheet, and between the saturable absorbing sheets. The laser output device according to claim 1, wherein the liquid is arranged. A step of bringing a saturable absorbing sheet containing carbon nanowalls into contact with the first end face of the first optical fiber, and
The step of bringing the saturable absorbing sheets into contact with each other and
The step of bringing the saturable absorption sheet into contact with the second end face of the second optical fiber, and
A method of manufacturing a laser output device including. Before executing any one or more of the steps of contacting the first end face, contacting the saturable absorbing sheets with each other, and contacting the second end face, the saturable The method for manufacturing a laser output device according to claim 3, further comprising a step of immersing the absorption sheet in an adhesive liquid.

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